Susceptibility pattern of methicillin resistant staphylococcus aureus to vancomycin and other alternate agents: Report from a private sector hospital laboratory

With increasing prevalence of methicillin resistant Staphylococcus aureus in clinical settings and injudicious use of antibiotics, resistance among MRSA against commonly used antibiotics is increasing. To assess the susceptibility pattern of MRSA against vancomycin, linezolid, tigecycline, rifampicin, fosfomycin fusidic acid, clindamycin, trimethoprim-sulfamethoxazole and teicoplanin, minimum inhibitory concentrations (MICs) for given antimicrobials were performed on 234 MRSA clinical isolates using automated VITEK 2 system. Vancomycin, linezolid, rifampicin, clindamycin, cotrimoxazole and teicoplanin susceptibilities were interpreted according to CLSI breakpoints, while tigecycline, fosfomycin and fusidic acid were interpreted according to BSAC breakpoints. All isolates were found susceptible to vancomycin, tigecycline, teicoplanin and linezolid. Non-susceptibility of the isolates for rifampicin, fusidic acid and fosfomycin was noted for 58(25%). Cotrimoxazole and clindamycin were found less susceptible showing high resistance rates of 61.5% and 42.3%, respectively. Vancomycin resistance was not found, however an increased MIC of 1 μg/ml was observed in about 25% of clinical strains. Increase in vancomycin MICs in MRSA is of concern and alternative antimicrobial options must be evaluated and considered for treatment of MRSA infections. Continuous antimicrobial surveillance is needed to monitor resistance patterns and detect possible emergence of vancomycin non-susceptible isolates.