Introduction to Helicobacter and H. pylori

Introduction to Helicobacter

• Helicobacter is a genus of Gram-negative bacteria.
• It has a helical shape.
• More than 35 species are included in this genus.
• H. pylori is a medically important species.
• It is found in the upper lining of the gastrointestinal tract and liver of mammals and some birds.

Helicobacter Pylori

• Many Helicobacter species exist, but H. pylori is medically significant.
• Previously known as Campylobacter pylori, it causes gastritis and gastric ulcers.
• Other Helicobacter species include H. cinnaedi, H. fenneliae, H. mustelae, and H.felis.

Epidemiology of H. pylori

• H. pylori is present in less than 20% of people under 30, increasing to 40-60% in those over 60.
• Asymptomatic individuals may also have the infection.
• Prevalence is higher in developing countries (possibly up to 80%).
• Person-to-person transmission is implicated in family clusters.
• Acute gastritis outbreaks suggest a common source of H. pylori.

H. pylori Structure and General Characteristics

• Gram-negative bacteria
• Size: 3 µm long, 0.5 µm diameter
• Helical/curved rod shape (not a spirochaete).
• Microaerophilic (requires less oxygen than the atmosphere)
• May appear coccoid after prolonged in vitro culture; not a cultural state.
• Has 2-6 unipolar, sheathed flagella but lacks fimbrial adhesins.

H. pylori Function and Virulence Factors

• Primarily found in the stomach's mucus layer.
• Neutralizes stomach acid by producing urease, converting urea to ammonia and carbon dioxide.
• This enables survival in the acidic environment.
• Can form biofilms, and convert between spiral and coccoid forms.
• Possesses 5 major outer membrane proteins, putative adhesins, porins, and iron transporters. It also has a flagellum-associated protein and proteins with unknown functions
• Produces substances such as hydrogenase, oxidase, catalase, and urease.

H. pylori Virulence Factors (continued)

• The main virulence factors include adhesins (e.g., BabA, SabA).
• Vacuolating cytotoxin VacA is produced.
• Cytokine production, response to infection, and host determinants (e.g., gastritis, peptic ulcers, or cancer) are influenced bacterial factors and cytokine polymorphisms.

H. pylori Transmission

• H. pylori is ubiquitous and transmitted by ingestion.
• Childhood infection prevalence is low compared to older adults (about 40-50%).

H. pylori Pathogenesis

• H. pylori, after ingestion, thrives at a pH of 6.0-7.0, penetrating deep into the mucus layer beside the epithelial surface.
• Neutralizes stomach acid with urease-produced ammonia, allowing for colonization.
• Multiple flagella facilitate rapid gastric mucus penetration.
• Mucinase and cytotoxin trigger inflammatory cell infiltration.
• Infection stimulates gastrin and gastric acid secretion, encouraging gastric metaplasia.

Diseases Caused by H. pylori

• Stomach and duodenal ulcers
• Chronic type B gastritis (superficial and atrophic) — possible progression to gastric adenocarcinoma

Clinical Findings

• Acute infections manifest as upper gastrointestinal illness with nausea, pain, vomiting, and fever.
• Symptoms typically last less than a week to 2 weeks.
• Chronic infection often persists for years. H. pylori may be a factor in gastric carcinoma and lymphoma

Diagnostic Laboratory Tests

• Specimens: Gastric biopsies, serum for antibody detection.
• Smears: Histological examination of biopsies. Gastroscopic procedure with biopsy is needed.
• Culture: H. pylori grows in 3–6 days at 37°C in a microaerophilic environment. Skirrow's medium is a primary isolation media.
• Antibodies: Serum antibodies persist even after eradication.
• Special Tests: 13C or 14C urea breath test—CO2 detection in breath signifies H. pylori presence.

Immunity

• Initial infection elicits an IgM antibody response.
• Later, IgG and IgA antibody responses develop chronically and systemically—and even at mucosal sites.
• Early treatment of H. pylori infection reduces antibody response potentially increasing the risk of repeat infection.

Symptoms

• Abdominal pain (ache or burning)
• Nausea, Vomiting
• Frequent belching, bloating
• Weight loss
• Difficulty swallowing, black or bloody stools, vomit that looks like coffee grounds

Treatment

• Triple therapy (Bismuth salts+metronidazole+amoxicillin/tetracycline)
• Bismuth salts+ranitidine+clarithromycin
• Proton pump inhibitors (e.g., omeprazole)+amoxicillin+clarithromycin

Prevention

• (5 methods of preventing H. pylori infection are not listed but the document states a need to list five ways.)

Explore the fascinating genus Helicobacter, which includes over 35 species, including the medically significant H. pylori. This quiz covers the structure, epidemiology, and implications of H. pylori on human health, specifically its role in gastritis and gastric ulcers. Test your understanding of this important bacteria and its impact on different populations.