ABSTRACT

       Typing of bacteria is an important part of epidemiological studies on nosocomial infections. Bacterial identification methods have dramatically improved in recent years, which is mainly due to advancements in the field of molecular biotechnology. In many cases, molecular techniques have replaced phenotypic typing methods.

Currently, a wide range of bacterial typing techniques is used that are different from one another in the aspects of study objectives, costs, reliability and discriminatory power. None of the typing methods can achieve all desired objectives of a study alone.

Different typing methods are used for various purposes including: 1. confirmation of epidemiological relationships in spread of an infection, 2. providing epidemiological hypotheses about epidemiological relationships between bacteria in the absence of epidemiological data, 3. describing the distribution of bacterial types and identification of affecting factors. Inferences of epidemiological studies depend on the chosen typing technique and objectives of the study.

Therefore, the typing technique can be useful and effective in increasing our understanding of the pathogenesis, transmission and prevention of possible diseases. The aim of this study was to evaluate various methods of molecular typing of bacteria and to compare these methods from different aspects.

      

ABSTRACT
       Background and Objective: 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.
        Methods: 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.
      Results: 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.
      Conclusion: 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.
       Keywords: Klebsiella Pneumoniae, Qnr protein, Borujerd.