Antimicrobial susceptibility and prevalence of extended-spectrum beta-lactamases in clinical strains of Klebsiella pneumoniae isolated from pediatric and adult patients of two Polish hospitals.

Klebsiella pneumoniae due to the presence of multiple antibiotic resistance mechanisms is one of the most threatening human pathogens nowadays. The aim of the study was to characterize antimicrobial susceptibility, presence of resistance mechanisms and the prevalence of selected genes encoding ESBLs in 170 K. pneumoniae isolates recovered from children and adults hospitalized in two Polish medical centers from 2008 to 2015. The phenotypic identification of strains was confirmed by amplification of mdh gene. ESBLs, metallo-beta- lactamases, Klebsiella pneumoniae carbapenemases and OXA-48 were detected using phenotypic tests. The blaCTX-M-1, blaTEM and blaSHV ESBL genes were amplified by PCR. Pediatric K. pneumoniae isolates displayed significantly higher resistance to piperacillin/tazobactam, cefoxitin, imipenem, amikacin and ciprofloxacin than strains obtained from adults (P<0.05). The presence of ESBLs, OXA-48, KPC and MBL was confirmed in 80.6%, 21.8%, 8.2% and 2.4%, respectively, of the tested strains. The CTX-M-1 enzymes were predominant (91.2%), followed by TEM (63.5%) and SHV (11.8%). The blaTEM was significantly more common in adults than in children (P<0.05). Dual or triple bla genes were observed in 55.9% and 8.2% of K. pneumoniae isolates. Further local epidemiological studies are required to monitor the dissemination of multidrug-resistant K. pneumoniae strains.