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Hospital superbugs developing ‘tolerance to alcohol disinfectants’

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A multidrug-resistant bacterial species that can cause infections in hospitals is becoming increasingly tolerant to the alcohols used in handwash disinfectants, according to Australian researchers.

They said analysis of bacterial samples taken from two hospitals in Melbourne over 19 years suggested that the species Enterococcus faecium was adapting to a “mainstay of infection control”.

“Bacterial adaptation is complicating infection control recommendations”

Study authors

The researchers warned that drug-resistant E. faecium infections had increased despite the use of alcohol disinfectants, and currently represent a leading cause of infections acquired in hospitals.

This alarming development prompted the team from Melbourne’s Doherty Institute to investigate whether E. faecium could be developing resistance to the alcohols used in hand rubs.

They screened 139 E. faecium isolates collected between 1997 and 2015 from the two hospitals and studied how well each isolate survived when exposed to diluted isopropyl alcohol.

The isolates gathered after 2009 were on average more tolerant to the alcohol compared to bacteria taken from before 2004, according to the study in the journal Science Translational Medicine.

The different isolates were then “seeded” onto the floors of mouse cages. The alcohol-tolerant isolates better colonised the guts of mice after cages were cleaned with isopropyl alcohol wipes.

Analysis of the bacterial genome revealed that the tolerant isolates harboured several mutations in genes involved in metabolism that conferred increased alcohol resistance, said the researchers.

They said: “These findings suggest that bacterial adaptation is complicating infection control recommendations, necessitating additional procedures to prevent E. faecium from spreading in hospital settings.”

However, the study authors said that examination of isolates from hospitals in other geographical regions was necessary before any major conclusions can be drawn.

“We need to be concerned about the possibility of emerging microbial resistance to alcohol and other disinfectants”

Pat Cattini

But they said their results indicated that efforts to tackle bacterial resistance should consider how microbes could adapt to alcohols and other ingredients used in disinfectants, as well as drugs.

Pat Cattini, vice president of the Infection Prevention Society, said: “Alcohol handrubs, which are effective against a large variety of bugs and are easy to apply, remain a key part of hand hygiene and should continue to be used in health and care settings.

“However, you should always wash your hands with soap and water rather than alcohol handrubs when dealing with faeces and other body fluids,” she said. “We do need to be concerned about the possibility of emerging microbial resistance to alcohol and other disinfectants.

“However, it isn’t immediately clear that this study, or other similar laboratory based studies, demonstrate a concern that is yet directly relevant to healthcare,” she added. 

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