Modeling the UV-C Inactivation Kinetics and Determination of Fluence Required for Incremental Inactivation of Cronobacter spp.

A study was undertaken to model the UV-C inactivation kinetics and determine the fluences required for the incremental inactivation of several strains of Cronobacter spp. suspended in clear phosphate-buffered saline (PBS). In total, 13 strains of Cronobacter spp. were individually suspended in PBS and treated with UV-C doses of 0, 2, 4, 6, 8, and 10 mJ cm -2 with a collimated beam device emitting UV-C at 253.7 nm. The log reduction from each treatment was identified using the plate count method and plotted against the UV-C dose and then curve fitted using several mathematical models. The UV-C dose required for incremental inactivation of each isolate was determined using both linear and nonlinear regression. For the 13 strains tested, a UV-C dose of 10 mJ cm -2 inactivated between 3.66 +/- 0.101 and 5.04 +/- 0.465 log CFU mL-1. The survival behavior of all strains was best fitted to the Weibull+tail model, with correlation coefficients between 97.17 and 99.71%, and was used to determine the fluences required for incremental inactivation. The UV-C fluences needed to inactivate 1 log (D10-value) of Cronobacter spp. in buffer were between 3.53 and 5.50 mJ cm -2, whereas a fluence greater than 6.57 mJ cm -2 was required to achieve a 4-log inactivation. A clear understanding of the UV-C dose-response of several strains of Cronobacter spp. lays the foundation to design effective UV-based disinfection systems.