Genetic Analysis of Fluoroquinolone Resistant Genes in Mycoplasma gallisepticum Field Isolates

Mycoplasma gallisepticum (MG) causes economic losses to poultry industry all over the world. This study aimed to investigate the emergence of fluoroquinolone (FQ) resistance in MG field isolates using sequence analysis of genes encoding the subunits of the drug’s target enzymes. The results showed that two MG isolates were resistant to fluoroquinolones. Amino acid mutations were recorded in gyrA at codons 59, 73, 157 and 174, gyrB at codons 415 in addition to Glu at 416 and ParC at codons 92 and 167. No mutations were observed in gyrE. Two-dimensional analyses illustrated that mutations in the resistant genes; gyrA, gyrB, and ParC were associated with alterations in the predicted protein structures of quinolone-resistance determining regions (QRDRs). These mutations were accompanied by elevation of minimum inhibitory concentration (MIC) profiles to FQ. It was concluded that the mutations in genes encoding DNA gyrase enzyme were the important causes for the appearance of FQ resistance MG isolates.