Enterobacteriaceae Flashcards
how would you differentiate Aeromonas spp from other beta-hemolytic GNB that are cream-color on MAC such as Salmonella and Shigella (NLFs)?
Like Vibrio and Plesiomonas, Aeromonas is oxidase positive; Salmonella and Shigella are Enterobacteriaceae which are all oxidase negative; Also most clinically sig aeromonads are indole-positive
Name all the Enterobacteriaceae you can think of, differentiated into Lactose and Non-lactose fermenters
LFs: E. coli, Klebsiella, Enterobacter; Citrobacter +/- NLFs: Salmonella, Shigella, Morganella, Serratia, Yersinia, Edwardsiella, Proteus, and Providencia
What antigens are used to help ID strains of E. coli, especially when causing serious enteric disease?
The O and H antigens; (K antigen can mask the O antigen during agglutination testing
What tests helps differentiate E. coli from Klebsiella if the E. coli looks mucoid (it is usually dry) and is not causing beta hemolysis?
E. coli is indole positive; So is K. oxytoca though, so citrate can help, as well as motility: E. coli is motile, and is citrate negative in contrast to Klebsiella pneumo and oxytoca
DIff E. coli and Klebs based on MR and VP
E. coli is MR+, VP = Klebs are MR =, VP +
what biochemical test is positive in Enterobacter that helps diff it from Klebsiella, since they look much the same on MAC, are both VP and citrate +
Ornithine decarboxylase, Enterobacter usually produces/ is POS
How is Enterobacter cloacae differentiated from E. aerogenes?
E. cloacae is Lysine decarboxylase NEG and Arginine dihydrolase POS; E. aerogenes is the opposite think CA: lA, La (cloacae, lowercase l, upper A for no lysine, yes arginine, and vice versa for aerogenes
what 3 Enterobacteriaceae are phenylalanine deaminase positive?
Proteus, Providencia, and Morganella
How could you diff Edwardsiella from the also H2S positive Proteus, since both are also clear and colorless on MAC, motile, and Proteus can be indole positive if vulgaris spp?
Edwardsiella tarda is PAD negative and urease negative
How are Providencia rettgeri and Morganella biochemically different from Proteus? How are they diff from each other then?
H2S negative; Morganella is citrate negative!!
What Shigella spp is most common in the U.S. and how can it be distinguished from other Shigella?
Shigella sonnei. It is the only ONPG positive SHigella ( late lactose fermenter)
what is the most serious serotype of Shigella (why?) and how is it diff from the other serotypes biochemically?
Serotype A, has both enterotoxin and neurotoxin. It is mannitol negative in contrast to the other 3 serotypes, and of courses ONPG negative (which only sonnei is positive for)
The Typhi/ paratyphi Salmonella are what in regards to citrate vs the other (animal reservoir) Salmonellas?
citrate negative; those that cause the usual GI illness (enterica subspecies enterica serotype Choleraesuis? but not Typhi) but not enteric fevers are citrate positive
