The Microbiological Quality of Pre-packed Sandwiches

A survey of the bacteriological quality of pre-packed sandwiches on sale in the UK is reported. A total of 91 sandwiches, of which 46 had been on display at ambient temperature, were analysed. Total viable counts were high: 38 per cent of all sandwiches had counts greater than 10⊃7. Coliforms were isolated from 37 per cent of the samples and at levels greater than 10⊃7 in 10 per cent. Listeria monocytogenes was isolated from 17 per cent of all sandwiches. Sandwiches that had been on display at ambient temperature had higher total viable counts and were more likely to contain listeria (28 per cent compared to 7 per cent for those stored at chilled temperatures). A small follow-up study of sandwich ingredients found high counts in salad. The significance to the public health of the high contamination rate by listeria is unclear. Nevertheless, it would seem appropriate to ensure that sandwiches are always adequately refrigerated.