Microbiology Cheat Sheet
Food Poisoning & H. Pylori
Food poisoning and H. pylori for NEET-PG and FMGE: Staph aureus, Bacillus cereus fried rice, botulism, CagA, urea breath test, and gastric cancer links.
MedNext Academy | 3 min read
Food Poisoning & H. Pylori
Food poisoning and H. pylori for NEET-PG and FMGE: Staph aureus, Bacillus cereus fried rice, botulism, CagA, urea breath test, and gastric cancer links.
This topic covers the agents of food poisoning classified by toxin mechanism, and the etiopathogenesis and diagnosis of Helicobacter pylori acid peptic disease.
High-yield lines
- Food poisoning intoxications from preformed toxin have rapid onset (1 to 6 hours) with prominent vomiting, while infections have delayed onset with prominent diarrhoea.
- Staphylococcus aureus is the most common cause of food poisoning, producing preformed heat-stable enterotoxins with a 1 to 6 hour onset, violent vomiting, and no fever.
- Bacillus cereus emetic type follows fried rice ingestion with preformed heat-stable cereulide toxin, while the diarrhoeal type follows meat with heat-labile toxin produced in vivo.
- Clostridium botulinum produces a preformed neurotoxin that blocks acetylcholine release, causing descending flaccid paralysis with no fever or sensory loss.
- Infant botulism results from ingested spores, most frequently from honey, that germinate and produce toxin in the immature gut, presenting as a floppy baby.
- The mouse bioassay is the confirmatory test for botulism, detecting toxin in serum, stool, or suspect food with antitoxin neutralisation.
- Clostridium perfringens food poisoning follows reheated meat with enterotoxin produced during sporulation in the gut and an 8 to 16 hour onset.
- Helicobacter pylori is a urease-positive, microaerophilic, spiral Gram-negative bacillus that neutralises gastric acid locally to survive.
- H. pylori CagA is injected via a type IV secretion system and is strongly associated with peptic ulcer, gastric adenocarcinoma, and MALT lymphoma.
- H. pylori is a WHO Group I carcinogen, causing over 90 percent of duodenal ulcers and 70 to 80 percent of gastric ulcers.
- The urea breath test and stool antigen test are the preferred non-invasive tests for both diagnosis and confirmation of H. pylori eradication.
- Serology cannot be used as a test of cure for H. pylori because antibodies persist for months after eradication.
- The rapid urease (CLO) test on gastric biopsy turns pink due to ammonia production and is affected by recent proton pump inhibitor use.
- Early-stage gastric MALT lymphoma may regress with H. pylori eradication therapy alone.
Mapped competency codes
- MI3.5
- MI3.6
Continue into the full chapter
This summary maps to MI3-gastrointestinal-and-hepatobiliary-system.
Frequently Asked Questions
Which food poisoning has the shortest incubation and no fever?
Staphylococcus aureus food poisoning, with a 1 to 6 hour onset, violent vomiting, and absence of fever due to preformed heat-stable enterotoxin.
What food is classically linked to Bacillus cereus emetic food poisoning?
Fried rice, due to preformed heat-stable cereulide toxin causing predominantly vomiting.
What is the best non-invasive test to confirm H. pylori eradication?
The urea breath test or stool antigen test, since serology remains positive long after eradication.
Which H. pylori virulence factor is linked to gastric cancer?
CagA, delivered via a type IV secretion system, is strongly associated with peptic ulcer, gastric adenocarcinoma, and MALT lymphoma.
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