Assessment of Ultraviolet-C Inactivation of Pseudomonas aeruginosa and Aspergillus flavus in the Anesthesia Workspace

Objective To determine the ultraviolet-C (UV-C) irradiation doses required to inactivate Pseudomonas aeruginosa and Aspergillus flavus contamination on polycarbonate surfaces using a triangular emitter configuration. Patients and Methods In this laboratory experiment, polycarbonate test carriers inoculated with >10 8 colony-forming units of P aeruginosa (MYA-15442) or A flavus (American Type Culture Collection 9643) were positioned 2.74 m from 3 linear UV-C emitters to determine minimally effective doses. Ten independent irradiation doses were evaluated for P aeruginosa (25-250 mJ/cm 2 ) and A flavus (50-2000 mJ/cm 2 ). Larger carriers were additionally evaluated for A flavus to model reduced cell clumping, simulating prior surface disinfection. Residual colony-forming units were quantified and compared with untreated controls to calculate log reductions. Finally, the efficacy of delivering these minimally effective doses through a triangular UV-C emitter configuration was assessed. Results For P aeruginosa , no growth was detected at any dose, including 25 mJ/cm 2 . For A flavus on standard carriers, inactivation occurred at 725 mJ/cm 2 , though no growth conditions were not achieved at any tested dose. However, on larger carriers (reduced clumping), no growth conditions for A flavus were achieved at 650 mJ/cm 2 . Delivery of 25 mJ/cm 2 for P aeruginosa and 650 mJ/cm 2 for A flavus through the triangular configuration resulted in undetectable growth. Conclusion A UV-C dose of 25 mJ/cm 2 is sufficient to attenuate P aeruginosa surface contamination. Conversely, A flavus inactivation will likely require manual high-level surface disinfection augmented with 650 mJ/cm 2 of UV-C irradiation.