The Frequency of qnr Genes in Extended-Spectrum β-lactamases and non-ESBLs Klebsiella pneumoniae Species Isolated from Patients in Mashhad, Iran

Since the fluoroquinolones are the broad-spectrum antibiotics, they affect both Gram-negative and Gram-positive bacteria. These antibiotics are widely prescribed by physicians. As a result, some bacteria, especially Enterobacteriaceae, have shown a resistance to this family of antibiotics. The current study aimed at detecting the frequency of qnrA, qnrB, and qnrS genes, novel plasmid-mediated quinolone-resistance genes, among extended-spectrum β-lactamases (ESBL)-positive and ESBL-negative Klebsiella pneumoniae isolates.
One hundred and thirty isolates of K. pneumoniae were collected from Imam Reza Hospital and its associated clinics from May 2011 to July 2012. The isolates were tested for ESBLs by the conventional methods. Polymerase chain reaction (PCR) was performed to amplify qnr A, B, and S.
Thirty-eight (29.3%) isolates were ciprofloxacin-resistant. Among 130 K. pneumoniae infectious isolates, 56 (43%) were capable of producing ESBL; 10.8% (n=14), 15.4% (n=20), and 20.8% (n=27) of ESBL-producing K. pneumonia were positive for qnrA, qnrS, and qnrB, respectively, and 13.8% (n=18) of the isolates harbored 2 or 3 qnr genes.
The results of the current study showed that quinolone-resistance genes were more frequent in ESBL-producing K. pneumoniae (37.5%) isolates, compared with the ESBL-negative isolates (20.89%). The prevalence of qnr genes was high in K. pneumoniae isolates, with higher frequency in ESBL-positive strains. Most of the isolates were positive for all 3 groups of qnr genes and the qnrB was the most common one.