Serological classification of Japanese isolates of Haemophilus paragallinarum using two serovar-specific monoclonal antibodies.

A serological classification of 106 Japanese isolates of Haemophilus paragalinarum recovered from 1960 to 1984 was performed by dot-blotting and hemagglutination-inhibition (HI) tests using two serovar-specific monoclonal antibodies (MAbs), E5C12D10 and F2E6. By the dot-blotting test, 49 of the isolates were serovar A and 55 isolates were serovar C, and the two remaining isolates did not react with either MAb. These two nontypable strains had no hemagglutinating activity against chicken erythrocytes and were nonpathogenic to chickens. Although 49 serovar A isolates were serotyped by the HI test, only 23 of the 55 serovar C isolates could be serotyped. The remaining 32 isolates could not be serotyped because no or low hemagglutinating activity could be detected. Our results indicate that H. paragallinarum serovars A and C have both been present in Japan since 1960, with serovar A isolates being dominant before 1970 and serovar C isolates more prevalent than serovar A since 1970.