Vancomycin-resistant enterococci (VRE) have emerged as important nosocomial pathogens in the past two decades all over the world and have seriously limited the choices available to clinicians for treating infections caused by these agents. Methicillin-resistant Staphylococcus aureus, perhaps the most notorious among the nosocomial pathogens, was till recently susceptible to vancomycin and the other glycopeptides. Emergence of vancomycin nonsusceptible strains of S. aureus has led to a worrisome scenario where the options available for treating serious infections due to these organisms are very limited and not well evaluated. Vancomycin resistance in clinically significant isolates of coagulase-negative staphylococci is also on the rise in many setups. This paper aims to highlight the genetic basis of vancomycin resistance in Enterococcus species and S. aureus. It also focuses on important considerations in detection of vancomycin resistance in these gram-positive bacteria. The problem of glycopeptide resistance in clinical isolates of coagulase-negative staphylococci and the phenomenon of vancomycin tolerance seen in some strains of Streptococcus pneumoniae has also been discussed. Finally, therapeutic options available and being developed against these pathogens have also found a mention. 1. Introduction Vancomycin was the first glycopeptide antibiotic to be discovered as early as 1950 [1]. However, its toxicity profile and the availability of less toxic alternatives like the beta-lactams made its use for gram-positive infections quite rare. It was only after the large-scale emergence and spread of methicillin-resistant S. aureus (MRSA) strains and extensive beta-lactam resistance that this agent gained prominence. And it was not until 30 years later that the first clinical isolates with reduced susceptibility to vancomycin were described. Vancomycin resistance was first described in isolates of Staphylococcus epidermidis [1]. Vancomycin resistance in enterococci was first described in Europe in the late 1980s and spread to much of the developing world. The first isolate of S. aureus with reduced susceptibility to vancomycin was reported from Japan in 1997 and had a vancomycin MIC in the intermediate susceptibility range [2]. Although primary vancomycin resistance has been described in many bacterial species like Erysipelothrix rhusopathiae, Lactococcus, Pediococcus, Lactobacillus, and so forth, which are intrinsically resistant to the glycopeptide, the current paper focusses on the problem of acquired glycopeptide resistance in gram-positive cocci. 2.
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