Current Understanding of the Transmission, Diagnosis, and Treatment of H. pylori Infection: A Comprehensive Review

International Journal of Medical, Pharmacy and Drug Research (IJMPD)
Article DOI: https://dx.doi.org/10.22161/ijmpd.7.2.1
Peer-Reviewed Journal Int. J. Med. Phar. Drug Re., 7(2), 2023
ISSN: 2456-8015
Int. J. Med. Phar. Drug Re., 7(2), 2023
Online Available at: https://www.aipublications.com/ijmpd/ 1
Current Understanding of the Transmission,
Diagnosis, and Treatment of H. pylori Infection: A
Comprehensive Review
Hend Sadeq Mohammed Aljaberi1, Nida Khalid Ansari1, Mengqiu Xiong1,
Hongxin Peng1, Bangshun He *,1,2 and Shukui Wang*,1,2
1Department of Laboratory Medicine, Nanjing First Hospital, Nanjing Medical University, China
2H. pylori Research Key Laboratory, Nanjing Medical University, Nanjing, China.
Received: 11 Feb 2023; Received in revised form: 14 Mar 2023; Accepted: 21 Mar 2023; Available online: 28 Mar 2023
©2023 The Author(s). Published by AI Publications. This is an open access article under the CC BY license
(https://creativecommons.org/licenses/by/4.0/)
Abstract
H. pylori infection is a prevalent bacterial infection that affects the gastric mucosa of humans, with a
prevalence ranging from 30% to 90%, depending on the region. The infection is a significant cause of
gastritis, peptic ulcer disease, and gastric cancer. In this comprehensive review, we discuss the current
understanding of the transmission, diagnosis, and treatment of H. pylori infection. We describe the risk
factors and epidemiology of the infection, along with its pathogenesis, which involves multiple virulence
factors that contribute to the colonization and survival of the bacteria in the acidic stomach environment.
Diagnostic tests for H. pylori infection include invasive and non-invasive methods, with the choice of test
depending on several factors. Treatment of H. pylori infection is aimed at eradicating the bacteria and
preventing complications. Antibiotic-based triple or quadruple therapy, in combination with acid-
suppressing agents, is the standard treatment, but antibiotic resistance is an emerging problem that needs
to be addressed. This comprehensive review provides a useful resource for clinicians, researchers, and
public health officials involved in managing H. pylori infection and its associated complications.
Keywords— Diagnostic, and Treatment, Epidemiology of H. pylori, H. pylori, Risk factors,
Pathogenesis.
I. OVERVIEW
H. pylori is a helical-shaped, microaerophilic, and
Gram-negative bacterium with a unipolar flagella
bundle (Figure 1 ) [1].which was first diagnosed in
gastric mucosa of patients suffering from gastritis
and peptic ulcer, it was then successfully cultured by
the two Australian doctors; Barry J Marshall and
Robin Warren, [2]. Noticeably, this discovery
contradicted the previously held scientific belief that
the stomach is a germ-free organ, and this discovery
resulted in the award.
of the Noble prize 2005 to Marshall and Warren in
Physiology and Medicine. Chronic infection of
H. pylori in humans is prevalent in more than half of
the world’s population [3]. Furthermore, H. pylori
may also be associated with gastric mucosa-
associated lymphoid tissue lymphoma, one of the
most prevalent extranidal non-Hodgkin lymphomas
[4]. There is evidence that this neoplasm is caused by
chronic gastritis caused by H. pylori. There is no
specific clinical presentation of this disease, which
can range from dyspepsia to the classic B-symptoms
associated with other lymphomas.

Aljaberi et al./ Current Understanding of the Transmission, Diagnosis, and Treatment of H. pylori Infection: A
Acute complications may also occur, including
intestinal obstruction, perforation, and hemorrhaging
[5]. However, only a few infected people are prone to
develop serious clinical symptoms of H. pylori
infection, which in turn is determined by several
factors which particularly depend on the host's
immune status, such as the presence of particular
receptors and the efficiency of inflammatory
responses. Clinical outcome of H. pylori infection also
depends on factors in the environment and strain
specificity that influence the pathogenicity of the
strains (strain diversity) [6].
Fig.1 H. pylori; Under a scanning electron microscope
(left), with its unipolar flagella is shown in a schematic
(right).[1]
1.1 Taxonomy of H. pylori
H. pylori has a helix-shaped shape (hence its name)
and to colonize the stomach, it can physically screw
itself into the lining. Scientific classification of the
bacteria is:
Kingdom: Bacteria
Phylum: Proteobacteria
Class: Epsilon Proteobacteria
Order: Campylobacterales
Family: Helicobacteraceae
Genus: Helicobacter
Species: H. pylori [7]
1.2 Gastric helicobacter species
To present, nine Helicobacter species capable of
hydrolyzing urea have been cultured from the
stomachs of humans and land animals (Table 1). [8].
The Lockard classification system divides these into
three types: Type 1 has a tapered end and a fusiform
to slightly spiral shape; Type 2 has sparsely
distributed periplasmic fibers and can be seen singly
or in groups of two to four, and has a spiral shape;
and Type 3 has a tightly coiled structure and lacks
periplasmic fibers.
Generally, stomach Helicobacter species isolated
from animals other than cats and dogs exhibit
distinct and sometimes similar morphology to H.
pylori. On the basis of 16s rRNA similarity,
a phylogenetic analysis of contemporary gastric,
enteric, and hepatobiliary Helicobacter species has
been conducted. [8].
Table 1 Human and land animal gastric Helicobacter [8]
TAXONOMY NATURAL HOST
H. acinonychis Cheetah
H. bizzeroni Dog
Candidatus Helicobacter
bovis
Cattle
H. felis Cat
H. heilmannii
Human, non-human
primate, pigs
Candidatus Helicobacter
suis
Pig
H. mustelae Ferret
H. nemestrinae Macaque
H. pylori Human, monkey,sheep
H. salomonis Dog
H. suncus Shrew
II. TRANSMISSION OF H. PYLORI INFECTION
The precise mode of route of H. pylori infection
transmission unproven. The H. pylori can spread
either directly from person to another or indirectly
from an infected person to the environment,
according to studies [9]. The human stomach is the
most significant reservoir of H. pylori, and it is
possible for pass from the stomach to the external
environment via feces, vomitus, or gastric
regurgitation [10].Currently, interpersonal
transmission is more likely than environmental
transmission. Transmission from person to person
can be primarily fecal-oral or oral-oral. In the last 30
years, it has been reported in numerous articles that
there are several potential sources and vectors of H.
pylori infections, as well as risk factors related to both
fecal-oral and oral-oral transmission routes, and

exposure to contaminated food, water, and animals.
They tried isolating H. pylori from feces, saliva, and
dental plaque [9].
2.1 Gastro-oral routes
H. pylori is acquired during infancy and transmission
may occur through the vomiting of achlorhydric
mucus. Transmission may occur through the gastric
juices, particularly as a result of vomiting in
childhood [11]. Studies reported percentages of H.
pylori isolated from the gastric juice of symptomatic
patients: A high concentration of the microorganism
is frequently found in vomit, where it appears to
survive outside of the human body in unbuffered
gastric juice. The results of these studies support the
hypothesis that gastro-oral transmission occurs in
unsanitary conditions, particularly during childhood
[12].
2.2 Oral-oral route
Despite the possibility that the human oral cavity
may serve as a source of H. pylori infection, It is not
certain whether the oral cavity can function as a
lasting reservoir for the microorganism, or if it is only
occasionally detected due to gastroesophageal reflux
or vomiting in the saliva or on the oral mucosa [13].
One might be first address if oral and gastric H. pylori
carriage are associated. A number of studies have
reported a relation between oral and gastric H. pylori
[14]. Saliva has been found to directly culture H.
pylori, and the DNA from both subgingival biofilm
and dental plaque has been amplified on numerous
occasions [15]. Oral-oral transmission involves
infants can be infected with H. pylori directly from
their mothers through their oral secretions.
Discordance of strain types between mother and
child is one of the negative arguments against oral-
oral transmission [16], Although this is debatable,
other reports indicate the presence of common
strains that infect couples [17].
2.3 Fecal-Oral Transmission
DNA of H .pylori has been frequently detected in
human feces, but there has been limited success in
cultivating H. pylori from feces because this organism
persists in a non-cultivable form (coccoid) [10]. Many
studies have established the relation between the
seroprevalence of hepatitis A virus and H. pylori,
suggesting similar (fecal-oral) mode of transmission
for both pathogens [18]. In addition, H. pylori has
been detected and cultured in samples of drinking
water. Consequently, the public water system has
been identified as a potential source of H. pylori
infection [19].
2.4 Contaminated water sources and food
Based on the analysis of the genome, it has been
determined that H. pylori is unlikely to multiply in
the environment. When kept refrigerated, H. pylori
can remain viable in water, milk, and a range of
foods for several days. This suggests that water or
food that is contaminated with H. pylori could pose a
risk of infection for humans [10]. In water, at 20–230
C, H. pylori could be cultured for up to 24 hours,
while at 160 C, it might to 3 days [20]. Among Lima
children living in low and high socioeconomic status
families, municipal water supply appears to be a
significant source of infection [21]. A mode of
transmission of H. pylori has also been described
through the consumption of raw vegetables [22], also
reported that the infection was more prevalent in
children who regularly consumed raw vegetables
and who swam in rivers and pools or used streams as
a source of drinking water [23]. Milk, meat, and
vegetables are among the food products analyzed.
Milk products have been the subject of the most
research, likely due to the fact that the infection is
typically acquired during childhood, when milk
consumption is prevalent [24].
2.5 Animal reservoirs
There is a possibility of zoonotic transmission of H.
pylori from non-primate reservoirs, but this
transmission has not been demonstrated [25].
In1990.strain of the bacteria was isolated from the
stomach of a pig, suggesting that pigs could serve as
a reservoir for this bacterium [26]. The hypothesis
was supported by other studies; by successfully
infecting pigs, specimens that subsequently
developed gastroenteritis were obtained [27].
A second study identified H .pylori in six cats using
16S rDNA sequencing [28]. However, no other
studies confirm these results. Further studies are
needed to determine whether cats are an important
route of transmission for H. pylori. According to the
available data, owners of cats are not at risk of
contracting H. pylori from their pets.

2.6 Interfamilial transmission
There is a higher prevalence of H. pylori infection
among children whose parents are infected than
among children whose parents are uninfected.
Molecular studies have demonstrated that family
members frequently share the same H. pylori
strain.[10]. It is likely that the infection transmitted
from one member of the family to another within the
family or contracted from an environmental source
within the family.
The spread of the infection appears to be facilitated
by close intrapersonal contact: childhood
overcrowding has been repeatedly identified as a
significant risk factor for the development of H. pylori
infection. Infection in both children and adults,
supporting the person-to-person transmission theory
[29]. In developing countries, with large families and
numerous siblings, sibling-sibling transmission may
be more significant [30], whereas in developed
countries, the average number of children per family
is low, mothers may play a crucial role [31]. The
majority of studies have not found fathers who are
positive for H. pylori to be significant risk factors for
their children's infection [32]. Child-to-adult
transmission appears to be improbable. A nine-year
follow-up study of 46 families in Japan revealed no
cases of transmission from an infected child to an
uninfected parent [33]. There was no higher
likelihood of H. pylori infection observed among
children who attended day care centers in Sweden,
compared to those who received care exclusively at
home [10].
III. RISK FACTORS FOR INFECTION
Exposure to the bacterium is a necessary condition
for the development of infection. It is dependent on
the characteristics of the infectious source and the
contact that results in exposure, but the infection and
persistence are also influenced by the host and the
bacterium. The successful establishment of an
infection in a new individual, the bacterium must
overcome numerous obstacles [34].
Exit from an infected individual,
Surviving outside the gastric niche,
New host introduction,
Gastric mucosa colonization, and;
Colonization maintenance.
Predominant person-to-person transmission is
hypothesized. This theory is based on the fact that
the infection tends to cluster within families [32] and
in institutionalized individuals in the absence of
consistent and verifiable environmental reservoirs
[35].
3.1 The family
Transmission of H. pylori primarily occurs within the
family context, with a child's likelihood of infection
being linked to the presence of infected family
members [32]. It is often suggested that family size
and residential crowding (persons per room or m2)
are risk factors for H .pylori infection and may be
considered indicators of the number of infected
members in a family [36]. Similarly, children living in
low-prevalence regions are more likely to become
infected if their families are connected to high-
prevalence areas, and these effects diminish with
each successive generation [37]. Infection in
adulthood can be predicted by the living conditions
during childhood in relation to acquiring H. pylori
from household members during childhood [38]. The
prevalence of mother-to-child transmission suggests
that having an infected mother is a more significant
risk factor for childhood infection than having an
infected father. The clustering of the infection on sib
ships has also been interpreted as evidence of
transmission among siblings. [32]. Although H. pylori
infection is usually contracted during early
childhood, certain epidemiological evidence suggests
that it could be transmitted within families during
adulthood as well. Having a spouse who is infected
has been identified as a risk factor for infection [39].
In addition, the risk of infection in adults has been
associated with having a greater number of children,
indicating that children may play a role as
transmission mediators within families [40].
3.2 Environmental and behavioral factors
Environmental and behavioral factors related to low
socioeconomic status have been investigated in
relation to H. pylori infection. Theoretically, the
observed clustering of H. pylori infection within
families may be due to a common environmental
source of the infection. Since the use of certain water
sources, like wells, has been correlated with the

infection, it has been suggested that contaminated
water may be the source [41].
However, other studies have not found an
association between the water source and infection
[23]. Furthermore, it has been suggested that H. pylori
have zoonotic potential, with reservoirs including
houseflies, cats, , and sheep, but these theories have
been contested [34]. Behavior factors may influence
H. pylori acquisition and persistence. Living in a
high-prevalence nation can facilitate infection, as
increasing bacterial exposure is possible due to
regular and close interaction with individuals who
are infected, as well as inadequate hygiene practices
[41]. Intimate contact has also been proposed as an
explanation for other observed risk factors, including
bedsharing and breastfeeding. It has also been
hypothesized that breastfeeding may provide
protection against early infection through passive
immunization. These results suggest that such
protection, if present, is of limited importance after
weaning [30]. Moreover, consumption of antibiotics
has been shown to negatively correlate with H. pylori
infection [34]. In a different study, a comparable
negative correlation was no longer observed once the
country of origin was taken into account, potentially
because low-prevalence countries have a higher rate
of antibiotic usage [38]. Several behavioral factors
have been identified as factors that influence the
likelihood of H. pylori infection in adults. Among the
examples are possible negative associations with
alcohol consumption [42], and possibly a positive
relationship with smoking, although data are
contradictory [38].
3.3 Host and bacterial factors
The ability of H. pylori strains to initiate and maintain
an infection in a specific host can be influenced by
various factors, including both the host and bacterial
characteristics, as well as their compatibility with one
another [43]. During childhood, transient infections
may occur when the bacteria are not optimally suited
for the new host and adaptation is not feasible or
quick enough, resulting in the infection being cleared
by the host [44]. Based on the fact that there is a
higher agreement of infection between monozygotic
twins (81%) compared to dizygotic twins (63%), it
has been proposed that a person's genetic makeup
plays a role in their susceptibility to H. pylori
infection. However, there are certain host factors that
may be linked to an increased susceptibility to
infection, though the particular genetic elements of
this predisposition remain unknown. It has been
suggested that the expression of blood group
antigens that mediate bacterial adhesion to the
gastric mucosa is crucial for susceptibility to H. pylori
infection [34].
The binding affinities of H. pylori strains have been
shown to be adapted according to the expression of
blood group antigens in various human populations,
according to some research [45]. Moreover,
individuals who release receptors into their bodily
fluids, which can act as detachable binding sites that
compete with tissue-bound receptors, have been
found to have a reduced risk of infection [46].
However, studies have raised questions about the
hypothesis that adhesion mediated by blood group
antigens plays a role in determining susceptibility to
infection [47]. The susceptibility to H. pylori infection
may also be influenced by the immune system. This
notion is supported by studies demonstrating that
alleles within the HLA-DQA1 human leukocyte
antigen locus are associated with infection. [48]. The
infection has also been correlated with a
polymorphism in the interleukin (IL)-1 receptor of
unknown functional significance [49].
Furthermore, low gastric acid secretion may promote
the spread of the bacterium, this may be particularly
important in young children and in cases of
infectious gastroenteritis [50]. Some studies have
found slightly higher in infection among males [38].
This tendency's causes are unknown, and other
studies have been unable to confirm this correlation
[44]. H. pylori has evolved a range of mechanisms for
survival in harsh gastric niches, which include the
ability to tolerate acid, to move, to adhere, to evade
immune system detection, and to adapt to the
environment. These traits play a role in the interplay
between the host and the bacteria and can affect the
acquisition and longevity of infection in animal
models. The first factors implicated in colonization
were acid tolerance and motility of bacteria [34].
These findings have been validated by global
mutagenesis techniques, which have also increased
the number of putative essential genes [51].
However, it is unclear how relevant these findings
are to human populations. In a Finnish population, it
has been shown that strains with the cag

pathogenicity island (PAI), a virulence factor,
disappear more rapidly than strains without the cag
PA [52]. The reduction in transmissibility or
persistence of cag PAI strains in this population
might explain this phenomenon. however, the
majority of infection in worldwide is cag PAI+ [53].
IV. EPIDEMIOLOGY OF H. PYLORI
INFECTION
4.1 Prevalence and geographical distribution
H. pylori is the most prevalent human infection
worldwide, colonizing over fifty percent of the
world's population with a wide variation in its
geographical distribution. Africa has the highest
prevalence of H. pylori at approximately 79.1%, while
Northern America and Oceania have the lowest at
24.4%. [3] (Figure 3). Rural areas have a higher
prevalence of the disease than urban areas reflects
differences in sanitation, socioeconomic status,
urbanization, and access to clean water [54].
Interestingly, the prevalence of H. pylori varies
between populations even in the same country.
Moreover, H. pylori prevalence varies between
different ethnic groups residing in the same country.
For instance, The prevalence of H. pylori infection
varies between non-white and non-Hispanic white
populations in the United States, with a range of
34.5% to 61.6% among non-whites and 18.4% to
26.6% among non-Hispanic whites[55]. Similarly,
Malaysian population comprise of Malay, Chinese
and Indians ethnic groups, the H. pylori prevalence in
Malay is (19.9%), Indians (50.7%) and Chinese (40%)
[56]. WHO has identified H. pylori as a Group I
carcinogen responsible for the development of gastric
adenocarcinoma. Infection with H. pylori is
responsible for nearly 89 % of gastric cancer cases
[57]. Previously, in China, complete eradication of H.
pylori infection has been shown to reduce gastric
cancer incidences from 25% to 16.67%. [58]. In
developed countries such as Canada, the United
States, and Northern Europe, the prevalence of H.
pylori is low and infection rates remain constant
compared to Africa, Latin America, India, and
Eastern Europe. This may be a result of enhanced
hygiene, sanitation, and the active elimination of
carrier state by antimicrobial therapies [59].
Furthermore, H. pylori shows high prevalence rates of
58 to 62% in India in patients with dyspeptic
symptoms [60].
Fig.2 Map represents the global prevalence of H. pylori. To
display smaller countries, certain regions magnified [3].
4.2 Incidence of H. pylori infection
Comparatively, the annual incidence of H. pylori
infection in industrialized countries is approximately
0.5%, compared to 4%–15% in developing countries
[61]. Living in an underdeveloped nation and
possessing a low economic status are well-
documented factors that increase the likelihood of
being at risk [62]. Retrospective longitudinal sero
surveys conducted primarily in industrialized
countries are the main source for incidence rates in
adults. Seroconversion (i.e., change in serostatus
from seronegative to seropositive) generally occurs at
a rate of less than 1% per year of follow-up,
indicating that adult infection appears to be a rare
occurrence. Seroreversion appears to occur at a
similar or higher frequency than seroconversion [10].
Few data exist regarding the prevalence of infection
between adults in developing countries. During 56
months of follow-up in Brazil, every year, a 1.1% rate
of seroconversion and a 0.2% rate of seroreversion
were observed [63]. In low-income countries, early
childhood incidence rates above 20% per year have
been reported [34].
V. CLINICAL MANIFESTATIONS OF H. PYLORI
INFECTION
Over 50% of the population of the world is infected
with H. pylori and causes histologic gastritis in all
patients; however, only 10 to 20 percent of infected
individuals develop ulcer disease and 1 to 2 percent

are likely to develop gastric cancer. Furthermore, the
severity and frequency of disease caused by H. pylori
are governed by various host and environmental
factors [64-66] (Figure 4).
Fig.3 Schematic graph illustrating the factors that are
responsible for gastric pathology and the subsequent
disease consequences [67].
The ability of H. pylori to maintain long-term
colonization is an important factor in the
development of diseases [34]. The symptoms of acute
H. pylori infection in adults usually include mild to
moderate dyspepsia and occasional vomiting, which
can begin a few days after infection, reach their
maximum intensity during the second week, and
then gradually decrease. The clinical course of
chronic H. pylori infection can vary greatly and is
influenced by factors such as the microbe itself, the
host, and the environment. In almost all infected
individuals, H. pylori causes chronic gastric mucosal
inflammation [10]. Gastritis develops rapidly and
persists following H. pylori infection. Along with its
persistence, chronic gastritis may gradually
transform into atrophic gastritis after several years of
infection. To H. pylori-positive adults, atrophic
gastritis is known to occur at a rate of 1-3% per year
[68]. Minorities of individuals infected with H .pylori
develop severe gastroduodenal disease, such as
Duodenal Ulcers (DU), gastric ulcers, and rarely
gastric adenocarcinomas or mucosa-associated
lymphomas (MALTs) [10]. To individuals who are
not infected with H. pylori, those who are infected
have a 4-6 times higher chance of developing peptic
ulcer disease. They also have a roughly 6 times
higher chance of developing non-cardia gastric
adenocarcinoma and gastric MALT lymphoma. In
people who are infected with H. pylori, the chances of
developing peptic ulcers during their lifetime are
roughly 6-20%. In western societies, the likelihood of
developing gastric cancer during one's lifetime is
around 1%-2%, while in Japan, it is 11%-12% or even
higher. A hypothesis suggests that being infected
with H. pylori during childhood could raise the
likelihood of developing stomach cancer at a later
stage of life. The study of Mongolian gerbils
indicated that early infection with H. pylori was
associated with a significant increase in susceptibility
to gastric chemical carcinogenesis compared to late
infection [10].
5.1 Anemia
Among the most important micronutrients for
animals and microorganisms, iron serves as a
cofactor for enzymes involved in oxygen and electron
transport, as well as DNA synthesis. During
infection, an iron retention mechanism reduces the
redistribution of iron from the cell cytosol to the cell
surface, as well as circulating transferrin and the
growth of invading pathogens [69]. Kato et al.
demonstrate bacterial isolates from iron deficiency
anemia patients, the SabA gene was highly
expressed, suggesting that this virulence factor may
contribute to anemia development [70]. Additionally,
H. pylori cause hypochlorhydria and atrophic
gastritis, as well as peptic ulcer disease and an
increased risk of gastric cancers. In this instance,
diminished iron absorption can result in iron
deficiency anemia [71]. In patients with atrophic
corpus gastroenteritis, intrinsic factor secretion is
impaired, hypochlorhydria may occur, and iron and
B12 may not be absorbed in the intestines as a result
[72].
5.1 Gastric cancer
Despite a decline in incidence in high-income
countries, gastric cancer is the second leading cause
of cancer-related death globally [73]. In 1994, the
World Health Organization categorized H. pylori as a
class 1 carcinogen due to its potential to cause cancer
in humans [34] . Subsequent studies have confirmed
the link between H. pylori infection and gastric
cancer, attributing approximately 70% of 35 non-
cardia adenocarcinomas to H. pylori infection [74].
However, a Few percentages of infected people
develop stomach cancer [75]. Individuals who have
low levels of gastric acid secretion and corpus-
predominant gastritis, a condition that results in

atrophic gastritis, loss of parietal cells, and
subsequent hypochlorhydria, are more likely to
develop gastric cancer [76]. There are several
postulated carcinogenic mechanisms, including
inflammation-induced epithelial turnover. In
addition, hypertrophy and hypochlorhydria of the
stomach can lead to impaired antioxidant absorption,
infection with carcinogenic microbes, and the
accumulation of carcinogenic compounds in the body
[75]. Infection with H. pylori upregulates the
proinflammatory cytokine IL-1, which is also a
potent acid secretion inhibitor. Hypochlorhydria and
cancer have been linked to polymorphisms believed
to increase IL-1 activity, evidence supporting the role
of gastric acidity in the development of cancer [77].
5.2 Gastritis
5.2.1 Acute gastritis
Significant inflammation of the distal and proximal
stomach mucosa, momentary nonspecific dyspeptic
symptoms, nausea, vomiting, and stomach fullness
characterize an acute infection with H. pylori. On the
basis of reports from patients who accidentally or
deliberately consumed H. pylori or acquired
infections through contaminated food or water, these
symptoms were identified. [78, 79].
5.2.2 Chronic gastritis
Persistent infection of H. pylori in the human Gut
correlates with the distribution of gastritis and the
level of acid secretion (Figure 4). The acid secretion
level has antagonistic effects on H. pylori. In
particular, H. pylori infects the gastric antrum, where
a low acid-secretory layer of parietal cells exists. This
infection is identified by a predominant antrum-
based gastric inflammation. In patients with deficient
acid secretion, bacteria are uniformly distributed
within the corpus and antrum, as well as in close
proximity to the gastric mucosa [80]. Persistent
inflammation of the corpus mucosa promotes
hypochlorhydria, in conjunction with local
inflammatory factor responses such as interleukin-
1(IL-1), which then produces suppressive responses
on parietal cell function, as evidenced by reports
indicating that eradication therapy increases acid
secretion in patients [81] Furthermore, patients with a
proinflammatory genotype are more likely to
develop chronic gastritis, making them prone to
intestinal metaplasia, atrophic gastritis, and
ultimately gastric cancers [77].
5.3 Peptic ulcer disease
The revelation that H. pylori is the cause of peptic
ulcer disease has resulted in a change in the
treatment approach for patients with ulcers [82].
Infected individuals face a lifetime risk of peptic
ulcer ranging from 3% in the United States to 25% in
Japan [83]. H. pylori is believed to be the cause of 95%
of DUs and 70% of gastric ulcers [84]. H. pylori-
induced gastritis, diminished somatostatin levels,
and increased gastrin and acid secretion are
associated with duodenal ulcers [83]. As a result of
gastric metaplasia in the duodenum, additional
bacterial colonization may occur, resulting in
duodenitis and epithelial damage. Gastric ulcers are
linked to corpus gastritis, which is believed to harm
the epithelial lining [75].
5.4 MALT Lymphoma
Among digestive system marginal zone lymphomas,
gastric MALT lymphoma (GML) is the most
prevalent. In accordance with epidemiological,
pathological, clinical, and bacteriological evidence,
the association between H. pylori and this lymphoma
is now well established [85]. H. pylori eradication
therapy is now regarded as the primary treatment for
low-grade GML [86, 87]. After eradicating the
bacteria with antibiotics, additional research has
indeed revealed a regression of GML lesions. 60% to
90% of patients can experience lymphoma regression
after H. pylori eradication [88]. The neoplastic cells of
GML are already sensitized to the antigens of H.
pylori if a reinfection occurs [89]. H. pylori infection
was the first bacterial infection to be categorized as a
type 1 carcinogen, the highest level, due to its link
with gastric adenocarcinoma. It has been extensively
studied since its discovery in order to identify
virulence factors or genetic markers. but H. pylori
strains associated with GML have received little
attention. [88].
5.5 Non-ulcer dyspepsia
Non-ulcer dyspepsia (NUD) or functional dyspepsia
refers to pain or discomfort in the upper
gastrointestinal tract without any observable
structural irregularities. The relationship between H.
pylori infection and non-ulcer dyspepsia has been
intensively studied. 30–60% of patients with

dyspepsia will be infected with H. pylori. However,
the rate of symptoms in the non-infected control
group is also comparable [90]. Therefore, there has
been considerable debate regarding the anticipated
outcome of H. pylori eradication in dyspepsia
patients. In a meta-analysis of non-ulcer dyspepsia
(NUD), according to a study, eradicating H. pylori
decreased the chance of experiencing dyspeptic
symptoms by 8% when compared to a placebo. The
study also found that eradicating H. pylori in 18
patients would be necessary to alleviate dyspeptic
symptoms in one patient [91]. Nonetheless, in
patients with functional dyspepsia, Maastricht IV
guidelines now recommend eradication, particularly
in regions with a high prevalence [87].
5.6 Insulin Resistance
The immune system is activated by H. pylori
infection, resulting in the production of
inflammatory cytokines such as tumor necrosis factor
(TNF-) as well as leptin and adipokines, which
mount an immune response against the
inflammation. Studies have shown that low levels of
leptin can cause insulin resistance (IR) due to
elevated levels of TNF- and IL-6 [92]. Inflammatory
cytokines can have a substantial impact on insulin
function by phosphorylating serine residues on
insulin receptor substrates, which interferes with
their interaction with insulin receptors. Thus,
diabetes can result from a breakdown in blood
glucose regulation [92].
VI. PATHOGENESIS OF H. PYLORI
INFECTION
In the past, it was believed that the gastric
environment was sterile due to its high acidity before
Warren and Marshall discovered that H .pylori [93].
To achieve in challenging conditions, the bacterium
employs several mechanisms to enhance its mobility,
robust adhesion to epithelial cells, and use enzymes
to establish an optimal microenvironment to sustain
infection [94].
Figure 4 Aspects of H. pylori infection. CagA:
Cytotoxin associated antigen A; VacA: Vacuolating
cytotoxin; DupA: Duodenal ulcer promoting gene A
protein; OipA: Outer inflammatory protein; GGT:
Gamma-glutamyl transpeptidase; TLRs: Toll-like
receptors [95].
In addition, the pathogenicity of this infection (GGT)
can be attributed to various virulence factors, such as
cytotoxin associated antigen A (CagA), vacuolating
cytotoxin (VacA), duodenal ulcer-promoting gene A
protein (DUPA protein), outer inflammatory protein
(OipA), and gamma-glutamyl transpeptidase [96].
Moreover, probably through a Th1-polarized
response against the pathogen, the host immune
system plays a crucial role in the infection's
progression (Figure 5) [95].
While most individuals with H. pylori infection do
not exhibit any symptoms, such infections raise the
likelihood of developing diseases like peptic ulcers
and gastric adenocarcinomas [97]. In this way, proper
clinical management precedes an accurate diagnosis
and is followed by effective treatment in order to
improve a patient's clinical outcome [98]. H .pylori
has been detected using a variety of invasive and
noninvasive diagnostic methods, and bacterial
resistance is a significant obstacle to eradicating
infection [99]. In this sense, in an effort to improve
treatment outcomes, new therapy regimens and
probiotic administration have been tried [100].
Moreover, several researchers have focused their
efforts on the development of vaccines against H.
pylori infection.
6.1 Colonization
There are different factors that are critical during H.
pylori colonization in the mucosa tissue of the
stomach (Figure 6)

6.1.1 Production of Urease
H. pylori is not an organism that prefers an acidic
environment, and the production of urease enzyme is
one of its signature strategies to neutralize the acidic
environment of the gastric lumen. For successful
colonization of the gastric mucosa, H. pylori requires
the presence of urease and its activation [78]. It has
been shown in the presence of urea, H. pylori can
tolerate a pH as low as 2.5, whereas in its absence, it
can tolerate a pH range between 8.0 and 4.0 [101]. It
contains a cluster of seven genes that control and
regulate the urease enzyme biosynthesis process
[102], and it has a complex structure composed of
twelve subunits of UreA and UreB.. [103].
H. pylori urease is a hydrolase enzyme that
hydrolyses urea to CO2 and NH3. In contrast to
ureases produced by other bacterial species, H. pylori
urease has a Km value of 0.8 Mmol/L, which enables
it to act on even minute amounts of urea (as low as 5
Mmol/L). Utilization of urea and production of NH3
generate acid-neutralizing capacity, which enables H.
pylori to maintain the proper pH in its periplasm and
microenvironment. Thus, regulation of the proton
motive force [104] . This strategy of H. pylori to
maintain a neutral pH intracellularly while the pH of
the surrounding environment remains low is a
peculiar characteristic of H. pylori. This is necessary
for the survival of H. pylori in acidic gastric juice.
Moreover, the generation of NH3 by the urease
enzyme in non-acidic environments may raise the
native pH above pH 7.0, which may explain why H.
pylori does not colonize niches other than the Gut.
Furthermore, it has been demonstrated H. pylori is
intolerant to alkaline conditions [105].
6.1.2 Response to the harsh environment in the
stomach
Jones and Zamble conducted an experiment in which
they simulated the acidic conditions of the human
stomach by exposing H. pylori to an external pH of
2.0 and observed the impact of a decrease in cytosolic
pH on the bacteria. As a result, nickel-responsive
transcription factors (HpNikR) activated
transcription of the ureA gene, demonstrating how
these bacteria adapt to harsh acidic conditions [106].
The data obtained allows for the correlation between
the acid adaptation of H. pylori and nickel
homeostasis to be made. The reduction in mucosal
bicarbonate secretion caused by H. pylori may protect
the gastric barrier from acid-induced damage to the
mucosa, plays a role in the development of duodenal
ulcers [107]. Through the transforming growth factor
beta (TGF)-mediated p38 mitogen-activated protein
kinase (MAPK) signaling pathway, H. pylori
downregulate the expression of two transporters of
cellular bicarbonate in the duodenal epithelium: (a)
the cystic fibrosis transmembrane conductance
regulator (CFTR) and (b) the solute linked carrier 26
gene family A6 (ALC26A6) [107]. In a comparative
transcriptomic analysis, Hathroubi et al discovered
that 8% of the genes examined exhibited differences
between H. pylori biofilm cells and planktonic cells.
The biofilm-downregulated genes were involved in
metabolism and translation, while Biofilm-
upregulated genes encode proteins involved in stress
response and flagellum formation [108]. Potentially
promoting the persistence of H. pylori in the stomach,
this biofilm formation.
Fig.5 Colonization strategies and establishment of gastric
mucosal infection by H. pylori [109].
6.2 Virulence factors
6.2.1 Outer membrane vesicles
virulence factors of H. pylori can be present in a
soluble form, attached to the cell surface, or delivered
into host cells through the host's type IV secretion
system (T4SS). Recently, there is a proposed
significant function of outer membrane vesicles
(OMVs) produced by H. pylori in the dissemination of
bacterial antigens. OMVs contain a variety of

biologically active compounds produced by H. pylori,
are capable of being internalized into host cells, and
as a consequence, in addition to influencing signaling
pathways, they can promote the apoptosis of gastric
epithelial cells as well as immune cells. This can have
the effect of either enhancing or suppressing immune
responses, resulting in the eventual onset of a disease
[110]. Through the utilization of protonography and
mass spectrometry, Ronci et al. confirmed the
existence of -carbonic anhydrase (CA) in OMVs
produced by H. pylori strains with planktonic and
biofilm characteristics. This work suggested that CA,
along with urease, may have a crucial role in
reducing the acidity of gastric juice caused by H
pylori [111]. The protein composition,
immunogenicity, and method of entry into host cells
of OMVs are influenced by their size. OMVs with
sizes ranging from 20-100 nm can enter host cells via
caveolin-dependent endocytosis, while OMVs with
sizes of 90-150 nm can enter through
macropinocytosis and endocytosis. These results
indicate the importance of OMVs in the pathogenesis
of H pylori and the possible use of OMVs in the
development of vaccines [112].
6.2.2 CagA
It is a bacterial protein called CagA, which induces
changes in morphology, alters their polarity, and
causes hummingbird-like phenotypes in epithelial
cells. This virulence factor can also trigger changes in
the cytoskeleton associated with gastric
adenocarcinoma development [113]. In addition to
the CagA gene, the cag pathogenicity island also
contains the code for a type IV secretion system
(T4SS) [114]. CagA and peptidoglycans are
translocated into host cells by this bacterial structure
[115]. In the host cell, CagA is tyrosine
phosphorylated at the Glu-Pro-Ile-Tyr-Ala (EPIYA)
motif, which consists of different EPIYA segments
(EPIYA-A, EPIYA-B, EPIYA-C, and EPIYA-D) in the
variable C-terminal region of the protein [116]. While
EPIYA-A and EPIYA-B segments are found in most
cagA-positive H. pylori strains, the EPIYA-C and
EPIYA-D segments are linked to Western and
Eastern strains, respectively [117] . Strains of H. pylori
with EPIYA-D or at least two EPIYA-C segments in
their cagA gene are related with an increased risk of
cancer [118]. Moreover, research on a Brazilian
population has revealed that relatives of individuals
with gastric cancer are more likely to be infected with
H. pylori strains containing two or more EPIYA-C
segments [119]. CagA is activated by
phosphorylation, resulting in the activation of SHP-2
(SH2-containing protein-tyrosine phosphatase),
which promotes the changes described above in the
cell [120].
6.2.3 Non-CagA virulence factors
Several virulence factors have been associated with
an increased ability of H. pylori to impair gastric
homeostasis. Among them, VacA gene is present in
almost all strains of bacteria, including H. Pylori, and
is a determinant of the pathogenicity of this
bacterium. VacA induces the creation of acidic
vacuoles within the cytoplasm of gastric epithelial
cells. This results in the destabilization of
mitochondria, cytoplasmic membranes, and
endomembranous structures, leading to the collapse
of cells [121]. Additionally, this protein may also be
responsible for activating and suppressing the
immune response, resulting in immunity tolerance
and persistent infection with H. pylori through
interactions with T-cells and antigen-presenting cells
[122]. This virulence factor is responsible for a series
of alterations that contribute to increased gastritis, as
well as the development of ulcers and cancer [123].
Another bacterial protein known as DupA appears to
give the bacterium with a higher level of acid
tolerance. It also has the potential to stimulate an
increase in the synthesis of IL-8 in the mucosa of the
antral gastric region. Elevated levels of IL-8 result in
mucosal inflammation and the influx of
polymorphonuclear leukocytes, potentially causing
gastritis and duodenal ulcers [124]. Notably, a link
between dupA-positive H. pylori strains and
duodenal ulcers has been established in Asian
countries, but not in Western countries [125].
Furthermore, the research has shown that the
presence of functional dupA in H. pylori strains
should be considered a protective factor against the
development of gastric cancer. [126]. The gene
products of dupA show similarity to the VirB4
ATPase, which plays a role in the construction of the
secretion machinery. Nonetheless, the precise
connection between dupA and H. pylori T4SS remains
to be elucidated [124]. OipA, an outer membrane
protein contributes to adhesion and inflammation by
stimulating the production of IL-8. The increased

number of investigations on this H. pylori virulence
factor stemmed from the identification of the link
between OipA and the increased incidence of peptic
ulcers and gastric cancer [127]. Since the expression
of the oipA gene is regulated by a repair process
called "slipped strand mispairing," which depends on
the quantity of CT dinucleotide repeats in the oipA 5'
region, the functional status of OipA has been
described as an important factor in the outcome of
the infection. This is because the expression of the
oipA gene is regulated by a repair process called
"slipped strand mispairing.". This process determines
whether oipA in a specific bacterial strain is
nonfunctional or functional, and the latter condition
is associated with higher stomach pathogenicity
[128]. Furthermore, it is plausible that OipA is linked
to modifications in -catenin signaling, reduction in
cell-cell junctions, and enhanced cell proliferation
[129]. H. pylori produces GGT, which is an enzyme
with N-terminal nucleophile hydrolase activity. GGT
can facilitate the conversion of glutamine into
glutamate and ammonia, and also catalyzes the
hydrolysis of glutathione into glutamate and
cysteinylglycine [96]. As a result of its activity,
reactive oxygen species (ROS) are produced, which,
like ammonia, cause cell cycle arrest, apoptosis, and
necrosis [130]. In addition, according to scientific
investigations, this enzyme inhibit T cell proliferation
and dendritic cell differentiation. [131]. Patients with
peptic ulcers have been found to have a greater GGT
activity than those with other gastroduodenal
disorders [132].
6.3 Immunologic aspects
H. pylori infection induces complex immune
responses, including innate and adaptive responses
[133]. Considering the initial exposure to the
pathogen, various H. pylori antigens such as
lipoteichoic acid, lipoproteins, lipopolysaccharide,
HSP-60, NapA, DNA, and RNA bind to gastric cell
receptors, including toll-like receptor (TLR) 1, TLR2,
TLR4, TLR5, TLR6, and TLR10 located on epithelial
cell membranes, and TLR9, found in intracellular
vesicles [134]. This connection stimulates, among
other signaling pathways, the activation of NF-B and
c-jun N-terminal kinase, followed by the release of
proinflammatory cytokines [135]. The injection of
CagA through T4SS does not only activate receptors
by pathogen-associated molecular patterns, but also
induces the production of cytokines, a process that is
dependent on the NF-B pathway [136]. Subsequently
Neutrophils and mononuclear cells infiltrate the
stomach mucosa, leading in the generation of nitric
oxide and reactive oxygen species [137]. In addition,
adaptive immunity's components, namely CD4+ and
CD8+ T cells, are also brought in. There may be a
preferential activation of CD4+ cells over CD8+ cells,
and a particular response is focused toward the
bacterium [138]. Studies suggest that in H. pylori-
positive patients, there is a Th1-polarized response in
terms of cytokine profiles, characterized by
decreased levels of the Th2 cytokine IL-4 and
increased levels of gamma interferon, tumor necrosis
factor, IL-1, IL-6, IL-7, IL-8, IL-10, and IL-18 [139].
Apart from IL-10, which appears to have a function
in controlling the inflammatory response, the other
cytokines that are elevated may contribute to the
proinflammatory effects that occur during infection
with H. pylori. Additionally, it is shown that an
increase in IL-17 is associated with H. pylori infection,
especially in adults [140]. The presence of H. pylori-
specific serum IgM antibodies in patient serum can
be detected 4 weeks after infection when it comes to
the production of immunoglobulins [141]. During
chronic infection, a variety of bacterial antigens are
targeted by IgA and IgG immunoglobulins in the
bloodstream [95] . The majority of H. pylori-positive
individuals do not experience symptoms of this
inflammation, however, it increases their risk of
developing duodenal and gastric ulcers as well as
stomach cancer in the long run [83].
VII. DIAGNOSTIC TESTS FOR DETECTION OF
H. PYLORI INFECTION
Infection with H. pylori is detectable by both invasive
and non-invasive diagnostics. The technique chosen
depends on the patient's requirements. Several
factors need to be taken into account, such as the
existence of warning signs, the application of non-
steroidal anti-inflammatory drugs (NSAIDs), and
being elderly (either over 45-50 years old or over 60
years old)[142], history of premalignant symptoms or
surveillance for a past malignancy mandates an
upper endoscopic assessment. Doctors can utilize
esophagogastric-duodenoscopy to visually inspect
the mucosa, take biopsy samples for histological
analysis, urease testing, bacterial culture, and,

potentially, molecular testing. In the absence of an
endoscopic suggestion, non-invasive diagnostics,
such as urea breath testing or stool antigen assay, can
be used to confirm the presence of an active infection.
In certain circumstances, a physician may employ
serology as a diagnostic tool to assist in the
identification of bacterial infections [143]. However,
the diagnostic approach can't be independent of the
availability of the test in the patient's area, how much
it will cost, or what the patient wants. Wang et al.
briefly review the current options and advances of
diagnostic tests and their associated clinical
applications, as well as the selection of diagnostic
tests for various clinical situations (Table 3) [144].
Table 2 Diagnostic options for H. pylori infection in various clinical settings and specific diagnostic test applications [144].*
Although serology is unaffected by local changes in the stomach, it should be evaluated with caution prior to further
management.
Methods
Gastroduodenal
bleeding
Post
gastrectomy
Post
eradication
therapy
Special applications
Rapid urease
test
√
Histology √
Culture Antibiotic sensitivity
Polymerase
chain reaction √ √
Antibiotic sensitivity, Virulence
factors, Environmental/oral sample
Urea breath test √ √
Stool antigen
test
√
Serology* √ √ √ Virulence factors
7.1 Non-Invasive Tests:
Non-invasive test can detect the active infection or
provide with information a previous infection.
7.1.1 Urea breath test
The diagnosis of H. pylori can be done non-invasively
through UBT. Based on a basic premise, to perform
UBT, patients ingest urea that has been tagged with 13
C or 14 C. H. pylori produces the enzyme urease,
which breaks down the urea into ammonia and 13 C-
labeled carbon dioxides. This 13 C carbon dioxide
then enters the bloodstream, travels to the lungs, and
is eliminated through exhalation [145]. Typically, it is
administered in combination with citrus juices, such
as lemon or orange, to postpone the process of gastric
emptying and enhance the duration of contact with
the mucosal lining. After drinking the test solution,
the exhaled air is collected in a sealed plastic bag 30
minutes later. Air sample analysis can be performed
using either a mass spectrometer or infrared
spectroscopy. The latter is considered a more
straightforward and cost-efficient alternative to mass
spectrometry. Infrared spectroscopy is the method of
choice for determining the 13C/12C isotope ratio. The
increase in labeled CO2 is expressed as a delta value
compared to the baseline (DOB). The DOB
measurement is directly associated with the bacterial
load of H. pylori, meaning a higher DOB value
indicates a higher bacterial load. Thus, based on the
presence of 13C in exhaled air, we can detect with
great accuracy whether a patient is infected with H.
pylori, and based on the value of the 13C/12C ratio, we
can evaluate the severity of infection. It is similar to
the 14C urea breath test, except that 13C is not a
radioactive isotope. The typical urea breath test
contains 75 mg of 13C. 13C-UBT has a sensitivity of
96–100% and a specificity of 93–100% [145, 146]. The
BREATH QUALITY UBT could be decreased to 15
minutes, according to one study, without
compromising the method's accuracy [147]. The
meta-analysis conducted showed that the test is
highly accurate in children of any age. For children
older than 6 years old, sensitivity was 96.6% and

specificity was 97.7%, respectively; for children
younger than 6 years old, sensitivity was 95% and
specificity was 93.5%. [148]. Recently, a new UBT
approach employing a tablet formulation of 13C-urea
has been proposed. This technique provides for
highly accurate breath sampling within 10 minutes
after ingesting a tablet. Using tablets has a benefit of
preventing the interaction between the urease-
producing bacteria in the oropharynx and the
formulation, which could cause inaccurate positive
results. This is one of the benefits of taking the
medication in this form [149, 150]. Although rare,
false-positive outcomes can occur in patients who
have undergone gastric resection or have
experienced a significant reduction in stomach
output, especially when endoscopy with biopsy has
been performed shortly before the test. The primary
cause of false-positive results is typically the
breakdown of urea by bacteria that possess urease in
the oral cavity or the stomach [151]. This is especially
common when achlorhydria or hypochlorhydria is
present. A few instances of false-negative outcomes
could be due to errors in the method of collecting and
storing exhaled air samples, or from physical
exertion before or during the test. As with most other
tests, a reliable UBT result may be obtained after
discontinuing PPIs for a period of two weeks, and no
earlier than four weeks after stopping antibiotics and
bismuth [145].
7.1.2 Stool Antigen Test
Tests that are easy to perform and designed to
identify H. pylori antigen in stool samples have been
shown to have a high level of accuracy in extensive
comparisons with identical tests [152]. In general,
stool monoclonal antibody tests are more precise
than stool polyclonal antibody tests, with a combined
sensitivity of 93% and specificity of 96% [153]. They
also demonstrated a high level of diagnostic accuracy
in pediatric settings, particularly when tests were
based on ELISA rather than immunochromatography
[154]. In a Houston Consensus Conference, a group
of 11 experts recommended using stool antigen
testing (or UBT) for the initial diagnosis of H. pylori
infection and post-treatment (when endoscopy is not
required) [142]. The UBT and the stool antigen test
both have the advantage of being able to evaluate the
entirety of the stomach's contents, in contrast to the
histology and RUT, which can only evaluate a small
portion of a biopsy specimen. Both stool antigen tests
and UBT are the most reliable methods of diagnosing
an active infection with H pylori, both theoretically
and practically. Nevertheless, any drug that lowers
H. pylori numbers below the threshold of detection
may result in false negative results, especially when
used in conjunction with a proton pump inhibitor,
bismuth-containing compound, or antibiotic [155].
7.1.3 Serology
A systemic immune response is brought on by H.
pylori infection of the stomach. Antibodies to H. pylori
can be detected in the blood anywhere from three to
four weeks after infection. The presence of these
antibodies can be ascertained using any one of the
following three techniques: an enzyme-linked
immunosorbent assay (ELISA), a latex agglutination
test, or a Western blotting analysis. Among these, the
ELISA test is the one that is used most frequently
[156] . Detection of IgG, IgA, and IgM antibodies in
the bloodstream is the basis of this technique. Since H
.pylori is a chronic infection, only a validated IgG test
can be used to detect it [157]. There are a number of
serologic tests available for the diagnosis of H. pylori;
they can be performed non-invasively, and quickly,
no special equipment is required, and can be used to
screen large populations for the presence of the
infection. However, Serology may be positive as a
result of a current infection at the time of the test, a
past infection, or cross-reacting non-specific
antibodies [158]. The production of immunoglobulins
(antibodies) against antigens is triggered by active
infection, previously acquired infection, or non-
specific cross-reacting antibodies [156]. Serological
tests are therefore able to be used for both the initial
diagnosis and confirmation of H. pylori infection.
Serological tests should not be used for therapeutic
follow-up after successful eradication because the
level of quantitative antibodies after successful
eradication, the population does not decline
significantly for a long time. Moreover, false-positive
serologic results are common in populations with a
low prevalence (40%) of H .pylori infection, since the
positive predictive value of serology is dependent on
the prevalence of H .pylori infection in the population
[159]. Serology is not recommended in such
populations, and if a serological test of H. pylori is
positive, further confirmation is necessary, such as a
biopsy culture, urea breath test, or stool antigen test.

Recent The use of proton-pump inhibitors,
antibiotics, bismuth preparations, gastrointestinal
hemorrhaging, or atrophy of the gastric mucosa does
not affect the serological results [157]. Serological
tests vary in their specificity and sensitivity. The
test's sensitivity and specificity were 85% and 79%,
respectively, according to a meta-analysis. According
to another study, the range of sensitivity was 76% to
84% and the range of specificity was 79% to 90%
[159]. Several investigations have shown that
elevated levels of anti-H. Pylori IgG antibodies are
linked to the severity of histological gastritis, the
density of bacteria in the mucosal lining, and the
presence of blood biomarkers for stomach function,
such as PGI, PGII, PGI/II ratio, and gastrin-17.
However, there have been other studies with
contradictory findings, making the results
inconclusive [160].
7.2 Invasive Tests:
7.2.1 Histology
By analyzing biopsy samples of stomach mucosa, it is
possible to detect H. pylori with a sensitivity of 95%
and a specificity of 98%. In addition, it makes it
possible to visualize the morphology of the stomach
at any time. To achieve a precise diagnosis, two
antral biopsies must be performed, one from the
gastric angulus and two from the corpus [161]. For
example, when biopsy samples were not obtained
from the angulus in 213 patients, 8% and 3% of cases
of atrophic gastritis and intestinal metaplasia were
missed, respectively [162]. There is some concern that
the widespread use of proton pump inhibitors (PPIs)
may lead to the development of an atypical gastritis
or bacterial density changes at several sites in the
body as a result of the use of these medications [163].
H. pylori infections can be accurately diagnosed
histologically by utilizing unique staining techniques,
immune stains, or digital pathology [164, 165].
However, according to a recent study, standard
hematoxylin-eosin staining was able to detect 94% of
H pylori, while special staining did not show the
same level of detection. [166].
7.2.2 Rapid Urease test
Upper endoscopy enables the collection of biopsy
specimens for urease testing. The approach takes
advantage of the organism's pre-formed urease; in
solutions containing urea, the enzyme releases
ammonia, resulting in an increase in pH and a color
change in the medium. The rapid urease test (RUT) is
a quick, simple, cost-effective, and very specific
method of diagnosing H. pylori infection. However,
in order to perform RUT, a high density of bacteria is
necessary. For instance, in the normal commercial
kits at least 104 bacteria must be present in the
stomach specimen [167]. It is possible to obtain false
negatives if you have recently taken antibiotics,
bismuth-containing compounds, or PPIs, especially
omeprazole and lansoprazole, or if your child is
younger than five years of age [168]. It has been
demonstrated that obtaining biopsies from the
corpus, as opposed to the antrum, or mixing antral
and corpus samples, increases RUT sensitivity [169,
170]. In contrast, Dechant et al. found that the rapid
urease test (RUT) is more effective than histology in
detecting H. pylori infection in patients who have
undergone treatment with PPIs or antibiotics [171].
7.2.3 Culture
As well as performing histological examinations and
RUTs, upper endoscopy can be employed to collect
gastric specimens in order to conduct bacterial
culture, susceptibility testing, and, ultimately,
organism genotyping. Although culture has a high
specificity, low sensitivity, because H. pylori are
difficult to grow, and requires the expertise of a
laboratory. Using a preheated 35Co blood agar and
transporting the material to the laboratory within 30
minutes of collection can improve sensitivity (BD
Diagnostics, Sparks, MD, USA) and a helicobacter
selective agar, containing polymyxin (Hy-
Laboratories, Rehovot, Israel) and the antibiotics
colistin. An alternative strategy to consider is to
culture the specimens under microaerophilic
conditions (using CampyGenTM, Oxoid, Hampshire,
UK) at 35°C for an extended period of 14 days, or to
modify the atmosphere by adding hydrogen, or by
treating the specimens with trypsin [172, 173].
7.2.4 Endoscopy
The development of high-resolution endoscopic
technology has made it possible to increase
diagnostic accuracy in the process of identifying
H. pylori infection and the lesions that are associated
with it. Advanced imaging methods with the highest
resolution include high-resolution microendoscopy,
optical coherence tomography, endocytoscopy, and

confocal laser endoscopy [174, 175]. At present, none
of these techniques allow for "optical biopsies" to be
widely available or specific enough to allow for a
real-time diagnosis of H. pylori infection. A study
involving 300 patients in Japan showed that the
conventional narrow-band imaging (NBI) technique
is strongly associated with the histopathologic
severity of H. pylori gastritis. The NBI mucosal
patterns showed five different degrees of H. pylori
gastritis (gastric atrophy, inflammatory infiltration,
and H. pylori density) [176] . Kawamura et al [177]
indicated endoscopic magnifying technique using
NBI demonstrated micromorphological differences
that correlated with histological findings among
individuals with distinct H.pylori-related diseases.
Confocal laser endomicroscopy is a functional
imaging method that can be used to identify
abnormalities in the mucosal barrier in patients with
H. pylori infection and IM [178]. Moreover, a new
endoscopic imaging technique called endocytoscopy,
in vivo histology and guided biopsies can be
obtained accurately and safely using this approach.
Endocytoscopy permits microscopic imaging at a
1,400-fold magnification, it allows for cellular
examination of mucosal structures and detection of H
.pylori in vivo [179].The current development of
functional and molecular-targeted imaging
technologies may be useful in diagnosing H. pylori
infections in real-time [180].
7.3 Molecular test
Molecular methods, such as polymerase chain
reaction (PCR), have increasingly been used to detect
and type H. pylori and related species, as well as
determine how susceptible these bacteria are to
antibiotics in recent years. Kalach et al [181], as a
result of the study, they concluded that quantitative
real-time PCR (qPCR) in detecting H. pylori infections
in gastric biopsies of French children, it is more
precise than routine culture, histology, or RUT alone.
It permits the detection of low bacterial loads. It has
been demonstrated that quantitative PCRs and
nested PCR techniques can detect H. pylori in
specimens such as inflammatory tooth pulp, saliva,
and dental plaque in the oral cavity [182, 183].
Comparatively to conventional methods, a novel
method for detecting 16S rRNA and ureC genes of H
.pylori using the GenomeLabTM Genetic Analysis
System (Beckman Coulter) has demonstrated high
performance [184]. Paraffin and formaldehyde used
for tissue preservation may reduce the efficiency of
subsequent molecular amplification of microbial
DNA. Rabelo-Goncalves et al [185] A study
compared the efficacy of five different commercial
DNA extraction methods and the phenol-chloroform
method for detecting H. pylori using PCR
amplification of the 16S rRNA gene in liver tissue
that had been formalin-fixed and paraffin-embedded.
Although samples extracted with phenol–chloroform
included the highest proportion of positive cases
(70%), there was no statistically significant difference
between the techniques. Infections caused by H.
pylori are being treated with omics-based methods.
Kim et al [186] through pyrosequencing 16S rDNA
amplicons of gastric biopsy specimens, H. pylori was
detected in all samples suspected to be positive for H.
pylori, as well as, shockingly, in sixty percent of the
samples that were thought to be negative for H.
pylori. In one work, SOLiD sequencing was done on
two H. suis genomes in order to generate appropriate
PCR primers. The researchers were successful in
finding H. suis DNA in gastric biopsy specimens
taken from mice that had been experimentally
infected [187]. Electrophoresis was performed using
two-dimensional (2D) gels [188] to compare the
cellular proteomes of H. pylori with non-pylori
Helicobacter species, including Helicobacter mustelae,
Helicobacter felis, Helicobacter cinaedi, Helicobacter
hepaticus, Helicobacter fennelliae, Helicobacter bilis, and
Helicobacter cholecystus. It was feasible to differentiate
between stomach and enterohepatic Helicobacter
species on the basis of their characteristic 2D protein
profiles. In order to detect the presence of
levofloxacin resistance directly in gastric biopsy
samples, Trespalacios et al. developed novel primers
for the identification of the N87I mutation in the
gyrA gene of H. pylori. The application of the new
primers resulted in an increase in the sensitivity of
the approach for predicting levofloxacin resistance
from 52 to 100 [189]. The efficacy of the GenoType
HelicoDR kit for the rapid detection of the A2143G
mutation in the 23S rRNA gene associated with
clarithromycin resistance and the N87K mutation
linked to fluoroquinolone resistance was evaluated in
42 H. pylori isolates. Compared to sequencing, the test
demonstrated a sensitivity and specificity of over
80% for the identification of clarithromycin and
fluoroquinolone resistance.; however, compared to

MIC results, it demonstrated a sensitivity of 55% for
detecting clarithromycin resistance [190].
VIII. TREATMENT OF H. PYLORI INFECTION
The Maastricht V/Florence Consensus Report, a
brand-new European standard for treating H. pylori
infection, suggests the following treatment plan
(Figure 7) [191]. At first, when there is less than 15%
of a region's population that is resistant to
clarithromycin, the conventional triple regimen of
proton pump inhibitors (PPI), amoxicillin, and
clarithromycin is advised. According to Murakami et
al., the standard triple regimen (Lansoprazole 30 mg
bi-day, 750 mg bi-day amoxicillin, and 400 or 800 mg
bi-day clarithromycin for 7 days) obtained a 97.3%
success rate in the elimination of the strains that are
sensitive to clarithromycin [192]. As a first-line
treatment for clarithromycin-resistant infections,
bismuth-containing quadruple therapy is
recommended for areas with a high level of
resistance (> 15%) to clarithromycin. An alternative
treatment option is non-bismuth quadruple
concomitant therapy (metronidazole , amoxicillin,
clarithromycin, and PPI) in regions in which
clarithromycin resistance is high, but metronidazole
resistance is low to intermediate [191, 193]. When
clarithromycin and metronidazole face significant
resistance in a particular region, the recommended
primary treatment option is bismuth-containing
quadruple therapy. In China, patients diagnosed
with H. pylori-induced chronic gastritis have a higher
success rate with first-line therapy consisting of ten
days of bismuth quadruple therapy as opposed to ten
days of normal triple therapy (86.1% vs. 58.4%, ITT
analysis) [194]. If both the initial treatment (triple or
non-bismuth quadruple therapy) and the second
treatment (quinolone-containing therapy) fail, then
the appropriate course of action is to use quadruple
therapy that includes bismuth. In France, 83% of
individuals treated with bismuth-containing triple
therapy were successfully eradicated [195].
It is recommended that after the failure of first-line
therapy with bismuth quadruple and second-line
therapy with quinolones, triple or quadruple therapy
with quinolones be used [191]. In areas where
clarithromycin resistance is high but metronidazole
resistance is low or moderate, the triple therapy
(which includes amoxicillin, metronidazole, and PPI)
may be a useful alternative if metronidazole was not
initially used as a treatment [196] . The third- and
fourth-line therapy reports are detailed in Tables 1, 2,
and 3. Quinolone-based treatment is one of the most
prevalent third-line regimens. Levofloxacin has been
frequently utilized as an H. pylori rescue medication
[197-199]. However, the efficiency of levofloxacin-
based therapy against gyrA mutation-positive
bacteria is insufficient; approximately 40%
eradication rates are seen [200]. As a result of using a
sitafloxacin-containing treatment, up to 70% of gyrA
mutation-positive strains were able to be eradicated
successfully [201, 202]. A randomized trial
demonstrated that the eradication rate of triple
regimens including sitafloxacin was superior to that
of triple regimens containing levofloxacin [203].
Therefore, currently, if available, sitafloxacin is the
most effective fluoroquinolone. However, quinolone
resistance is easily acquired, and some strains acquire
double mutations in gyrA that confer a high level of
resistance [204]. In contrast, it has been reported that
rifabutin-containing medication is a third-line
treatment [205]. Due to the rarity of rifabutin
resistance, H. pylori strains resistant to numerous
antibiotics can be defeated by rifabutin-containing
therapy. However, Rifabutin-containing therapy
should be used with caution due to side effects such
as leukopenia and thrombocytopenia, as well as the
occurrence of multi-resistant strains of Mycobacterium
tuberculosis [206]. In terms of the duration of
rifabutin-containing therapy, 10-day or longer
therapy was superior to 7-day therapy [206, 207]. An
eradication rate of 83.3% was reported for 10-day
regimens containing rifabutin and 94.1% for 14-day
regimens [207]. In terms of PPI dosage, rifabutin
therapies with high dose PPI achieved more effective
eradication than standard PPI dosage [208]. The
presence of bismuth had an additional effect on the
metabolism of rifabutin-containing regimens.
Contrary to what most people believe, the use of
high-dose PPI and amoxicillin as a third-line
treatment regimen can be a useful alternative [209-
211]. Rabeprazole (10 mg qid) and amoxicillin (500
mg qid) for 14 days were previously reported to have
an eradication rate of 63.0% [209]. There is no
significant difference between the eradication rates
achieved with quinolone- or rifabutin-containing

therapies; however, there are fewer worries about
some problems and the development of new drug
resistance with high-dose PPI and amoxicillin
combination therapy. Vonoprazan, a the first-of-its-
kind potassium-competitive acid blocker with a
potent effect on inhibiting stomach acid secretion, is
highlighted. There was a clear improvement in the
efficacy of the vonoprazan, amoxicillin, and
clarithromycin triple regimen when compared with
the standard lansoprazole, amoxicillin, and
clarithromycin triple regimen (82.0 vs. 40.0%) for
eradicating clarithromycin-resistant strains [192].
There are only limited reports of vonoprazan-
containing regimens that exclusively use a triple
therapy approach [212]. Therefore, it is
recommended to consider alternative regimens that
include vonoprazan, such as bismuth-quadruple
therapy or concomitant therapy.
Fig.6 The Maastricht V/Florence Consensus Report-
aligned treatment strategy for H. pylori infection is
presented. [191].
IX. RECURRENCE OF INFECTION
Recrudescence and reinfection are thought to be the
mechanisms behind the recurrence of H. pylori.
Recrudescence is not a sign of successful eradication
but rather the return of the original strain of H. pylori
after a brief suppression. Instead, genuine reinfection
happens when a patient contracts the original strain
of H. pylori or a different strain after eradication is
complete [213]. There has been evidence that late
recurrence is responsible for the high recurrence rates
during the first three to twelve months after cure. A
verified absence of H. pylori for a year following
therapy is a credible sign of eradication effectiveness
without recrudescence. It appears that low-efficacy
medication merely temporarily suppresses the H.
pylori infection in the gastric mucosa rather than
curing it or removing it entirely from the host [214,
215]. The recurrence of H. Pylori infection after
successful eradication is one of the most challenging
aspects of its management. Most recurring cases are
presumably caused by recrudescence rather than
reinfection because the frequency of recurrences
declines over time, dropping off dramatically after
the first year, and identified strains (before and after
therapy) are typically genetically identical. In adults,
reported "real" reinfection rates typically ranged
from 0 to 23.4%. There were significantly lower
annual "real" reinfection rates within the first year of
eradication than reported annual recurrence rates
within those first few years following eradication
[213]. H. pylori reinfection may also be caused
through intrafamilial transmission; the presence of
this organism in asymptomatic family members may
encourage transmission between households [216]. In
developed countries like Europe and the USA, the
rate of H. pylori reinfection following eradication
medication is incredibly low. Zendehdel et al.
reported an annual reinfection rate of approximately
1% [215] . Contrary to western populations, which
have reported low rates of H pylori reinfection,
developing countries have reported high rates of
recurrence [217, 218]. Therefore, Due to the increased
danger of re-exposure, it's possible that the high
frequency of H. pylori infection is linked to a high rate
of infection recurrence following eradication [12].
Genetic factors may also be at play; those who have
successfully eradicated H. pylori may still be
susceptible to reinfection when exposed to H. pylori-
positive individuals [216]. There have been a number
of publications written about the occupational risk of
H. pylori infection. Matysiak-Budnik [219]
demonstrated a link between work exposure and a
higher risk of infection. Williams [220], too, said that
endoscopic staff members have higher job risk.
X. CONCLUSION
H. pylori infection is a major public health concern
with significant morbidity and mortality worldwide.
In this comprehensive review, we have highlighted
the current understanding of the transmission,
diagnosis, and treatment of H. pylori infection. The
risk factors and epidemiology of H. pylori infection

have been discussed, along with the clinical
manifestations and pathogenesis of the infection.
Diagnostic tests for detection of H. pylori infection
have been described, along with the various
treatment options available for H. pylori infection.
Although significant progress has been made in our
understanding of H. pylori infection, challenges
remain, particularly in the areas of antibiotic
resistance and the development of effective
treatments. In addition, the role of H. pylori infection
in the development of extra-gastric diseases, such as
cardiovascular disease and diabetes, remains an
active area of research. In conclusion, continued
efforts are needed to improve the diagnosis,
treatment, and prevention of H. pylori infection.
These efforts will require collaboration among
researchers, clinicians, public health officials, and
policymakers. By working together, we can reduce
the burden of H. pylori infection and its associated
complications, and improve the health outcomes of
individuals affected by this infection.
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Current Understanding of the Transmission, Diagnosis, and Treatment of H. pylori Infection: A Comprehensive Review

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Current Understanding of the Transmission, Diagnosis, and Treatment of H. pylori Infection: A Comprehensive Review