Bacteriological quality of organically grown leaf lettuce in Norway

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Abstract
Aim: To investigate bacteriological quality in organically grown leaf lettuce, including the presence of selected pathogenic bacteria, and to obtain information about organic lettuce production, including fertilizing regimes. Methods and Results: Altogether 179 samples of Norwegian organically grown lettuce were collected from 12 producers. Escherichia coli was isolated from 16 of the lettuce samples, but in 12 of these contamination was sufficiently low (−1) that they would be considered to be of acceptable bacteriological quality. Escherichia coli O157 and Salmonella were not detected in any of the samples. Listeria monocytogenes serogroups 1 and 4 were isolated from two samples. Conclusions: Organic lettuce produced in Norway was generally of acceptable bacteriological quality, but the results show that contamination of organic lettuce with E. coli and L. monocytogenes do occasionally occur. Significance and Impact of the Study: These results suggest that organically grown lettuce may be contaminated with E. coli and L. monocytogenes during cultivation.