gyrA and parC genes mutations in quinolone-resistant clinical isolates of Pseudomonas aeruginosa / 中国药理学通报

ABSTRACT

Aim To study gyrA and parC mutations of clinical Pseudomonas aeruginosa strains. Methods MIC values of 55 clinical P.aeruginosa isolates were determined by agar dilution test and 1 sensitive strain and 8 resistant strains were selected with standard sensitive strain ATCC27853 as control, the quinolone determining region (QRDR) of the gyrA and parC genes were amplified by PCR, the lengths of PCR products were 351 bp and 397 bp. The gyrA PCR products(351 bp) were digested with enzyme sacⅡ. The gyrA and parC gene were sequenced. Results In this study, gyrA genes of all resistant strains had an ACC to ATC mutation in codon 83, leading to the amino acid substitution of an isoleucine for a threonine, and three high level resistant strains also showed a GAC to GGC mutation in codon 87, leading to the substitution of a glycine for an aspartic acid. In addition, four resistant strains also had an TCG to TTG mutation in codon 87 of parC gene, leading to the amino acid substitution of a serine for a leucine. The strains with both gyrA and parC mutations were two to sixteen times more resistant than the strains which had only gyrA mutations. At the same time, a silent mutation (CAC to CAT) in codon 132 of gyrA gene and a silent mutation(GCT to GCG) in codon 115 of parC gene occured, which did not lead to amino acid change. Conclusion The mutations of 83 and 87 codons of gyrA and the mutatations of 87 codon of parC gene were related to fluroquinolone resistance, and the mutations of the 83 codon of gyrA gene were more important.