Serotypes of 'Pasteurella' anatipestifer isolates from ducks in Singapore: a proposal of new serotypes.

'Pasteurella' anatipestifer (Pa) isolates from local ducks were typed by slide and tube agglutination tests using antisera against representative strains of existing serotypes. As the strains of serotype 13 and serotype 17 were found to be serologically identical, it is proposed that they be jointly designated as serotype 13. It is also proposed that the English serotype P, represented by strain HPRS 2565, be adopted as a replacement for the existing serotype 4 which has been excluded as Pa. Three new serotypes were identified among the 352 isolates from ducks in Singapore. It is proposed that these new serotypes be designated as serotypes 17, 18 and 19 under the present classification system.