Antibiotic sensitivity

[Jay Mone']

First, be careful;  the presence of a gram positive cocci does not 
mean that you are looking at S. aureus.  Not that it really matters 
though, since you merely want to kill the thing.
Depending on the source of the microbe, antibiotic sensitivity will 
differ.  Most hopspital-acquired Staphylococci are 
penicillin-resistant, and also display differing sensitivities against 
other beta-lactams.  However,. if the treating physician has not 
ordered an MIC, the best place to begin to do manual testing is to use 
Mueller-Hinton agar as the plate media.  Grow a broth culture from an 
isolated colony off of an MSA plate.  Standardize the turbidity to 
that of a 0.5 MacFarland standard, and try the follwing antibiotics:

Penicillin
Methicillin 
Ampicillin +sublactam or clavulonic acid
Vancomycin
Nafcillin
Oxacillin
Cefmandole or other cephalosporins