Beef and lamb on sale in Sweden are a common source of human exposure to potentially pathogenic Shiga toxin-producing E. coli (STEC), based on findings from a study.
The work summarized the results of four surveys from different periods, which looked at the occurrence and characteristics of STEC in beef, lamb, and leafy greens on the Swedish market.
According to scientists in the International Journal of Food Microbiology, such data is required when assessing the public health risk of varying types of STEC in different foods and establishing risk management measures.
The occurrence of STEC was investigated in 477 samples of beef, 330 samples of lamb, and 630 samples of leafy greens. The detection of virulence genes such as Shiga toxin (stx) 1, stx2, and eae was performed. All STEC isolated from food samples was further characterized through whole genome sequencing.
STEC was isolated from 2 to 14 percent beef samples and 20 percent to 61 percent lamb samples, depending on the origin. STEC was not isolated from leafy greens, although stx genes were detected in 11 samples.
Imported products less compliant
Five of the 151 sequenced STEC isolates from meat contained stx2 and eae, and four had the stx2a subtype. This gene is strongly associated with severe human diseases, especially with the eae gene.
Isolates from beef belonged to 20 serotypes, including O22:H8, O26:H11, O157:H7, and O171:H2. Isolates from lamb belonged to 28 types, of which O91:H14 was the most common, followed by O128:H2 and O174:H8. Two beef and lamb isolates were O157 and contained genes for stx2 and eae.
STEC was rare in whole meat samples of domestic beef in the Swedish retail market, whereas such bacteria were frequently found in ground (minced) meat and whole meat samples of imported beef and domestic and imported lamb.
Three hundred domestic beef samples were taken from 2015 to 2016, and STEC was isolated six times. Seventeen of 135 samples of EU-imported beef were positive from 2010 to 2011, and STEC was detected in six of 42 samples from South America in the same time period. E. coli O157 was found twice—three samples from imported beef contained two or three variants of STEC isolates.
41 of 95 samples for domestic lamb were STEC positive from 2017 to 2018. In the same period, 36 of 59 imported EU samples and 30 of 149 samples, mainly from New Zealand, were also positive. STEC O157 was detected once, and 16 samples contained two different STEC isolates. No STEC was isolated from domestic, imported, or mixed-origin leafy greens in 2012 and 2013.
All analyses were performed at the Swedish Food Agency (Livsmedelsverket), except for the sample preparation for domestic beef, which was done by the National Veterinary Institute (SVA).
Belgian Listeria situation
In Belgium, another study published in the same journal looked at Listeria monocytogenes in pre-packed, plant-based ready-to-eat food with a shelf life of more than five days.
Products were vegetarian and vegan deli sandwich slices, fresh mixes of leafy vegetables, and multi-ingredient salad bowls.
During a retail survey, Listeria monocytogenes was detected in one of 51 vegetarian and vegan deli sandwich slices and six of 48 batches of multi-ingredient salad bowls. However, levels were below ten colony-forming units per gram (CFU/g).
Challenge tests were performed to determine the growth potential of Listeria in nine pre-packed, plant-based RTE food products. In six tests, growth was supported.
Researchers evaluated data from 2017 to 2022, including notifications, recalls, and outbreaks linking Listeria with such foods. They also determined the prevalence of Listeria monocytogenes with a literature review and used monitoring results from the Belgian Federal Agency for the Safety of the Food Chain (FASFC).
(To sign up for a free subscription to Food Safety News, click here.)