Tolerance of clinical vancomycin-resistant Enterococcus faecium isolates against UV-C light from a mobile source

Area of Science:

• Microbiology
• Infectious Diseases
• Environmental Hygiene

Background:

• Hospital-acquired infections pose a significant risk.
• Automated 'no-touch' disinfection systems, including UV-C irradiation, are employed for terminal room cleaning.
• The efficacy of UV-C against clinical pathogen isolates versus laboratory strains requires further investigation.

Purpose of the Study:

• To analyze the susceptibility of clonally divergent vancomycin-resistant enterococci (VRE) clinical isolates to UV-C irradiation.
• To compare the UV-C resistance of VRE clinical isolates with a standard laboratory strain (Enterococcus hirae ATCC 10541).

Main Methods:

• Ten clonally divergent VRE clinical isolates and E. hirae ATCC 10541 were tested.
• Contaminated ceramic tiles were irradiated with UV-C doses of 50 and 22 mJ/cm² at distances of 1.0 and 1.5 m, respectively.
• Bacterial reduction was quantified via culture after irradiation.

Main Results:

• UV-C susceptibility varied significantly among VRE strains, with some being up to tenfold more tolerant than others.
• The laboratory strain E. hirae ATCC 10541 showed intermediate susceptibility.
• The most tolerant VRE isolates, particularly ST1283, demonstrated significantly lower reduction at 22 mJ/cm² compared to E. hirae ATCC 10541.

Conclusions:

• Standard UV-C doses effective against laboratory strains may be insufficient for eliminating tolerant clinical VRE isolates.
• Future validation of automated UV-C disinfection devices should utilize the most tolerant clinical isolates.
• Longer UV-C exposure times may be necessary to ensure effective disinfection in real-world hospital settings.