By J. Darrel Hicks, Contributing Writer

Hospital wastewater plumbing systems are large and complex with low-flow areas that allow stagnation and biofilm formation. The water in a hospital is designed never to freeze, with average water temperatures in the 70s, and this labyrinth of pipes provides warm, dark, moist areas that are perfect breeding grounds for bacteria. 

Hospital sink waste traps and drains are reservoirs for carbapenem-resistant enterobacteriaceae (CPE). Once CPE becomes established, contamination might not be confined to one sink and can spread through the wastewater plumbing system. Outbreaks of carbapenem-resistant organisms are commonly found in ICUs and immuno-compromised patients. But the acquisition of infection from sink drains might be more widespread among inpatients than previously thought. 

Sink drains have been identified as important reservoirs for 16 multi-drug-resistant Gram-negative bacteria. Bacteria form biofilms in pipes from which cells can be released during sink use and spread outside the drains in droplets or as aerosols. 

As a result, surfaces in the patient-care environment can become contaminated, which might lead to healthcare-associated infections (HAI) and outbreaks. Bacterial drain reservoirs are difficult to eradicate because commonly used hospital-grade disinfectants have no effect on these biofilms. 

Biofilm — collections of microorganisms — stick to each other and adhere to surfaces in moist environments, including the insides of pipes. It can last in drains for long periods and are often difficult or even impossible to remove. 

Pouring disinfectants into sinks has only a modest, transient effect because the disinfectants flow rapidly down the drain, failing to provide adequate contact time and penetration into areas harboring biofilm-associated bacteria, non-tuberculosis mycobacteria, non-fecal coliforms, fungi and protozoa. 

There are only three EPA-registered products with kill claims for bacteria in biofilm. Environmental services managers should select a disinfectant that eliminates all dangerous pathogens and those found in biofilm. 

Sodium dichloroisocyanurate (NaDCC) has the unique ability to be more powerful at destroying biofilm, bacteria, viruses and fungi like CPE yet is safer than those mentioned previously. Some NaDCC products have both biofilm and CPE claims while having a 0/0/0 hazard rating, neutral pH and the lowest EPA toxicity category IV. 

Tests of a foam application with a 3.13 percent hydrogen peroxide and 0.05 percent peracetic acid disinfectant suppressed sink drain colonization much longer than poured liquid disinfectants, due to its enhanced contact time and penetration into biofilm. The foam product is EPA-registered to kill pseudomonas aeruginosa and staphylococcus aureus biofilms with a five-minute contact time. But the optimal frequency of application is uncertain. Researchers proposed that a frequency of drain disinfection occur every three to five days to be effective. 

Long-term effects on plumbing pipes were undetermined and would need to be studied further. A reduction to 2 log10 CFU was deemed effective, but the level of reduction required to minimize the risk of dispersal — splashing — of organisms is uncertain. The cost of just the disinfectant for one treatment was estimated to be less than $2 not including labor. This application is labor intensive and depends on the manpower to apply the foam disinfectant regularly. 

J. Darrel Hicks, BA, MESRE, CHESP, Certificate of Mastery in Infection Prevention, is the past president of the Healthcare Surfaces Institute. Hicks is nationally recognized as a subject matter expert in infection prevention and control as it relates to cleaning. He is the owner and principal of Safe, Clean and Disinfected. His enterprise specializes in B2B consulting, webinar presentations, seminars and facility consulting services related to cleaning and disinfection. He can be reached at darrel@darrelhicks.com, or learn more at www.darrelhicks.com.