Occurrence and persistence of carbapenem-resistant <i>Klebsiella pneumoniae</i> complex in urban rivers of the São Paulo metropolitan region

AIMS: Urban aquatic environments are increasingly recognized as important components in the persistence and dissemination of antimicrobial-resistant bacteria. This study investigated the occurrence, antimicrobial resistance profiles, and genomic characteristics of carbapenem-resistant Klebsiella pneumoniae complex isolated from urban rivers in São Caetano do Sul, part of the São Paulo Metropolitan Region, Brazil. METHODS AND RESULTS: Between October 2023 and October 2024, 39 surface water samples were collected from two urban streams and processed using selective culture, MALDI-TOF identification, antimicrobial susceptibility testing, and whole-genome sequencing. Among 144 K. pneumoniae complex isolates recovered, 43 (29.9%) were resistant to meropenem. All meropenem-resistant K. pneumoniae isolates carried the blaKPC gene, while one Klebsiella quasipneumoniae isolate harbored blaNDM. Multilocus sequence typing revealed high genetic diversity, with predominance of global disseminated high-risk lineages, including ST11 and ST258. The repeated detection of identical sequence types across different sampling sites and time points suggests environmental persistence within the urban river network. CONCLUSION: These findings demonstrate that urban surface waters act as reservoirs for clinically relevant carbapenem-resistant Klebsiella lineages, highlighting the importance of environmental surveillance as part of applied strategies to monitor antimicrobial resistance in urban settings.