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28 Cards in this Set
- Front
- Back
21.1
Enterobacteriaceae |
- family that most enteric bacteria belong to
- escherichia, salmonella and shigella - transmission of these bacteria -> fecal-oral route |
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21.2
salmonella and shigella |
- both primary pathogens
0 unequivocally asociated with disease when found in a host organism -- not found in our normal flora |
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21.3
escherichia |
- some strains are primary pathogens while some are opportunistic pathogens and can cause infections of the host becomes debilitated
- opportunistic strains of escherichia are found in our normal flora - shigella is non-motile |
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21.4
general physical features of enterobacteriaceae |
- gram negative rods (.5 x 2u)
- most are motile and peritrichous (have mutliple flagella) |
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21.5
general biochemical/metabolic features |
- facultative anaerobes
- ferment glucose, oxidase negative 1. these two features distinguish Enterobacteriaceae from other enteric bacteria such as vibrio cholera 2. API strip: positive or negative tests. distinct biochemical and commercial tests that can be used to ID individual enterobacteriacea species. |
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21.6
subtryping of Enterobacteriaceae species based on serotyping: |
O-antigen: outer cell wall lipopolysaccharide unique to G- organisms
H-antigen: flagellum K-antigen: also known as Vi-antigen (for VIrulence) in salmonella. capsule |
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21.7
media for selective isolation and differentiation of Enterobacteriaceae from stool medium:selective agent: differentiation |
MacConkey:Bile salts:Lactose
EMB:Dyes:Lactose Hektoen Enteric:Bile salts:Lactose, sucrose, salacin, H2S SS Agar:Bile salts:lactose, H2S enteric bacteria are resistant to high bile salt concentrations, and that commensal bacteria utilize lactose |
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21.8
Escherichia coli |
- most abundant facultative anaerobe found in the gut, though not the most abundant species
- Gi and urinary infections, neonatal meningitis, and septicemia - gram negative rod - size 0.5 - 2 u - motile: peritichous flagella - fimbriae/pili: many types adhesins |
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21.9
Escherichia Coli associated infections |
- Urinary tract: uropathogenic
- GI tract: Enterotoxigenic E. coli (ETEC) Enteropathogenic E. coli (EPEC) Enterohemorrhagic E. coli (EHEC) enteroaggregative E. coli (EAEC) diffuse aggregative E. coli (DAEC) - Neonatal meningitis: K1 encapsulated |
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21.10
Enterohemorrhagic E. coli (EHEC) |
- O157H7
- causes hemorrhagic colitis - very bloody diarrhea |
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21.11
Enterohemorrhagic escherichia coli (EHEC) transmission vehicle |
- feces
- beef - unpasteurized milk - apple cider - water |
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21.12
enterohemorrhagic E. coli mechanism of pathogenesis: attachment and effacement |
1. loose attachment to microvilli on gut epithelium -> host cell formation of a pedestal on which the bacteria can grow
2. tight attachment results in destruction (effacement) of remaining microvilli, decreasing epithelial absorption of nutrients and water anc causing diarrhea 3. release of Shiga toxin(s) Stx1 and Stx2 which are cytotoxic to capillary endothelial cells and results in hemorrhagic blood loss |
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21.13
how long does the EHEC infection last? |
- usually 5-7 days, majority of ppl recover
- can result in hemlytic uremic syndrome (HUS) |
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21.14
Hemolytic Uremic Syndrome (HUS) |
- death in 10% of children < 10 years
1. blood/toxin disseminates, gets into kidneys 2. renal failure results from destruction of glomerular endothelial cells by toxin |
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21.15
selection and differentiation of EHEC |
- MacConkey-Sorbitol (v. MacConkey-Lactose) agar because O157H7 cannot metabolize sorbitol while commensal bacteria can
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21.16
Salmonella |
- member of enterobacteriaceae
- lactose negative - motile - H2S producer |
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21.17
species of salmonella |
- traditional: speciation based on O and H antigens. thousands of species,
- modern: based on DNA typing. 2 types: Salmonella enterica, Salmonella bongori |
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21.18
salmonella enteritidis |
- characteristic of majority of species
- cause of bacterial gastroenteritis (diarrhea, cramping, mild fever0 - reservoir: GI tract of domesticated animals, birds, reptiles - transmission: poultry, eggs, contaminated foods |
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21.19
salmonella typhi |
- mostly just a problem in the developing world
- cause of typhoid fever that last 3-4 weeks - reservoir: humans - transmissionL contaminated food/water, exacerabated by 'carrier state' in which the gallbladder gets chronically infected and secretes the bacteria into the intestine |
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21.20
salmonella mechanism of pathogenesis: |
- invasion of intestinal epithelium
- passage through intestinal epithelium into submucosal tissues - phagocytosis by neutrophils and macrophages (macrophages can kill S. enteriditis but not S. typhi -> S. typhi results in a disseminated infection |
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21..21
shigella |
- enterobacteriacea family
- lactose negative - nonmotile - cause dysentery |
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21.22
shigella species |
- shigella dysenteriae (classic bacillary dysentery, produces shiga toxin, most severe infections)
- shigella sonnei - shigella flexneri - shigella boydii |
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21.23
what is and causes of: bacillary dysentery (vs. amoebic dysentery) aka Shigellosis |
- frequent, small volume diarrhea associated with blood mucus in the feces, abdominal cramping and tenesmus (inability or difficulty to completely empty the bowl at defecation - can be painful)
1. reservoir: humans 2. transmission vehicles: contaminated food and water. low infectious dose (200 bacteria) |
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21.24
mechanism of pathogenesis for shigella |
- invasion of intestinal epithelium
- lateral cell-to-cell spread via commandeering of host ell cytoskeleton. replication kills cells, casuing epithelium to get sloughed off (mucoid stool) |
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21.25
campulobacter jejuni |
- not a member of enterobacteriacea
- Gram - helical rod. 0.4-0.5 u, single polar flagellum - microaerophilic - 42C reservoir: wild and domestic animals, birds, (42C body temp) Transmission: contaminated water (most common bacterial infection in the US - 2.5 million cases/year |
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21.26
mechanism of pathogenesis campulobacter jejuni |
i. invasion of intestinal epithelium
ii. passage through intestinal epithelium into submucosal tissues iii. phagocytosis by neutrophils and macrophages (GBS) |
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21.27
Guillain-Barre syndrome (GBS) |
- immune system attacks GM1 gangliosides of the peripheral nervous system that resemble oligosaccharides made by C. jejuni (molecular mimicry)
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21.28
relative incidences of enteric infections |
- camphylobacter infections > salmonella > shigella > E. coli
- most infections in summer months - male: female = 3:1 - age: higher in babies and the elderly, highest in males 20-29 |