Germicidal effect of UVC light on clinical isolates and reference strains from an intensive care unit

de la Cruz R.H.; Lizárraga M.M.; Carrasco H.Y.E.; Fernández H.C. · Anales de la Facultad de Medicina (2026) · DOI: 10.15381/anales.v87i2.32412

Resumen

Introduction. Ultraviolet C (UVC, 254 nm) disinfection is an alternative strategy for reducing pathogens in hospital settings; however, its effectiveness varies according to the physiological state of bacteria and post-treatment environmental conditions. Objective. To evaluate UVC light ability to inactivate clinical isolates and reference strains of Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli, considering growth stage, biofilm, and possible photoreactivation. Methods. In vitro experimental study with three integrated assays. Standardized suspensions (0.5 McFarland) were exposed to 13.5–2952 mJ/cm2. Susceptibility was compared in adaptation (0 h), exponential (2–8 h), and stationary (24 h, with biofilm) phases, and visible light blocking post-irradiation was evaluated. Viability by colony count (CFU/mL). ANOVA and t tests (α = 0.05). Results. Complete inactivation in initial phase with doses ≥801 mJ/cm2. viable Duringbacteria exponential persisted phase, even maximum at maximum reduction dose,at especially 4 h (6.71E.log coli 10 (3.2 with ×40.5 106 mJ/cm2). CFU/mL).In Visible stationary light allowed phase, E. coli recovery (21-fold increase; p = 0.003). Light blocking achieved complete inactivation of P. aeruginosa and A. baumannii with ≥30 mJ/cm2. Conclusions. UVC effectiveness depends on growth stage and post-treatment light exposure. © (2026), (Universidad Nacional Mayor de San Marcos, Facultad de Medicina). All rights reserved.

Instituciones: Universidad Nacional Mayor de San Marcos; Universidad Nacional de San Antonio Abad del Cusco