What Cleaning Solution Works Best on Pathogenic Breeding Grounds Found in Hospital Room Sinks?

Infection control teams concerned about how hospital sink drains can breed reservoirs of antibiotic-resistant pathogens should consider having environmental services (EVS) personnel clean those drains every 3 to 5 days with a mixture of hydrogen peroxide, octanoic acid, and peroxyacetic acid foam.

That, according to results of a study published recently in Infection Control & Hospital Epidemiology.¹ Investigators with the Medical College of Wisconsin compared the effects of 2 different disinfectants on colony-forming units (CFU). They’d found in an earlier study that sink drains adjacent to toilets in patients’ hospital rooms had more Klebsiella pneumoniae carbapenemase (KPC) genes than did sink drains farther away from toilets. In this earlier study, investigators then compared a hydrogen peroxide product with bleach, with the former being more effective at decreasing CFU. 

“Here [in the new study], we aimed to determine the ideal frequency of sink drain disinfection and to compare the effectiveness of 2 different hydrogen peroxide disinfectants at decreasing CFU in sink drains,” the authors write. 

Investigators conducted their study in 26 rooms of the medical intensive care unit of a 565-bed teaching hospital in Milwaukee. Each room has 2 sinks, 1 next to the toilet and 1 near the entrance of the room. Investigators only looked at the sinks next to the toilets. 

Investigators named the 2 disinfectants involved products A and B. Product A consisted of hydrogen peroxide, octanoic acid, and peroxyacetic acid. Product B consisted of hydrogen peroxide-based disinfectant. 

“Product A came ready to use and product B required dilution according to the manufacturer’s instructions (6 ounces of disinfectant per gallon of water),” the study stated. “Both products were applied using foaming devices by a single environmental services (EVS) staff member.” 

The 26 sinks were assigned to 3 groups: product A, product B, and sinks that were not disinfected. An EVS team member designated the sinks and did not tell other team members until after the analysis was completed. The daily cleaning schedule was not changed. 

To take samples, investigators inserted swabs as far down the sinks’ strainers as they could. The walls of the sinks were swabbed in 360-degree circular motions. The samples were taken the day before the products were used, and then again after their use on days 1, 3, 5, and 7. The samples were obtained in the morning and processed within 4 hours of collection. 

“Quantification of gram-negative burden was determined by serial dilution in saline plated to MacConkey agar, and dilutions that contained 20–200 colonies were used for CFU determination,” the study stated. “The means of the natural logarithm (Ln) of CFUs (1 þ CFU) and their 95% confidence intervals for all 3 groups were compared for each sampling day.” The CFU reduction among the 3 groups was compared using linear regression and analysis of variance. 

The 3 groups had similar baseline counts of CFU (and those counts remained unchanged for the control group throughout the experiment), but after the first use of the disinfectants, investigators “observed a significant reduction in the CFU in the group treated with product A compared to its baseline counts (11.95 CFU/mL to 2.01 CFU/mL P < .01).” 

The baseline CFU counts for product B also decreased, but that change wasn’t statistically significant. On day 3, there was also a greater CFU reduction in the sinks treated with product A than sinks treated with product B. 

“The CFU counts for all 3 groups returned to baseline levels on days 5 and 7,” the study states. 

EVS staff said it took more work to apply product B than product A because product B needed to be diluted. “Both products required a maximum of 30 seconds per sink to apply, were easy to use and dispense, and created minimal odor,” the study stated. 

The investigators did not determine the ideal frequency of disinfection. 

“Based on our results, relative affordability and easiness of application, regular application of a mixture of hydrogen peroxide, octanoic acid, and peroxyacetic acid foam (every 3–5 days) should be considered in settings where there is concern that sink drains are acting as reservoirs of resistant pathogens,” the study states. “Nevertheless, the clinical relevance of sink disinfection using the products tested in this study and their impact on different pathogens should be further evaluated.” 

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Q&A: A Conversation With Silvia Munoz-Price, MD, PhD 

Infection Control Today® reached out to the study’s corresponding author, Silvia Munoz-Price, MD, PhD, about the reality of cleaning hospital sink drains. Munoz-Price is an enterprise epidemiologist and professor of medicine at the Medical College of Wisconsin. 

Infection Control Today: To your knowledge, do EVS staff clean sinks the way they should be cleaned? 

Munoz-Price: The sink bowls are likely disinfected as frequently as the rest of the surfaces within patient rooms. However, sink drains are probably rarely (if ever) disinfected in most hospitals. 

ICT: How many hospitals use the hydrogen peroxide, octanoic acid, and peroxyacetic acid foam solution that you found most effective? 

Munoz-Price: I am not sure. My hospital uses oxycide for regular disinfection of room surfaces. 

ICT: Is the cleaning of hospital sinks done in a scattershot way, do you think? 

Munoz-Price: I actually think the sink drains are rarely cleaned or disinfected in most hospital settings. Out of sight, out of mind. 

ICT: Do EVS staff need to become more cognizant of the importance of disinfecting hospital sink drains? 

Munoz-Price: Sink drain disinfection is not standard practice yet. It is unclear if sink drains play a relevant role in horizontal transmission of organisms across all inpatient units. Finally, disinfecting sinks, especially with foam applicators, can be time consuming which could impact disinfection of other surfaces. 

References:

Ramos-Castaneda JA, Faron ML, Hyke J, et al. How frequently should sink drains be disinfected? Infect Control Hosp Epidemiol. 2020 Jan 10:1-3. doi: 10.1017/ ice.2019.316. [Epub ahead of print].