Effect of Ultraviolet-c (UVc) light and Ozone on the Survival of Mycobacterium Abscessus Complex Organisms Associated with Cystic Fibrosis
Authors: Moore John Edmund , Millar Beverley Cherie 
Published: September 2022

Background:
Members of the Mycobacterium abscessus complex have now emerged as clinically significant respiratory pathogens in people with cystic fibrosis (CF), potentially leading to increased disease severity, antibiotic treatment, and persistence dilemmas. Many of these species are resistant to disinfectants and biocides commonly used to clean and disinfect the hospital environment, thus necessitating the need to examine innovative ways to eliminate these organisms from such environments. It was, therefore, the aim of this study to examine the individual effect of ultraviolet-c (UVc) light (λ = 254 nm) and ozone (O3) on the growth of the M. abscessus complex organisms, as well as on seven other clinically significant CF pathogens, including Achromobacter spp., Burkholderia gladioli, Burkholderia cenocepacia, Burkholderia multivorans, Pseudomonas aeruginosa, Staphylococcus aureus, and Stenotrophomonas maltophilia.

Methods:
Bacterial isolates (n = 46), including M. abscessus complex (n = 6) (M. abscessus subsp abscessus [n = 2], M. abscessus subsp. bolletii [n = 2], M. abscessus subsp. massiliense [n = 2]), and other CF pathogens (n = 40) including Achromobacter spp., B. gladioli, B. cenocepacia, B. multivorans, P. aeruginosa, S. aureus, and S. maltophilia, were exposed for 1 h to UVc light (254 nm), as well as to ozone (O3; 26 ppm).

Results:
UVc light inactivated all M. abscessus complex organisms (n = 6), as well as the 40 isolates from the other genera and species. No bacterial species tested was able to survive the UVc treatment. O3 was unable to inactivate all isolates of M. abscessus subsp. abscessus (n = 2), M. abscessus subsp. bolletii (n = 2), and one isolate of M. abscessus subsp. massiliense, but killed one strain of M. abscessus subsp. massiliense. Overall, O3 inactivated only 20% of total isolates, allowing the posttreatment growth of the remaining 80% of isolates. There was no difference in the growth dynamic of P. aeruginosa from the environmental waters which had received O3 treatment and the control (untreated with O3). Bacterial growth, while occurring post-O3 treatment, was not as prolific in all remaining organisms, as in the untreated controls, demonstrating some but limited antibacterial effect.

Conclusions:
From the data presented by this study, UVc light at 254 nm was effective at eliminating all organisms examined, including members of the M. abscessus complex. Given the refractory nature of these organisms against conventional wet chemical disinfection, UVc potentially offers a physical method to control and eliminate the survival of these organisms on health-care surfaces and fomites. For many CF species examined in this study, these data represent the first reports of the organisms susceptibility to UVc light. Further work is now required to establish time/distance parameters incorporated into newly designed innovative devices, to allow disinfection protocols to be optimized, and delivered to exploit this vulnerability with these nontuberculous mycobacterial organisms, as well as with the other bacterial species examined.