ABSTRACT
Infection caused by vancomycin resistant enterococci (VRE) leads to adverse outcome and is a real challenge. Despite increasing reports of VRE in different countries, there is scanty data on this issue from India. A total of 685 enterococci were isolated from various clinical samples from January to December 2004. Antimicrobial susceptibility was performed as prescribed by National Committee for Clinical Laboratory Standards (NCCLS). Vancomycin resistance was confirmed by minimum inhibitory concentration (MIC). Resistant phenotype was determined by Polymerase chain reaction (PCR). Of 685, 456 (67%) were E. faecalis and 229 (33%) were E. faecium. Resistance to various antibiotics in E. faecalis and E. faecium was as follows: ampicillin 33% and 54%, erythromycin 91% and 86%, ciprofloxacin 69% and 81%, tetracycline 50% and 54% and high level gentamicin resistance in 62% and 77% respectively. Vancomycin resistance was confirmed in 10 (1.4%) cases by MIC and all had Van A phenotype by PCR. Emergence of vancomycin resistant enterococci is of great concern because of its epidemic potential and scanty therapeutic options. Prompt diagnosis and efficient infection control measures can restrict its spread.
Subject(s)
Enterococcus faecalis/drug effects , Enterococcus faecium/drug effects , Gram-Positive Bacterial Infections/epidemiology , Vancomycin Resistance , Anti-Bacterial Agents/pharmacology , Bacterial Proteins/genetics , Carbon-Oxygen Ligases/genetics , Gram-Positive Bacterial Infections/microbiology , Humans , India/epidemiology , Microbial Sensitivity Tests/methods , Polymerase Chain Reaction , Vancomycin Resistance/geneticsABSTRACT
Detection of oxacillin resistance in coagulase-negative staphylococci (C-NS) by phenotypic methods is often difficult. The present study compared the National Committee for Clinical Laboratory Standards (NCCLS) revised guidelines of phenotypic methods with a mecA-based polymerase chain reaction (PCR) for C-NS. Ninety clinical C-NS isolates were tested for oxacillin resistance by disk diffusion (1-microg disk), minimum inhibitory concentration (MIC) breakpoint (0.5 microg/ml) after 24 h, and mecA-based PCR. The sensitivity and specificity of disk diffusion was 80% and 93%, and the sensitivity and specificity of the MIC breakpoint after 24 h was 84% and 91%, respectively, against PCR as gold standard. Eleven strains (7 mecA-positive and 4 mecA-negative) showed discordant results between MIC breakpoint after 24 h and PCR. Six of the 7 mecA-positive and all 4 mecA-negative discordant strains had inducible oxacillin resistance and beta-lactamase hyperproduction, respectively. The present study concludes that inducible oxacillin resistance and beta-lactamase hyperproduction are the major causes of discordant results between phenotypic methods and mecA-based PCR, and need special attention.
