Background and Aim :
Klebsiella pneumoniae being widely recognized as a nosocomial,multidrug-resistant and a heterogeneous pathogen which requires critical genetic characterizationto be discovered to provide more comprehensions about the characterization of this pathogen invarious infections. We aimed at to characterize ۱۲۴ ESBL producing, carbapenem and quinoloneresistant clinical K. pneumoniae isolates collected over a five year period, through serotyping,determination of virulence factors, antibiotic resistance testing, and enterobacterial repetitiveintergenic consensus-polymerase chain reaction (ERIC-PCR).Methods : All typical colonies of K.pneumoniae isolated were initially confirmed by PCR andtested for being hyper virulent phenotypically followed by antimicrobial susceptibility test. MICsof ciprofloxacin was determined by E-test. Multiplex PCR based screening was done for plasmidmediated quinolone resistance (PQMR), integrase genes and efflux pump genes. The Mast® D۶۸Ctest detected the presence of ESBLs and AmpCs phenotypically, and later presence of ESBL andAmpC genes was observed by PCR. Presence of carbapenemase genes were evaluated by PCR.Capsular serotyping and capsule-associated virulence genes were studied using the molecularmethod. All strains were fingerprinted by ERIC-PCR.Results : All K.pneumoniae isolates had a positivity for the internal transcribed spacer region (K.pneumoniae ۱۶S–۲۳S) confirming as K. pneumoniae. Of all isolates, ۵۹% were typeable. Majorityof isolates (۸۸.۹%) were resistant to cephalosprins while, ciprofloxacin and carbapenem resistancewas evident in ۴۱.۳% and ۲۴% strains respectively. ESBL production was observed in ۷۳%isolates. Frequency of qnrA, qnrB and qnrS was ۳.۷%, ۱۰.۵% and ۹.۷% respectively while ۴۷.۶%and ۴.۸% isolates were positive for aac(۶’)-Ib and ۴.۸% qepA respectively. Integron ۱ and ۲ andboth ۱ and ۲ were noticed in ۳۸.۱%, ۱۷.۵ and ۶.۳% respectively. We identified ۱۷ different ERICpatterns. Frequency of blaOXA-۴۸, blaKPC, blaNDM, blaVIM and blaIMP genes was found as۷۸.۸%, ۱۴.۷۵%, ۱۹.۶۷%, ۱۱.۴۷% and ۴.۹۱ respectively. Our study evidenced virulence-associatedgenes including, capsules, encoding lipopolysaccharides, regulators of hypermucoviscosity,adhesins, iron acquisition systems, enterobactin, allantoin metabolism and those which help toovercome innate host immunity.Conclusion : Our findings highlights the importance of surveillance of K. pneumoniae in clinicalinfections. The genetic surveillance is important in understanding the pathogenic characteristics ofK. pneumoniae isolates.