Distribution of serotvpes and Apx-genes in Actinobacillus pleuropneumoniae isolated from Danish SPF herds

摘要

The serotypes of Actinobacillus pleuropneumoniae (Ap) most commonly isolated from clinical samples at the Danish Veterinary Laboratory (DVL) are serotype 2 (60 percent), serorype 5 (10 percent), and serotype 6 (30 percent), whereas serotypes 1, 7, 8, 10 and 12 are isolated more sporadically. Serotypes 3, 4, 9 and 11 have never been isolated in Denmark. The distribution of serotypes isolated at DVL has been quite stable during the last decade. The objective of this study was to investigate the serotype distribution of Ap isolated from Danish SPF-herds and the distribution of virulence factors in these strains. Eighty-five Ap strains originating from infected SPF-herds were selected from the clinical material investigated at DVL in 1997. The strainswere serotyped by latex agglutination, and if necessary, by immunodiffusion and MA. The distribution of the RTX toxin genes (Apxf-III) was investigated by PCR. Earlier investigations have shown that a stable relationship exists between the serotypes andthe composition of their Apx-operons. The distribution of the genes was compared to the Apx gene pattern of the reference serotype strains of Ap. The production of RTX-toxins is regarded as an important determinant of virulence for Ap.