In vitro Quinolones Susceptibility Analysis of Chinese
Mycoplasma bovis Isolates and their Phylogenetic Scenarios based
upon QRDRs of DNA Topoisomerases Revealing a Unique Transition in
ParC
1State
Key Laboratory of Agriculture Microbiology, Huazhong Agriculture
University, Wuhan 430070, China; 2College of Veterinary
Medicine, Huazhong Agriculture University, Wuhan 430070, China;
3Department of Pathology, Faculty of Veterinary Science,
University of Agriculture, Faisalabad-38040, Pakistan; 4College
of Animal Science, Huazhong
Agriculture University, Wuhan 430070, China; 5Wuhan
Keqian Animal Biological Products Co Ltd, Wuhan 430070, China
*Corresponding author:
aizhen@mail.hzau.edu.cn
Abstract
Mycoplasma bovis can cause different systemic problems in cattle, and
recently has been resulted in huge economic losses in China. In vitro
susceptibilities of 26 twice sub-cultured Chinese M. bovis field isolates
were determined at physiological pH including PG45 through broth micro-dilution
method. Except Huanggang isolate, all isolates and PG45 were in the sensitive
range for levofloxacin, lomefloxacin and ciprofloxacin, whereas, for norfloxacin
and nalidixic acid, they had shown intermediate resistant and complete resistant
patterns, respectively. The multiple sequence analysis revealed point mutations
in QRDRs of gyrA and parC genes of Huanggang isolate resulting in
amino acid substitutions at positions 83 (S-F) in GyrA (E. coli
numbering) and 80 (S-I) in ParC proteins, the latter is reported for first time
in M. bovis. Conclusively, fluoroquinolones are the potential veterinary
therapeutic agents for mycoplasmosis in China and resistance to these agents
comes through point mutations in QRDRs of gyrA and parC genes with
ParC and GyrA mutation orientation.