Staphylococcus aureus Exotoxins and Their Detection in the Dairy Industry and Mastitis

Abstract

Staphylococcus aureus constitutes a major food-borne pathogen, as well as one of the main causative agents of mastitis in dairy ruminants. This pathogen can produce a variety of extracellular toxins; these include the shock syndrome toxin 1 (TSST-1), exfoliative toxins, staphylococcal enterotoxins (SE), hemolysins, and leukocidins. S. aureus expresses many virulence proteins, involved in evading the host defenses, hence facilitating microbial colonization of the mammary glands of the animals. In addition, S. aureus exotoxins play a role in the development of both skin infections and mastitis. Indeed, if these toxins remain in dairy products for human consumption, they can cause staphylococcal food poisoning (SFP) outbreaks. As a result, there is a need for procedures to identify the presence of exotoxins in human food, and the methods used must be fast, sensitive, reliable, and accurate. It is also essential to determine the best medical therapy for human patients suffering from S. aureus infections, as well as establishing the relevant veterinary treatment for infected ruminants, to avoid economic losses in the dairy industry. This review summarizes the role of S. aureus toxins in the development of mastitis in ruminants, their negative effects in the food and dairy industries, and the different methods used for the identification of these toxins in food destined for human consumption.

Keywords: Staphylococcus aureus; Staphylococcus aureus detection; exotoxins; food-borne pathogen; mastitis; staphylococcal food poisoning.

Figure 1

Mechanisms of T-cell activation: (A) Conventional T-cell activation by antigen presenting cells (APC) and (B) the association of three proteins, S. aureus Sags, MHC class II, and the TCR β-chain, act as an unconventional activation complex, that triggers uncontrolled activation of T-cells. Image from Tuffs et al., 2018 [3], under Creative Common License.

Figure 2

Distribution of clonal complexes (CC) in S. aureus strains isolated from the milk of different ruminant species: (A) goat (n = 34), (B) cow (n = 78), and (C) sheep (n = 15). Image modified from Merz et al., 2016 [1], under Creative Commons Attribution License (CC BY).