Newest data on fluoroquinolone resistance mechanism of isolates in Jiangsu Province of China.

Background: To determine the prevalence, antimicrobial susceptibility patterns and related presence of mutations in quinolone resistance-determining region (QRDR) genes and plasmid-mediated quinolone resistance (PMQR) among isolates obtained from Jiangsu Province, China.

Methods: A total of 400  clinical isolates collected during 2012-2015 were identified by biochemical and serological methods, and the antimicrobial susceptibility pattern was evaluated using the disc-diffusion method. PCR and DNA sequencing were accomplished to identify mutations in , , and , and the presence of , , , , , and genes were also detected.

Results: Of all the , 75.8% were resistant to nalidixic acid, and 37.0% were categorized as norfloxacin resistant. Overall, 75.5% of isolates possessed mutations (Ser83Leu, Asp87Gly/Asn and His211Tyr), while 84.3% had mutations (Ser80Ile, Ala81Pho, Gln91His and Ser129Pro). The most prevalent point mutations in and were Ser83Leu (75.5%, 302/400) and Ser80Ile (74.5%, 298/400), relatively. Besides, the Gln517Arg alternation in was detected in 13  isolates and no mutations were identified in . PMQR determinations of , and were detected among 16 strains (4.0%).

Conclusions: The results presented here show that fluoroquinolone resistance in these clinical isolates result from mutations in chromosome, besides, despite the low prevalence of PMQR determinants in Jiangsu, it is essential to continue surveillance PMQR determinants in this area.