Deoxyribonucleic Acid Relatedness among Strains of Haemophilus parasuis and Other Haemophilus spp. of Swine Origin

Abstract

The levels of cross-hybridization between deoxyribonucleic acids from Haemophilus parasuis, Haemophilus pleuropneumoniae, and unnamed Haemophilus taxon C were less than 15%. The levels of deoxyribonucleic acid complementarity between H. parasuis strains belonging to serovars 1 to 4 and polyacrylamide gel electrophoresis type I and II strains were very high (86 ± 7%), but the levels of complementarity between strain Nagasaki (serovar 5, polyacrylamide gel electrophoresis type II) and the remaining strains of H. parasuis were rather low (64 ± 5%). Our results indicate that, with the exception of serovar 5, the species H. parasuis comprises a rather homogeneous, genetically closely related group of bacteria. A further division of H. parasuis strains into subspecies according to their polyacrylamide gel electrophoresis peptide profiles is not justified on the basis of deoxyribonucleic acid sequence homologies. However, the taxonomic position of serovar 5 needs further investigation.