Objective: To determine the most sensitive and feasible method for surveillance of the hospital aquatic environment for detection of carbapenemase-producing Enterobacterales (CPE) and extended-spectrum β-lactamase-producing Enterobacterales (ESBLE).

Methods: This study focused on hospital sink P-traps and toilets, comparing the yield of liquid collection with swabbing for sampling. Additionally, sample processing by direct culturing on selective media was compared with culturing following overnight enrichment. Bacterial species were identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry, and the production of ESBLE or CPE was confirmed using phenotypic or immunochromogenic methods.

Results: In total, 32 sink P-traps and 20 toilets were sampled in two wards of a university hospital. The different sampling techniques (liquid collection and filtering, swabbing) and processing methods (without or with cefotaxime, temocillin/imipenem enrichment) were applied, separately for ESBLE and CPE detection, for all sinks and toilets, resulting in 520 samples. Of the 32 sink P-traps sampled, 21 (65.6%) were positive for ESBLE and eight were positive for CPE (25.0%) with at least one of the sample methods. Of the 20 toilets sampled, 10 (50.0%) were ESBLE positive and nine (45.0%) were CPE positive. For sink P-traps, swabbing and liquid collection showed comparable results. Although enrichment only led to a marginal increase in detection sensitivity, it facilitated the subsequent microbiological analysis. For toilets, water collection was more sensitive than rim swabbing.

Conclusion: These results suggest that swabbing of sink P-traps and water collection from toilets, combined with enrichment, are the most suitable methods for the detection of multi-drug-resistant pathogens in the hospital aquatic environment.