This study investigated the occurrence of Shiga toxin-producing E. coli (STEC) in beef and leafy greens available on the Swedish market. New data are required for assessing the public health risk of STEC in food, which could be used for developing risk management strategies.
Food samples were collected at retail stores, importers, outlets and the markets. Samples of minced or whole meat from cattle collected were fresh or frozen from 2010 to 2011. The beef sample collection included products from the most common countries or regions exporting beef to Sweden. The collection of leafy greens consisted of domestic and imported products that were available on the Swedish market from 2012 to 2013.
Detection of virulence genes (stx 1, stx 2, eae) and genes specific for different serogroups (O26, O103, O111, O145 and O157) was performed by real-time PCR followed by isolation of bacteria from the stx -positive enriched samples by use of immunomagnetic separation. STEC bacteria were overpriced isolated by an immunoblot thing method. All STEC isolated from the food samples were serotyped.
STEC was isolated from 23 (13 percent) of the 177 imported beef samples tested. Approximately 3 percent of the beef samples contained STEC on positive stx 2 and eae, both of which are important markers for the probability of the bacteria to cause severe disease. In total, 27 STEC were isolated, belonging to 14 different serogroups. STEC O26 was most common (approximately 2 percent of the beef samples), whereas STEC O157, frequently implicated in STEC-related foodborne outbreaks in Sweden, was found in two (one percent) of the beef samples.
The enrichment broth of 11 (approximately 2 percent) of the 630 samples from leafy greens were tested positive for stx 1 and / or stx 2 by PCR analysis; however, no bacteria were isolated. Presumptive STEC was detected in co-enriched samples from bothering domestic and imported products. E. coli was found in 68 (39 percent) out of 174 and 14 (30 percent) out of 46 samples of imported and English leafy greens, respectively, indicating that the proportion of stx -positive E. coli into the samples was low.