Ultraviolet C decontamination: analysis of its impact on surface contamination in controlled atmosphere area

Background
In accordance with Good Manufacturing Practices (GMP), microbiological sampling using contact agars and glove prints are performed daily in controlled atmosphere area (CAA). The analysis of non-conformities revealed a probable contamination of surfaces by contact with manufacturing sheets and labels entering into CAA throughout ongoing production. A method for disinfecting these probable contaminants using ultraviolet C (UVC) prior to entry into the CAA was carried out. The aim of this study was to compare the results of microbiological sampling of surfaces and gloves in the CAA before and after implementing this technical solution.

Methods
The Byola^® 250 decontamination box was used. The radiation wavelength was 254 nm and the power was 0.98 mW/cm². A 5-minute cycle delivers a dose of 294 mJ/cm² and the electric consumption was 0.01666 KWh. Microbiological samples are: surface of screen and balance of the robot production system (positioned in a class A laminar air-flow hood), and glove prints of the operator (class A) and assistant-operator (class B). Results of sampling before (10/13/2021 - 07/15/2022) and after installation of UVC (07/15/2022 - 04/19/2023) were compared: numbers of non-conformities, positive samples and Colony Forming Units (CFUs) per sampling point, using a Student’s statistical test, with two-sided hypothesis at a 5% risk of alpha error.

Results
In class B, a statistically significant reduction of non-conformities, positive samples and CFUs was demonstrated: divided by 10.5 (21 vs. 2), 1.9 (95 vs. 49) and 4.6 (415 vs. 90) respectively. In class A, a downward trend was observed on manipulator’s gloves. Regarding contact points on the robot, no difference was observed on the balance and a significant increase of screen contamination was detected.

Conclusion
The introduction of UVC decontamination reduced the number of non-conformities on operators’ gloves. These results meet expectations and demonstrate the effectiveness of this rapid disinfection method throughout ongoing production. A change in the position of the screen under the laminar air flow hood could explain the increase in screen contamination. To improve class A results, a longer cycle or a more powerful model (Byola^® 300 decontamination box, power: 3.21 mW/cm²) could be considered.