What grows in the sink splash zone

The hospital sink drain microbiome can harbour opportunistic pathogens and antimicrobial resistance genes. Patients may be exposed to waterborne pathogens via water outlets and sink drains. We have previously shown that water from a clinical handwash basin can splash up to 2 m away from the sink/tap. Here we wanted to identify which organisms could be cultured from environmental sampling within the splash zone.

Queen Elizabeth Hospital Birmingham (QEHB) is a large UK tertiary centre. We placed an SAS Super 180 air sampler within the splash zone at approximately 1 m from a tap on a clinical handwash basin in the critical care unit and undertook sampling both with and without the tap running. All Gram-negative organisms were cultured and any carbapenemase producing Enterobacterales (CPE) isolated were sequenced.

Environmental sampling undertaken when the tap was running yielded a variety of organisms, with Gram-negative isolates including Citrobacter freundii, Enterobacter kobei, Enterobacter cloacae, Enterobacter asburiae, Pseudomonas aeruginosa and Sphingobacterium multivorum. Amongst these, we identified one CPE, C. freundii isolate QE-SINK-CF1, which carried a plasmid bearing the bla_KPC-2 gene. Structural variants of this plasmid have been involved in clinical infections at QEHB. Control sampling without the tap running yielded no Gram-negative organisms.

Here we show that a variety of Gram-negative micro-organisms, including CPE, can be cultured from within the 2-m sink splash zone. This latest work provides further evidence healthcare settings should consider splash zones and waterborne pathogen transmission risk.