The drainome: longitudinal metagenomic characterization of wastewater from hospital ward sinks to characterize the microbiome and resistome and to assess the effects of decontamination interventions.

Background: Hospital drains and water interfaces are implicated in nosocomial transmission of pathogens. Metagenomics can assess the microbial composition and presence of antimicrobial resistance genes in drains ('the drainome') but studies applying these methods longitudinally and to assess infection control interventions are lacking.

Aim: To apply long-read metagenomics coupled with microbiological measurements to investigate the drainome and assess the effects of a peracetic-acid-containing decontamination product.

Methods: Twelve-week study in three phases: a baseline phase, an intervention phase of enhanced decontamination with peracetic acid, and a post-intervention phase. Five hospital sink drains on an intensive care unit were sampled twice weekly. Each sample had: (1) measurement of total viable count (TVC); (2) metagenomic analyses including (i) taxonomic classification of bacteria and fungi (ii), antibiotic resistance gene detection, (iii) plasmid identification; and (3) immunochromatographic detection of antimicrobial residues.

Findings: Overall TVCs remain unchanged in the intervention phase (+386 cfu/mL, SE 705, P = 0.59). There was a small but significant increase in the microbial diversity in the intervention phase (-0.07 in Simpson's index, SE 0.03, P = 0.007), which was not sustained post-intervention (-0.05, SE 0.03, P = 0.08). The intervention was associated with increased relative abundance of the Pseudomonas genus (18.3% to 40.5% (+22.2%), SE 5.7%, P < 0.001). Extended spectrum β-lactamases were found in all samples, with NDM-carbapenemase found in three drains in six samples. Antimicrobial residues were detected in a large proportion of samples (31/115, 27%), suggesting use of sinks for non-handwashing activities.

Conclusion: Metagenomics and other measurements can determine the composition of the drainome and assess the effectiveness of decontamination interventions.