Staphylococcal enterotoxins (SEs) are extracellular proteins, produced mainly by Staphylococcus aureus, which cause staphylococcal food poisoning (SFP) when ingested. Here, a novel SE was identified from two strains, which were identified as the causative microbes of the SFP outbreak that occurred in Tokyo in 2004. Both strains harbored the SEA gene, but its production was lower than that of other SEA-producing SFP isolates. Whole-genome sequencing analysis demonstrated that both strains harbored a SE-like gene besides sea. Phylogenetic analysis revealed that the amino acid sequence deduced from the SE-like gene belonged to the SEB group. Therefore, this gene was presumed to be a novel SE gene and termed “SE02.” The stability of SE02 against heating and proteolytic digestions was a little different from that of SEA. SE02 has both superantigenic and emetic bioactivities. Namely, SE02 activated mouse splenocytes and exhibited emetic activity in the common marmoset. SE02 mRNA was highly expressed in both isolates during the exponential phase of cultivation. In addition, SE02 protein was produced at 20 °C and 25 °C, which reflects the actual situation of SFP. SE02 appears to be a novel emetic toxin that was likely the causative toxin in combination with SEA in the SFP outbreak.

葡萄球菌肠毒素（SEs）是主要由金黄色葡萄球菌产生的细胞外蛋白，摄入时会引起葡萄球菌食物中毒（SFP）。在这里，从两个菌株中鉴定出了一种新颖的SE，它们被确定为2004年在东京发生的SFP暴发的致病微生物。两个菌株都带有SEA基因，但其产量低于其他产生SEA的SFP分离株。全基因组测序分析表明，除了海洋外，这两种菌株都带有SE样基因。系统发育分析表明，从SE样基因推导的氨基酸序列属于SEB组。因此，该基因被推定为新的SE基因，被称为“ SE02”。SE02对加热和蛋白水解消化的稳定性与SEA略有不同。SE02具有超抗原性和催吐生物活性。即，SE02激活了小鼠脾细胞，并且在普通exhibit猴中表现出催吐活性。在培养的指数阶段，SE02 mRNA在两种分离物中均高表达。另外，SE02蛋白是在20°C和25°C下产生的，这反映了SFP的实际情况。SE02似乎是一种新型催吐毒素，很可能是SFP爆发中与SEA结合的致病性毒素。