A Practical Assessment of the Disinfectant Efficacy of UV Light with and without Ozone Using a Novel Transfer Hatch in a Research Animal Facility

Abstract

Most in vivo animal research and breeding using mice and rats in China takes place in facilities under barrier conditions. Items being moved across the barrier are typically disinfected using UV radiation in a transfer hatch. However, the time periods necessary for this disinfection technique are inefficient, and disinfection is frequently incomplete, especially if concealed surfaces are present. The current study used a newly developed transfer hatch incorporating both UV and ozone disinfection to examine disinfection efficacy against 4 bacteria species (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii). Disinfection trials used UV and ozone, applied separately and in combination, for up to 30 min. Separate and combined treatments were also tested with a UV barrier. We found that if UV radiation has direct contact with surfaces, it is an efficient disinfection method. However, where surfaces are concealed by a UV barrier, UV radiation performs relatively poorly. The results of this study indicate that a combination of UV and ozone produces the most effective disinfection and is markedly quicker than current disinfection times for UV applied on its own. This novel transfer hatch design therefore allows more complete and efficient disinfection, improves workflow, and reduces barrier breaches by pathogens that may affect animal health and welfare and compromise research outcomes.

Figure 1.

The novel transfer hatch used in this study.

Figure 2.

Model effect plots for effect on CFU counts (ly) compared with (Figure 2A) duration of disinfection exposure (t, 1: 0 min, 2: 5 min, 3: 10 min, 4: 15 min, 5: 20 min, 6: 3 min). Figure 2B. Method of disinfection (method [uncovered/covered = without/with UV barrier], 1: UV uncovered, 2: Ozone uncovered, 3: UV + ozone uncovered, 4: UV covered, 5: Ozone covered, 6: UV + ozone covered, for all bacterial species and all exposure durations tested). Figure 2C. Species identity (species, 1: E. coli, 2: S. aureus, 3: P. aeruginosa, 4: A. baumannii) for all methods and all exposure durations tested.

Figure 3.

Predicted values of bacterial colony counts (CFU: ly) associated with different disinfection methods based on the statistical model and indicating method effect over time (t) (Time, 1: 0 min, 2: 5 min, 3: 10 min, 4: 15 min, 5: 20 min, 6: 30 min; Method [uncovered/covered = without/with UV barrier], 1: UV uncovered, 2: ozone uncovered, 3: UV + ozone uncovered, 4: UV covered, 5: Ozone covered, 6: UV + ozone covered).

Figure 4.

Plot illustrating interaction effects for disinfection trial variables on bacteria colony counts (CFU: ly) for species x disinfection method (Species, 1: E. coli, 2: S. aureus, 3: P. aeruginosa, 4: A. baumannii; Method [uncovered/covered = without/with UV barrier], 1: UV uncovered, 2: Ozone uncovered, 3: UV+ ozone uncovered, 4: UV covered, 5: Ozone covered, 6: UV+ ozone covered).