Survival traits of Cronobacter sakazakii and Cronobacter maloniticus exposed to lethal Far-UVC 222nm and blue light 405nm

Cronobacter spp., recognised as a foodborne pathogen, presents a significant risk to neonates and vulnerable groups emphasizing the necessity for effective management. This study investigates the efficacy of a dual light system, combining far-UVC (222 nm) and blue light (405 nm), in combating this bacterial threat. We explored the survival phenotypes of Cronobacter sakazakii and Cronobacter maloniticus under lethal dual light exposure, after 30 minutes of light treatment, strain-dependent sensitivity was observed, with 21 out of 27 strains being fully inactivated within 290 mJ/cm² of far-UVC and 23800 mJ/cm2 of blue light. Survivors, identified as Cronobacter spp., were detected, indicating bacterial resistance. Pigment production was also examined before and after the light treatment. All tested Cronobacter sakazakii exhibited yellow colonies on tryptic soy agar, whereas creamy white colonies were seen on milk agar. Colorimetric analysis verified the difference in pigment production on the two agar types. Light treatments had minimal impact on survivor pigment production, except for one isolate that lost pigment after light treatment on tryptic soy agar, resulting in failure to grow during subsequent enrichment. This research provides new evidence to understand the impact of dual light treatment on bacterial survival, contributing to the development of safer and more effective strategies in pathogenic bacteria control.