Surveillance of Escherichia coli and Klebsiella spp. in hospital sink drains

Enterobacterales includes important human pathogens causing a wide spectrum of clinical disease. In healthcare settings, sinks and other wastewater sites have been shown to be reservoirs of antimicrobial-resistant *E. coli* and *Klebsiella* spp., particularly in the context of outbreaks of resistant strains amongst patients. Without focusing exclusively on resistance markers or a clinical outbreak, we demonstrate that many hospital sink drains are abundantly and persistently colonised with diverse populations of *E. coli*, *Klebsiella pneumoniae* and *Klebsiella oxytoca*, including both antimicrobial-resistant and susceptible strains. Using whole genome sequencing (WGS) of cultured isolates, we show that environmental bacterial populations are largely structured by ward and sink, with only a handful of lineages, such as *E. coli* ST635, being widely distributed, suggesting different prevailing ecologies which may vary as a result of different inputs and selection pressures. Using metagenomics from 20 sink-timepoints, we show that sinks also harbour many clinically relevant antimicrobial resistance genes. Our study reinforces the potential role of sinks in contributing to Enterobacterales infection and antimicrobial resistance in hospital patients, something that could be amenable to intervention.