Abstract

Objective: To investigate plasmid-mediated resistance mechanisms and clonal spread in colistin-resistant Klebsiella pneumoniae isolates obtained from a tertiary-care hospital in Türkiye.

Methods: Between October 2017 and August 2020, 2567 K. pneumoniae isolates were screened for colistin resistance. Isolates identified as resistant by automated systems were confirmed by broth microdilution. Multiplex polymerase chain reaction (PCR) was used to detect mcr-1 to mcr-5 genes, and molecular typing was performed using arbitrarily primed PCR (AP-PCR).

Results: Of 2567 isolates, 44 were identified as colistin-resistant, and 41 were confirmed by broth microdilution. The MIC₉₀ and MIC₅₀ values were 64 µg/mL and 16 µg/mL, respectively. No mcr genes were detected. AP-PCR identified two genotypes; genotype 1 was predominant (90%), suggesting clonal spread. Most isolates were obtained from intensive care units.

Conclusion: Although plasmid-mediated resistance was not detected, genotypic clustering suggests clonal spread and possible horizontal transmission. These findings highlight the need for routine molecular surveillance and effective infection control measures.

Keywords: Klebsiella pneumoniae, colistin resistance, mcr genes, AP-PCR, clonal dissemination, molecular epidemiology