Staphylococcus aureus harbouring egc cluster coding for non-classical enterotoxins, involved in a food poisoning outbreak, Romania, 2012 / Staphylococcus aureus purtător de gene codante pentru enterotoxine non-clasice (cluster egc), implicat într-un focar de toxiinfecţie alimentară, România, 2012

In March 2012, a food poisoning outbreak was reported in a Romanian county, with a total number of 30 children affected. The symptoms (vomiting, diarrhea and abdominal pain), with onset within 1-2 hours after the ingestion of a particular food (milk), suggested a possible staphylococcal aetiology. An outbreak investigation was carried out, in accordance with the national surveillance methodology and 25 samples: stool (n=9), vomit (n=5), nasal swabs (n=9), and milk (n=2) were collected from the affected children, food handlers and suspected food. All isolated strains were sent to the Reference Centre for Staphylococci within the “Cantacuzino” National Institute of Research-Development for Microbiology and Immunology, Bucharest, Romania, for confirmation and further analysis. The aim of this study was to increase the reference laboratory capacity to confirm staphylococcal food poisoning (SFP) outbreak by defining the molecular basis of toxicity of Staphylococcus aureus (S. aureus) isolates and assessing their genetic relatedness. PCR methods have been used to detect 14 enterotoxin genes and the expression of some of these genes was proved by using a reverse transcription real-time PCR. Pulsed-field gel electrophoresis (PFGE) and Staphylococcus protein A coding gene sequence typing (spa typing) have been used to track the origin of the S. aureus contamination and to confirm the food poisoning outbreak.

Two enterotoxigenic S. aureus strains isolated from milk, twelve isolated from patients and two from food handlers were of the same spa- type (t902) and revealed an indistinguishable SmaI macrorestriction pattern after a PFGE analysis. All these strains harboured the same toxin genes profile, namely the enterotoxin gene cluster (egc), which strongly supports the evidence that the milk was the incriminated food vehicle of the outbreak and a food-handler was the most likely source of the staphylococcal food poisoning (SFP) incident.