Prevalence of Plasmid-Mediated Quinolones Resistance among Klebsiella pneumoniae Strains Isolated from Hospitals in Borujerd, Iran

Klebsiella pneumoniae is one of the most common causes of bacterial infections. Presence of plasmid-mediated quinolone resistance genes causes low level of resistance in K. pneumoniae. This study investigated the prevalence of resistance to quinolones and fluoroquinolones, and the frequency of qnrA, qnrB and qnrS genes among K. pneumoniae strains.

The study was performed on 100 K. pneumoniae strains isolated from hospitals in city of Borujerd (Iran) during April to September 2014. Susceptibility of the isolates to nalidixic acid, ciprofloxacin, norfloxacin and ofloxacin was evaluated. Minimum inhibitory concentration (MIC) of ciprofloxacin was determined using ciprofloxacin Etest strips. Polymerase chain reaction was performed to detect qnrA, qnrB and qnrS genes in quinolone-resistant isolates using specific primers.

The results showed that 38% of the isolates were resistance to both nalidixic acid and ciprofloxacin. The prevalence of ofloxacin- and norfloxacin-resistant isolates was determined to be 18% and 15%, respectively. The MIC values for ciprofloxacin were ranging from 0.064 to ≥256 μg/ml. In addition, four ciprofloxacin-resistant isolates (10%) had MIC of ≥256 μg/ml. The qnrA gene was not detected in any of the quinolone-resistant isolates. Moreover, 23.6% (n=9) and 5.2% (n=2) of the quinolones-resistant isolates contained the qnrB and qnrS genes, respectively.

Although 38 isolates were ciprofloxacin-resistant, the qnrB, qnrS genes were detected in a small number of isolates. This indicates the involvement of factors other than the qnr genes in resistance of these isolates to quinolones.