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Studies: Sinks and floors are a much bigger infection risk than once thought


May 18, 2017

New findings suggest sink splashes and floors are overlooked hazards

Several new studies published recently in medical journals suggest that hospital floors and sinks may deserve a little more time from your cleaning staff.

In the first, a study by a team of researchers from the University of Virginia, Charlottesville, studied the pathways bacteria take when they travel. It specifically found that potentially deadly bacteria, such as E. coli, find their way outside of sinks due to splashing. Additionally, when left to mature, the bacteria are able to form an infectious biofilm that can stack its way up from the inner pipework of the hospital’s plumbing into the strainer of the sink. The results of the study were published in the May issue of Applied and Environmental Microbiology, a publication of the American Society for Microbiology.

“Many recent reports demonstrate that sink drain pipes become colonized with highly consequential multidrug resistant bacteria, which then result in hospital-acquired infections,” the report’s authors wrote. “This work found that a staged mode of transmission involving biofilm growth from the lower pipe to the sink strainer and subsequent splatter to the bowl and surrounding area occurs rather than splatter directly from the water in the lower pipe. We have also demonstrated that bacterial transmission can occur via connections in wastewater plumbing to neighboring sinks.”

According to a report in Health Facilities Management (HFM) magazine, the team at the University of Virginia used a green fluorescent protein expressing E. coli and tracked how wastewater transfers from the sink drain and into the surrounding area. The researchers did not observe bacteria traveling directly from the P-trap (the curved pipe often found underneath a sink) to the sink’s basin or surrounding countertop. However, when the bacteria were allowed to mature, they formed a biofilm that slowly traveled from the P-trap up to the strainer over the course of seven days. As a result of this growth, the study found that the bacteria could be dispersed via splashes as far as 30 inches away from the sink in some cases. Essentially, the bacteria seem to always find a way to spread despite the efforts of hospitals to keep sinks and other treatment areas clean.

According to the HFM report, the researchers say the study is important in helping us understand how bacteria from sink wastewater can affect vulnerable patients and influence sink design and cleaning to improve infection control efforts. The study did not, however, offer suggestions for how hospitals could do a better job of cleaning sinks or reducing splashes that could potentially spread infectious germs.

So does this study mean you can stop encouraging staff to wash their hands? Of course not. According to the World Health Organization (WHO), many healthcare-associated infections are preventable through good hand hygiene. Handwashing is a cheap and effective method of preventing the spread of antibiotic-resistant diseases, which are expected to annually kill 10 million people worldwide by 2050. Most infection control experts agree that those working in hospitals should be washing their hands—or at least using hand sanitizer—before and after caring for each patient, after using the bathroom, and after any time they contact a surface that could be contaminated with germs. In a hospital, that could be anywhere, so in a typical work shift, staff could theoretically be required to wash their hands hundreds of times.

Getting healthcare workers to wash their hands at all is apparently a major problem, though. In a study published in the April issue of the American Journal of Infection Control (AJIC), researchers secretly chronicled 330 hand hygiene observations at 15 facilities and found that a frighteningly low 37% of observed staff washed their hands.

Floors another probable infection source

A second study, published in the March issue of the AJIC, found that hospital room floors may be an overlooked source of infection. The study essentially found that because items in the patient treatment room may touch the floor, pathogens on floors can rapidly move to the hands via high-touch surfaces throughout the room.

“In a survey of five hospitals, we found that floors in patient rooms were frequently contaminated with pathogens and high-touch objects such as blood pressure cuffs and call buttons were often in contact with the floor,” wrote the authors of the study. “Contact with objects on floors frequently resulted in transfer of pathogens to hands.”

In the study by Abhishek Deshpande, MD, PhD, and colleagues, researchers cultured 318 floor sites from 159 patient rooms (two sites per room) in five Cleveland-area hospitals. The hospital rooms included both Clostridium difficile infection (CDI) isolation rooms and non-CDI rooms. Researchers also cultured hands (both gloved and bare, to simulate different scenarios of people picking things up off the floor) as well as other high-touch surfaces such as clothing, call buttons, medical devices, linens, and medical supplies.

The researchers found that floors in patient rooms often were contaminated with methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococci, and C. difficile, with C. diff being the most frequently recovered pathogen in both room types.

So what does this mean for hospital rooms and the way hospitals clean them? In the short term, probably not much. Cleaning protocols at most hospitals are pretty much standardized, and aside from telling people they can’t put anything on the floors, there isn’t much that can be done to completely sterilize those surfaces. But the authors of the study do offer a few suggestions to give hospitals food for thought:

Educate on the dangers. Since floors are frequently quite dirty and thus contaminated, hospitals should educate staff and visitors about the importance of not placing high-touch objects and equipment on the floor if possible.

Conduct better floor cleaning. It’s probably a good idea for hospitals to reexamine how they clean their floors. The study authors noted that sporicidal disinfectants used to clean rooms and kill germs such as C. diff are not typically used on floors.

“In particular, because C. difficile spores were frequently recovered from floors in CDI and non-CDI rooms, there is a need to identify approaches that are effective in reducing the burden of spores on floors,” the authors wrote.

In addition, some hospitals have turned to disinfecting rooms with germ-zapping robots, which are machines that emit high-powered ultraviolet light to help kill infectious organisms. While highly effective when used in conjunction with a regular cleaning program, the author noted that the devices were used in only one of the study hospitals, and there only in CDI rooms. Hospitals should research the cost-effectiveness of introducing these machines into their cleaning program.

What else picks up the germs? The study authors suggest much more research can be done about how pathogens are transferred from one place to another. Your mother probably didn’t like your shoes tracking in mud from the outside, and it’s a good idea to think about how your shoes today could be carrying germs from room to room. Germs may also hitch a ride on things such as wheeled carts, and handbags or suitcases placed on the floor. According to the study authors, another recent study also suggests wheelchairs could be a major source of pathogen transmission.

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