Researchers have tested frozen breaded chicken products in England following a Salmonella outbreak, finding several contaminated items and types of the bacteria, according to a recent report.

A Salmonella Enteritidis outbreak involving several strains occurred in 2020 with more than 400 reported cases in the UK. Public health agencies in England, Wales, Scotland and Northern Ireland investigated the incident caused by three Salmonella Enteritidis strains.

Children younger than 16 years old were mostly affected, and results of a UK epidemiological study provided strong evidence of an association with raw frozen breaded chicken products, intended to be eaten cooked. Almost 100 cases were also reported in Denmark, Finland, France, Germany, Ireland, the Netherlands, Poland and Sweden. One in five were hospitalized and one person died.

Initially, Salmonella Infantis was detected in a sample from chicken in a patient’s freezer in England but later Salmonella Enteritidis was also isolated.

Chicken product survey findings
The outbreak prompted a survey to examine the presence and levels of Salmonella and E. coli in raw frozen reformulated poultry products in England in 2020.

From 483 chicken samples tested between October and December 2020, including two from patients’ homes, Salmonella was found in 42 of them. Detection of six types of Salmonella was in products from six production plants in Poland, Ireland and the UK, according to the study published in the International Journal of Food Microbiology.

More than a quarter of 30 samples from Ireland were positive for Salmonella. As were nearly 16 percent of 154 samples from Poland and 6 percent of 159 UK samples. Salmonella was detected in products from six of 10 major retailers.

Salmonella detection was associated with elevated levels of generic E. coli. Salmonella Enteritidis was detected in 17 samples, Salmonella Infantis in 25, Salmonella Newport in four and Salmonella Java, Livingstone and Senftenberg in one each.

Salmonella Enteritidis was present with Salmonella Infantis in five samples and with Salmonella Livingstone in one. In co-contaminated samples, Salmonella Enteritidis was outnumbered by other salmonellas from 2 to 100-fold.

Scientists said it was unclear how multiple contaminations occurred for products in the study. It could be a result of inter- or intra-flock contamination by different strains or because of multiple contamination events from sites within factories, ingredients including poultry meat, or during packaging and transport prior to, or after production.

The highest rate and levels of Salmonella were in breaded comminuted and reformed chicken products, so these may pose a greater risk than other types, said researchers. However, detection of Salmonella in a range of products has widened the scope of risky items, as previous data had focused on breaded reformed chicken products.

Long shelf life and packing issues
Salmonella Enteritidis outbreak strains were detected in six products linked to two production plants in Poland that supplied UK sites. Contaminated products were produced during a six-month period in 2020.

Salmonella Infantis was the most frequent type detected in chicken products. It was linked to two current and two historical illnesses but researchers said it was possible more people could be sick.

A patient sample was found to match one of the Salmonella Newport strains while no evidence for infections associated with the Salmonella Java, Senftenberg or Livingstone isolates from chicken were detected in UK disease datasets in 2020 and 2021.

Remaining shelf-lives were from seven to 22 months for the samples where Salmonella was detected.

Cardboard or plastic packaging did not always keep all of the product in, with breaded coatings and crumbs seen in retailers’ freezers. Although outer surfaces of individual chicken products were less contaminated than inner portions, the study shows cross-contamination risks for consumers and retailers, during purchase, transport to the home and within kitchens.

“The study highlights how results of food testing can enhance our understanding of foodborne salmonellosis outbreaks involving multiple Salmonella strains and provides information to support future quantitative microbial risk assessment,” said researchers.

“The results also highlight the importance of recognizing co-contamination of foods with multiple Salmonella types and has provided essential information for detecting and understanding outbreaks where multiple strains are involved.”

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