Clonal dissemination of carbapenem-resistant Klebsiella pneumoniae in outpatients as fecal-carriages: predominance of the high-risk clone ST231.

BACKGROUND: Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a critical threat to public health due to its ability to accumulate multidrug-resistance (MDR) and to spread silently via gastrointestinal carriage. While hospital-associated CRKP has been well documented, little is known about its prevalence and clonal dynamics among outpatients. METHODS: In this cross-sectional study, 300 stool samples were collected from outpatients without any gastrointestinal symptoms from April to September 2023. K. pneumoniae isolates were recovered on imipenem-supplemented MacConkey agar and identified by biochemical testing. Antimicrobial susceptibility was determined by disk diffusion and broth microdilution tests. ESBLs and predominant carbapenemase genes were detected by PCR. Clonal relatedness was evaluated by PCR-based ompK36 typing and multi-locus sequence typing (MLST). RESULTS: Forty K. pneumoniae isolates (13.3% carriage rate) were obtained, of which 45% considered as CRKP, while over 50% exhibited MDR profiles. ESBLs and carbapenemase genes were prevalent as follows: blaSHV (87.5%), blaTEM (55%), blaCTX-M-15 (37.5%), blaNDM-1 (22.5%), blaOXA-48 (27.5%), and blaKPC-2 (0%). An elevated imipenem minimum inhibitory concentration (MIC) > 128 µg/mL was observed. The ompK36 group D variants, which are associated with this high level of resistance, predominated (30%). MLST identified ST231 as the sole lineage among OXA-48 and NDM-1 producers. CONCLUSION: Fecal carriage of CRKP among outpatients is both common and driven by highly resistant, high-risk clones-most notably ST231-underscoring the emergence of community reservoirs. Integrated One Health surveillance, expanded antimicrobial stewardship beyond hospitals, and targeted infection control measures are urgently needed to curb dissemination of CRKP.