Salmonella enterica serovar Enteritidis biofilm lifestyle induces lower pathogenicity and reduces inflammatory response in a murine model compared to planktonic bacteria

SirA, CsrBC and HilD form in vivo a regulatory cascade that controls the SP1-1 and SPI-2 gene expression when Salmonella Typhimurium is in the intestinal lumen and are required for cecal colonization and liver dissemination in the avian model

When Salmonella Typhimurium grows in LB in vitro, BarA/SirA system induces the expression of CsrB/C, that sequester the regulator CsrA, thus derepressing HilD regulator. HilD activated induces HilA and SsrB expression, central regulators of SPI-1 and SPI-2, respectively. We analyze the in vivo contribution of these genes in 1-day- and 1-week-old chickens infected with a Wild Type strain of S. Typhimurium and the ΔsirA, ΔcsrB/C and ΔhilD mutants. CFUs determination in liver and cecum showed that the mutants colonized both organs in lower amounts compared with WT strain in both chicken models and they were affected in the ability to produce histological injuries in these organs. We analyzed whether these genes operate in cascade in vivo and prior to intestinal invasion, by analyzing hilA, ssrAB, hilD, csrB and sirA expression in the cecal contents of chickens inoculated with Wild Type and mutants 120 min after inoculation. Expression of hilA and ssrB, but not csrB and sirA, was decreased in ΔhilD strain. Expression of hilD, hilA and ssrB, but not sirA, was decreased in samples of ΔcsrB/C. In SirA absence, expression of all genes was decreased. Our findings demonstrate that SirA, CsrB/C and HilD conform a regulatory cascade in vivo, when Salmonella is in intestinal lumen and this cascade controls the expression of HilA and SsrB prior to intestinal invasion. We also demonstrate that these genes are necessary for the production of lesions during S. Typhimurium infection in chickens.

Prevention and Control of Human Salmonella enterica Infections: An Implication in Food Safety

Salmonella is a foodborne zoonotic pathogen causing diarrhoeal disease to humans after consuming contaminated water, animal, and plant products. The bacterium is the third leading cause of human death among diarrhoeal diseases worldwide. Therefore, human salmonellosis is of public health concern demanding integrated interventions against the causative agent, Salmonella enterica. The prevention of salmonellosis in humans is intricate due to several factors, including an immune-stable individual infected with S. enterica continuing to shed live bacteria without showing any clinical signs. Similarly, the asymptomatic Salmonella animals are the source of salmonellosis in humans after consuming contaminated food products. Furthermore, the contaminated products of plant and animal origin are a menace in food industries due to Salmonella biofilms, which enhance colonization, persistence, and survival of bacteria on equipment. The contaminated food products resulting from bacteria on equipment offset the economic competition of food industries and partner institutions in international business. The most worldwide prevalent broad-range Salmonella serovars affecting humans are Salmonella Typhimurium and Salmonella Enteritidis, and poultry products, among others, are the primary source of infection. The broader range of Salmonella serovars creates concern over multiple strategies for preventing and controlling Salmonella contamination in foods to enhance food safety for humans. Among the strategies for preventing and controlling Salmonella spread in animal and plant products include biosecurity measures, isolation and quarantine, epidemiological surveillance, farming systems, herbs and spices, and vaccination. Other measures are the application of phages, probiotics, prebiotics, and nanoparticles reduced and capped with antimicrobial agents. Therefore, Salmonella-free products, such as beef, pork, poultry meat, eggs, milk, and plant foods, such as vegetables and fruits, will prevent humans from Salmonella infection. This review explains Salmonella infection in humans caused by consuming contaminated foods and the interventions against Salmonella contamination in foods to enhance food safety and quality for humans.

Effect of Lactobacillus reuteri S5 Intervention on Intestinal Microbiota Composition of Chickens Challenged with Salmonella enteritidis

To understand the mechanism of lactic acid bacteria against Salmonella enteritidis infection; we examined how lactic acid bacteria regulated the intestinal microbiota to resist infection by pathogenic bacteria. The probiotic strain Lactobacillus reuteri S5 was used to construct an animal model of S. enteritidis infected broilers. A high-throughput sequencing technology was used to analyze the regulatory effects of L. reuteri S5 on the structure of the intestinal microbiota of broilers infected with S. enteritidis; and to examine the possible defense mechanism they used. Our results showed that the administration of L. reuteri S5 reduced colonization of S. enteritidis (p < 0.05), decreased intestinal permeability (p < 0.05), and reduced the bacterial displacement likely due by S. enteritidis colonization (p < 0.05), suggesting some enhancement of the intestinal barrier function. Furthermore, L. reuteri S5 increased the number of operational taxonomic units (OTUs) in the chicken cecal microflora and the relative abundance of Lactobacillaceae and decreased the relative abundance of Enterobacteriaceae. These results suggest that the lactic acid bacterium L. reuteri S5 protected the intestinal microbiota of chickens against S. enteritidis infection.

Electrochemical Control of Biofilm Formation and Approaches to Biofilm Removal

This review deals with microbial adhesion to metal-based surfaces and the subsequent biofilm formation, showing that both processes are a serious problem in the food industry, where pathogenic microorganisms released from the biofilm structure may pollute food and related material during their production. Biofilm exhibits an increased resistance toward sanitizers and disinfectants, which complicates the removal or inactivation of microorganisms in these products. In the existing traditional techniques and modern approaches for clean-in-place, electrochemical biofilm control offers promising technology, where surface properties or the reactions taking place on the surface are controlled to delay or prevent cell attachment or to remove microbial cells from the surface. In this overview, biofilm characterization, the classification of bacteria-forming biofilms, the influence of environmental conditions for bacterial attachment to material surfaces, and the evaluation of the role of biofilm morphology are described in detail. Health aspects, biofilm control methods in the food industry, and conventional approaches to biofilm removal are included as well, in order to consider the possibilities and limitations of various electrochemical approaches to biofilm control with respect to potential applications in the food industry.