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Bacterium

Helicobacter pylori

Common name: H. pylori

Harmful Digestive Gut Mucosa
Harmful
Effect
Digestive
Impact
Gut, Mucosa
Location
Common
Prevalence
Last reviewed: April 4, 2025

Peptic ulcers, gastric cancer, MALT lymphoma; paradoxical protection against allergies and esophageal diseases

Prevalence: Global prevalence ~43% (declining from 58% in 1980-90); higher in developing countries

Interacts with: Gastric microbiota, Intestinal microbiota, CagA oncoprotein, VacA toxin

Overview

Scientifically accurate microscopy-style illustration of Helicobacter pylori showing its characteristic gram-negative spiral or curved rod with multiple unipolar sheathed flagella

Helicobacter pylori is a Gram-negative, microaerophilic, spiral-shaped bacterium that colonizes the human stomach. Discovered in 1982 by Barry Marshall and Robin Warren (Nobel Prize 2005), it infects approximately 43% of the global population and is classified as a Class I carcinogen by WHO.[1]

Global Epidemiology

Current Prevalence[1]

  • Global: Declined from 58.2% (1980-90) to 43.1% (2011-22)
  • Africa: Highest prevalence (70.1%)
  • Oceania: Lowest prevalence (24.4%)
  • Children: 32.3% globally; 43.2% in low/middle-income vs 16.3% in high-income countries

Risk Factors

  • Lower socioeconomic status
  • Crowded living conditions
  • Poor sanitation
  • Lower universal health coverage

Virulence Factors

CagA (Cytotoxin-Associated Gene A)[2]

  • Translocated via Type IV Secretion System into host cells
  • Undergoes tyrosine phosphorylation at EPIYA motifs
  • East Asian CagA: Binds SHP2 100-fold more strongly than Western type
  • Activates oncogenic pathways: Ras-ERK, Wnt-β-catenin, YAP
  • Induces epithelial-mesenchymal transition (EMT)
  • Degrades tumor suppressors: p53, RUNX3, ASPP2

VacA (Vacuolating Cytotoxin A)

  • Pore-forming toxin inducing vacuoles in host cells
  • s1/m1 and i1 genotypes: Strongest association with gastric cancer
  • Induces apoptosis via mitochondrial pathway
  • Inhibits T and B cell proliferation
  • Causes endoplasmic reticulum stress

Urease

  • Constitutes ~10% of total bacterial protein
  • Neutralizes gastric acid for survival
  • 1.1 MDa dodecameric complex with bi-nickel catalytic center
  • Promotes angiogenesis via PI3K-AKT-mTOR pathway

Associated Diseases

Correa Cascade[3]

H. pylori infection progresses through sequential stages:

  1. Chronic non-atrophic gastritis (nearly all infected individuals)
  2. Chronic atrophic gastritis
  3. Intestinal metaplasia
  4. Dysplasia
  5. Gastric adenocarcinoma

Clinical Manifestations

Disease Association
Chronic gastritis Virtually all infected individuals
Peptic ulcer disease 15-20% of infected persons
Gastric adenocarcinoma 1-3% lifetime risk
MALT lymphoma ~90% of cases H. pylori-associated

MALT Lymphoma

  • ~75% of H. pylori-positive cases achieve complete remission through eradication
  • CagA is key driver of lymphomagenesis
  • Bacteria induce chronic inflammation attracting lymphoid cells

Antibiotic Resistance Crisis

Current US Resistance Rates[4]

Antibiotic Resistance Rate
Metronidazole 42.1%
Clarithromycin 31.5%
Levofloxacin 31.6%
Amoxicillin 3.0%
Tetracycline 0.9%
Rifabutin 0.2%

Resistance Mechanisms

  • Clarithromycin: 23S rRNA mutations (A2142G, A2143G, A2142C)
  • Metronidazole: rdxA/frxA gene mutations preventing prodrug activation
  • Levofloxacin: gyrA mutations at codons 87 and 91
  • Biofilm formation: Increases antibiotic tolerance up to 1,000-fold

Current Treatment Recommendations

  • First-line: Bismuth quadruple therapy (14 days)
  • Alternative: Rifabutin-based triple therapy
  • Emerging: Vonoprazan-based regimens show promise

Paradoxical Protective Effects

Growing evidence suggests H. pylori may protect against certain conditions:[5]

Allergic Diseases

  • Childhood asthma: OR 0.63 for cagA+ strains
  • Allergic rhinitis: OR 0.55 for childhood onset
  • Atopic eczema: Inverse association
  • Mechanism: Induces regulatory T cells that suppress allergic inflammation

Esophageal Diseases

  • GERD: Strong inverse association with cagA+ strains
  • Barrett's esophagus: Protective effect
  • Esophageal adenocarcinoma: Inverse correlation

Proposed Mechanisms

  • Reprograms dendritic cells toward tolerogenic state
  • Shifts immune response toward Th1/Treg dominance
  • Protection most effective when infection acquired in early life
  • Influences neuroendocrine peptides (leptin, ghrelin)

Clinical Implications

Eradication Benefits

  • Prevents peptic ulcer recurrence
  • Reduces gastric cancer risk
  • Achieves MALT lymphoma remission in most cases
  • Restores DNA repair functions

Considerations Against Universal Eradication

  • Rising esophageal diseases in developed countries
  • Increasing allergic and autoimmune disorders
  • Gut microbiome disruption from antibiotic treatment

Documented Strains

26695 (ATCC 700392)

Helicobacter pylori 26695

Extensive research
ATCC 700392 DSM 17374
Genome referencePathogenesis researchVaccine developmentComparative genomics

Key Findings

–

Genome reference

1,667,867 bp; 1,590 CDS; first H. pylori genome published

First organism to have its complete genome sequenced with functional analysis of a gastric pathogen; the reference genome against which all H. pylori field research is compared; cagPAI present, vacA functional

SS1 (Sydney Strain 1)

Helicobacter pylori SS1

Extensive research
Standardized mouse model of H. pylori infectionVaccine developmentPathogenesis research

Key Findings

↓

Mouse infection model

Achieves 10^6-10^7 CFU/g tissue colonization consistently; cagA and vacA positive

The universal standard for H. pylori mouse pathogenesis research; virtually all published mouse studies from 1997 onward use SS1; the only widely available cagPAI+ strain with consistently reproducible mouse colonization

NCTC 11637 (ATCC 43504)

Helicobacter pylori NCTC 11637

Moderate research
NCTC 11637 ATCC 43504 DSM 4867
Bacteriological type strainQuality control reference for culture and diagnosticsSerodiagnostic reference antigen

Key Findings

–

Type strain

1,680,937 bp genome; Marshall-Warren Nobel Prize reference strain

The official type strain of H. pylori; associated with Marshall and Warren's Nobel Prize-winning discovery; contains cagPAI with Western-type cagA

Associated Conditions

→ Peptic ulcers

Related Organisms

B
Bacillus cereus Digestive
B
Bacillus coagulans Digestive
B
Bacillus subtilis Digestive
B
Bacteroides dorei Digestive
B
Bacteroides fragilis Digestive
B
Bacteroides thetaiotaomicron Digestive

Frequently Asked Questions

What is Helicobacter pylori?

Helicobacter pylori is a bacterium found in the human microbiome.

Where is Helicobacter pylori found in the body?

Helicobacter pylori is primarily found in the Gut, Mucosa.

What are the health impacts of Helicobacter pylori?

Helicobacter pylori primarily impacts Digestive and is potentially harmful for human health.

Research References

  1. Li Y, Choi H, Niedzwiedzka-Stadnik M, et al.. Global prevalence of Helicobacter pylori infection between 1980 and 2022: a systematic review and meta-analysis. Lancet Gastroenterology & Hepatology. 2023. doi:10.1016/S2468-1253(23)00070-5 ↩
  2. Ansari S, Yamaoka Y. Helicobacter pylori Virulence Factors Exploiting Gastric Colonization and its Pathogenicity. Toxins. 2019. doi:10.3390/toxins11110677 ↩
  3. Salvatori S, Marafini I, Laudisi F, et al.. Helicobacter pylori and Gastric Cancer: Pathogenetic Mechanisms. International Journal of Molecular Sciences. 2023. doi:10.3390/ijms24032895 ↩
  4. Ho JJY, Kaur SS, Nayak SS, et al.. Prevalence of Antibiotic Resistance in Helicobacter pylori: A Systematic Review and Meta-analysis in the United States. Gastroenterology. 2022. doi:10.1053/j.gastro.2021.11.005 ↩
  5. Blaser MJ, Chen Y, Reibman J. Does Helicobacter pylori protect against asthma and allergy?. Gut. 2008. doi:10.1136/gut.2007.133462 ↩