SALMONELLA-ENTERICA SEROVAR GALLINARUM BIOVAR GALLINARUM IN LAYERS - EPIDEMIOLOGIC INVESTIGATIONS OF A RECENT OUTBREAK IN DENMARK

Despite the fact that no firm evidence was obtained, epidemiological investigations of a recent Danish outbreak of fowl typhoid indicated that the infection might have been introduced by contaminated crates from a German slaughterhouse. Fourteen Danish and five German isolates of Salmonella enterica serovar Gallinarum biovar gallinarum obtained from recent outbreaks in Denmark and Germany were characterized by phenotypic and genomic methods. Phenotypic characters, plasmid profiling, plasmid restriction profiling and ribotyping strongly indicated that Danish and German isolates were of the same clone. Pulsed-field gel electrophoresis of genomic DNA digested with Xba I, however, separated Danish and German isolates. This observation was confirmed when Not I was used for digestion of DNA. This enzyme also separated German isolates into two groups. However, differences observed between pulsed-field gel electrophoresis profiles of Danish and German isolates did not exclude the possibility of epidemiological relatedness. The use of several molecular methods is consequently highly recommended when conducting epidemiological investigations of outbreaks at the level of individual isolates.