Poor conditions at a production site likely contributed to a Salmonella outbreak that sickened more than 60 people in Italy, according to researchers.

In the summer of 2022, a foodborne outbreak involving 63 people occurred in the Marche region of central Italy. A common food exposure among cases was a roasted, ready-to-eat (RTE) pork product called porchetta. Porchetta is made from boned, seasoned, and roasted swine carcass meat. Roasting lasts from five to eight hours, depending on size of the animal, followed by blast chilling to 4 degrees C (39.2 degrees F).

Porchetta was produced by a local manufacturing plant and distributed to at least two retail stores, one of which was the retail outlet for the factory, according to the study published in the journal Microorganisms.

Monophasic Salmonella Typhimurium was isolated from samples collected at the manufacturing plant and at both retail stores, as well as in porchetta sampled at one store. 

Patient details
Monophasic Salmonella Typhimurium is the third most commonly reported Salmonella type behind infections in the EU. However, in Italy, it is the serovar most frequently isolated from humans.

From mid-July to the first week of September 2022, an increase in clinical strains of Salmonella was observed. The number received was double that collected in the same period over the two previous years, which suggested an outbreak of salmonellosis, said researchers.

Overall, 33 cases were male, and the most affected age group was 5 to 14 years old, with 26 cases. Patients were reported between July 14 and Sept. 7 and included 22 in July, 37 in August, and five in September. The peak of cases was recorded between July 21 and 27. In total, 29 people were hospitalized.

In 10 of 43 epidemiological investigations, the consumption of a roasted, RTE pork product, porchetta, was commonly reported, together with the names of shops from which it had been purchased. Two retail stores, in the province of Fermo, were identified wher some patients had purchased the same type of food a few days prior to onset of symptoms. This allowed officials to determine that one brand of porchetta produced by one firm and sold at two outlets could be of interest.

An inspection in August at the food production plant revealed poor hygiene practices and poor maintenance of the facility, particularly in the cooking areas and for equipment used for the production of porchetta. Inadequate procedures regarding the identification and management of critical control points (CCPs) were also revealed.

Conflicting information about the actual production process compared to that described in the self-monitoring manual in relation to the temperatures used to cook and blast chill the product was provided by the food business during an interview.

Improvements made after suspension
Porchetta production was suspended at the end of August. Officials ordered cleaning, disinfection, and maintenance to be carried out at the site, along with an expert review of procedures based on HACCP principles. Suppliers of the pork meat were located in Abruzzo and Umbria.

Production resumed in mid-October, following an inspection by authorities and the verification of compliance with instructions. By then, separate equipment was being used in the raw- and cooked-meat-processing areas.

Following isolation of the outbreak strain from environmental samples obtained at the retailers, authorities asked for the sanitation of all surfaces and all equipment in food-related areas in the retail shops. Training of workers at the retailers and production plant on the management of cooked products to prevent further recontamination was also conducted.

Six of 25 food and environmental samples tested positive for Salmonella and five were monophasic Salmonella typhimurium. They were a Teflon chopping board for cutting porchetta, a wooden chopping board, a porchetta knife, and a porchetta sample at a retailer as well as a transporting board for cooked porchetta at the food plant.

Researchers said it was not possible to establish the origin of contamination at the factory, nor was it possible to clarify whether the clone originally contaminated swine meat at the slaughterhouse and level of the meat suppliers or if it was initially an environmental contaminant at the production site.

However, as no similar monophasic Salmonella Typhimurium was isolated from swine carcasses at the Abruzzo slaughterhouse and only strains unrelated to the outbreak were found from swine at the Umbrian slaughterhouse, scientists said it was likely that contamination occurred at the plant. Post-cooking contamination of porchetta at the site could be the result of persistence of Salmonella in the environment as a consequence of equipment being shared between raw- and cooked-meat-processing areas and the lack of sanitation procedures.