A Staphylococcus aureus outbreak in Italy has been associated with food handler contamination, based on findings from a study.
The outbreak was because of the contamination of food from an asymptomatic food handler. Staphylococcal food poisoning (SFP) is caused by the ingestion of preformed staphylococcal enterotoxins (SEs), produced by enterotoxigenic strains of coagulase-positive staphylococci (CPS), mainly Staphylococcus aureus.
“The investigated outbreak can be considered as a typical Staphylococcal intoxication in which food handlers carrying enterotoxin-producing Staphylococcus aureus in their noses or on their hands are regarded as the main source of food contamination,” said the study.
In August 2019, a staphylococcal food poisoning outbreak occurred in a nursing home in Piedmont, Italy. Eleven people had gastrointestinal symptoms, nausea and headache about three hours after food consumption. They recovered after 10 hours and nobody required hospitalization.
The epidemiological investigation among people that consumed the meal at lunch identified chicken salad as the most likely source of the outbreak, found the study published in Zoonoses and Public Health.
Need to follow good hygiene practices
Nasal swabs were collected from personnel involved in food handling that were on duty on the day and the day before the outbreak, including the cook and the cook’s helpers, and analyzed for Staphylococcus aureus.
Staphylococcus aureus was isolated from seven samples, including one vomit sample from a guest of the nursing home, two food samples of chicken salad with and without mayonnaise and nasal swabs from four people working in the kitchen of the home.
Overall, 69 people consumed the meal prepared by the internal canteen. Out of 33 people who ate the chicken salad, nine guests and two healthcare professionals were symptomatic. The menu was pasta with pesto and fresh tomatoes, pasta with oil, chicken salad with or without mayonnaise and cooked vegetables.
Staphylococcus aureus isolates were classified into four sequence types (STs): STs 72, 45, 22 and 1162. Four ST-72 isolates originated from vomit, chicken salad with and without mayonnaise, and the nasal swab of one food handler working the day before the outbreak during the meal preparation of chicken salad and other foods. The incident was the first reported foodborne intoxication due to Staphylococcus aureus ST-72 in Italy, said scientists.
Researchers hypothesized the outbreak was caused by a worker that contaminated the chicken salad by failing to follow good hygienic practices.
“Early identification of the source of food contamination during a foodborne outbreak is of crucial importance for robust contact tracing, cohorting and other infection control practices. Staphylococcal intoxications are usually self-limiting and without severe consequences, but in the case of an outbreak within a home for the elderly the rapid identification of the source of contamination can be crucial.”
(To sign up for a free subscription to Food Safety News, click here.)
