should monitor genes as one of the major contributors to disease.”
ENVIRONMENTAL HYGIENE
Environmental challenges and solutions for IP & C
In the presentation,“ Is it Time to Rethink Environmental Surface Disinfection in Healthcare Settings?” Jean-Yves Maillard, a professor of pharmaceutical microbiology at Cardiff University in the UK, reviewed the definitions of cleaning and disinfection, emphasizing that it is impossible to sterilize the surface to achieve an absence of microorganisms, but the role of disinfection is to render a surface‘ safe’ is a vague concept.
“ The problems are still the same, and that is the rapid spread of microorganisms,” Maillard said.“ A study by Reynolds, et al.( 2019) showed the rapid spread of a viral tracer on surfaces within six hours on all surfaces and hands sampled, reaching maximum contamination levels two hours after inoculation. Room door handles and nurses station chair arms yielded the highest concentrations. Virus concentrations decreased by 94.1 percent after the disinfectant spray intervention, but the point is that you will have microbial regrowth post-cleaning and disinfection, that is inevitable, and it occurs very rapidly.”
Maillard continued,“ A study by Bogusz, et al.( 2013) examined near-patient surface contamination following detergent cleaning. Aerobic colony counts dropped from around 6.7 CFU / cm2 initially to about 3.5 at four hours but rebounded to about 4.9 at 24 hours and 5.3 at 48 hours. Many sites exceeded cleanliness standards after 24 hours post-cleaning. Most high-touch surfaces became contaminated again within 4 hours; by 24 to 48 hours contamination levels approached pre-cleaning baselines across most surfaces. In the UK where I am from, cleaning in hospitals happens every 24 hours, in the early mornings and very shortly after, you’ ve got high microbial load back on your surfaces. So, it is an ongoing challenge.”
Maillard mentioned numerous factors affecting cleaning efficacy.“ Disinfectant product efficacy has been widely described, their formulations and delivery systems, how the product is used, and the targeted pathogens, and compliance by the cleaner. As we know, different pathogens have different susceptibility to disinfectants, and we know there are spores resistant to some disinfectants – particularly alcohol, quaternary formulations, and we all have seen the schematic of susceptibility of organisms to disinfectants. A real problem are the biofilms and protonic cells in suspension; they are
What we have found is without mechanical removal, you don’ t address DSBs completely. Importantly, how do we measure how safe the surface is post-disinfection? Empirically, we are looking at one parameter, the log reduction, but it is advisable to look also at transfer postdisinfection. To me, the surface is safe when you have a much lower microbial load, but that load is not being transferred.”— Dr. Jean-Yves Maillard
very susceptible to your disinfectant, right? But they are 10 times less susceptible if they form a hydrated biofilm. Dry surface biofilms( DSBs) on surfaces are even less susceptible. DSBs are widespread on surfaces in hospitals( 90 percent to 95 percent of surfaces sampled). Their depth is not visible to the naked eye, and the surface may look clean. DSBs contribute to pathogens’ survival despite cleaning and disinfection. DSBs cannot be detected by swabbing or contact plates when surfaces are dried. When they are disturbed by mechanical forces as the surfaces are wiped, then you are potentially transferring all those microorganisms from that surface to other surfaces. Ledwoch, et al.( 2021) showed that pathogens from 69 percent of samples could be transferred following wet wiping with sterile water. 54 percent of samples continued to transfer bacteria following 1,000 ppm NaOCI treatment.”
In the Ledwoch study, keyboards from nursing stations in three hospitals and a dental practice were analyzed for bacterial contamination. Surfaces were pre-treated to remove planktonic bacteria so that any remaining bacteria were presumed to be associated with biofilm. Bacterial transfer from keyboard keys was studied following wiping with sterile water or sodium hypochlorite. The presence of multidrug-resistant organisms( MDROs) was sought using selective culture. Moist swabbing did not detect bacteria from any keyboard samples. Use of enrichment broth, however, demonstrated MDROs from most samples. Gram-negative bacteria were recovered from almost half( 45 %) of the samples, with methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococcus and MDR Acinetobacter spp. recovered from 72 percent, 31 percent and 17 percent of samples, respectively. Isolates were transferred from 69 percent of samples after wiping with sterile water, and from 54 percent of samples after wiping with 1,000 ppm sodium hypochlorite.
The authors note,“ While moist swabbing failed to detect bacteria from keyboards, pathogens were recovered using enrichment culture. Use of water- or NaOCl-soaked wipes transferred bacteria from most samples tested. This study implies that hospital keyboards situated outside the patient zone commonly harbor dry surface biofilms( DSBs) that offer a potential reservoir for transferable pathogens. While the role of keyboards in transmission is uncertain, there is a need to pursue effective solutions for eliminating DSBs from keyboards.”
Maillard, who was a co-author on the Ledwoch study, added,“ These are complex communities of microorganisms, and you will find environmental organisms, particularly Gram-positives, that can withstand desiccation, particularly Acinetobacter, and we have identified VRE and MRSA as well. We have models in the lab to really examine DSBs. It takes about 12 days to form an artificial DSB in the lab, and this helps us measure the efficacy of disinfection. What we have found is without mechanical removal, you don’ t address DSBs completely. Importantly, how do we measure how safe the surface is post-disinfection? Empirically, we are looking at one parameter, the log reduction, but it is advisable to look also at transfer post-disinfection. To me, the surface is safe when you have a much lower microbial load, but that load is not being transferred. What we see from studies is that not all disinfectant products address DSBs. And then if you touch these surfaces with DSBs, you can transfer those biofilms to other surfaces.”
ENVIRONMENTAL HYGIENE
Examining technology to address surface hygiene challenges
In the presentation“ Self-Disinfecting Surfaces and Continuous Room Disinfection,” David J. Weber, MD, MPH, a professor of medicine, associate chief medical officer of UNC Medical Center, and medical director of the Department of Infection Prevention at UNC Medical Center in Chapel Hill, N. C. reviewed the numerous technologies that currently exist in the marketplace to facilitate disinfection in the healthcare environment.
“ Thirty years ago, Bob Weinstein pointed out that most infections in the hospital come from the patient’ s endogenous flora,” Weber reminded attendees.“ He did note that you can get exogenous flora transmission and hypothesized that about 20 percent of infections would come from the environment,
24 • www. healthcarehygienemagazine. com • nov-dec 2025