(Part 2) Molecular characterization of Mycobacterium ulcerans DNA gyrase and identification of mutations reduced susceptibility to quinolones in vitro

Buruli ulcer disease (BU) is an emerging chronic ulcerating illness caused by the environmental mycobacterium, as Mycobacterium ulcerans (Mul), which primarily affects the skin, subcutaneous tissue, and occasionally bones. It is recognized by the WHO as a neglected tropical disease1). BU is gradually increasing with approximately 2,000 to 5,000 new annual reported cases2). However, the reasons for increases in the past few years have not been understood3). Recently, drug therapy against Mul has been administered through anti-mycobacterial antibiotics, including rifampicinbased combinations with either streptomycin, amikacin, or clarithromycin4). Early and non-severe stages of BU can be treated with an 8-week regimen of rifampicin (10 mg/kg orally, once daily) combined with clarithromycin (7.5 mg/kg per body weight, twice daily), streptomycin (15 mg/kg intramuscularly, once daily), fluoroquinolone (FQ) or other antibiotics. FQ is effective antibiotics against Mul in vitro and in vivo5). Evidence exists that DNA topoisomerase II is the therapeutic target of the drug. Remarkably, Mul expresses only DNA gyrase from a gyrB-gyrA contig in the complete genome and this enzyme is the sole target of FQs. However, the detailed molecular mechanism of Mul DNA gyrase and the mechanisms of FQ resistance were not determined. Our study aimed to determine the functional analysis of Mul DNA gyrase activities in vitro from Mul shinshuense and Agy99 strains. DNA gyrase subunits of both strains were Jpn J Lepr 91, 55-57(2022)