An epidemiological study of Salmonella enterica serovar 4, 12 : b :- in broiler chickens in Denmark

Epidemiological investigations of isolates of Salmonella enterica serovar 4 , 12:b:- were carried out to establish particular molecular markers to assi gn isolates to a common origin. Plasmid profiling demonstrated that over 50 % of 291 isolates, obtained between 1991 and 1996, were plasmid-free. The r emaining isolates exhibited a common trend in plasmid content of 105 and 2 kb. Although no specific correlation to any particular source within the po ultry industry was discernible using plasmid analysis, there were indicatio ns of clonality with local divergence. Ribotyping with EcoRI demonstrated l imited discriminative potential as 96% of the isolates expressed a common p rofile. Ribotyping with HindIII failed to further differentiate the isolate s. IS200 (PstI) typing and PFGE (NotI and XbaI) afforded some degree of fur ther discrimination with selected isolates. Each technique produced four pr ofiles, but dominant profiles were also apparent. Eighteen variables were s elected for multivariate logistic regression analysis in order to identify risk areas associated with broiler flocks within the industry. An increased risk for S. 4. 12:b:-infection was only associated with the feedmills used . Random effects at the house and/or farm level were also found to be stati stically significant. Of the 16 feedmills associated with the isolation of 4, 12:b:-, six were deemed to be significant risk factors. (C) 2001 Elsevie r Science BN. All rights reserved.