Effects of a pulsed light-induced stress on Enterococcus faecalis



Sylvie Chevalier, Laboratoire de Microbiologie Signaux et Microenvironnement, EA4312, Université de Rouen, 55 rue Saint Germain, 27000 Evreux, France. E-mail: sylvie.chevalier@univ-rouen.fr



Pulsed light (PL) technology is a surface decontamination process that can be used on food, packaging or water. PL efficiency may be limited by its low degree of penetration or because of a shadow effect. In these cases, surviving bacteria will be able to perceive PL as a stress. Such a stress was mimicked using low transmitted energy conditions, and its effects were investigated on the highly environmental adaptable bacterium Enterococcus faecalis V583.

Methods and Results

In these laboratory conditions, a complete decontamination of the artificially inoculated medium was performed using energy doses as low as 1·8 J cm−2, while a treatment of 0·5, 1 and 1·2 J cm−2 led to a 2·2, 6 and 7-log10 CFU ml−1 reduction in the initial bacterial population, respectively. Application of a 0·5 J cm−2 pretreatment allowed the bacteria to resist more efficiently a 1·2 J cm−2 subsequent PL dose. This 0·5 J cm−2 treatment increased the bacterial mutation frequency and affected the abundance of 19 proteins as revealed by a global proteome analysis.


Enterococcus faecalis is able to adapt to a PL treatment, providing a molecular response to low-energy PL dose, leading to enhanced resistance to a subsequent treatment and increasing the mutation frequency.

Significance and Impact of the Study

This study gives further insights on Ent. faecalis capacities to adapt and to resist to stress.