Molecular Studies on Fluoroquinolone Resistant Mycoplasma gallisepticum Isolates From Broiler Flocks

Abstract

Mycoplasma gallisepticum ( MG ) is considered the most important pathogenic species causing avian Mycoplasmosis. It is sensitive to antimicrobials whose action sites are other than the bacterial cell wall, such as tetracyclines, macrolides and quinolones. Resistance to fluoroquinolones is mainly due to chromosomal mutations in quinolone resistant determinig regions (QRDRs) of genes encoding the subunits of the drug’s target enzymes, DNA gyrase and topoisomerase IV, which are essential for DNA replication. Our study designed for determination of minimum inhibitory concentration (MIC) of fluoroquinolones against 15 field isolates by the broth microdilution method also molecular detection of MG virulence gene (mgc2 gene) and mutation in QRDRs of Egyption fluoroquinolones resistant MG field isolates. Our results showed that two MG isolates were resistant to both veterinary-use and human-use fluoroquinolones. In addition, nucleotide sequence analysis revealed mutations in QRDR of gyr B ( Ser-437→Leu and Asp- 549→ Asn ).