A Salmonella outbreak that sickened more than 130 people in Chile may have been caused after food was contaminated with a strain used to monitor test performance.
The Salmonella Abony outbreak occurred from January to April 2024. Genomic evidence indicated that the outbreak strain was a clone of a reference strain, which is routinely used in microbiological quality control testing.
According to information published in the magazine Emerging infectious diseasesFrom January to March, two healthcare centers in Santiago diagnosed 134 cases of salmonellosis: 29 at UC-Christus and 105 at Clínica Alemana. All isolates were submitted to the Instituto de Salud Pública de Chile for serotyping.
Salmonella Abony was found by culture in 56 of the 97 cases. Of these, 33 patients were male and 23 were female. Forty were under 18 years of age, 17 required hospitalization and 10 had bacteremia.
18 of the 56 isolates from the outbreak were subjected to whole genome sequencing. The samples came from blood, urine and feces.
Outbreak of the rare Salmonella type
According to data from the Government of Chile, 287 isolates of Salmonella Abony were collected in 12 of 16 administrative regions between January and April. Some isolates may come from the same patient. The infected people ranged in age from younger than 1 to 82 years old. More than 200 isolates originated from Región Metropolitana, and 165 were obtained in February 2024.
However, scientists did not have additional epidemiological information, such as the food that sick people consumed, so they could not investigate the source of the outbreak.
Previous studies from Brazil and Nigeria reported on Salmonella Abony infections, and cases from Brazil were associated with the consumption of foods containing chicken meat.
The reference strain, WDCM 00029, is widely used as a control strain for testing culture media performance. Many suppliers sell it as certified lyophilized or ready-to-use reference material for quality control of food, water and environmental testing.
Researchers said the evidence suggests the Salmonella Abony outbreak was caused by contamination of an unknown vehicle with the common reference strain. The findings raise concerns about the safety of bacterial quality control strains. Physicians and health authorities should request strain characterization when rare or unreported serovars cause human infections.
Data from the Chilean Food Safety and Quality Agency (ACHIPIA) shows 728 outbreaks in 2022, with 3,764 cases, 131 hospitalizations and one death.
The three main causes of outbreaks between 2016 and 2021 were Salmonella, scombroid (histamine) fish poisoning and Norovirus. Salmonella infections were mainly associated with ready-to-eat foods, meat products or egg products.
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