Molecular characteristics of ofloxacin mono-resistant Mycobacterium tuberculosis isolates from new and previously treated tuberculosis patients.

BACKGROUND

Ofloxacin (OFX) resistant Mycobacterium tuberculosis (MTB) isolates have been increasingly observed and are a major concern in recent years. This study investigated the genetic mutations associated with OFX resistance among clinical OFX mono-resistant MTB isolates from new and previously treated tuberculosis patients.

METHODS

A total of 50 unrelated OFX mono-resistant MTB isolates were analyzed. For all isolates, the quinolone resistance determining regions of gyrA and gyrB were PCR amplified and sequenced.

RESULTS

Single mutations in the quinolone resistance determining regions of gyrA (positions D94A, G, N, and Y; A90V; and S91P) and gyrB (positions T539A and E540D) were observed in 62% (31/50) and 4% (2/50) of all OFX mono-resistant isolates, respectively. No differences were detected between the proportions of isolates with mutations in gyrA/gyrB from new and previously treated tuberculosis patients (P=.820).

CONCLUSIONS

Although mutations in gyrB were rare, they were as important as mutations in gyrA in predicting OFX resistance in MTB in Tianjin, China.