Chemical Used to Kill Superbug in US Hospitals No More Effective Than Water

Strong bleach is no match for hospital superbugs, new research suggests.

Superbugs are disease-causing bacteria that are both highly virulent and resistant to most commonly used antibiotics. These drug-resistant microbes infect more than 2 million people in the United States every year, according to the U.S. Centers for Disease Control and Prevention, killing at least 23,000.

Many hospitals rely on strong disinfectants like high-concentration bleach to remove superbugs from their scrubs and surfaces. But a new study from the University of Plymouth in the United Kingdom, published in the journal Microbiology, suggests that these chlorinated cleaning products might not be as effective as we once thought.

The team focused their investigations on a bacterium called Clostridioides difficile which affects roughly half a million Americans every year, causing around 29,000 deaths in the U.S. alone. Infection results in life-threatening diarrhea and inflammation in the colon and mostly affects people who are in or have previously been in the hospital.

"C. difficile is a serious pathogen that causes antibiotic-associated diarrhea and is a huge problem in the USA and globally," co-author Tina Joshi, an associate professor in Molecular Microbiology at the University of Plymouth, told Newsweek.

"With incidence of anti-microbial resistance on the rise, the threat posed by superbugs to human health is increasing. But far from demonstrating that our clinical environments are clean and safe for staff and patients, this study highlights the ability of C. diff spores to tolerate disinfection at in-use and recommended active chlorine concentrations."

In their study, Joshi and colleagues exposed dormant spores of C. difficile to three clinically in-use concentrations of sodium hypochlorite (bleach). The spores were then put on surgical scrubs and patient gowns and examined under a scanning electron microscope to establish if they had undergone any changes after the bleach treatment. And what they found was shocking.

The spores were completely unaffected. Indeed, the high concentration bleach used in hospitals was no more effective at damaging the spores than plain water.

"Understanding how these spores and disinfectants interact is integral to practical management of C. diff infection and reducing the burden of infection in healthcare settings," Joshi said. "However, there are still unanswered questions regarding the extent of biocide tolerance within C. diff and whether it is affected by antibiotic co-tolerance. With [antimicrobial resistance] increasing globally, the need to find those answers—both for C. diff and other superbugs—has never been more pressing."

Joshi said that peracetic acid-based solutions or hydrogen peroxide might provide an effective alternative to bleach, but more work is needed to determine how best to keep the superbugs at bay.

"[Our study] shows we need disinfectants, and guidelines, that are fit for purpose and work in line with bacterial evolution, and the research should have significant impact on current disinfection protocols in the medical field globally."

Update 11/24/23, 12:08 p.m. ET: This article was updated with comment from Tina Joshi.