Clinical epidemiologists have long viewed hospital sink drains as potential reservoirs of pathogens (McBain et al., 2003). Numerous studies have identified Pseudomonas aeruginosa (Davane et al., 2014, Lalancette et al., 2017) and carbapenemase-producing Enterobacteriaceae (Kotsanas et al. 2013, De Geyter et al., 2017) as bacterial inhabitants of hospital sink drains. As further examinations of bacterial populations in sink drain occur around the globe, it appears that virtually any pathogen capable of causing a hospital-acquired infection (HAI) is likely to be found in the sink drains of any hospital.
Despite all these investigations of bacterial populations in drains, it was not initially clear how these reservoirs can contaminate the environment. What was clear, however, was that bacteria in drains are likely to contaminate the environment if they can “escape” the drain and reach the surrounding surfaces. In 2018, Kotay et al. demonstrated that bacteria from drains and traps disperse into the surrounding environment via droplets rather than via aerosol. In another study from 2017, Kotay et al. observed that droplets can contaminate surfaces around drain openings by up to a distance of 75 cm (30 inches). Linked together, these studies indicate that patient contamination from sink drain bacteria is not as direct as it appears. Sink use must produce droplets and sinks must have bacterial counts of over 105 CFU/mL to observe a contamination of the surrounding surfaces. Also in 2017, Kotay et al. demonstrated that Escherichia coli biofilm can migrate from the surface of the drain’s P-trap to the sink strainer at a rate of around 2 inches per day. In the same study, Kotay et al. showed that inoculation of the drain pipes 10 cm (4 inches) below the strainer does not seem to produce contaminated droplets on the surrounding counter.
Drains are unusual surfaces. They are heavily soiled, wet, hard to reach and used for high soil load discharge. Sanitizing drain pipes, therefore, cannot be approached in the same way as sanitizing other surfaces such as countertops, desks, and tables. The nature of the drain environment promotes the growth of biofilms. In some locations, biofilms are exposed to trace amounts of antibiotics and may develop resistance. In a healthcare setting, it is important to keep this breeding ground under control. Nutrients, water, and microbes are constantly being reintroduced in drains. It is therefore unrealistic to expect no bacterial contamination with a single treatment or a permanent log reduction with no further interventions.
Our approach is to view drain contamination from a risk management perspective. Based on the literature cited, if the draining treatment can sufficiently lower bacterial counts and if periodical treatments prevent bacterial migration (recolonization) from the P-trap to the strainer, then the risk of contaminating the surrounding surfaces will be both minimal and controllable.
In 2016, Stjärne Aspelund et al. examined the potential of using acetic acid as a decontamination method for sink drains. In 2017, Marchand et al. also compared the in vitro efficacy of various chemicals for killing bacteria in a biofilm and for removing the biofilm structure. In 2018, Marchand et al. presented the results of a new study showing the synergistic anti-biofilm effect of peracetic acid and a blend of selected surfactants. Peracetic acid is created by the reaction of acetic acid and hydrogen peroxide. Also in 2017, Marchand et al. demonstrated the efficacy of peracetic acid for killing Pseudomonas grown in a biofilm. Marchand et al., have performed numerous other studies to demonstrate the in vitro efficacy of Bioassure, a disinfectant that contains peracetic acid and a surfactant (unpublished data).
Our main objective is to determine if treatment with Bioassure, a DIN-registered disinfectant carrying a specific claim against biofilms, can lower the bacterial contamination in inner drain pipes and P-traps.
This study demonstrates the efficacy of Bioassure on inner drain pipe contamination. Results on P-trap contamination are also conclusive. In 2017, Kotay et al., mentioned that it takes a P-trap contamination of 5 logs or more for droplets from the drain to contaminate surrounding surfaces. In 2018, Kotay et al., demonstrated that bacteria can migrate quite quickly up the surface of an inner drain pipe and reach the strainer. Also in 2018, Kotay et al., demonstrated the when a strainer is contaminated, it can contaminate droplets emerging from the drain and contribute to the contamination of the surrounding areas. The results presented here show that following one complete Bioassure treatment, P-trap contamination drops significantly below 5 log and that Bioassure treatment significantly reduces contamination on the surface on the inner drain pipe, thereby limiting strainer contamination. These findings are encouraging and should support the use of Bioassure as an efficient method for controlling bacterial contamination in sink drains in a hospital setting.
André Côté
Assistant Director, Microbiology & Regulatory Affairs Sani Marc
For the methodology and results of the study, see our full scientific article: Field Study on the Efficacy of Bioassure Treatment at sanimarc.com/bioassure.
