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Chlorine disinfectants used in hospitals are no more effective than water

A study from the University of Plymouth has revealed startling findings about the efficacy of chlorine disinfectants used in hospitals. Despite their widespread use for cleaning scrubs and surfaces, these disinfectants fail to kill Clostridioides difficile (C. diff), a major cause of antibiotic-associated sickness in healthcare settings.

The study was led by Dr. Tina Joshi, associate professor in Molecular Microbiology, and Humaira Ahmed, a fourth-year Medicine student. The team found that even high concentrations of bleach used in hospitals do not affect C. diff spores. 

Antimicrobial resistance 

The research indicates that using chlorine chemicals as a surface disinfectant is no more effective than using plain water. This revelation is particularly concerning given the rising antimicrobial resistance (AMR) globally. The overuse of biocides, such as chlorine disinfectants, is contributing to this increase in AMR. 

The study authors are calling for urgent research to identify alternative strategies to disinfect C. diff spores, emphasizing the need for disinfectants and guidelines that are effective against evolving bacterial threats.

C. diff spores tolerate disinfection 

“With incidence of antimicrobial 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,” said Dr. Joshi.

“It 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.”

C. diff, a microbe causing diarrhea, colitis, and other bowel complications, infects millions annually worldwide. It is responsible for approximately 29,000 deaths each year in the USA and almost 8,500 in Europe. The incidence of C. diff infection was rising even before the COVID-19 pandemic in the UK.

Focus of the study 

Prior research by Dr. Joshi and colleagues showed C. diff spores’ survival against recommended concentrations of sodium dichloroisocyanurate, used in liquid form and in personal protective fabrics like surgical gowns. 

The new study took this further by testing the response of C. diff spores to different concentrations of sodium hypochlorite, a common ingredient in bleach. The spores were placed on surgical scrubs and patient gowns, with no significant morphological changes observed under scanning electron microscopes.

Unanswered questions remain 

Dr. Joshi, a member of the Microbiology Society Council, emphasized the importance of understanding the interaction between these spores and disinfectants. 

“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. However, there are still unanswered questions regarding the extent of biocide tolerance within C. diff and whether it is affected by antibiotic co-tolerance,” said Dr. Joshi.

“With AMR increasing globally, the need to find those answers – both for C. diff and other superbugs – has never been more pressing.”

The research was published during World Antimicrobial Awareness Week in the journal Microbiology.

Video Credit: Microbiology Society

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