[In vitro susceptibilities of clinical isolates of Staphylococcus aureus]

In vitro susceptibilities of 350 strains of Staphylococcus aureus to ampicillin (ABPC), methicillin (DMPPC), cloxacillin (MCIPC), cefazolin (CEZ), cefmetazole (CMZ), cefmenoxime (CMX), latamoxef (LMOX) and 5 non-beta-lactam antimicrobial agents were determined according to the standard method of Japan Society of Chemotherapy. Frequencies of the appearance of resistant organisms (MIC greater than or equal to 12.5 micrograms/ml) to beta-lactam antibiotics were 45% for ABPC, 27% for DMPPC, 11% for MCIPC, 24% for CEZ, 15% for CMZ, 36% for CMX and 51% for LMOX. To non-beta-lactam antimicrobial agents, resistant strains appeared at 31% to gentamicin, 15% to amikacin, 0.6% to minocycline (MINO), 1% to norfloxacin (NFLX) and 65% to fosfomycin (FOM). More than 80% of DMPPC-resistant strains were also resistant to LMOX, CMX, ABPC, FOM, and CEZ, but most of those were susceptible to MINO and NFLX. Incidence of DMPPC-CEZ resistant S. aureus was 23% of the 350 strains tested. As stated above, multiply resistant strains of S. aureus are present throughout different hospitals in Okinawa.