Global transcriptional response to vancomycin in Mycobacterium tuberculosis

We characterized the variation of M. tuberculosis transcriptional profile in response to inhibitory and subhinibitory concentrations of vancomycin. Whole genome microarrays were employed to profile gene expression in M. tuberculosis H37Rv in response to inhibitory or subinibitory concentration of vancomycin. Inhibitory conditions were achieved by exposing bacteria to 400 µg/ml of vancomycin, a concentration exceeding 10 times the minimum inhibitory concentration (10X-MIC); in these conditions bacterial replication arrested rapidly without killing. Subhinibitory conditions were obtained growing the cells in the presence of 5 µg/ml of vancomycin (1/8-MIC) which allowed bacteria to grow with the same profile as untreated cells, although at a reduced rate. Following the addition of vancomycin at a concentartion 10X-MIC, the culture was incubated 1 h, or 4 hrs, and then analyzed to identify which genes were expressed differentially.