Vancomycin Mic Creep Among Methicillin-Resistant Staphylococcus aureus: A Report

Abstract

The objective of the study was to analyze the vancomycin MIC distribution against bloodstream MRSA isolates for a period of 1 year in India. This retrospective study analyzed 71 blood stream MRSA strains isolated at a tertiary care hospital in India between January 2008 and December 2008. The vancomycin MIC was determined by broth microdilution method. Only one isolate per patient was analyzed. The range of vanocmycin MIC for the 71 isolates in this study was varied between 0.25-3 µg mL-1. Only 29 isolates had MIC less than 1 µg mL-1 and 17 isolates MIC were more than 2 µg mL-1. In this study the phenomenon of vancomycin MIC creep was noticed in more than 75% of MRSA bloodstream isolates. We suggest further in vivo studies to determine the clinical significance of this MIC creep.