A New Insight into the Bactericidal Mechanism of 405 nm Blue Light-Emitting-Diode against Dairy Sourced Cronobacter sakazakii

Abstract

(1) Background: Limited evidence exists addressing the action of antimicrobial visible light against Cronobacter sakazakii. Here, we investigated the antimicrobial effects of blue-LED (light emitting diode) at 405 nm against two persistent dairy environment sourced strains of C. sakazakii (ES191 and AGRFS2961). (2) Methods: Beside of investigating cell survival by counts, the phenotypic characteristics of the strains were compared with a reference strain (BAA894) by evaluating the metabolic rate, cell membrane permeability, and ROS level. (3) Results: The two environment isolates (ES191 and AGRFS2961) were more metabolic active and ES191 showed dramatic permeability change of the outer membrane. Notably, we detected varied impacts of different ROS scavengers (catalase > thiourea > superoxide dismutase) during light application, suggesting that hydrogen peroxide (H2O2), the reducing target of catalase, has a key role during blue light inactivation. This finding was further strengthened, following the observation that the combined effect of external H2O2 (sublethal concentration) and 405 nm LED, achieved an additional 2–4 log CFU reduction for both stationary phase and biofilm cells. (4) Conclusions: H2O2 could be used in combination with blue light to enhance bactericidal efficacy and form the basis of a new hurdle technology for controlling C. sakazakii in dairy processing plants.

Antimicrobial photodynamic inactivation as an alternative approach to inhibit the growth of Cronobacter sakazakii by fine-tuning the activity of CpxRA two-component system

“…Despite these encouraging advances, the bactericidal efficacy still needs to be further potentiated. Wu et al (2021) stated that C. sakazakii cells were more resistant to a single intervention of either blue light or 0.02% H 2 O 2 , but the combined intervention attenuated its survival up to 5~6 log CFU. Whilst this approach did not truly take advantage of light irradiation, aPDI solved this issue by adding photosensitizer to the system, triggering photodynamic activity to kill bacteria (3.6 log).…”

Isolation and Molecular identification of Cronobacter sakazakii isolated from different foodstuffs and infant stools

“…However, this result disagrees with those of Holý et al (2021), who recorded a lower incidence of 0.41%, and with Abd El-Tawab et al (2019), who reported zero incidence of C. sakazakii from milk powder samples.As Cronobacter sakazakii can form biofilms, heat-tolerant, and resistant to desiccation, it represents a risk to food safety when it comes to powdered milk and its products, particularly powdered infant formula products. As a result, it might endure a long period in the processing environment (Ling et al, 2020;Wu et al, 2021…”