Protecting food from bacterial contamination is crucial for ensuring its safety and avoiding foodborne illness. Serratia marcescens is one of the food bacterial contaminants that can form biofilms and pigments that spoil the food product and could cause infections and illness to the consumer. Food preservation is essential to diminish such bacterial contaminants or at least reduce their pathogenesis; however, it should not affect food odor, taste, and consistency and must be safe. Sodium citrate is a well-known safe food additive and the current study aims to evaluate its anti-virulence and anti-biofilm activity at low concentrations against S. marcescens. The anti-virulence and antibiofilm activities of sodium citrate were evaluated phenotypically and genotypically. The results showed the significant effect of sodium citrate on decreasing the biofilm formation and other virulence factors, such as motility and the production of prodigiosin, protease, and hemolysins. This could be owed to its downregulating effect on the virulence-encoding genes. An in vivo investigation was conducted on mice and the histopathological examination of isolated tissues from the liver and kidney of mice confirmed the anti-virulence activity of sodium citrate. In addition, an in silico docking study was conducted to evaluate the sodium citrate binding ability to S. marcescens quorum sensing (QS) receptors that regulates its virulence. Sodium citrate showed a marked virtual ability to compete on QS proteins, which could explain sodium citrate’s anti-virulence effect. In conclusion, sodium citrate is a safe food additive and can be used at low concentrations to prevent contamination and biofilm formation by S. marcescens and other bacteria.

Emergence of antimicrobial resistance among the most important bacterial pathogens is recognized as a major public health threat affecting humans worldwide. Infections caused by resistant bacteria lead to up to twofold higher rates of adverse outcomes compared with similar infections caused by susceptible strains. The negative impacts of antibacterial resistance can be measured at the patient level by increased morbidity and mortality, at the healthcare level by increased resource utilization, higher costs and reduced hospital activity and at the society level by antibiotic treatment guidelines favoring increasingly broad-spectrum empiric therapy. In this study 67 isolates were collected from patients admitted to ICUs of Zagazig University Hospitals, Sharqia, Egypt. The isolates were biochemically identified and their susceptibility to different antimicrobials were tested by Kirby-Bauer standard disk diffusion method. The results showed that the recovered bacteria had high degree of resistance to different antimicrobial classes and 86.25 % were multi drug resistance (MDR). In conclusion high rate of MDR were found in this study that necessitate strict antibiotic dispensing policy to reduce the increased antibiotic resistance.

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