Disinfection of hospital sink drains enriches pseudomonadota and efflux pump-mediated antibiotic resistance in reestablished biofilms.

Antimicrobial resistant pathogens and associated infections represent major public health threats affecting healthcare facilities, with sink drain biofilms serving as reservoirs for many of these bacteria. Despite attempts at sink drain biofilm disinfection and removal, drain biofilms inevitably regrow, and disinfection may shape the returning microbial communities and their resistance profiles. We applied culture-based and metagenomic approaches to study these drain disinfection effects on microbial community abundance, taxonomy, and antimicrobial resistance in operational hospital sinks. Drain biofilms regrew to baseline densities in approximately four days. Regrown biofilms contained more viable carbapenem-resistant bacteria and were dominated by Pseudomonadota, including Cupriavidus and Pseudomonas. Long-read sequencing revealed an increase in multidrug efflux pump genes after disinfection, which confer broad resistance to antibiotics and disinfectants. This work provides mechanistic insights into how disinfection influences sink drain biofilm ecology and the enrichment of antimicrobial resistance, with implications for infection prevention strategies in healthcare environments.