Citation: Khan, M.; McDonald, M.; Mundada, K.; Willcox, M. Efficacy of Ultraviolet Radiations against Coronavirus, Bacteria, Fungi, Fungal Spores and Biofilm. Hygiene 2022, 2, 120–131. https://doi.org/10.3390/ hygiene2030010 Academic Editors: Honghua Hu, Dayane de Melo Costa and Stephanie Dancer Received: 27 June 2022 Accepted: 10 August 2022 Published: 12 August 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Article Efficacy of Ultraviolet Radiations against Coronavirus, Bacteria, Fungi, Fungal Spores and Biofilm Mahjabeen Khan 1, *, Murray McDonald 2 , Kaustubh Mundada 2 and Mark Willcox 1 1 School of Optometry and Vision Science, UNSW, Sydney, NSW2052, Australia 2 Mobile UV Innovations, Melbourne, VIC 3070, Australia * Correspondence: mahjabeen.khan@unsw.edu.au Abstract: Ultra-violet (UV) C (200–280 wavelength) light has long been known for its antimicrobial and disinfecting efficacy. It damages DNA by causing the dimerization of pyrimidines. A newly designed technology (MUVi-UVC; Mobile UV Innovations Pty Ltd., Melbourne, VIC, Australia) that emits UVC at 240 nm is composed of an enclosed booth with three UVC light stands each with four bulbs, and has been developed for disinfecting mobile medical equipment. The aim of this project was to examine the spectrum of antimicrobial activity of this device. The experiments were designed following ASTM E1052-20, EN14561, BSEN14476-2005, BSEN14562-2006 and AOAC-Official-Method- 966.04 standards for surface disinfection after drying microbes on surfaces. The disinfection was analyzed using Staphylococcus aureus (ATCC 6538), Pseudomonas aeruginosa (6294), Candida auris (CBS 12373), spores of Aspergillus niger (ATCC 16404), coronavirus (SARS-CoV-2 surrogate ATCC VR-261) as well as a methicillin-resistant Staphylococcus aureus (SA31), a carbapenem- and polymyxin-resistant Pseudomonas aeruginosa (PA219), Escherichia coli K12 (ATCC 10798) and Salmonella typhi (ATCC 700730). The parameters of time, the number of lights and direction of the sample facing the lights were examined. The MUVi-UVC was able to kill 99.999% of all of the tested bacteria, fungi, coronavirus and bacteria in the biofilms if used for 5 min using all three lights in the setup with the glass slides in a vertical position. However, for fungal spores, 30 min were required to achieve 99.999% killing. There was a small but insignificant effect of having the surface horizontally or vertically aligned to the UV lights. Therefore, this UVC device is an effective technology to disinfect medical devices. Keywords: UVC radiation; biofilms; coronavirus; bacteria; fungi; fungal spores; disinfection 1. Introduction Ultraviolet light (UV) has been used for many years to disinfect contaminated surfaces, as well as for treating infections. Ultraviolet radiation has a shorter wavelength than visible light, but is longer than x-rays [1]. UV radiation is divisible into four spectra, based on its wavelengths, and these are UV (100–200 nm), UVC (200–280 nm), UVB (280–315 nm) and UVA (315–400 nm) [1,2]. UVC is the most effective at killing different types of microorganisms [3]. UVC inactivates microorganisms by damaging their genetic material [4,5]. The UVC range, particularly between 250–270 nm, is absorbed by nucleic acids, with 262 nm being the peak germicidal wavelength [3]. The DNA or RNA of microorganisms is damaged by the dimerization of the nucleic acid bases, particularly pyrimidines, which prevents microbial replication and reduces viability [1,5]. Compared to routine disinfection, UVC has several advantages such as killing a broader range of microorganisms, taking less time to kill vegetative bacteria, being eco-friendly, generally safe to use (provided appropriate protective clothing and equipment are used), having relatively low costs, and the associated technology being generally easy to operate [6,7]. However, as it is light, it does have a disadvantage of shielding or shadowing [8], whereby the places not in the direct line of sight of the UVC source do not obtain adequate disinfection. This can be overcome Hygiene 2022, 2, 120–131. https://doi.org/10.3390/hygiene2030010 https://www.mdpi.com/journal/hygiene