Popular Hospital Disinfectant Ineffective Against Common Superbug

Research conducted during World Antimicrobial Awareness Week examines the effects of employing suggested chlorine-based chemicals to combat Clostridioides difficile, the leading cause of antibiotic-related illness in healthcare environments worldwide.

A recent study reveals that a primary chlorine disinfectant used in hospitals fails to eliminate the leading cause of antibiotic-associated illness in healthcare settings worldwide. This finding comes from research conducted by the University of Plymouth.

The study shows that Clostridioides difficile spores, also known as C. diff, remain completely unaffected despite being treated with high concentrations of bleach used in many hospitals. In fact, chlorine-based chemicals are no more effective than plain water in disinfecting surfaces against these spores.

Urgent Need for Effective Disinfection Methods

Writing in the journal Microbiology, the study's authors say susceptible people working and being treated in clinical settings might be unknowingly placed at risk of contracting the superbug.

As a result, and with the incidence of biocide overuse only serving to fuel rises in antimicrobial resistance (AMR) worldwide, they have called for urgent research to find alternative strategies to disinfect C. diff spores in order to break the chain of transmission in clinical environments.

Research published during World Antimicrobial Awareness Week has shown that one of the primary chlorine disinfectants currently being used to clean hospital scrubs and surfaces does not kill off spores of Clostridioides difficile, the most common cause of antibiotic-associated sickness in healthcare settings globally. Credit: Microbiology Society

Dr Tina Joshi, Associate Professor in Molecular Microbiology at the University of Plymouth, carried out the study with Humaira Ahmed, a fourth-year Medicine student from the University's Peninsula Medical School.

Dr Joshi, said: "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. It shows we need disinfectants, and guidelines, that are fit for purpose and work in line with bacterial evolution, and the research should have a significant impact on current disinfection protocols in the medical field globally."

Global Impact of C. diff Infections

C. diff is a microbe that causes diarrhea, colitis, and other bowel complications and is known to infect millions of people all over the world each year.

It causes around 29,000 deaths per year in the USA, and almost 8,500 in Europe, with the most recent data showing that the incidence of C. diff infection was increasing prior to the start of the COVID-19 pandemic in the UK.

Previously, Dr Joshi and colleagues had demonstrated the ability of C. diff spores to survive exposure to recommended concentrations of sodium dichloroisocyanurate in liquid form and within personal protective fabrics such as surgical gowns.

The new study examined spore response of three different strains of C. diff to three clinical in-use concentrations of sodium hypochlorite. The spores were then spiked onto surgical scrubs and patient gowns, examined using scanning electron microscopes to establish if there were any morphological changes to the outer spore coat.

Dr Joshi, who is on the Microbiology Society Council and Co-Chairs their Impact & Influence Committee, added: "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. With AMR increasing globally, the need to find those answers – both for C. diff and other superbugs – has never been more pressing."

Reference: "Clostridioides difficile spores tolerate disinfection with sodium hypochlorite disinfectant and remain viable within surgical scrubs and gown fabrics" by Humaira Ahmed and Lovleen Tina Joshi, 21 November 2023, Microbiology.
DOI: 10.1099/mic.0.001418