Changes in lipopolysaccharide‐ related endotoxicity of food‐borne pathogens in response to safety treatments practised in South Africa

This paper aims to evaluate the influence of pasteurization, ultra high temperature (UHT) treatment and sodium benzoate preservation on the LPS‐related endotoxicity of food‐borne pathogens Escherichia coli, Salmonella enteritidis and Pseudomonas aeruginosa.

The paper sees that selected bacteria were subjected to laboratory simulations of commercially used heat treatments. In the case of sodium benzoate preservation, the bacteria were grown in the presence of a sub‐lethal dose of this preservative. Cells and debris were subjected to LPS extraction, GC‐MS analyses and endotoxicity measurement with the chromogenic Limulus Amebocyte Lysate (LAL) assay.

The heat treatments and preservation method influenced the LPS‐related toxicity of each organism in a different manner. Increases in LPS‐related toxicity were noted in the LPS liberated from UHT‐treated E. coli and S. enteritidis and pasteurized E. coli and P. aeruginosa. Toxicity of the membrane associated LPS of UHT‐treated E. coli and pasteurized S. enteritidis was also elevated. Sodium benzoate resulted in E. coli cells with LPS with related toxicity levels almost double compared to that of the control cells. S. enteritidis LPS also demonstrated an increase in toxicity, while that of P. aeruginosa was rendered less toxic.

Toxicity could still be detected even after sterilization treatments like UHT, suggesting that viability and toxicity are not necessarily connected and that the toxicity of LPS molecules that remain in food products after treatment should be considered. Although ingestion of LPS originating from Gram‐negative bacteria is a fairly new concept, the effect that these toxins might have on members of society with compromised immune systems and individuals suffering from gastrointestinal diseases cannot be ignored.

The paper introduces a unique insight into food safety treatment‐induced toxicological changes related to LPS originating from food‐borne organisms, a factor that is currently unexplored in the South African food industry.