gyrA and gyrB mutations in ofloxacin-resistant Mycobacterium tuberculosis clinical isolates in Thailand

Abstract

In order to identify mutations in gyrA and gyrB genes in 92 ofloxacin-resistant Mycobacterium tuberculosis (OFX r -MTB) clinical isolates collected from Siriraj Hospital, Mahidol University and Chest Disease Institute, Thailand. The quinolone resistance-determining regions (QRDR) of gyrA and gyrB in all 92 OFX r -MTB isolates were amplified using polymerase chain reaction and sequenced. There were 70 isolates with point mutations associated with ofloxacin resistance. In gyrA QRDR, 69 isolates had mutations in gyrA Gly88 (Ala/(75), Ala90 (Val), Ser91 (Pro) and Asp94 (Gly/Ala/His/Asn), the latter being the most common (42%). Only one isolate was found with mutation at position Asp495 (Asn). The other 22 isolates had no mutations in both gyrA and gyrB QRDR. Thus, point mutations in gyrA and gyrB QRDR were responsible for OFX r -MTB clinical isolates in Thailand.