Conflicting results of Gram-Negative unknown

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Conflicting results of Gram-Negative unknown

Post by Jrh21854 » Sun Dec 01, 2013 8:25 pm

I think the major issue here is that the Hektoen Enteric agar is not on the flow chart that was provided. We were also not taught anything about it until the day unknows were distributed. My teacher did confirm that my results for the HE agar were negative meaning that it could not be of the Shigella family or the Samonella family. Shigella species is the only bacteria listed under non-motile. This means that something is either wrong with my HE results, which I doubt or there is something I'm not connecting about the pigment aspect of the flow chart and my conflicting UREASE AND CITRATE TESTS.

My interpretation of the results are listed below as well as a version of the flow chart my professor provided

ANY help would be appreciated. My Unknown papers are due tomorrow...

1. MacConkey Agar
*Negative for lactose fermentation
No color change in media (remained pink)

2. Eosin Methylene Blue agar
* Conflicted about results, believed to be negative
Pink growth with slight darkening around the edges

3. Hektoen Enteric agar
*CONFLICTED about results, believed to be negative for lactose fermentation
If this is the case then unknown cannot be of the Sigella or Samonella species
Flow chart and other results are leading to Shigella species so something is wrong
Green growth with salmon-colored colonies

4. TSI agar
*Negative for lactose fermentation
Red slant/Yellow butt
No sulfer reduction

5. Urea slant
*Conflicted about results; believed to be negative for urease production
Color change in media from peach to yellow

*The next step of the flow chart asks if the urease test is pigment positive or pigment negative...not quite sure what that means. Has never been discussed in lab

6. Indole test
No cherry red ring on top of liquid layer

7. Citrate test
Positive indicator would be color change of the media from green-ish blue to ROYAL blue
In before and after pictures there does not appear to be any color change and no growth on the slant

8. Motility test
*Negative for motility
No red spreading throughout media

FLOW CHART looks something like this

TSI SLANT (ALKALINE/ACID) = Lactose Negative

Sulfer reduction of TSI slant= Negative then must be Urease NEGATIVE
* I am sure the unknown is negative for sulfer reduction
*I am not sure of what the results of the Urease test are (leaning toward negative)

If urease-negative then is either PIGMENT-POSITIVE OR PIGMENT-NEGATIVE

If urease-negative then must be Indole-negative
*I am sure that the unknown is Indole-negative

Either Citrate-positive OR Citrate-negative

Either Motile or non motile
* I am sure that the unknown is non motile

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