Emergence of vancomycin resistant Staphylococcus aureus(VRSA) from a tertiary care hospital from northern part of India

Abstract

BACKGROUND: Glycopeptides such as vancomycin are frequently the antibiotics of choice for the treatment of infections caused by methicillin resistant Staphylococcus aureus (MRSA). For the last 7 years incidence of vancomycin intermediate S. aureus and vancomycin resistant S. aureus (VISA and VRSA respectively) has been increasing in various parts of the world. The present study was carried out to find out the presence of VISA and VRSA in the northern part of India. METHODS: A total 1681 staphylococcal isolates consisting of 783 S. aureus and 898 coagulase negative staphylococci (CoNS) were isolated from different clinical specimens from various outpatient departments and wards. All S. aureus and 93 CoNS were subjected to MIC testing (against vancomycin, teicolplanin and oxacillin); Brain Heart Infusion (BHI) vancomycin screen agar test; disc diffusion testing, and PCR for mecA, vanA and vanB genes detection. RESULTS: Out of 783 S. aureus two S. aureus strains were found to be vancomycin and teicoplanin resistant (one strain with MIC 32 microg/ml and the other strain with MIC 64 microg/ml); six strains of S. aureus have shown to be vancomycin intermediate (two strains with MIC 16 microg/ml and four strains with MIC 8 microg/ml); and two strains with teicoplanin intermediate (MIC 16 microg/ml). One CoNS strain was resistant to vancomycin and teicoplanin (MIC 32 microg/ml), and two CoNS strains were intermediate to vancomycin and teicoplanin (MIC 16 microg/ml). All VRSA, VISA and vancomycin resistant CoNS had shown growth on BHI vancomycin screen agar (vancomycin 6 microg/ml) and were mecA PCR positive. None of these isolates have demonstrated vanA/vanB gene by PCR. CONCLUSION: The present study reveals for the first time emergence of VISA/VRSA from this part of world and indicates the magnitude of antibiotic resistance in and around the study area. The major cause of this may be unawareness and indiscriminate use of broad-spectrum antibiotics.