Background: Sink drains have been identified as a source of antimicrobial resistant organism (ARO) outbreaks in healthcare settings. AROs can colonize sink drains long-term, and these reservoirs can seed infections in patients. Despite this, there is currently no recommended protocol for sink drain hygiene. We sought to identify possible transmission links in a non-outbreak setting, and then tested the use of a hygiene intervention to reduce ARO presence in sink drains. 

Methods: In our first study, we sampled environmental surfaces including sink drains in two buildings; in one, we collected environmental swab samples from a stem cell transplant and oncology (SCT) ICU (old ICU) for its last month of operation. In the other, we collected environmental swab samples prior to patient move-in, and then across the first year of operation in a new SCT ICU (new ICU). Swabs were selectively cultured, and ARO isolates were subjected to whole-genome sequencing (WGS). We also collected remnant fecal samples and isolates from blood stream infections to identify strain sharing with environmental surfaces. In our second study, we later collected more environmental and clinical samples from the new ICU rooms while implementing a novel foamed-peracid based hygiene intervention at two cadences: 1x/week and 5x/week. We monitored changes in recovery of all microbial growth as well as changes in specific organisms and strains recovered.

Results: We found that sink drains housed the most ARO burden over other surfaces sampled. The most frequent AROs isolated were Pseudomonas aeruginosa and Stenotrophomonas maltophilia, and WGS analysis identified lineages of P. aeruginosa present in sink drains prior to patient move-in to the new ICU and patient infections, suggesting movement between the two sources. In the second study, we continued sampling of the new ICU surfaces, and confirmed continued sink drain carriage of several P. aeruginosa and S. maltophilia lineages across 4 years. After implementing the hygiene intervention, we found significant reductions in Gram negative bacterial growth of up to 85% in 5x/week rooms; reductions were not significant in 1x/week. However, we observed significant reductions in Pseudomonas spp. and Stenotrophomonas spp. at both intervention frequencies, and up to 100% and 95% in the 5x/week rooms, respectively. Following intervention periods, we observed new strains of P. aeruginosa replaced the old strains, while for S. maltophilia the old strains tended to return.

Conclusions: AROs for reservoirs in sink drains and can be associated with infections even in non-outbreak settings. There is a critical need for standardized hygiene interventions to reduce or eliminate these reservoirs to reduce risk to patients. A foamed-peracid based intervention may effectively reduce ARO burden, but further work is required to establish protocols. 

Learning Objectives:

1. Describe the role of hospital sink drains as long-term reservoirs for antimicrobial-resistant organisms (AROs) and their potential to contribute to patient infections.

2. Interpret whole-genome sequencing data and environmental sampling results to identify transmission links between sink drain AROs and clinical infections.

3. Evaluate the effectiveness of a foamed-peracid based hygiene intervention at different cleaning frequencies in reducing ARO burden in healthcare environments.