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GI Course

Diarrhea Causing Bacteria

Salmonella Classification Gram neg Bacilli, Enterobacteriaceae (facultative anaerobe), Non Lactose fermenter, Motile with H2S+
Shigella Classification Gram neg Bacilli, Enterobacteriaceae (facultative anaerobe), Non lactose fermenter, Non motile H2S negative.
Shigella Characteristics superficial mucosal membrane invasion, Colonoscopic view would show luminal narrowing and mucosal inflammation, NEUTROPHILS.
What is the infectious dose of Shigella? It is very low (10-200) because it is highly resistant to pH and therefore spreads very easily (fecal-oral route).
What is the most common for of Shigella? Shigella sonnei, this is the most mild form and the most common in the US and Europe.
What organism produces Shiga Toxin? Shigella dysenteriae
How does Shiga toxin work? It cleaves an adenine residue from the 28S rRNA of the large 60S eukaryotic ribosomal subunit. This blocks protein synthesis which leads to colonocytes die by apoptosis.
How does Shigella invade? It enters through the M cell in the ileum or colon, enters the macrophage at the basalar side where it eventually escapes. It then enters through the basalar side of an adjacent cell and moves laterally from there.
Why does Shigella only remain on the epithelium rather than move systemic? This is because Neutrophils at the basalar side keep the organism contained. IL-8 and IL-18 are released by apoptotic macrophages which recruit these neutrophils.
Which Salmonella causes typhoid fever? Salmonella Typhi and Salmonella paratyphi.
What are the two predominant clinical syndromes of Salmonella? Enteritis and typhoid fever.
The most frequent manifestation of Salmonella infection is? Gastroenteritis
Symptoms of Salmonella Gastroenteritis: exudative inflammatory infiltrate in the intestine that are dominated by a massive neutrophil influx. Diarrhea due to disrupted epithelial barrier from inflammation.
Invasion of Typhoid fever: (Salmonella) invade ileal mucosa and evade neutrophils resulting in systemic spread. Organisms rapidly access the lymphatics, travel to mesenteric lymph nodes and enter the bloodstream.
How does typhoid fever replicate? It survives and replicates in macrophages and monocytes which leads to waves of bacteremia marking the symptomatic phase of the disease.
What happens after typhoid fever gets into gall bladder? The person can become a chronic carrier.
Salmonella typhi pathogenesis: Type III secretion system. Bacterial proteins are released in an enterocyte which causes actin rearrangement which allows bacterial uptake. Once inside the bacterium multiply inside vacuoles. Again type III allows it to escape
How does Salmonella Typhi make it to the blood stream? Once it survives inside the cell it enters a macrophage (only typhoid fever strains survive this) and are taken to the mesenteric lymph node. Some bacteria enter the thoracic duct and enter the bloodstream causing a transient bacteremia.
Enteroinvasive E.coli close cousin of shigella sonnei. INVASIVE, non motile. Produces dysentery-like diarrhea and fever. Type III secretion system, escape vacuole and multiply, assemble actin tails to propel laterally through the epithelium.
Yersinia classification Gram neg bacilli, enterobacteriaceae, non-lactose fermenter, non motile and H2S negative.
Yersinia enterocolitica More common in Northern Europe and Canada due to non pasteurization of certain dairy products. acute diarrhea and vomiting in young children. INVASIVE. Liver and spleen abscesses and an inflammatory colitis. REITER'S SYNDROME.
Reiter's syndrome reactive polyarthritis is a sequelae of several enteric pathogens (Yersinia, campylobacter, salmonella, shigella and V. parahaemolyticus) Urogenital or intestinal infection. Symptoms in joints (arthritis), eyes or urogenital tract.
Campylobacter jejuni classification Gram neg Bacilli, facultative anaerobe,
Campylobacter jejuni characteristics Vibrio-like organism that is one of the most common bacterial causes of acute diarrhea in US. Wet mount shows gull-winged organisms with darting motility.
Campylobacter clinical symptoms prodrome of fever, headache, myalgia and malaise. Cramps and abdominal pain with profuse diarrhea that is often bloody.
Campylobacter pathogenesis ingest food from contaminated food or water. Organisms multiply in small intestine and invade mucosal layer. May spread to mesenteric lymph nodes. Bacteremia and Reiter's syndrome. GUILLAIN-BARRE SYNDROME
Guillain-Barre Syndrome Acute paralytic disease of the peripheral nervous system. Preceded by C. jejni infection. Possible mech: antibodies developed against the LPS antigens cross-react with peripheral nerve tissue (ganglioside mimicry; GM1) and host response causes nerve damag
Listeria monocytoenes classification Gram + Bacilli, Non spore forming, Aerobe, Motile.
Listeria monocytogenes characteristics Outbreaks of febrile gastroenteritis - major concern for the food industry. Grows well at cold temps (refrigerator) and under low pH and high salt. Consumed in unpasteurized milk products and undercooked meats and raw veggies.
Listeria monocytogenes symptoms watery diarrhea, fever, headache myalgias and abdominal cramps but little vomiting.
Created by: 622988909