Combination of UVC light with antimicrobial agents for enhanced disinfection of surfaces and liquids

Environmental changes and intense human activities enlarge the risks of infectious diseases and emphasize the growing importance of disinfection actions. Ultraviolet irradiation and chemical disinfectants such as hydrogen peroxide, peracetic acid, and chlorine-based compounds are the most commonly used for microbial control in different settings, namely water and food processing industries, hospitals, and other healthcare settings. But when applied individually, both ultraviolet radiation and chemical disinfectants present several limitations, which have led to a continued effort to develop new and enhanced disinfection technologies. Different research teams have been investigating the efficiency of pairing germicidal ultraviolet light (UVC) with antimicrobial agents, due to their potential for achieving better disinfection results and overtaking specific drawbacks. Since each technology has different molecular targets - UVC mainly interferes with nucleic acids while disinfectants affect the structural integrity of the microorganism - their combination may have the potential to increase synergistically the disinfection performance. This not only provides additional confidence in the quality of disinfection practices but also improves their safety allowing the use of low doses of disinfectants and reduces the formation of toxic disinfection byproducts (DBPs). However, the action of a disinfectant may be affected by many factors (i.e., the presence or absence of organic matter, type of microorganisms, presence of biofilms, exposure time). This variety of influencing factors has been slowing the research in novel disinfection strategies. This study reviews antimicrobial combinations of UVC with antimicrobial agents for the disinfection of surfaces, and liquids. The impact of the antimicrobial combinations, modes of action, and parameters affecting their inactivation efficacy against different types of microorganisms are also highlighted. The limitations of the current experimental design are emphasized, and optimized strategies are proposed to allow accurate comparison between combined disinfection systems.