In vitro activity of vancomycin and teicoplanin against coagulase negative staphylococci.

OBJECTIVES With the increase in nosocomial infections caused by coagulase negative staphylococci (CNS), laboratory diagnosis of CNS with reduced susceptibility to glycopeptides (vancomycin and teicoplanin) has become important. This study was designed to determine the glycopeptide susceptibility of clinical isolates of methicillin resistant coagulase negative staphylococci (MRCNS) at the department of microbiology, government medical college and hospital, Amritsar, India. METHODS A total of 250 CNS isolated from various clinical specimens were speciated and their methicillin resistance was detected by studying the minimum inhibitory concentration (MIC) of oxacillin by macrobroth dilution method. Glycopeptide susceptibility of 130 methicillin resistant strains obtained was determined for vancomycin by vancomycin screen agar test, MIC of vancomycin by macrobroth dilution/and E test. Teicoplanin susceptibility was determined using teicoplanin disc diffusion test and MIC was determined by macrobroth dilution method. RESULTS All the MRCNS isolates were found to be susceptible to vancomycin and teicoplanin. MIC of vancomycin ranged between ≤0.5 µg/ml to 1 µg/ml and of teicoplanin from ≤0.5 µg/ml to 2µg/ml. CONCLUSION Continuous monitoring of MIC of vancomycin in MRCNS is required to prevent the emergence of vancomycin resistance in these multidrug resistant organisms.