Establishment, validation and use of the Kielstein-Rapp-Gabrielson serotyping scheme for Haemophilus parasuis

Objectives To produce antisera to the 15 recognised reference strains of th e Kielstein-Rapp-Gabrielson (KRG) serotyping scheme for Haemophilus parasui s, validate those sera and use them to serotype 46 Australian field isolate s of H parasuis. Design Antisera were produced in rabbits and validated by cross-testing wit h the reference strains and re-testing 15 Australian field isolates of H pa rasuis that had been previously serotyped in the United States of America. The validated antisera were then used to determine the serovar of 46 Austra lian isolates. Results Monospecific antisera were produced for 14 of the 15 KRG serovars o f H parasuis. Two Australian field isolates, confirmed previously as serova rs 1 and 7, were used to produce monospecific antisera far serovars 1 and 7 respectively. The antiserum for serovar 4 gave a one-way cross reaction wi th the antigen of serovar 14. The typing antisera correctly typed all 15 H parasuis that had been previously typed by antisera produced overseas. The 46 field isolates were shown to belong to serovars 2 (two isolates), 4 (one isolate), 5 (18 isolates), 12 (two isolates) and 13 (four isolates). The r emaining 19 isolates were non-typable. Conclusion Serotyping of H parasuis isolates is now available in Australia. H parasuis serovars 5 and 13 remain the predominant serovars present in Au stralian pigs.