Bacterial recolonization of hospital sink biofilms

Abstract

Background: Hospital sink drains are known reservoirs for many pathogens that cause healthcare-associated infections (HAIs). Drain bacteria can migrate up to the drain cover and then spread to surrounding surfaces and patients through droplet dispersal during sink use. Therefore, cleaning sink surfaces represents a key intervention strategy to limit transmission between drains and patients. Aims: In this study, we aimed to: (1) characterize microbial community taxonomy and abundance in sink components and (2) evaluate the kinetics and sources of bacterial recolonization onto sink surfaces after cleaning. Methods: Drainpipes, drain covers, sink basins, drinking water, and p-trap liquid from hospital sinks in New Haven, CT, USA were sampled before and after intervention surface cleaning/disinfection (N = 251). Bacterial abundance and taxonomy were assessed via culture counts, digital droplet PCR, MALDI-ToF, and 16S rRNA gene amplicon sequencing. Findings: Drain biofilms had median bacterial abundance of 1.80 × 108 16S rRNA gene copies/cm2 and 2.06 × 106 cfu/cm2, which correlated with bacterial abundance on sink surfaces. Hallway sinks, which were used more frequently than patient room sinks, had higher bacterial abundance. Drain microbial communities largely consisted of novosphingobium and sphingobium, with detection of acinetobacter, pseudomonas, legionella, and stenotrophomonas. Sink surfaces had abundant mycobacterium, methylobacterium–methylorubrum, and sphingobium, as well as genera common to skin microbiomes (e.g., corynebacterium, staphylococcus, streptococcus). Immediately after cleaning/disinfection, culturable bacteria were generally undetectable on drain covers; bacterial gene copies were reduced but rebounded to over 80% of pre-cleaning levels within 24 h. After seven days, 9.2% of recolonizing bacteria were derived from drains, and 15.7% were from tap water. Conclusion: This study contributes to our understanding of factors that influence pathogen abundance on hospital sink surfaces and limitations of routine cleaning and disinfection.