Gram Positive Rods - Catalase Positive

[thurley999]

Hello I am doing a research presentation, and the whole idea round it all was to identify an unknown organism, which I still haven't been able to do. I swabbed this organism from a public bathroom sink handle, and need desperate help identifying it as soon as possible.

My results were:
Gram Positive Rods
Nitrate negative
Citrate negative
Catalase Positive +
Oxidase negative
Oxidation-Fermentation - no sugar metabolism
phenol red broth w/mannitol ---- -/-
phenol red broth w/detrose ------ A/-
Methyl Red negative
Voges-Proskauer Negative
SIM (Sulfur Reduction) negative
SIM (Indole Production) negative
SIM (motility) Positive +
Urease negative

and it seems my organism was a facultative anaerobe (i believe that's correct for growing best with O2, and still being able to grow without O2)


I've looked through Bergies Manual, but haven't had much luck figuring it out, if you could help me I would greatly appreciate it, thankyou.

[billw]

How long and how wide are they? Are spores present? Those will help to narrow down whether or not you have a Bacillus (looks likely). If it is a Bacillus, you are probably going to need to do a few more tests to decide on a probable species.

[thurley999]

actually I was thinking it was Bacillus Cereus based on my results, and it did have spores present to answer your questions. thanks for the reply.

[billw]

You have several tests that conflict with B. cereus (MR, VP, Citrate). Have you looked at B. sphaericus?

An amylase test would help with deciding on a Bacillus.

[thurley999]

Oh i didn't notice that thank you. I'm looking into B. sphaericus right now.

We didn't do the amylase test in my microlab, and unfortunately we had to get rid of our organisms, and rely only on the tests that we have already done. But i'll looking into your suggestion, thankyou.

[Punker]

Most Gram-positive bacilli encountered in clinical specimens represent normal flora which are contaminants, including members of the genera Bacillus, Lactobacillus, and Corynebacterium. Gram-positive rods which are potential pathogens are often identified by a stain other than the Gram stain (e.g., acid-fast stain for Mycobacterium and modified acid-fast stain for Nocardia). Listeria and Erysipelothrix are uncommon isolates whose identification relies on colony morphology and biochemistry, as discussed below.

On a direct Gram stain of a clinical specimen, Bacillus, Lactobacillus, and Corynebacterium all have distinctive, characteristic morphologies and arrangements so that in fact the genus designation is usually apparent from the Gram stain alone, although catalase testing of colonies is also very helpful (the anaerobic clostridia are or may be indistinguishable from Bacillus on Gram stain). However, all three of these genera contain numerous species and all demonstrate wide ranges of variation in microscopic morphology.
Read more: http://members.tripod.com/piece_de_resi ... s/mgpr.htm