A hospital-associated bacterial species has become increasingly resistant to alcohol disinfectants over time, Australian researchers have determined.
Enterococcus faecium is now a leading cause of nosocomial infections and cases have increased despite the use of alcohol disinfectants such as hand rubs and disinfectants, say the authors of the study, which appears in Science Translational Medicine.
They analysed the alcohol tolerance of 139 hospital isolates of E. faecium obtained between 1997 and 2015 in two major hospitals and found that E. faecium isolates after 2010 were 10-fold more tolerant than older isolates.
A mouse gut colonisation model of E. faecium transmission then demonstrated that alcohol-tolerant E. faecium resisted standard 70% isopropanol surface disinfection, which resulted in greater mouse gut colonisation compared to alcohol-sensitive E. faecium. Adaptation was confirmed via bacterial genomic signatures. Alcohol-tolerant E. faecium accumulated mutations in genes involved in carbohydrate uptake and metabolism. Mutagenesis confirmed the roles of these genes in the tolerance of E. faecium to isopropanol.
"These findings suggest that bacterial adaptation is complicating infection control recommendations, necessitating additional procedures to prevent E. faecium from spreading in hospital settings," said the authors. They acknowledged it will be important to test whether alcohol tolerance is emerging in other E. faecium populations.