Survey of healthcare-associated sink infrastructure, and sink trap antibiotic residues and biochemistry, in 29 UK hospitals.

Background: Hospital sinks are linked to healthcare-associated infections. Antibiotics and chemicals in sink traps can select for pathogens and antimicrobial resistance (AMR). Optimising sink design and usage can mitigate sink-to-patient dissemination of pathogens, but large-scale surveys of hospital sink infrastructure are lacking.

Methods: Twenty-nine UK hospitals submitted photos and metadata for sinks across three wards (ICU/medical/surgical; January-March 2023). Photos were used to classify sink design as "optimal" according to guidelines and published studies. Sink trap aspirates were dipstick-tested for antibiotics and chemistry. Logistic regression was used to characterise associations of ward type and sink location with optimal sink design or detectable trap antibiotics.

Results: Of 287 sinks surveyed 111 were in ICUs, 92 in medical wards and 84 in surgical wards; 77 were in medicines/drug preparation rooms, 97 on patient bays, 25 in patient side-rooms and 88 in sluice rooms. Sink-to-bed ratios ranged from 0.23-2.83 sinks/patient bed and were higher on ICUs (1.21 versus 0.82 and 0.84 on medical and surgical wards, respectively; p-value=0.04). The median sink-to-patient distance was 1.5m (IQR: 1.00-2.21m). Sink design varied widely; it was deemed "optimal" for 65/122 (53%) sinks in patient bays/side-rooms and "optimal" design was associated with side-room location (p-value=0.04). Antibiotics were detected in 95/287 (33%) sink traps and were associated with medicines/drug preparation rooms (p<0.001). Sink trap chemicals detected included metals, chlorine, and fluoride.

Conclusions: Sinks are common in hospitals, frequently close to patients, and often sub-optimally designed. Commonly used antibiotics were detected in a third of sink traps and may contribute to the selection of pathogens and AMR in these reservoirs, and subsequent transmission to patients.