Isolation of Escherichia coli O157 in pigs at slaughter in Northern Italy
A study of VTEC 0157 intestinal carriage was performed in pigs at slaughter, carrying out surveys respectively in the Veneto and the Lombardia regions of Italy within a common research project. The study was conducted for 15 months, starting in June 2002. As a minimum, a sample size of 300 samples was defined for each survey, assuming an expected prevalence of 1%, C.l. 95%, accuracy 5% One gram samples of Intestinal content from the distal gut were tested for E. coli O157 using an isolation method based on immunomagnetic separation. In the survey performed in the Veneto region, all the 397 samples collected from pigs of 132 farms tested negative for VTEC O157, but one E. coli O157 harbouring the eae gene only was isolated. In the survey performed in the Lombardia region, VTEC 0157 was detected in 3 (0.63%, 95% C I 0.12- 1.81) of the 480 sampled p1gs from 3 (2.80%, 95% C.l. 0.58- 7.97) of the 107 farms of origin. Therefore in the study a total of 877 pigs were tested in 15 slaughters of two regions, with a prevalence of 0.34% 95% C.l. 0.07- 0 99) of positive pigs from 1.26% (95% C. I. 0.25- 3.62) of the herds. In one of the positive farms also cattle were reared with pigs, even if housed separately, and in a follow-up investigation VTEC 0157 strains sharing more than 96% homology with the pig strain were found in cattle.