Gut bacteria Flashcards
Salmonella
Enterobacteriaceae family.
Gram negative.
Systemic infection (typhi).
Vaccine exists (typhi).
Typhi and paratyphi: Infect macrophages, allowing them to spread systemically. Can cause osteomyelitis, arthritis, and endocarditis. Can colonize gall bladder. Human-to-human fecal-oral route. Vaccine exists and is recommended for travelers (but not children).
Non-typhi: Gastroenteritis only. Found in poultry, eggs, dairy, ground beef, pet turtles.
Both: Produce H2S, diagnostic on plate. Do not ferment lactose.
Tx: ampicillin, trimethoprim, ciprofloxacin.
Shigella
Enterobacteriaceae family.
Gram negative.
Dysentery.
No vaccine.
Non-motile rod, no capsule, does not ferment lactose. Does not produce H2S (used to differentiate from Salmonella). Human-to-human fecal-oral transmission; infects mostly children. Ipa proteins allow entry into phagocytes, and are the target of antibodies. Polymerize host actin to move within cell. Induce apoptosis, pro-inflammatory reaction. Dysentery is blood and mucus in stool or diarrhea. Straining upon defecation.
Tx: Self-limiting. Do not give antidiarrhetics. Ampicillin, trimethoprim, ceftriaxone.
UPEC
(uropathogenic E. coli) Enterobacteriaceae family. Gram negative. UTIs. No vaccine.
Listeria monocytogenes
NOT enterobacteriaceae family.
Gram positive.
Systemic disease.
No vaccine.
Can acquire from cantaloupes and soft cheeses. Can grow in the refrigerator and in high-salt concentrations. Motile aerobic rod bacteria. Escape from phagocytes (via listeriolysin O, activated by low pH), polymerize host actin to project into other cells. Can be transmitted from mother to fetus in utero. At risk patients are those with deficient cellular immunity.
Tx: gentamicin + penicillin/ampicillin
EHEC
(Enterohemorrhagic E. coli) Enterobacteriaceae family. Gram negative. Hemolytic colitis, HUS, diarrhea. No vaccine.
Makes shiga toxin. Attaching and effacing lesions. Can infect cattle intestines; spreads to beef, unpasteurized cider, spinach, sprouts. Cannot ferment sorbitol (diagnostic; grows on MacConkey agar). Can ferment lactose.
Tx: Self-limiting. Do not give antidiarrhetics. Don’t use antibiotics, as they aggravate pathology.
Campylobacter
NOT enterobacteriaceae family.
Gram negative.
Gastroenteritis.
No vaccine.
Comma-shaped, microaerophilic, thermophilic, non-fermentative, motile, flagellum. Bloody diarrhea can be acute, and can ulcerate colon, ileum, jejunum. Neutrophil infiltration. Can trigger Guillain-Barré and reactive arthritis. Fecal-oral transmission. Reservoir in chickens, can pass to cow milk. Common cause of diarrhea.
Tx: fluid replacement. If severe, azithromycin or erythromycin.
Helicobacter
NOT enterobacteriaceae family.
Gram negative.
Peptic and duodenal ulcers.
No vaccine.
Curved rods, multiple flagella, highly motile, microaerophilic. Urease converts urea to NH3 and CO2, locally neutralizes stomach acid for survival. Peptic mucus layer has pH of 7.0; this is where H. pylori live. Toxin is VacA, an anion channel that inserts into stomach epithelium. Second toxin is CagA, which increases IL-8 release and forms pedestals. Only infects humans. Urease is diagnostic, via radio-labeled urea breath test. Associated with adenocarcinoma and B cell lymphoma. 10-15% of people get gastric ulcers.
Tx: PPI + macrolide + ß-lactam.
EPEC
(Enteropathogenic E. coli) Enterobacteriaceae family. Gram negative. Infant diarrhea. No vaccine.
Same as EHEC, but does not make shiga toxin.
EAEC
(Enteroaggregative E. coli) Enterobacteriaceae family. Gram negative. Infant diarrhea. No vaccine.
ETEC
(Enterotoxogenic E. coli) Enterobacteriaceae family. Gram negative. Traveler's diarrhea. Vaccine exists.
Campylobacter
NOT enterobacteriaceae family.
Gram negative.
Gastroenteritis.
No vaccine.
Comma-shaped, microaerophilic, thermophilic, non-fermentative, motile, with flagella and one or both poles. Can ulcerate colon, ileum, jejunum. Neutrophil infiltration. Can trigger Guillain-Barré and reactive arthritis. Reservoir in chickens, can pass to cow milk.
Tx: fluid replacement. If severe, azithromycin or erythromycin.
Vibrio
NOT enterobacteriaceae family.
Gram negative.
Osmotic diarrhea.
Vaccine exists.
Curved rods, single flagellum, require NaCl, oxidase positive, only serotypes 01 and 0139 produce cholera toxin. Cholera toxin triggers Gs, increases cAMP, increases NaCl efflux, massive loss of water. Grow in oysters, clams, mussels, and dirty water. Causes rice-water stool (diagnostic). Kills by electrolyte loss, 60% mortality if untreated.
Tx: Fluid and electrolyte replacement. Azithromycin + doxycycline/ciprofloxacin.
EIEC
(EnteroInvasive E. coli) Enterobacteriaceae family. Gram negative. Invasion similar to Shigella. No vaccine.
