Efficacy of stable liquid chlorine dioxide in the cleaning of drinking systems for laboratory rats in non-standardised vivarium conditions

Abstract

The study evaluated the disinfection efficacy of stabilised liquid chlorine dioxide (Dioxy active supra, 0,3%) on water dispensers used for laboratory rats in a vivarium operating outside the standards prescribed by the European Council Directive 2010/63/EU. Sweabs were taken from all drinkers before and after disinfection and inoculated on three microbiological media: nutrient agar, MacConkey agar, and XLD agar. Before treatment, abundant and diverse bacterial growth was recorded, including colonies of Enterobacteriaceae and other opportunistic microorganisms. After immersion of the drinkers and metal taps in the liquid chlorine dioxide solution for 15 minutes, a significant reduction—or complete inhibition—of bacterial colonies was observed on all media. Quantitatively, the disinfectant achieved more than 95% efficiency on nutrient agar and approximately 100% on MacConkey and XLD agar. These findings confirm the strong bactericidal properties of stable liquid chlorine dioxide, attributable to its oxidative mechanism and biofilm-disrupting capacity. The disinfectant proved effective against both Gram-positive and Gram-negative bacteria, without producing odours or residues that could negatively affect animal welfare. In conclusion, stabilised liquid chlorine dioxide represents a safe, highly efficient and practical solution for maintaining the hygienic integrity of drinking systems in laboratory animal facilities, thereby ensuring reliable experimental outcomes and compliance with welfare standards.