I know we can use McConkeys Agar for gram -ve bacteria, however due to some reasons the only agar available at the moment is TSA. I am working on Acinetobacter and there were times when I have noticed the growth of lactobacillus. That is why I am eager to know if we can modify TSA in such a way that it supports the growth of gram -ve bacteria only? I also have MHA and BHI available, can we make them selective as well?
Try using an antibiotic that only targets gram positive bacteria (eg. beta-lactams or vancomycin).
The reason that MacConkey is selective for gram negative is the use of bile salts and crystal violet. So in theory you could add those two agents to your media (in other words make a TSA based version of MacConkey). the suggestion of Robert Adolf Brinzer is also good. I think most gram - are fairly tolerant to vancomycin. However I would not suggest beta-lactams, those are still quite inhibitory to gram - bugs but just at higher concentrations in general.
Trypticase soy agar, Formula may be adjusted and/or supplemented as required to meet performance specifications.
TSA is often the base medium for other types of agar. For example, blood agar (GS) plates are made by enriching TSA plates with defibrinated sheep blood, and chocolate agar is made by additional.
You can add bile salts. and crystal violet for Gram-negative bacilli
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