Correlating Minimum Inhibitory Concentrations of ofloxacin and moxifloxacin with gyrA mutations using the genotype MTBDRsl assay

MTB MICs were found to be consistently lower for MXF than for OFX among isolates with the same gyrA mutation (e.g. Ala90Val). The majority of MTB isolates containing mutations at Asp94Ala, Asn/Tyr, Gly and His in gyrA were associated with a moderate level of resistance to MXF (MIC = 2.5 μg/ml), although 3 isolates with the mutations Asp94Asn/Tyr/Gly were associated with a high level of resistance to both fluoroquinolones (MXF MICs = 5.0-8.0 μg/ml, OFX MICs = ≥10.0 μg/ml).