Use of molecular fingerprinting to assist the understanding of the epidemiology of Salmonella contamination within broiler production

1. We analysed Salmonella isolates by conventional sero- and phage-typing, as well as by molecular techniques within the broiler production chain in two integrated companies. The most prevalent serovars were selected for genetic fingerprinting. 2. Isolates were first screened by plasmid profiling; subsequently, the most common plasmid types within the prevalent zoonotic serovars (enteritidis and typhimurium) and S. agama were further characterised by PstI-SphI ribotyping, and XbaI pulsed field gel electrophoresis (PFGE). 3. Salmonella binza, S. kedougou, and S. 4,12:d:- were endemic in the feed mills over long periods of time, and a variety of plasmid types for each of the serovars were found in the premises. 4. A similar situation was found with S. binza and S. senftenberg within the hatchery in company B. The Salmonella serovars which were resident in those locations were also the ones most widely distributed throughout the broiler flocks. 5. Plasmid profiling was useful to subdivide clusters of isolates within serovars, but for each serovar a high percentage (36 to 79%) of the isolates tested fall within a prevalent plasmid type. 6. A more detailed genetic analysis of the isolates by a multiple typing approach allowed for further strain differentiation, and allowed some epidemiological conclusions to be drawn.