Breaking Down Resistant Rumors and C diff Disinfectants

July 30, 2019

Not all disinfectants are created equal and here's why we need to remember that.

EDITOR'S NOTE: A previous version of this story incorrectly stated that NaDCC based disinfectants are not used in the United States. Clostridioides difficile (C diff) is one of the infections that stops people in their tracks, from infection preventionists to providers and nurses alike. Roughly half a million Americans will contract this bacterial infection every year, and 20% will relapse after treatment. Moreover, 1 in 11 people with health care-associated C diff who are over 65 years of age will die within 1 month of their diagnosis. Studies have shown that the cost of managing and treating C diff infections are quite significant at around $18,000.

On top of these startling statistics, C diff also poses a challenge because the bacterium is particularly environmentally hardy. When it’s in its spore form, it’s quite resistant to disinfectants and ultimately requires bleach-based products (Clorox has become the strongest tool in our arsenal to combatting C diff). Moreover, even alcohol-based hand sanitizers aren’t enough to get rid of the bug, which requires health care workers and patients to use soap and water as a way to get the spores off through friction.

One recent study in the United Kingdom, though, sought to test the hardiness of C diff on hospital gowns and stainless steel, while also assessing the efficacy of disinfectants. Investigators first wanted to evaluate the role of gowns as fomites in C diff transmission, as there has been suspicion that they could play an active role. Studying this first relationship, the research team found that when they applied spores in sterilized water at various concentrations to the surgical gown, the number of recovered spores did not increase over time, which means that any transmission would occur within the first 10 seconds of contact. Since the gowns are capable of trapping these spores though, it is a critical reminder to only use them once and discard immediately after use.

The second part of the study though, is the one that has gotten more attention. The investigators sought to treat the gowns with disinfectant to test its efficacy and whether it would help with the bioburden. The research team found that after being treated with the 1000 ppm chlorine-based disinfectant for 10 minutes, the gowns still were able to pick up and hold the C diff spores. This concern over resistance sent shockwaves and many news outlets picked up on this as an indicator of what’s on the horizon. But an issue with the study was the disinfectant that was used.

First and foremost, as an infection preventionist and the first to stand on my soapbox to shout about the perils of antimicrobial resistance, I know that the efficacy of our disinfectants will eventually fail. The issue with this study is that much of the media coverage speaks broadly of a chlorine-based disinfectant and goes into little detail about what exactly what used. For my infection prevention peers, you know that not all disinfectants are alike and, well, some just weren’t designed for combatting hardier bugs like C diff. This is the playbook we live by in health care.

The disinfectant the investigators used was sodium dichloroisocyanurate (NaDCC), which is a pretty stable form of chlorine that can disinfect water as well as surfaces/objects, but is not a hypochlorite (like bleach).NaDCC is different than bleach, and has a lower pH, meaning that its antimicrobial capabilities are different. Although there are benefits to NaDCC in that it has a reserve disinfecting capability. Although this study sheds light on how easily gowns can become contaminated with C diff spores, the takeaways regarding types of disinfectants should be taken in context.

This study highlights the need to test disinfectants and continuously monitor their efficacy against microorganisms, especially those that are more environmentally hardy. It should also be a reminder that the variety of disinfectants and biocides being used is likely to show variation in different regions and those results are not always comparable to other health care regions.