Staphylococcal enterotoxin M causes intestine dysfunction via activating inflammation

Staphylococcal enterotoxins are considered as causative agents for staphylococcal food poisoning. Although newly identified SEM exhibits mild emetic activity in a cynomolgus monkey, but the distinct role of it in staphylococcal foodborne diseases has not been deeply understood. In the present study, the secretion of SEM in vivo from a clinical S. aureus strain SA004 associated with food poisoning was assayed. Like S. aureus strain SA004, SEM also promoted interferon- secretion into the blood of BALB/c mice and caused extensive inflammatory cell invasion, loss of epithelium, and villous blunting in the duodenums. The monoclonal antibody against it countered these detrimental effects and inhibited bacterial growth in mice. The results suggested that SEM might participate in triggering staphylococcal food poisoning via activating inflammatory reaction and causing intestine dysfunction. Practical applicationsThis study provides evidence for the biological properties of SEM and is in support of the in vivo biological activity of toxin-specific monoclonal antibody. In this experiment, monoclonal antibody against SEM could neutralize SEM in blood secreted by S. aureus, inhibit inflammatory factor interferon- production, depress bacterial growth, and protect the mice from duodenum damage. All these suggest that toxin-neutralizing antibody could offer a successful opportunity to block virulence factors in vivo.