Phenotypic and genotypic characterization of carbapenemase-producing Klebsiella pneumoniae clinical isolates in Bushehr province, Iran

The growing spread of carbapenemase-producing Klebsiella pneumoniae (CPK) poses a worldwide threat due to the swift spread of mobile genetic elements containing carbapenemase genes, limited options for treatment, and high mortality rates. The aim of this study was to detect and characterize CPK using phenotypic and genotypic methods. A total of 151 K. pneumoniae clinical isolates were collected from hospitals in Bushehr province. The modified carbapenem inactivation method (mCIM), EDTA-modified carbapenem inactivation method (eCIM), and OXA-48 disk test were used for phenotypic confirmation of carbapenemase production. The resistance genes, including bla(KPC), bla(NDM), bla(OXA-48), bla(IMP), bla(VIM), and bla(GES), were detected by PCR, followed by sequencing. Antimicrobial susceptibilities revealed colistin as the most effective of all tested antimicrobial agents. Totally 12 (7.94%) CPK were identified. PCR results indicated that bla(NDM-1) and bla(OXA-48) genes accounted for 11(91.6%) and 4 (33.3%) of carbapenemase-producing isolates, respectively. It is notable that the coexistence of bla(NDM) and bla(OXA-48) genes was seen in 3 (25%) isolates. Given coexistence situations, our results highlighted that the priority of eCIM was the recognition of metallo-beta-lactamases, and OXA-48 disk test revealed high specificity to recognize bla(OXA-48) gene. Therefore, there is no single phenotypic test considered to be suitable for all situations, and indeed to distinguish diverse types of carbapenemase, the genotypic method is by far the best and most precise. Our findings underscore the emergence of K. pneumoniae coharboring bla(NDM-1) and bla(OXA-48) and emphasize the need for thorough observation and precautions.