Glycopeptide and oxacillin activity against Staphylococcus aureus isolates at a tertiary care center in Lebanon

ABSTRACT

Worldwide reports have noted the emergence of glycopeptides-intermediate Staphylococcus aureus [GISA]. However, data from Lebanon is lacking. We conducted a study to determine the minimum inhibitory concentrations [MICs] for oxacillin [OXA], vancomycin [VAN] and teicoplanin [TEC] against consecutive clinical isolates of S. aureus at a tertiary care center in Lebanon. The categorization of isolates as susceptible, intermediately-resistant, or resistant was based on the OXA agar screen plate [OS] and the 1 /micro g OXA disk diffusion [OD] according to the National Committee for Clinical Laboratory Standards [NCCLS] guidelines. The MICs of OXA, VAN and TEC against these isolates were determined using the E-test. We tested 147 S. aureus isolates, 108 of which were methicillin-resistant [MRSA] and 39 methicillin-susceptible [MSSA]. The rar ges of MICS [micro g/ml] among MRSA and MSSA isolates respectively were OXA 1.5 >/= 256 and 0.19-3; VAN 1-3 and 1.5-3; TEC 0.094-3 and 0.19-2. The MIC50/90 [micro g/ml] for MRSA versus MSSA isolates were, respectively 24/ MRSA [around 38%], these strains remain fully susceptible to VAN and TEC. We did not detect any GISA at this tertiary care referral medical center in Lebanon