Relationship between serotype, virulence and SDS-PAGE protein patterns of Haemophilus parasuis

141 Haemophilus (H.) parasuis and 8 H. parasuis-like strains from different farms were serotyped according to Morozumi and Nicolet (1986 b) as well as to Bakos et al. (1952). It was possible to classify 72.8% of the investigated strains. 7 out of 12 serotypes have been described for the first time. The high specificity in the agar gel precipitation test was not reproducible in the more sensitive dot-blot procedure. The dot-blot results point to a participation of non-immunogenic polysaccharides in the detection reaction. The serotypes SV 1, SV 5, SV Jena 6 and SV Jena 10 proved to be highly virulent in SPF pigs, SV 2 and SV 4 were of medium virulence. The other serotypes were found to be nonvirulent. Unencapsulated strains and isolates of serotype SV 5 prevailed in animals with Glasser's disease. 23 H. parasuis and 3 H. parasuis-like strains were examined in sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). On the basis of protein profiles of whole-cell lysates, 23 of them could be assigned to 5 groups. Apart from the highly virulent strains of serovar 1, which belonged to PAGE type III, all other highly virulent strains of the serovars SV 5, SV Jena 6 and SV Jena 10 were grouped into PAGE type I. No correlation could be found between PAGE type on the one hand and virulence or origin of isolates on the other hand.