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37 Cards in this Set
- Front
- Back
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Describe some general characteristics which are used to differentiate gram-negative bacilli |
Utilization of glucose (fermenter, oxidizer, asaccharolytic)
Oxidase reaction (positive or negative)
Growth of MAC (growth or no growth) |
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General (environmental) characteristics of Enterobacteriaceae |
Most commonly encountered GNB in clinical specimens. Found in soil, water, sewage. Many are present in intestinal tract of animals and humans ("fecal coliforms") and can be opportunistic pathogens. |
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Which Enterobacteriaceae species are primary intestinal pathogens (i.e. are not commensal flora)? |
Shigella Salmonella Yersinia enteropathogenic E. coli |
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General biochemical characteristics of Enterobacteriaceae |
Grow on BA, CHOC Facultative anaerobes
*Glucose fermenters *Oxidase negative *Nitrate reducers
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Tribe Echerichia -- name the genera |
Genus Escherichia coli Genus Shigella
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Tribe Klebsielleae -- name the genera |
Genus Serratia Genus Klebsiella Genus Enterobacter Genus Hafnia |
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Tribe Salmonelleae -- name the genera |
Genus Salmonella |
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Tribe Citrobacteriaceae -- name the genera |
Genus Citrobacter |
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Tribe Proteeae -- name the genera |
Genus Proteus Genus Providencia Genus Morganella |
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Tribe Yersinieae -- name the genera |
Genus Yersinia |
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Tribe Edwardsielleae -- name the genera |
Genus Edwardsiella |
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Name the Enterobacteriaceae lactose fermenters |
E. coli Klebsiella (mucoid) Enterobacter (mucoid) possibly Citrobacter |
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Name the Enterobacteriaceae that produce H2S |
Proteus sp Salmonella sp Citrobacter freundii possibly Edwardsiella tarda |
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Name the non motile Enterobacteriaceae |
Shigella Klebsiella Y. entercolitica @ 35C |
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Name the Enterobacteriaceae that are deaminase positive |
Tribe Proteeae
i.e. Proteus sp Providencia sp Morganella sp |
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Name the Enterobacteriaceae that are Gelatinase and DNase positive |
Serratia mercascens |
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list the IMViC results for E. coli, Klebsiella, and Enterobacter |
E. coli + + - - Klebsiella - - + + Enterobacter - - + + |
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What types of infections do E. coli species cause? |
Urinary tract infections - most common cause of all UTI and kidney infections
Septicemia & Meningitis - especially in neonates
Gastroenteritis |
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Name the types of gastroenteritis caused by E. coli |
EPEC - Enteropathogenic.
ETEC - Enterotoxigenic.
EIEC - Enteroinvasive.
EHEC - Enterohemorrhagic.
EAEC - Enteroaggregative.
DAEC - Diffusely adherent. |
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Describe the pathology of enterohemorrhagic (EHEC) E. coli |
Caused by E. coli O157:H7 and others.
Shiga toxin binds to endothelial cells, causes inflammatory response. Macrophages/neutrophils damage endothelium. Water diarrhea progesses to blood diarrhea. No WBCs found in stool. Associated with TTP and HUS. |
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EPEC |
Enteropathogenic E. coli. Common in young children, outbreaks in nurseries and daycares, stool has mucous but not blood |
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ETEC |
Enterotoxigenic E. coli. "Traveler's Diarrhea." Watery diarrhea, no blood, self-limiting. |
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EIEC |
Enteroinvasive E. coli. Invasion and destruction of intestinal mucosa. Watery diarrhea with blood. |
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EAEC |
Enteroaggregative E. coli. Watery diarrhea caused by bacterial adherence to mucosal surface. May persist for more than 2 weeks. |
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DAEC |
Diffusely adherent E. coli. Associated with UTIs and diarrhea, esp. in children and pregnant women. |
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Describe typical Klebsiella species colony morphology |
Colonies are typically mucoid due to presence of capsule |
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Describe typical Proteus species colony morphology |
Swarming colonies on non-inhibitory media--wavelike spreading across the surface of agar
Swarming is inhibited on MAC, EMB |
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What infections are caused by Salmonella species? |
Causes enteric fever and varying degrees of gastroenteritis.
Enteric fever = caused by Salmonella serotype Typhi and serotype Paratyphi
Gastroenteritis = caused by Salmonella enteritica |
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What are potential sources for Salmonella? |
Ingestion of contaminated food
Handling of pets (cold-blooded animals)
Asymptomatic carriers who harbor the infection in their gall bladder and shed the organism in their feces |
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Describe the pathology of enteric fever caused by Salmonella |
Organism invades intestinal mucosa, gains entrance to lymphatic system and bloodstream. Phagocytized by PMNs and are released into the blood stream. Finally, they invade the gall bladder and other parts of the intestinal tract.
Develops 9-14 days after ingestion of contaminated food or water |
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Describe the pathology of gastroenteritis caused by Salmonella |
Occurs 8 to 36 hours after ingestion Vomiting, nausea, diarrhea NO invasion of blood stream Self-limiting in healthy individuals (antibiotics/antidiarrheal agents can prolong carrier state) |
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Describe the infections caused by Yersinia species |
Yersinia pestis - causes The Plague
Yersinia entercolitica - causes acute gastroenteritis with fever and headache |
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What are the types of plague? |
Bubonic - swelling of lymphnodes, vector is rat flea (Man is accidental host)
Pneumonic - secondary to bubonic infection, organisms multiply in bloodstream and respiratory tract, can be transmitted person to person
Septicemic - bloodstream infection w/out buboes |
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What are the three type of antigenic determinants used for serological identification of Enterobacteriaceae? |
O antigen - produced by all bacteria, lipopolysaccharide, heat stable, somatic antigen of the cell wall
K antigen - surrounds cell wall, covers O antigen, heat labile, produced by some organisms, polysaccharide (is the "Vi" antigen in Salmonella typhi). If O antigen testing shows no results the K antigen may be covering it. Boil organism for 30 minutes to destroy K antigen.
H antigen - flagellar antigen on bacteria that possess flagella, heat labile |
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Describe the infections caused by Shigella species |
Causes dysentery aka shigellosis Includes bloody stools, mucous, and numerous WBCs Humans are only known reservoir - oral/fecal transmission Usually self-limiting and confined to GI tract Takes fewer than 200 bacilli for infection in healthy individuals |
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Name the four serotypes of Shigella |
Shigella dysenteriae (Group A) (most severe) Shigella flexneri (Group B) Shigella boydii (Group C) Shigella sonnei (Group D) (least severe) |
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Which types of media inhibit Enterobacteriaceae? |
CNA agar - selects for GPC Mannitol Salt agar - selects for Staph species |
