Prevalence and characteristics of shigatoxin-producing Escherichia coli and Listeria monocytogenes strains isolated from minced meat in Switzerland.

A total of 400 minced meat samples from 240 small butcheries in Switzerland were collected and analysed for the presence of Shigatoxin-producing E. coli (STEC) and Listeria monocytogenes. The samples comprised 211 samples of minced beef and 189 samples of minced pork. Shigatoxin-producing E. coli was isolated from 7/400 (1.75%) samples. In particular, 5/211 (2.3%) minced beef samples and 2/189 (1%) minced pork samples were contaminated. Serotyping of the seven strains yielded five different serotypes. but none of the strains belonged to O157:H7. Two STEC strains harboured stx1 and stx2 and five strains harboured stx2c genes. Furthermore, four strains harboured one or more additional virulence factors. However, none of the strains was positive for eae. L. monocytogenes was isolated from 43/400 (10.75%) samples. Nineteen of the 43 strains belonged to serotype 1/2a, two to serotype 1/2b, 12 to serotype 1/2c and 10 to 4b. Forty-two strains harboured the Lhly and 43 strains the plcA genes. Macrorestriction analysis of the L. monocytogenes strains using SmaI yielded 12 different PFGE-patterns. The predominating pattern G was associated to the serotype 1/2c.