Bacteria Identification

[tina87]

Hi! I'm new to this forum and would greatly appreciate any help or advice on this topic!!! I'm currently in a microbiology lab course in college and we have to identify an unknown bacteria. I have performed a series of tests on my unknown and I really believe it is Salmonella. However, there is still some doubt because some of my results don't match typical Salmonella reactions. So I was wondering if someone could confirm my theory or if they could lead me to a helpful website because I have searched for hours trying to find everything! I just want to be 100% sure that I'm correctly identifying this bacteria.

 

Here are my test results:

 

Unknown Bacteria: bacillus with "rotten" smell

Gram Stain: (-)

Catalase Positive

Amylase Negative

Caseinase Negative

 

TSI agar slant: color of the butt changed to yellow

there was a black cluster at the bottom

there was also a bubble on the side of the tube

 

SCA agar slant: Citrate Negative

 

MacConkey Plate: agar changed to a brownish color

colonies were white/colorless

 

MSA Plate: no reaction

 

LevineEMB Plate: colonies were dark velvet with a metallic sheen

agar was still dark maroon color

 

Thioglycollate media: growth at top of tube (lots of turbidity)

pink tint disappeared

 

My main concern lies with the reaction on the LevineEMB Plate. The only bacteria I found that had that kind of reaction was E.coli. However, E.coli doesn't generate H2S (black cluster) in the TSI agar slant - so I'm very confused!

Could there possibly be another bacteria that I haven't found?

Any advice and/or help will be greatly appreciated!!!!

Thank You!!!!

[between_bean]

Hello, maybe you cross contaminated your agar plates during testing. You probably didnt but maybe you did? How many times did you test, were the results the same every time?

[zoidia]

From my notes it says in your TSI, if the butt turned yellow it means glucose was fermented. So its yellow and you said the it was negative for the Citrate tube, and left with a blue slant (not green which is positive) . So, if your Citrate remained blue it could be Enterobacter aerogenes. If it was green- e coli...

 

 

hope this helps