A foodborne outbreak caused by staphylococcal enterotoxins in cheese sandwiches in northern Italy

Abstract

Staphylococcus aureus can produce numerous toxins, including staphylococcal enterotoxins, namely, SEs, SEA to SEE, SEG to SEI, and SER to SET. They have demonstrated emetic activity and can cause food poisoning outbreaks (FBOs). Here, we report a multidisciplinary investigation conducted by authorities competent in food safety in collaboration with veterinary and health and hygiene services. The issue was foodborne intoxication which involved eight members (aged 12–74 years) of the same family. Notification reported that time to symptom onset was about 3 hours after lunch, which suggests that the food contained preformed toxins. Ham and cheese used for the preparation of sandwiches consumed by all symptomatic relatives were suspected to be the source of FBO. The day after symptoms appeared, samples were collected at the restaurant and delivered to the food safety laboratory. All analyses performed on official food samples are validated according to ISO 17025:2017 and accredited. The cheese subsamples were all positive for coagulase-positive staphylococci CPS (range: 1.1*103 CFU/g to 8.1*103 CFU/g). The pooled sample tested positive for staphylococcal enterotoxin D (SED) at 0.649 ng/g. This concentration can cause symptoms of FBO. Following the notification of suspected food poisoning, a rapid response by the district food safety agency is necessary. In the case described here, the multidisciplinary collaboration facilitated the collection of samples at the food business plant aimed at identifying a suspected source of intoxication and to withdraw unsafe food from the market.