Antibiotic resistance and molecular characteristics of OXA-48-producing Klebsiella pneumoniae isolates from northeastern Poland

BACKGROUND: Resistance of Klebsiella pneumoniae to carbapenems is complex and involves the production of carbapenemases. Infections caused by carbapenemase-producing K. pneumoniae represent a significant public health concern due to the limited treatment options available. OBJECTIVES: The aim of the study was to identify OXA-48-like-producing K. pneumoniae isolates, characterize their multidrug resistance phenotypically and genetically, and classify them into appropriate sequence types (STs). MATERIAL AND METHODS: The study was conducted on 3 K. pneumoniae isolates producing OXA-48 carbapenemase obtained from patients hospitalized at the University Hospital of Bialystok, Poland. Identification and antimicrobial susceptibility testing were performed using the automated VITEK 2 system and the broth microdilution method for colistin. Screening for OXA-48 production was performed using a disc containing 30 μg of temocillin. Carbapenemase production was confirmed using the Carba NP test. The presence of the blaOXA-48 gene and genes encoding resistance to quinolones (qnrA, qnrB, qnrD, qnrS) and aminoglycosides (aac(3)-Ia, aac(6')-Ib, ant(4')-IIa, ant(2")-Ia, and aph(3")-Ib) was detected using polymerase chain reaction (PCR). The ST of the isolates was determined based on sequence analysis of conserved housekeeping genes (rpoB, gapA, mdh, pgi, phoE, infB, tonB). RESULTS: Analysis of antimicrobial susceptibility revealed that the tested strains were resistant to all tested β-lactam antibiotics and exhibited resistance to amikacin, gentamicin, ciprofloxacin, colistin, and trimethoprim-sulfamethoxazole. Polymerase chain reaction analysis revealed the presence of the aac(6')-Ib and aph(3")-Ib genes encoding aminoglycoside-modifying enzymes in all OXA-48-positive strains. Among the genes encoding quinolone resistance, qnrS was detected in all tested isolates. Multilocus sequence typing (MLST) revealed that 2 OXA-48-positive strains belonged to ST15, whereas 1 isolate belonged to ST2193. CONCLUSIONS: Two sequence types of K. pneumoniae, ST15 and ST2193, producing OXA-48 carbapenemase and exhibiting resistance to aminoglycosides and fluoroquinolones associated with the aac(6')-Ib, aph(3")-Ib, and qnrS genes, respectively, were identified.