Detection of plasmid-mediated quinolone resistance determinants in clinical non-fermentative bacteria and ciprofloxacin sensitive Enterobacteriaceae strains

Objective To investigate the prevalence of three types of plasmid-mediated quinolone resistance (PMQR) determinants in clinical non-fermentative bacteria and ciprofloxacin. sensitive Enterobacteriaceae strains Methods Totally 600 clinical strains isolated from January 2008 to June 2013 were used in this study, including 419 non-fermentative bacteria strains and 181 Enterobacteriaceae strains sensitive to ciprofloxacin. The non-fermentative bacteria strains consisted of 130 strains of Acinetobacter baumannii complex, 100 strains of Pseudomonas aeruginosa, 80 strains of Burkholderia cepacia, 60 strains of Stenotrophomonas maltophilia, 25 strains of Elizabethkingia meningoseptica, 16 strains of Acinetobacter lwoffii and 8 strains of Chryseobacterium gleum. The Enterobacteriaceae strainss sensitive to ciprofloxacin included 69 strains of Enterobacter cloacae complex, 62 strains of Escherichia coli, 35 strains of Klebsiella pneumoniae and 15 strains of Citrobacter freundii. The qnrA,qnrB,qnrS,aac(6')-Ib and qepA genes were detected by PCR, and qnr gene type and aac(6')-Ib-cr were identified by DNA sequencing. Conjugation experiment was conducted to study the transmission of antimicrobial resistance. Results The qnr,aac(6')-Ib and qepA genes were not identified in 419 non-fermentative bacteria strains. The qepA gene was not identified in 181 Enterobacteriaceae strains. Four qnr-positive strains were detected among 181 Enterobacteriaceae strains, including 2 qnrA1-positive strains (1 Klebsiella pneumoniae strain and 1 Escherichia coli strain) and 2 qnrB4-positive strains (2 Enterobacter cloacae complex strains). 12 strains among 181 Enterobacteriaceae strains harbored aac(6')-Ib-cr gene, including 6 Escherichia coli strains, 3 Enterobacter cloacae complex strains and 3 Klebsiella strains. Conjugation experiments demonstrated that the antimicrobial determinants could be transferred to the recipient strains in 7 of 16 strains harboring qnr or aac(6')-Ib-cr gene. Conclusion In Enterobacteriaceae strains, the PMQR genes existed not only in clinical strains resistant to ciprofloxacin,but also in clinical strains sensitive to ciprofloxacin. The PMQR genes might not exist in non-fermentative bacteria stains in Wenzhou.