Annex O3.3:

EVOLUTION OVER TIME OF GENETIC PROFILES OF ISOLATES FROM THE SAME FARMS USING PFGE AND VNTR

Isolates of SE were analysed from four commercial laying farms (Farms 1, 2, 5 and 11). Isolates were collected at the start and end of the study and these were compared by PFGE, ribotyping and VNTR. Results are shown in Figure 1. On farm 11 the isolates collected at the start and end of the study had identical PFGE and VNTR profiles. There were some small difference in the ribotyping profiles of these isolates among the very weak bands, which probably indicate experimental differences rather than changes in the isolate. On farms 1 and 5 isolates collected at the start and end of the study had different XbaI-PFGE profiles and PstI-SphI ribotyping profiles, suggesting that there may have been some changes in the isolates present on the farm during the study. However, the phage-type of the isolate and VNTR profile remained unchanged. Based on available data, isolates collected from farm 2 differed slightly using all molecular techniques including VNTR. The results suggest that there were some minor alterations in the isolates collected on the farm at the start and end of the study. It was found that PstI-SphI ribotyping gave better discrimination than PFGE or VNTR for S. Enteritidis.

In addition, SE isolates that did not persist from farms 3, 4, 6, 7, 8, 12, 34, and 37 were examined by PFGE and VNTR. The methods used in this study were unable to discriminate persistent and non-persistent S. Enteritidis. All non persistent isolates differed in their PstI-SphI ribotyping. Isolates had three different XbaI-PFGE profiles and three distinct VNTR allelic profiles (Figure 2).

Figure 1. Dendrogram generated by Gel Compar II software showing the relationship of XbaI-PFGE profiles and PstI-SphI Ribotyping profiles of S. Enteritidis collected at the start and end of study on four farms. The analysis of bands was performed using the Dice coefficient and unweighted pair group method with arithmetic averages (UPGMA). Profiles are clustered based on the PstI-SphI Ribotyping profiles.

Figure 2. Dendrogram generated by Gel Compar II software showing the relationship of XbaI-PFGE profiles and PstI-SphI Ribotyping profiles of non-persistent S. Enteritidis from eight farms. The analysis of bands was performed using the Dice coefficient and unweighted pair group method with arithmetic averages (UPGMA). Profiles are clustered based on the PstI-SphI Ribotyping profiles.