Molecular Characterization of Drug Resistant Indigenous Methicillin Resistant Staphylococcus aureus (MRSA) Strains

Abstract

Methicillin resistant Staphylococcus aureus (MRSA) complicates therapy of critical infections in hospitalsand livestock animals, globally. MRSA strains have also been escalated in community. The worldwide dissemination of MRSA (Hospital and Community acquired MRSA, and Livestock and food confined MRSA) with persistently varying drug resistance phenotypes and genotypes, and emerging novel molecular types is progressively being explored. Such continually modifying strains challenge the current therapeutic options. Therefore, it is crucial to survey regularly the prevalence of MRSA resistance patterns and its molecular types. MRSA strains (n=100) collected from various hospitals and diagnostic laboratories of Karachi, and their drug resistance patterns and MICs were found out and presence of mecA gene was confirmed by PCR. Literature was gathered from PubMed, Medline, PakMedinet, Google scholar and web of science etc. to detect the ratio of MRSA in hospitals, community, and livestock in Pakistan. The HA-MRSA was found with highest ratios (76%) in Lahore and CA-MRSA (57%) were recorded in Islamabad.All HA-MRSA were 100% resistant to Penicillin, Methicillin and Ampicillin and 90% Oxacillin-resistant, 87% Cefoxitin-resistant, 84% Amoxicillin-clavulanate-resistant, 77% Tobramycin-resistant, 71% Erythromycin and Ciprofloxacin-resistant, and 67% Norfloxacin-resistant. Increased MICs of Vancomycin, Teicoplanin and Linezolid has been recorded. Resistance genes and molecular types (mecA, dfr(B), mecC,blaZ, gyrA, gyrB, grlA, grlB, ropB, aacA-aphD1, erm(A), erm(C), fos(A), vat(C), vat(B), tet(K), tet(M), agrI, agrII, agrIII, and SCCmec types; I, II, III, IV, and VI) have been reported in many HA-MRSA. Present study confirmed the presence of mecA gene in 96% of HA-MRSA.