Charcterization of Type II Topoisomerase Gene Mutations in Clinical Isolates of Mycoplasma Hominis Resistant to Fluoroquinolones

Objective: To analyze type Ⅱ topoisomerase genes inclinical isolates of fluoroquinolone-resistant Mycoplasmahominis. Methods: Eight isolates of M.hominis cross resistant to 6fluoroquinolones were selected from 103 clinical strains ofM.hominis using a broth microdilution method. Type IItopoisomerase genes were amplified by PCR and directlysequenced. Nucleotide sequences were compared to sequencesfrom a susceptible strain (M.hominis PG2I). Results: MICs of resistant Mh isolates were 4- to 512-fold higher than MICs from the susceptible reference strain.Sequence comparison revealed a C to T change at 113nt ingyrA QRDR led to the substitution of Ser83 by Leucine and noamino acid change in gyrB. A change of G to T at 134nt inparC QRDR led to the substitution of Ser80 by Isoleucine anda G to A change at 70nt in parE QRDR led to the substitutionof Aspartic acid by Asparagine. Conclusion: These results suggest that a C to T change atll3nt in gyrA, a G to T change at 134nt in parC and a G to Achange at 70nt in patrE are associated with fluoroquinoloneresistance of M.hominis.