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Bacteriology of helicobacter pylori
- Gram Negative
- Spiral-shaped bacterium
- With 4-6 unipolar flagellae
- Microaerophilic (5% O2)
- Strongly urease positive
Prevalence of H. pylori
- Global prevalence >50%
- developing countries > developed countries
Mode of transmission of H. pylori
- Nosocomial due to contaminated endoscopes
- Drinking water and food
Risk factors of H. pylori
- Poor socio-economical development
- Low education
- Poor hygiene condition in childhood
- Crowded families
- Absence of sanitary drinking water
- Absence of sewage disposal facilities
Pathology of H. pylori
Chronic infection à chronic superficial gastritis + atrophy
Foci of infection of H. pylori
- Gastric antral epithelium and foci of peptic ulceration
- Found in mucus gel layer over gastric epithelium and some may invade intracellularly into the epithelial cells and into lamina propria
Virulence factors of H. pylori
- Colonization: urease, motility, adherence
- Persistence: inaccessibility to immune attack
- Altered gastric physiology
- Vacuolating cytotoxin (vacA gene), cytotoxin-associated gene A protein (cagA gene) à tissue injury and carcinogenesis
4 Diseases in Stomach caused by H. pylori
- Chronic superficial gastritis
- Peptic ulcer
- Gastric adenocarcinoma of body and antrum
- Gastric MALT lymphoma (mucosa-associated lymphoid tissue- type low grade B cell lymphoma)
5 types of diagnosis of H. pylori infection
- Bacteriological diagnosis ** for antibiotic sensitivity test
- Urease-based test
- Stool antigen detection test
- Histopathological diagnosis
- Antibody detection **for epidemiological studies
What is the sample taken for bacteriological diagnosis of H. pylori infection?
Endoscopic gastric mucosal biopsies transported in sterile saline in microaerophilic culture à may give rise to sampling error
What to look for in histopathological diagnosis of H. pylori infection?
- Diffuse distribution
- Presence of inflammation
Special stain for H. pylori
What are the samples for serology looking for H. pylori infection?
What’s the difference between enzyme immunoassay and immunochromatographic assays in stool antigen detection tests for diagnosis of H. pylori?
- EIA: lab-based using monoclonal antibodies + better accuracy
- Immunochromatographic assays: rapid in office setting + relatively low sensitivity
What are the two types of urease-based tests?
- Rapid urease test (using biopsies of gastric mucosa)
- urea breath test
What’s the difference between eradication and clearance?
- Clearance = absence of detectable organisms immediately after stopping therapy
- Eradication = absence of detectable organisms >/= 4 weeks after stopping therapy
What are the Agents used for eradication of H. pylori?
- Anti-Pylori Can Really Make Tummy Better
- Ranitidine bismuth citrate
- Metronidazole (nitroimidazole)
Which of the eradication agents of H. pylori has resistance?
- Nitroimidazole (e.g. metronidazole)
What are the eradication regimens for H. pylori?
- Triple therapy (PPI-based/ bismuth-based)
- Ranitidine bismuth citrate-based therapy
- Quadruple therapy and second-/third-line treatment
- Sequential therapy
What is triple therapy?
- PPI-based: PPI + Clarithromycin + amoxicillin/ metronidazole (10-14 days)
- Bismuth-based: bismuth + metronidazole + amoxicillin/ tetracycline
- Yet both have low eradication power due to resistance to metronidazole/ clarithromycin
What is ranitidine bismuth citrate-based therapy?
Ranitidine bismuth citrate + clarithromycin + (amoxicillin/ metronidazole)
What is quadruple therapy and second-/third-line treatment of H. pylori infection?
- PPI + bismuth + two antibiotics (TM/ AC)
- PPI + 3 antibiotics (MAC)
- Levofaloxacin- or moxifloxacin-based regimens
What is sequential therapy of H. pylori infection?
5D of PPI + amoxicillin à 5D of PPI + C+ M
What are the 4 normal intestinal defence mechanisms?
- gastric acidity
- intestinal motility
- enteric normal flora -> colonization resistance
- specific immunity
What are the normal flora of the stomach?
- alpha-hemolytic streptococci
- swallowed oral bacteria
What are the normal flora of the duodenum?
- alpha-hemolytic streptococci
- transitory oral bacteria
What are the normal flora of the colon?
4 Control measures of enteric infectios
- public health measures
- non-specific host factors
Principles of therapy of infectious diarrhoea
- Fluid replacement (oral rehydration solution ORS)
- Antimotility agents (avoided in invasive infections)
What are the 3 types of toxins and their respective examples?
- secretory toxins e.g. Vibrio Colerae, enterotoxigenix E. Coli, Clostridium Perfringens
- cytotoxins e.g. Shigella, enterohaemorrhagic E. Coli, Clostrium Difficile
- neurotoxins e.g. Clostridium botulinum, Staphylococcus aureus, Bacillus cereus