Bacteria Can Spread From Sink Drains to Surrounding Areas

By Will Boggs MD

March 07, 2017

NEW YORK (Reuters Health) - Bacteria colonizing hospital sink P-traps can be spread to sink strainers and basins and surrounding countertops, researchers report.

"The waste water end of sinks should be considered as a possible reservoir when investigating transmission chains of hospital-acquired multidrug-resistant pathogens in patients,” Dr. Amy J. Mathers from University of Virginia Health System, Charlottesville, Virginia told Reuters Health by email.

Numerous reports have linked pathogens found in sink traps to those found in patients, but there has been little work to understand the microscale transmission dynamics.

Dr. Mathers and colleagues used a designated handwashing sink lab gallery to model dispersion of green fluorescent protein-expressing E. coli from sink wastewater to the surrounding environment.

Seven days after inoculation of one P-trap with the bacteria, all sink P-traps in the sink gallery were colonized with the bacteria, the authors reported online February 24th in Applied and Environmental Microbiology.

After adding a nutrient regimen to each sink for an additional seven days, the bacteria were also detected in the strainers of two sinks.

Fluorescent microspheres inoculated four inches below the strainer did not disperse to the sink basin or surrounding countertop when the faucet was run, but there was dispersion when the sink bowl was coated with the microspheres.

With higher water flow rates and backup of water over the strainer, dispersal was detected on the sink bowl.

Dispersion of fluorescent bacteria was much more extensive when the strainer was allowed to be colonized prior to the dispersion experiment.

“How to remedy the issue remains unclear,” Dr. Mathers said. “Because there are biofilms involved in a location where it is physically difficult to remove them (inside a drain pipe which is often physically inaccessible in hospital sinks), chemical interventions alone usually have only had a temporary effect. This is because the organisms remain deep in the biofilm and the bleach may only be able to access and kill bacteria in the top layer.”

Dr. Ines Zollner-Schwetz from Medical University of Graz, Austria has reported on contaminated handwashing sinks as the source of a clonal outbreak of Klebsiella oxytoca on a hematology ward. She told Reuters Health by email, "The findings are an important step forward in understanding the way bacteria spread from sinks to patients."

"The transmission of bacteria between sinks via a common pipe and the role of the biofilm produced by bacteria are the most interesting findings of this manuscript," she said.

Dr. Christoph Fusch from McMaster University, Hamilton, Ontario, Canada, who has studied self-disinfecting sink drains as a way to reduce the Pseudomonas aeruginosa bioburden in a neonatal intensive care unit, told Reuters Health by email, "These findings confirm previous reports about the risk that standard sinks add to the incidence of nosocomial infections."

His advice: "Raise awareness; reduce number of sinks; make sure that faucets are at the center of drainage; and use siphon disinfectors."


Appl Environ Microbiol 2017.


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