In-vitro activity of linezolid and other antimicrobial agents against methicillin resistant staphylococci

ABSTRACT

To evaluate the in-vitro activities of linezolid, vancomycin, ciprofloxacin, gentamicin, amikacin, trimethoprim and fusidic acid, against methicillin resistant isolates. Three hundred and twenty two non-duplicate archived Staphylococcal isolates recovered from routine cultures performed in the microbiology laboratory from wounds, and abscesses swabs, urine, blood, pus, derived from both in- and out patients were tested. A total of 274 S. aureus and 76 CNS clinical isolates were included in the study, 46.7% were MRSA and 21% methicillin resistant CNS [MRCNS]. None of the strains was found to be resistant to linezolid and vancomycin. The resistance rates of MRSA isolates to antibiotics were as follows 86% to gentamicin, 84.3% to fusidic acid, 80% to trimethoprim, 78.2% to ciprofloxacin and 76.5% to amikacin. Similar trend were also obtained for MRCNS isolates. The majority [70%] of MRSA isolates were resistant to all used classes of antibiotics in the study, while only 4.3% were sensitive to such antimicrobial agents. Due to the high prevalence of multi-drug resistant MRSA, this study has provided valuable baseline information to clinicians regarding the benefit of linezolid, suggesting that it can be used as an alternative drug in such severe life threatening infections caused by MRSA, especially if the side effect of vancomycin was observed