Almost 50 people fell ill in France with Salmonella infections this past year linked to chicken from one slaughterhouse. Salmonella in beef from Germany was also documented.

Without whole genome sequencing (WGS), the persistent low-level outbreak could have gone undetected, according to a presentation at the European Scientific Conference on Applied Infectious Disease Epidemiology conference, organized by the European Centre for Disease Prevention and Control.

Scientists recommended strengthening surveillance by systematic sequencing of all human, food and environmental Salmonella isolates.

In June 2020, the National Reference Centre for Salmonella reported to Santé Publique France a cluster of Salmonella serotype 4,5,12:i:- cases identified by WGS since January 2020.

Forty-nine cases were detected with 46 living in the Ile-de-France region. They ranged in age from a few months to 76 years old with a median of 3 years old. Among 24 people interviewed, symptom onset ranged from Jan. 15 to Oct. 18, 2020. Nine patients were hospitalized but no deaths were recorded.

Twenty-three patients reported having eaten chicken and eight sick people bought meat directly from one slaughterhouse. Investigations on the place of purchase for other cases was hampered by inadequate traceability documentation of distribution channels, officials reported.

Inspections at the slaughterhouse identified several hygiene deficiencies in equipment maintenance and staff practices. In late July, the outbreak strain was isolated in chicken and environmental samples at the site.

The slaughterhouse was closed from the end of July to late September and hygiene practices were corrected. Four sick people interviewed, out of 10, reported after the closure of the slaughterhouse, all ate chicken bought before it was closed and frozen after purchase. No further cases were identified after mid-October 2020.

Salmonella in beef from Germany
In another presentation, the national reference lab informed the Norwegian Institute of Public Health (FHI) of a possible outbreak in late February this year after five Salmonella Enteritidis cases were identified by WGS with four of them being hospitalized.

In total, 30 ill people were identified, with more women than men sick, ranging from 2 to 91 years old with a median age of 59 years old. Patients lived in nine different counties. Thirteen people were hospitalized, one developed sepsis, but no deaths were reported.

Eight sick people were interviewed with a standardized questionnaire on Salmonella to assess food consumption one week before symptom onset. The others had a targeted questionnaire focusing on ground meat and beef products. Overall, 15 of 19 patients interviewed consumed bovine ground meat while eight ate uncooked ground meat.

After the Norwegian Veterinary Institute shared WGS data of recent Salmonella Enteritidis isolates from meat samples it was found that one isolate from a bovine carcass from Germany matched the outbreak strain. This strain was also detected in patients from Denmark and France but investigators could not confirm the same source.

Advice for the Norwegian residents told them not to consume raw ground meat and importers were reminded to follow the regulations. A review of import testing guidelines for meat was also recommended.

Listeria in trout sickened 50
A third presentation gave more details on incidents that had previously been reported. It involved a deadly Listeria outbreak linked to smoked trout.

The Listeria monocytogenes outbreak affected four countries and was detected by whole genome sequencing of clinical isolates in Germany in October 2020.

From September 2020 until August 2021, 54 patients were identified, of which 33 were male. The age range was 0 to 93 with a median of 79 years old. Three people died. Two cases were pregnancy-associated, of which one was a newborn with sepsis and meningitis.

Forty-nine ill people were reported in Germany, two each in Austria and Denmark and one in Switzerland. Sixteen of 19 interviewed patients had eaten smoked trout.

The same type of Listeria monocytogenes that had made people sick was found in smoked trout from one brand analyzed in Bavaria, Germany, and in a sample of an empty pack of trout from the refrigerator of one patient in Rhineland-Palatinate, Germany.

Investigations at the processing plant in Denmark identified Listeria monocytogenes but it was not the same type that had sickened people and the source of contamination was not found.

As smoked trout was the probable outbreak vehicle it was recalled in Germany in December 2020 and Danish food authorities increased controls in the trout processing facility. After the recall, the number of cases decreased, with the last one in May 2021 in Germany.