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Microbiological Quality of Retail Imported Unprepared Whole Lettuces: A PHLS Food Working Group Study

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A study of imported unprepared whole lettuces sampled from supermarkets, greengrocers, shops, and market stalls found that all were of acceptable microbiological quality. Twenty-seven out of 151 (18%) imported lettuce samples had Enterobacteriaceae levels of 104 CFU/g or more. However, these bacteria that constitute part of the natural microflora of unprepared vegetables may also be derived from the soil and/or by poor handling. The pathogens, Salmonella spp., Shigella spp., Campylobacter spp., Escherichia coli O157:H7, Vibrio cholerae, Listeria monocytogenes, and also Escherichia coli, an indicator of fecal contamination, were not detected in any imported lettuces, indicating that hygiene, harvesting, and production practices were good. Imported lettuces with Enterobacteriaceae levels of 104 CFU/g or more varied with type of retail premises and the temperature at which the lettuces were displayed. Samples from greengrocers, shops, and market stalls were more likely to contain Enterobacteriaceae at levels in excess of 104 CFU/g than those from supermarkets.

Document Type: Research Article

Affiliations: 1: Environmental Surveillance Unit, Public Health Laboratory Service, Communicable Disease Surveillance Centre, 61 Colindale Avenue, London NW9 5EQ, UK 2: Food Hygiene Laboratory, Public Health Laboratory Service, Central Public Health Laboratory, 61 Colindale Avenue, London NW9 5HT, UK 3: Lincoln Public Health Laboratory, County Hospital, St. Anne's Road, Lincoln LN2 5RF, UK

Publication date: April 1, 1999

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