Expression of Staphylococcal Enterotoxins under Stress Encountered during Food Production and Preservation.

Jenny Schelin,Sophia Johler,Yusak Budi Susilo

doi:10.3390/toxins9120401

Abstract

Staphylococcal food poisoning (SFP) is the most prevalent cause of food-borne intoxications worldwide. Consumption of enterotoxins preformed in food causes violent vomiting and can be fatal in children and the elderly. While being repressed by competing bacteria in most matrices, Staphylococcus aureus benefits from crucial competitive advantages in foods with high osmolarity or low pH. During recent years, the long-standing belief in the feasibility of assessing SFP risk based on colony-forming units of S. aureus present in food products has been disproven. Instead, researchers and food business operators are acutely aware of the imminent threat arising from unforeseeable enterotoxin production under stress conditions. This paradigm shift led to a variety of new publications enabling an improved understanding of enterotoxin expression under stress conditions encountered in food. The wealth of data provided by these studies is extremely diverse, as it is based on different methodological approaches, staphylococcal strains, stressors, and enterotoxins. Therefore, in this review, we aggregated and critically evaluated the complex findings of these studies, to provide readers with a current overview of the state of research in the field.

Highlights

Staphylococcal enterotoxins (SEs) preformed by S. aureus during growth in food are a common cause of staphylococcal food poisoning (SFP)
As the heat-stable SEs are preformed during growth of S. aureus in food and cannot be reliably inactivated through food processing [4], prevention of S. aureus growth and toxin formation in food is key to minimizing the risk of intoxication
The results of this study showed that mild stress conditions mimicking those encountered during food production and preservation can lead to significant changes in seb promoter activity, with glucose and NaCl stress reducing seb promoter activity, while lactic acid increased seb promoter activity

Summary

Introduction

Staphylococcal enterotoxins (SEs) preformed by S. aureus during growth in food are a common cause of staphylococcal food poisoning (SFP). The microbial safety guidelines of food products are determined by the acceptable concentration of viable cells (CFU per g or mL) present in a defined amount of food sample [26,27] This is partly based on earlier studies demonstrating that a critical population size of 105 CFU/g or mL is required for the presence of detectable amounts of enterotoxins [28]. No apparent linkage between absolute cell number or growth rate and enterotoxin production/levels was detected, suggesting that assessment of the intoxication risk associated with a food item based solely on the level of. A study on SFP outbreaks in the UK between 1969 and 1990 found different amounts of viable S. aureus cells, varying from not detectable to 1.5 × 1010 CFU/g, in the investigated food samples [31], a finding consistent with outbreak investigations elsewhere [23]. The aforementioned challenges emphasize the need for additional, more sensitive and robust tools for SE detection and quantification

Effect of Food-Related Stressors on the Expression of SEA-SED

Findings

Conclusions