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3 - Foodborne Bacteria

3 - Foodborne Bacteria - Foodborne Bacteria Jan 13 Bacteria...

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Foodborne Bacteria Jan 13 – Jan 18, 2010 Bacteria involved in foodborne illness How are bacteria identified/classified? Morphology Metabolism o Respiration requirements Environmental tolerances Morphology Shape o Bacilli (rod-shaped) Some bacilli bacteria have flagella for mobility in liquid environments (ex. Salmonella spp) o Cocci (round-shaped) ( ex. Enterococci) Reaction to staining o Uses crystal violet; if bacteria takes up the gram stain, it means it’s gram positive. If it doesn’t then it’s gram negative Gram positive – purple colour (bacteria took up the gram stain) Gram negative – pink colour (bacteria didn’t take up gram stain) Metabolism Respiration requirements: Aerobic bacteria require O 2 Anaerobic bacteria do not require O 2 (ex. Clostridia spp) Facultative anaerobic bacteria can grow in presence or absence of O 2 (ex. Salmonella spp, Escherichia coli O157:H7, staphlycoccus aureus) Microaerophillic bacteria - very specific O2 concentration requirement (3-6%) (ex. Campylobacter jejuni) Environmental tolerances: Temperature environments o Thermophiles can grow at high temperatures o Psychrophiles can grow at low, fridge temps (ex. Listeria monocytogenes) Osmotic environments o Halophile can grow at high salt concentrations (ex. Vibrio cholera) The best before date on food products is usually referring to an unopened product Bacterias Campylobacter jejuni Gram negative, microaerophillic, spiral/S-shaped Relatively common Self-limiting disease (easy for a relatively healthy person to overcome this) Symptoms: abdominal pain, bloody diarrhea Onset of symptoms: 2-5 days; Duration: 2-7 days Source and mode of transmission: o Raw milk, poultry, and meats o Only a small number of cells are required for infection o Transmission by cross-contamination Escherichia coli O157:H7 aka “hamburger disease” Gram negative, facultative anaerobic, bacilli cells Causes infection or toxin-mediated infection Glycol-polysaccharide Self-limiting disease Symptoms: severe abdominal pain, nausea, vomiting, bloody diarrhea, kidney failure ( leads to Hemolytic uremic syndrome)
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Foodborne Bacteria Jan 13 – Jan 18, 2010
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