Time-Course Study of the Antibacterial Activity of an Amorphous SiOxCyHz Coating Certified for Food Contact

Food grade disinfectants based on hydrogen peroxide/peracetic acid and sodium hypochlorite interfere with the adhesion of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Listeria monocytogenes to stainless steel of differing surface roughness

This study aimed to evaluate the potential of the bacterium Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Listeria monocytogenes to adhere to stainless steel discs with differing degrees of surface roughness (Ra = 25.20-961.90 nm). Stainless steel is a material commonly used in the food industry for processing equipment, which is regularly exposed to cleaning procedures. The investigation included the commercial disinfectants hydrogen peroxide/peracetic acid and sodium hypochlorite which were evaluated for their antibacterial and anti-adhesion activity. The adhesion was assessed by the standard plate count method, while the broth microdilution method CLSI M07-A10 was used to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the disinfectants. Based on the MIC values, both disinfectants exerted significant inhibitory effects with MIC values for hydrogen peroxide/peracetic acid and sodium hypochlorite of 250 µg ml-1 and 500 µg ml-1, respectively. Whereas the MBC values were equal to the MIC for all bacteria except for E. coli with values 2-fold higher than the MIC. Obtained results also revealed that all tested bacteria were able to adhere to stainless steel surfaces, although differences were found for strains and surface roughness. The lowest adhesion rate of each strain was recorded on the roughest stainless steel disc at a Ra of 961.90 nm. Further, at a concentration of 1 MIC, the disinfectant sodium hypochlorite reduced initial bacterial adhesion to stainless steel surfaces to a significantly greater extent than the disinfectant hydrogen peroxide/peracetic acid. These findings are consistent with the results obtained by Scanning Electron Microscopy (SEM) analysis, which indicates the great applicability of the tested disinfectants for the control of bacterial adhesion in the food industry.

Zinc Oxide Nanoparticles (ZnO-NPs) Induce Cytotoxicity in the Zebrafish Olfactory Organs via Activating Oxidative Stress and Apoptosis at the Ultrastructure and Genetic Levels

Nanotechnology has gained tremendous attention because of its crucial characteristics and wide biomedical applications. Although zinc oxide nanoparticles (ZnO-NPs) are involved in many industrial applications, researchers pay more attention to their toxic effects on living organisms. Since the olfactory epithelium is exposed to the external environment, it is considered the first organ affected by ZnO-NPs. Herein, we demonstrated the cytotoxic effect of ZnO-NPs on the olfactory organ of adult zebrafish after 60 days post-treatment. We opted for this period when fishes stop eating their diet from the aquarium, appear feeble, and cannot swim freely. Our study demonstrated that ZnO-NPs induced significant malformations of the olfactory rosettes at histological, ultrastructural, and genetic levels. At the ultrastructure level, the olfactory lamellae appeared collapsed, malformed, and twisted with signs of degeneration and loss of intercellular connections. In addition, ZnO-NPs harmed sensory receptor and ciliated cells, microvilli, rodlet, crypt, and Kappe cells, with hyper-activity of mucous secretion from goblet cells. At the genetic level, ZnO-NPs could activate the reactive oxygen species (ROS) synthesis expected by the down-regulation of mRNA expression for the antioxidant-related genes and up-regulation of DNA damage, cell growth arrest, and apoptosis. Interestingly, ZnO-NPs affected the odor sensation at 60 days post-treatment (60-dpt) more than at 30-dpt, severely damaging the olfactory epithelium and irreparably affecting the cellular repairing mechanisms. This induced a dramatically adverse effect on the cellular endoplasmic reticulum (ER), revealed by higher CHOP protein expression, that suppresses the antioxidant effect of Nrf2 and is followed by the induction of apoptosis via the up-regulation of Bax expression and down-regulation of Bcl-2 protein.

A Time-Course Study on a Food Contact Material (FCM)-Certified Coating Based on Titanium Oxide Deposited onto Aluminum

Aluminum is the second most widely used metal worldwide. It is present as an additive in cosmetics, pharmaceuticals, food, and food contact materials (FCM). In this study, we confirm the bactericidal effect of a special anodizing method, based on TiO2 nanoparticles (DURALTI®) deposited on aluminum disks with different roughness and subjected to two sanitizing treatments: UV and alcohol 70%. Consequently, we perform a time-course evaluation against both Gram-negative and Gram-positive bacteria to better frame the time required to achieve the best result. Approximately 106 CFU/mL of Escherichia coli ATCC 25922; Salmonella Typhimurium ATCC 1402; Yersinia enterocolitica ATCC 9610; Pseudomonas aeruginosa ATCC 27588; Staphylococcus aureus ATCC 6538; Enterococcus faecalis ATCC 29212; Bacillus cereus ATCC 14579 and Listeria monocytogenes NCTT 10888 were inoculated onto each aluminum surface and challenged with UV and alcohol 70% at 0, 15", 30", 1', 5', 15', 30', 1, 2, 4 and 6 h. DURALTI® coating already confirmed its ability to induce a 4-logarithmic decrease (from 106 to 102 CFU/mL) after 6 h. Once each sanitizing treatment was applied, an overall bacterial inhibition occurred in a time ranging from 15'' to 1'. The results are innovative in terms of preventing microbial adhesion and growth in the food industry.