Two Salmonella outbreaks were linked to dried sausages produced around the same time by one company in France, according to a study.
The outbreaks affected 44 people who consumed dried pork sausages contaminated by two different types of Salmonella.
Salmonella Bovismorbificans infected a total of 33 people from September to November 2020 and 11 patients with monophasic Salmonella Typhimurium from October to December 2020.
Epidemiological investigations by Santé publique France linked the outbreaks to dried pork sausages from the manufacturer France Salaison produced between September and November 2020. Three recalls of dried pork products were issued in November, affecting eight supermarkets.
Multi-strain outbreaks not being found?
Salmonella Bovismorbificans and monophasic Salmonella Typhimurium were isolated from different food samples, but both strains were identified in only one sample by qPCR.
Outbreaks caused by multiple types of Salmonella may go undetected by standard procedures in microbiology laboratories. Current diagnostic protocols target single-agent infections, but not multi-serotype ones. The findings highlight the need to improve procedures to better detect contamination of food products by different strains of Salmonella, said researchers in the journal Eurosurveillance.
In the Salmonella Bovismorbificans outbreak, 19 children under the age of 13 were sick with a range of a few months to 69 years old, and 17 were female. Symptom onset ranged from Sept. 22 to Nov. 16, 2020, and seven patients were hospitalized.
Santé publique France interviewed 23 cases of their parents. Twenty-three people reported shopping at one supermarket chain; 22 consumed dried pork sausages and 17 bought the same France Salaison brand. Loyalty card numbers helped identify unreported purchases in four other cases.
In the monophasic Salmonella Typhimurium outbreak, patients ranged from 2 months to 49 years old and seven were male. The 2-month-old child was a secondary case. Three people were hospitalized, and symptom onset ranged from Oct. 27 to Dec. 14, 2020.
Nine cases reported recent consumption of dried pork sausages and eight of them indicated the same brand and supermarket as the other outbreak.
Recall measures to control incident
Traceback tests on the batch suspected of the Salmonella Bovismorbificans outbreak in November 2020 by the manufacturer and local food lab were negative for Salmonella. However, dried pork sausage leftovers from this batch provided by a patient were sent to the National Reference Laboratory and Salmonella Bovismorbificans were isolated.
“Although post-purchase contamination by the patient might be possible, the epidemiological data and the absence of new cases following the recalls and withdrawals strongly supported the hypothesis that the product was contaminated before the sale,” said researchers.
In January 2021, following the identification of the second outbreak caused by monophasic Salmonella Typhimurium, investigations uncovered another batch of incriminated products from the same manufacturer. Reinforced self-control was performed by the firm and monophasic Salmonella Typhimurium was isolated from one sample.
Monophasic Salmonella Typhimurium was also found in the retested sample of leftovers but at lower levels than Salmonella Bovismorbificans.
Contamination at the producer was suspected but no investigations upstream were performed, as they are not required, and staff resources were scarce, according to the study.
A first recall and withdrawal were issued in mid-November 2020 by the supermarket Leclerc involving two types of Saint Azay brand dried pork sausages. A few days later, two more batches of sausages from two other brands were recalled as they were produced with the same raw meat as the first brand. A third alert covered sandwiches of a fourth brand made with sausages from the implicated producer and sold at five supermarkets. All suspected batches of dried pork sausages from the manufacturer with production date up to Dec. 8, 2020, were removed from the market.
Contaminated dried pork sausages were distributed in Belgium, Luxemburg, Poland, Portugal, and Slovenia but no related illnesses were recorded.
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