The use of optical oxygen sensing and respirometry to quantify the effects of antimicrobials on common food spoilage bacteria and food samples

Microbial spoilage and foodborne diseases cause significant economic and productivity losses. There is a need for novel approaches and antimicrobial treatments to extend shelf life of products, improve quality and microbial safety, and reduce spoilage and waste, and new assessment methods. Traditional assays for testing the toxicity of antimicrobials are time consuming, labour intensive, give crude estimations of toxicity, and cannot analyse complex samples such as crude food homogenates. Using a model antimicrobial compound Lauroyl Arginate Ethyl Ester (LAE), we describe a new analytical methodology based on optical oxygen sensing and respirometry to investigate the effects of various antimicrobial treatments on pure bacterial cultures, meat microbiota and packaged meat samples. By measuring and analysing the time profiles of O₂ probe signal (phosphorescence lifetime) in incubating test samples, we were able to visualise the toxic effects of LAE on the different bacterial specie, generate time and dose response curves, calculate EC50 and generation times of test organisms. The new multi-parametric toxicity testing platform allows for rapid, automated and parallel analysis of multiple samples under a range of antimicrobial concentrations and conditions.