VeriZon wrote:
After doing the standard tests, I am getting vague results that I can't determine which organism is present. Does anyone know which of the following gram negative rods grow a pinkish color on nutrient agars and on the slant of a phenylalanine agar. I know definitively that it motile (SIM test) TSI was yellow butt with red slant, and kept getting citrate positive, (but lets ignore that one)I did all the other standard tests, but got results completely in between. If you want to know the results just ask. So I really need to know which of these usually grow pink on nutrient agars. The possibilities are
E.Coli
Pseudomonas aeroginosa
Citrobacter fruendii
Enterobacter aerogenes
Enterobacter cloacae
Klebsiella pneumoniae
Serratia marcescens
Proteus mirabilis
Proteus vulgaris
Proteus morganii
Thank you so much!
|
| bactitech
Forum Elite
Topics: 25
Posts: 492
|
First test you should ALWAYS do is an oxidase test. Oxidase positive will rule out Ps. aeruginosa on your list. Also, PSAE is not K/A on TSI. E. coli is citrate negative, oxidase negative, indole positive. Have you done indole testing? This should be done on a medium with tryptophane in it (blood agar) or your SIM tube (add indole reagent, read reaction on the top immediately).
If it is motile, that rules out Kleb. pneumoniae, which is nonmotile. Phenylalanine agar needs a reagent added to it. You do not read it by color on its slant. You must add ferric chloride to it. If it turns dark with ferric chloride (read immediately) you are in the Proteus/Morganella/Providencia group. Urea reaction is important with this group (did you do one of these?). Likewise, SIM agar should have indole reagent added to it for indole testing.
Verizon - I think you need to sit down with your reactions and go over basic micro 101 reactions here. You have not given enough information to key out this organism without the rest of your reactions.
ALWAYS do oxidase first. ALWAYS do an indole if it is oxidase negative. These two reactions will tell you LOTS about your bug. What is it's lactose reaction on MacConkey agar? Is it purple or pink (lactose fermenter)? Is it clear (nonlactose fermenter)? Oxidase reaction is very important with NLF's. Only one LF can give an oxidase positive reaction (Aeromonas).
Post some more reactions and perhaps we can help you better.
___________________
Clinical Microbiology since 1974
|
|
| |
| | | 
