Resistance Levels and rpoBGene Mutations among In Vitro-Selected Rifampin-Resistant Mycobacterium tuberculosisMutants

ABSTRACTThe distribution and resistance levels of 189 in vitro-selected rifampin-resistant Mycobacterium tuberculosismutants of Beijing and other genotypes were determined. Apart from a higher amount of codon 522 point mutations and large deletions, a spread of mutations similar to that reported for clinical isolates was seen. Most mutations were correlated with high-level resistance; a lower level, or a MIC of <16 mg/liter, was associated with codon 522 mutations. Multiple mutations were detected in two Beijing mutants.