Abstract
Salmonella spp. is an important foodborne agent of salmonellosis, whose sources in humans often include products of avian origin. The control of this bacterium is difficult especially when Salmonella spp. is organized into biofilms. We hypothesized that the novel nanocomposites of ZnO nanocrystals doped with silver (Ag) and silver oxide (AgO) nanocrystals (ZnO:Ag-AgO) synthesized by the coprecipitation method could control or prevent the formation of Salmonella Enteritidis (SE) and Salmonella Heidelberg (SH) biofilm and its entry into turkey eggs. The diffraction characteristics of ZnO and AgO showed sizes of 28 and 30 nm, respectively. The Zn to Ag substitution into the ZnO crystalline structure was evidenced by the ionic radius of Ag+2 (1.26 Å), which is greater than Zn+2 (0.74 Å). For the SE analyses post-biofilm formation, the ZnO:Ag-AgO was not able to eliminate the biofilm, but the bacterial load was lower than that of the control group. Additionally, SE was able to infiltrate into the eggs and was found in both albumen and yolk. For the SH analyses applied onto the eggshells before biofilm formation, the ZnO:Ag-AgO treatment prevented biofilm formation, and although the bacterium infiltration into the eggs was observed in all treated groups, it was significantly smaller in ZnO:Ag-AgO pre-treated eggs, and SH could not reach the yolk. There was no difference in pore size between groups; therefore, the inhibition of biofilm formation and the prevention of bacterium entry into the egg were attributable to the use of ZnO:Ag-AgO, which was not influenced by the egg structure. Although the amount of Ag and Zn in the shell of the ZnO:Ag-AgO group was greater in relation to the control, this difference was not detected in the other egg components. In the search for new measures that are effective, safe and viable for controlling microorganisms in poultry farming, the application of a nanocomposite of Ag-doped ZnO and AgO nanocrystals appears as an alternative of great potential to prevent Salmonella sp biofilms in eggshells and other surfaces.
Highlights
The control of microorganisms is a primordial action for poultry production due to the potential risk of transmission of pathogenic organisms to humans and other animals throughout the entire food chain
We have demonstrated that a novel nanocomposite of Ag-doped Zinc oxide (ZnO) and AgO nanocrystals has been successfully used as a preventive measure to control biofilm formation, and Salmonella Enteritidis (SE) and Salmonella Heidelberg (SH) infiltration into turkey eggs
We have confirmed the Ag doping with substitution of Zn by Ag into the ZnO crystalline structure, by demonstrating that the Ag+2 has an ionic radius (1.26 Å) greater than Zn+2 (0.74 Å)
Summary
The control of microorganisms is a primordial action for poultry production due to the potential risk of transmission of pathogenic organisms to humans and other animals throughout the entire food chain. Among the most important microorganisms, Salmonella spp. may be considered one of the most important foodborne agents in the European Union and the United States (Center for Disease Control CDC, 2016; EFSA, 2017) and may cause significant damage to the poultry industry as well as to public health. Products of avian origin represent 47% of salmonellosis sources in humans (Center for Disease Control CDC, 2016). Control of the different serotypes of Salmonella spp. is required throughout the entire poultry production cycle. Embryonated eggs, equipment, facilities, vehicles and other materials involved in the process must undergo an efficient disinfection to control these microorganisms. Formaldehyde has been chosen as one the main disinfectant agent of eggs, its use has been restricted (BRASIL, 2008), openning space to other disinfectants, such as the peracetic acid (PA)
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