(Enterobacteriaceae) Tribe Yersineae – Flashcards
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| Tribe Yersineae |
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| Yersinial infections are zoonotic infections that usually affect rodents, small animals and birds. Humans are accidental hosts. Gr |
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| Important characteristics of Yersineae |
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| Gram neg coccobacillary rod, but not true "straight" bipolar staining rod MR: Positive VP: Negative Motile at 22 degrees Celsius, but not at 35 degrees Celsius Urea: Positive (rapid) |
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| Clinically important Yersineae spp. |
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| Y. pestis Y. enterocolitica Y. pseudotuberculosis |
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| Yersina pestis |
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| Cause of the plague Organisms are endemic in rodent populations in Southeast Asia and in the Southwestern U.S. Transmission is by rodent flea or respiratory aerosols from infected humans |
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| Yersinia pestis cell wall produces an endotoxin that |
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| Produces multiple organ failure which leads to death |
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| Septicemia of Yersinia pestis |
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| Dissemination of bubonic form into the bloodstream. Large amounts of organisms are found in blood be transmitted by transfusions |
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| Pneumonic plague |
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| Caused by Yersinia pestis. It is the most serious form and is highly contagios, spread via respiratory droplets and rapidly fatal if left untreated. Can be treated using streptomycin |
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| Lab identification of Yersinia pestis |
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| Specimens: Aspirates from buboes, lmyph nodes and respiratory specimens Biochemiccaly inert, need to be sent to the reference lab for ID. Rarely seen in the US. |
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| Yersinia enterocolitica |
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| Production of heat stable enterotoxin that causes diarrhea. May mimic appendicitis and cause septicemia and peritonitis Transmitted through animal reservoirs (birds, pigs, cows) and contact with infected animals. It can also be seen in raw milk, water and other food sources. |
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| Yersinia enterocolitica organisms can survive what? |
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| Pasteurization and multiply at 4 degrees Celsius |
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| Yersinia enterocolitica lab identification |
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| Done only on request KOH broth (reduces the amount of NF. Place specimen in broth for 4-5 mins and transfer to CIN agar) Incubate at 22 degrees Celsius for 48 hours. Colonies on CIN will be dark pink with translucent borders |
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| CIN agar |
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| Cefsulodin, irgasin, novobiocin: reduces NF Mannitol: Carbohydrate source Neutral red: pH indicator |
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| Yersinia pseudotuberculosis |
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| Primarily a disease of rodents and birds More common in Europe than the US Causes a penumonia-like illness that mimics TB in disease presentation; however organisms are not related at all |
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| Differentiation between Yersinia pestis and Yersinia enterocolitica |
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| Motility: Enterocolitica is positive for motility at 25 degrees Celsius while Pestis is not ONPG: Enterocolitica is positive and pestis is negative Urea: Enterocolitica is positive and pestis is negative Ornithine: Enterocolitica is positive and pestis is negative Sucrose: Enterocolitica is positive and pestis is negative |
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| What is the only genus in the Tribe Citrobactereae |
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| Only genus is Citrobacter |
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| What are the clinically significant species of the Citrobacter genus? |
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| Citrobacter freundii Citrobacter koseri (formerly c. diversus) Citrobacter amalonaticus |
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| Key biochemicals of the Citrobacter genus |
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| MR: Positive VP: Negative Citrate: Positive Motility: Positive ONPG: Positive Lysine decarboxylase: Negative |
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| Citrobacter spp |
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| Found in soil/water NF of stool Opportunistic pathogen Causes UTI's, pneumonia and septicemia |
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| Colonial morphology of Citrobacter spp |
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| BAP: Large, wet, mucoid colonies MAC: Pink colonies "donuts" C. freundii looks like E. coli) XLD: Yellow colonies (C. freundii is H2S positive yellow colonies with black centers) |
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| Citrobacter freundii |
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| Resistant to antibiotic therapy. Resistant to ampiciliin and cefazolin H2S: Positive (May be initially confused with Salmonella spp in stool culture, but Salmonella spp is H2S positive and lactose negative) Indole: Negative Ornithine decarboxylase: Negative |
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| Citrobacter koseri |
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| Indole: Positive Malonate: Positive Adonitol: Positive |
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| Citrobacter amalonaticus |
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| Indole: Positive Malonate: Negative |
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| Tribe Escherichiae includes what generas? |
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| Eschericia spp Shigella spp |
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| Key biochemicals of Escherichiae |
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| PAD: Negative Urea: Negative MR: Positive VP: Negative H2S: Negative Citrate: Negative |
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| Escherichia spp. |
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| Only 1 clinically significant species: E. coli NF of stool Most common cause of community-acquired UTI's (esp. females) Also causes wound infections, pneumonia, septicemia and meningitis |
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| E. coli is usually not considered a pathogen if isolated from stool. However, there are some what? |
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| Extremely virulent strains that may cause intestinal disease |
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| Enteropathogenic E. coli (EPEC) |
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| Causes diarrhea, esp in infants Disease is caused by toxin Toxin production is carried on a plasmid which may be transferred to other organisms |
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| Enterotoxigenic E. coli (ETEC) |
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| Causes profucse, watery diarrhea Resembles cholera Due to production of enterotoxin Also known as "Traveler's diarrhea" |
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| Enteroinvasive E. coli (Alkalens-dispar) |
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| Causes dysentery-like illness similar to Shigella Stool contains increased WBC's, RBC's and mucus |
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| Hemorrhagic colitis (E. coli O 157:H7) |
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| Causes severe diarrhea with bloody stools Undercooked ground beef (and other foods) are a source Can cause hemolytic uremic syndrome (HUS) MAC with sorbitol: clear colonies (E. coli O 157:H7 is sorbitol negative) |
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| Escherichia coli colonial morphology |
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| MAC: 95% are rapid lactose fermenters; pink "donuts" BAP: Large, wet, gray, Beta-hemolytic colonies (most) XLD: Yellow colonies EMB: Green colonies with metallic sheen |
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| Key biochemicals for Escherichia coli |
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| Donuts on MAC Indole: Postive ONPG: Positive MR: Positive VP: Negative Citrate: Negative Sensitive to most antibiotics (Except ampicillin, SXT) |
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| Shigella spp. |
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| Always considered a pathogen Causes bacillary dysentery (severe ab cramps with blood and mucus in stools) Organism does not penetrate past the intestinal mucosa Rarely causes extra-intestinal infections unlike Salmonells app. |
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| Shigellosis |
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| Production of a heat stable enterotoxin (Shigatoxin) |
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| More Shigella spp facts |
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| No animal reservoir Infection is obtained through fecal oral route (usually water) Organism can survive temperature and pH extremes (stomach acids) |
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| Shigella spp are highly infectious. Infection occurs with how many organisms? How long is the incubation period? |
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| Infection can occur with as little as 50-100 orgnaisms Inc. period is 36-72 hours |
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| Shigella colonial morphology |
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| BAP: Large, wet, gray colonies MAC: Clear colonies XLD: Clear colonies |
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| Key biochemical characteristics of Shigella spp |
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| ONPG: Negative Motility: Negative MR: Positive VP: Negative H2S: Negative PAD: Negative Mannitol: Positive (except S. dysenteriae) |
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| Serological identification of Shigella spp |
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| Antisera available for all 4 types ("o" antigen) Organisms may need to ne boiled for 10-15 mins to remove the "k" antigen |
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| Clinically significant Shigella spp. |
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| S. dysenteriae (serogroup A) S. flexneri (Serogroup B) S. boydii (Serogroup C) S. sonnei (Serogroup D) 80% of all US isolates |
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| Clinically important features of Shigella spp |
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| Always considered pathogen Very low inoculum needed Non-motile |
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| Tribe Edwardsielleae contains only one genus with three clinically significant species |
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| Edwardsiella spp Edwardsiella tarda Edwardsiella hoshinae Edward ictaluri |
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| Edwardsiella spp resembles E. coli, but is different how? |
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| Edwardsiella is H2S positive and lactose negative |
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| How can Edwardsiella spp be pathogenic |
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| Natiral reservoir occurs in reptiles and freshwater fish May be a cause of diarrhea Seen in wound infections associated with trauma related to aquatic accidents |
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| Edwardsiella tarda key biochemicals |
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| H2S: Positive MR: Positive VP: Negative Indole: Positive Motility: Positive Lysine: Positive Ornithine: Positive TSI: K/A H2S ONPG: Negative |
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| Edwardsiella colonial morphology |
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| MAC: Clear colonies |
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| Edwardsiellaeae habitat |
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| Natural reservoir occur in reptiles and freshwater fish. Seen in wound infections associated trauma related to aquatic accidents |
