S. aureus mannitol fermentation

[allawayr]

Long story short - Me and a friend are working on a college microbiology project involving the isolation of S. aureus from the environment. We're using a selective media (Chapman-stone agar) to isolate. Luckily, we did isolate a staphylococcus. We'd like to ID it - but at the current time it could be either S. aureus or S. epidermis. The difference between these two is mannitol fermentation. Unfortunately, we're out of bromocresol purple (the recommended indicator for this agar).

 

Does anyone have any recommendations for quick and dirty methods for determining lac fermentation? (we have no API strips avaliable). Also, our autoclave is broken (and we'd need professor supervision to use it anyway), and we don't have access to a huge array of stains/indicators. I did try using crystal violet - that did not go very well (I think it was too concentrated). Regardless, any suggestions would be extremely helpful.

 

Thanks!

 

-Rob

[Mr Skeptic]

I'd recommend not messing with microbiology with broken equipment

 

To see if fermentation occurred, you may be able to see gas bubbles forming, or acid or alcohol by products.

[allawayr]

Yeah...our autoclave was working at one point but no longer! Ideally there should be an acid byproduct (that would have been indicated by the bromocresol purple that we didn't have or the crystal violet- but that didn't work).

[Mr Skeptic]

Shouldn't any pH indicator for the appropriate pH range work?

[allawayr]

Ideally the crystal violet would have worked but it didn't. Apparently bromocresol purple changes between 5.2-6.8. Methyl red or azolitmin would work nicely but the bio department doesn't seem to have any. (Or at least our professor doesn't).