Need URGENT help identifying unkown bacteria!

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Need URGENT help identifying unkown bacteria!

Post by graymonkey44 » Tue Aug 02, 2011 1:35 pm

So I'm in microbiology class and our last project we need to do is identify an unknown bacteria.

We inoculated 3 plates a Nutritional Agar plate, Blood Agar, and endo Agar.

The morphology was convex, more circular(mucoid on the blood agar), even margins, and a whitish/clear color.

In the nutrient broth, in a test tube, there was sediment, turbidity, the color was a yellowish/white, and was unsure of the pellicle. I thought there wasn't but I'm going to check again.

When I took a gram stain I found the following:

Cocci in clusters
Spores -
Motility +
Gram -
Acid fast -

The Biochemical results I got were:

Catalase +
Indole -
Methyl Red -
Voges-Proskauer -
Hydrogen Sulfide-
Nitrate Reduction +
In Phenol Red Glucose it produced an Acid and a gas
Phenol Red Sucrose Acid and gas
Phenol Red Lactose it was a slight dark orange- so I put negative

In the plates-
Endo agar- there was a lot of growth and a pinkish color, so that would further confirm that it's gram negative and the reddish color should make it Lactose positive. So there's conflicting results right there

Blood agar- A lot of growth as well, I believe it was Beta hemolytic.

Mannitol Salt tube- There was growth, but it was clear. Not yellow, so it couldn't ferment the mannitol

The Triple Sugar Iron tube showed A red slant and yellow on the bottom
Growth +
Gas production +
Multiple sugar fermentation - (Only showed glucose)
Hydrogen Sulfide - (No black)

Litmus MilkWas unsure of this, it was white in the whole test tube except for like half an inch space at the top where it was a purple color, similar what it original looks like) I wasn't really sure if there was a curd or not because it seemed like it was still liquid, but it was very thick.

Acid ?
Alkaline ?
Hard curd -
Soft curd ? I think it may have been a rennet curd
Reduction + due to the white color
Peptonization -

So this is where I'm completely lost. He has a list of bacteria that it could be and makes it a little easier by giving us a growth temperature, so we can easily divide them. Mine was between 25-30 degrees Celsius.

The only two that I could think of that are anywhere near my results would be either:

Neisseria subflava
Enterobacter aerogenes

The only conflicts i have with N. subflava is that it is Hydrogen sulfate postive, and I did 2 tests that show it is negative. I know it's capable of fermenting sucrose and glucose, but am unsure if it can make gas from it.

The conflict I have with E. aerogenes is that it is capable of fermenting Mannitol salt and it tests positive for the VP test. Also, it's more rod shaped than cocci so I am unsure of that. Also E. aerogenes is a slow fermenter of lactose, so that could explain the results of the Endo agar and the Phenol red results.

The only other thing I could think of is that my results were somehow contaminated because two people next to me weren't doing the correct aspetic technique. When they were inoculating their tubes, the wouldn't wait for their inoculating loop to cool all the way and just going right in the tube so it would make a hiss sound. So that could have created an aerosol and their bacteria could have gotten into my testing tubes.

I really need some help on this because I'm completely lost. Thanks for your time.

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Location: Vishakhapatnam, Andhra Pradesh, INDIA

Re: Need URGENT help identifying unkown bacteria!

Post by greatmicrobiologist » Thu Aug 25, 2011 11:01 am

your test got a conflict.
I was going through your results and from initial i was thinking of a Streptococcus sp
I will say that please do the IMViC test once more and streak it in Endo agar.

Are you sure about the Neisseria subflava
Enterobacter aerogenes

Can you do the Presumtive and Confirmed test?
Where from the cultures have been isolated must be facultative anaerobe as it can withstand the aseptic conditions you are into.

I am also confused with your results. So i want a review. Can you perform some of your tests again and post here?
Last edited by canalon on Thu Aug 25, 2011 2:32 pm, edited 1 time in total.
Reason: remove unecessarily long quote for clarity
Saumyadip Sarkar
Student of M.Sc. Microbiology,
GITAM Institute of Science,
GITAM University, AP, India

e-mail: [email protected]

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