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19 Cards in this Set
- Front
- Back
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H pylori specs
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gram-neg; curved bacilli; resides in mucus gel layer overlying gastric mucosa; colonizes for years to decades; multiple flagella at one pole; nutritionally fastidious; microaerophilic; urease producers
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microaerophilic
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grow ideally in an atmosphere of reduced O2 (~5%)
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urease
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catalyzes hydrolysis of urea into ammonia and CO2
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what occurs following ingestion of H pylori
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period of intense bacterial proliferation and gastric inflammation with concomitant hypochlorhydria which may last for weeks
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what occurs after initial acute inflammation
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ineffective humoral response, but may regulate intensity of inflammation; gastric pH restored wnl and infected ppl remain assymptomatic for years of life
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atropphic gastritis
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loss of epithelial glands; occurs over decades and is risk factor for gastric cancer
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CagA
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marker and effector for damage; increased IL-8 levels in mucosa; linked to peptic ulcer disease
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CagA and epithelial cells
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translocated into host epithelial cells following H pylori attachment-then modified by tyrosine phosphorylation-then activates several host signaling pathways
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what do the signaling cascades induced by CagA in epithelial cells cause
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induce IL-8 secretion and stimulate cytoskeletal rearrangements
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VacA
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cytotoxin that induces vacuolation of cells in culture; increase infiltration of gastric antrum by neutrophils; can induce apoptosis
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H pylori and gastrin levels
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downregulates somatostatin-producing D cells in gastric mucosa which leads to elevated gastrin levels and enhanced gastric acid secretion
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how does H pylori affect duodenum
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epithelium in duodenum changes to gatric type due to increased acid levels, allowing infection by H pylori
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gastrin and cancer
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in vitro, it stimulates epithelial cell proliferation
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what causes increased risk of MALT and stomach lymphomas
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T cells react with H pylori antigens and produce cytokines supporting uncontrolled growth and proliferation of B cells
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arginase
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confers protection against host inflammatory molecule nitric oxide
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stains for H pylori
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Giemsa stain; Warthin-Starry stain-more sensitive, but more costly
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biochemical confirmation of H pylori is based on
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urease, catalase, oxidase
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eradication 85% from H pylori with what treatment
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PPI and 2 antibiotics for 7-10 days (usually clarithromycin and either metronidazole or amoxicillin)
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second line therapy for H pylori eradication
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quadruple therapy = PPI, bismuth subsalicylate, metronidazole, and tertracycline for 14 days
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