Research – Microbiological quality of ready-to-eat salad products collected from retail and catering settings in England during 2020-21 

Journal of Food Protection

Salad and other fresh produce were collected in England from retail and catering during 2020-21 and  were tested for Salmonella, Shiga-toxin producing Escherichia coli (STEC), Listeria , Bacillus cereus , and generic E. coli. Of the 604 samples collected , 57% were from retail and 43% from catering: 61% were either salad leaves or salad leaves mixed with other products. Equal numbers of samples were prepacked or loose and 50% were refrigerated at the time of sampling. Combining results for all microbiological parameters, 84% were interpreted as satisfactory, 12% as borderline and 4% as unsatisfactory. One sample (prepacked  leaves, cucumber and tomato from a caterer) was categorised as unacceptable/potentially injurious due to detection of STEC O76, no STEC from human infections in the UK matched this isolate. No Salmonella enterica were detected but L. monocytogenes was recovered from 11 samples, one at 20 CFU/g the remainder at <20 CFU/g. B. cereus was detected at borderline levels (10 3 – <10 5 CFU/g) in 9% of samples and at an unsatisfactory level (>10 5 CFU/g) in one. E. coli were detected in 3% of samples at borderline (20 – <10 2 CFU/g) and in 4% at unsatisfactory (>10 2 CFU/g) levels. There was a significant association between the detection of L. monocytogenes and borderline/unsatisfactory levels of E. coli . There were no generic risks detected in association with the higher levels of B. cereus, STEC or Listeria but elevated levels of E. coli were predominantly confined to loose products from the UK and collected from caterers in the summer or autumn of 2021. Amongst the L. monocytogenes isolates, only one matched that from human cases and was recovered from a prepacked mixed salad from a catering business in 2021. This isolate was the same strain as that responsible for a multi country outbreak (2015-18) associated with Hungarian-produced frozen sweetcorn: no link to the outbreak food-chain was established.

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