Ecological dynamics of three persistent opportunistic pathogens in hospital sinks and their potential antagonistic bacteria

Sinks contaminated with opportunistic pathogens are a source of hospital-acquired infections, responsible for morbidity and mortality in neonatal intensive care units (NICUs). Understanding pathogen behavior in sinks is essential for preventing their spread. Only a few studies have examined how sink environments affect pathogen distribution through changes in drain microbiota. This research uses an integrative approach to study three major bacterial pathogens: <i>Pseudomonas aeruginosa</i>, <i>Stenotrophomonas maltophilia</i>, and <i>Serratia marcescens</i>. Sink drains in two NICUs were sampled during 2-month and 5-month periods. The diversity and abundance of opportunistic pathogens were determined at the genotypic level. Their occurrence was analyzed considering microbial communities, water parameters, faucet design, and sink usage. <i>P. aeruginosa</i>, <i>S. marcescens</i>, and <i>S. maltophilia</i> were found in 47%, 39%, and 67% of drain samples, respectively. Low genotype diversity was observed within sinks, with 1-3 genotypes per species/sample. Dominant genotypes persisted throughout the sampling periods, showing the persistence of opportunistic pathogen strains in drains. Quantification of the studied bacterial sequence types ranged from 10³ to 10⁷ DNA copies/mL. The heterogeneous spatial distribution of the three species between individual sink drains was primarily attributed to changes in community composition, chlorine concentrations, and faucet design. We isolated a strain of <i>Delftia tsuruhatensis</i> (Dt1S33), whose presence in the sink environment was negatively correlated with the three opportunistic pathogens. Dt1S33 reduced the capacity of the pathogens to form biofilms in laboratory co-cultures. These findings underscore the key roles of biotic and abiotic factors in the colonization of sink drains by pathogens.IMPORTANCEHospital sinks are critical reservoirs for opportunistic pathogens (OPs), increasing the risk of healthcare-associated infections, especially in vulnerable populations such as neonatal intensive care unit (NICU) patients. Our study found that 39%-67% of sink drains were persistently colonized by <i>Pseudomonas aeruginosa</i>, <i>Serratia marcescens</i>, and <i>Stenotrophomonas maltophilia</i>, with a limited number of genotypes dominating for months. Colonization patterns in drains varied between NICUs, mainly influenced by microbial community composition and sink design. Notably, <i>Delftia tsuruhatensis</i> presence was negatively correlated with OP colonization and inhibited OP biofilm formation <i>in vitro</i>. These results highlight the interplay of abiotic and biotic factors in sink colonization and suggest that antagonistic bacteria could help reduce pathogen persistence. Understanding these dynamics is crucial for developing targeted interventions to mitigate infection risks in high-risk hospital settings.