Identification and measurement of staphylococcal enterotoxin‐like protein I ( SE l l) secretion from Staphylococcus aureus clinical isolate

Aims Staphylococcus aureus ( Staph. aureus ) produces a wide variety of staphylococcal enterotoxins ( SE s) and staphylococcal enterotoxin‐like ( SE l ) proteins, which are the most causative agents of staphylococcal food poisoning. In contrast to classical SE s ( SEA to SEE ), the relationship between the novel SE s/ SE l s ( SEG to SE l X) and staphylococcal food poisoning is not elucidated. This study is aimed to establish a system to detect staphylococcal enterotoxin‐like protein I ( SE l I) for analysis of staphylococcal food poisoning. Methods and Results SE l I was characterized in a Staph. aureus clinical isolate associated with food poisoning; there was an amino acid substitution Thr145Ala compared to previously identified SEI from Staph. aureus 04‐02981. Subsequently, SE l I was expressed, purified, and the poly‐ and monoclonal antibodies against it were prepared. Using these antibodies, a highly sensitive sandwich enzyme‐linked immunosorbent assay ( ELISA ) that specifically detected and measured SE l I secretion from the Staph. aureus clinical isolate in LB medium, milk and bloodstream was developed. Conclusions The ELISA system has been successfully applied for analysing SE l I secretion in vivo and in vitro . Significance and Impact of the Study The highly sensitive ELISA should make it attractive for quantifying SE l I in food hygiene supervision and clinical diagnosis in near future.