​Increasing reports have linked colonized sink traps to nosocomial infections, but the mechanism of transmission has been unclear. The authors of an article in Applied and Environmental Microbiology have identified a mechanism by which multidrug-resistant pathogens from the P-trap of sink drains can grow upward to contaminate the sink strainer, which can then result in droplet contamination of the surrounding areas when the faucet is used. P-traps are integral components of sinks that provide a water barrier to prevent sewage gases from drifting upward; this retained water creates favorable conditions for antibiotic-resistant microorganisms to survive and develop resistant biofilms. Researchers describe a detailed methodology carried out in a gallery of sinks set up to mimic hospital handwashing sinks. Green fluorescent protein (GFP)-expressing Escherichia coli placed in P-traps and subjected to intermittent water exposure were sustained for 14 days but did not grow or move upward toward the sink strainer. However, when researchers promoted colonization with a nutrient regimen designed to mimic their observations of items commonly disposed of in hospital sinks (e.g., intravenous fluids, feeding supplements, and leftover beverages), a GFP-E. coli-containing putative biofilm extended upwards, reaching the sink strainer in seven days. Droplet contamination from the sink strainer then reached surfaces including the sink bowl and plates, faucets, faucet handles, and counter areas near the faucets. Researchers also identified contamination of adjacent P-traps (i.e., sink-to-sink transmission of E. coli) that occurred with only time and water—not requiring provision of nutrients. They called this finding "key" for illustrating that "premise plumbing may be a more continuous system with shared microbiology rather than a single isolated sink."

HRC Recommends: Risk managers may wish to share the study findings and methods with leaders from environmental health and facilities management as well as infection control specialists to determine how findings may apply to the organization. Because it focused on bacterial growth in handwashing sinks, this study is also a good reminder of the critical importance of effective hand hygiene on patient safety. Strategies to promote hand hygiene include establishing a multidisciplinary team, measuring compliance and assessing the organization's hand hygiene program, determining reasons for noncompliance, implementing multimodal strategies, providing ongoing training, educating patients and visitors, and giving feedback to healthcare workers on hand hygiene performance.