The Impact of UV Radiation on Biofilms of Multi-Drug Resistant Nosocomial Bacteria

AIM & BACKGROUND: Germicidal ultraviolet radiation is widely used in healthcare settings for broad-spectrum sterilization. UV radiation damages microbial DNA by inducing pyrimidine dimerization. However, a comprehensive assessment of UV sterilization efficacy against nosocomial bacterial strains known for biofilm formation remains unexplored. This study aims to evaluate the sterilization effectiveness of UV irradiation on prevalent healthcare-associated pathogens with biofilm-forming potential. METHODOLOGY: Common pathogens, including Staphylococcus aureus, Methicillin-resistant S. aureus, Escherichia coli, and Pseudomonas aeruginosa, were cultivated on their specified bacteriological media. Selected strains were reconfirmed using 16s PCR. Antimicrobial susceptibility testing was performed using the Kirby-Bauer disk diffusion method and CLSI guidelines. Biofilm potential was assessed using a 96-well titer plate method. The titer plates were exposed to a UV germicidal emitter (254nm) at a distance of 50 cm inside a biological safety cabinet. Germicidal activity was evaluated using viability tests, crystal violet assays, scanning electron microscopy, and reconfirmed by atomic force microscopy, the results of exposed and non-exposed biomasses were compared statistically. RESULTS: S. aureus and MRSA were eradicated within 5 minutes of UV exposure, while P. Aeruginosa and E. Coli required 15 to 20 minutes for complete eradication. However, there was no significant difference in the biomass and ultrastructure of UV-exposed microbial biofilms compared to controls. This study demonstrates that UV disinfection is effective against biofilm-producing, multi-drug resistant pathogens. However, it does not affect the biofilm and extracellular polymeric substances of all pathogens. The biofilm of P. Aeruginosa was found to be the most resilient.