Epidemiological study of Salmonella enteritidis strains of animal origin in Belgium

Since 1987, the number of cases of salmonellosis caused by Salmonella enteritidis has considerably increased in Western Europe. Comparison of endemic animal strains isolated in Belgium from 1976-84 with strains isolated from 1987 on shows that the strains which cause the current epidemic have no features distinguishing them from the previously-isolated strains and that furthermore, they do not constitute a bacterial clone. They belong to 13 different lysotypes and in most cases remain sensitive to antibiotics. Nevertheless, the lysotype 33 (which belongs to the phage type 4 has increased significantly. It encompasses 37% of the animal strains isolated in Belgium from 1987-9, but only 7% of the strains isolated from 1976-84. It is worth noting that the endemic as well as the epidemic strains contain a virulence plasmid sharing sequence similarities with the FIB and FIIA plasmid replicons and with the VirA and VirB virulence regions of the S. typhimurium virulent plasmid: pIP1350.