Phenotypic characterisation of Pasteurella multocida isolates from Australian pigs.

A phenotypic characterisation of 150 isolates of bacteria previously identified as Pasteurella multocida was performed. All the isolates had been obtained from Australian pigs in the three eastern States of Queensland (110 isolates), New South Wales (21 isolates) and Victoria (19 isolates). Seven different biochemical biovars were recognised amongst the isolates. A total of 100 isolates (67%) were assigned to biovar 3, previously shown to be the most common biovar in isolates of P. multocida from Australian poultry [Fegan, N., Blackall, P.J., Pahoff, J.L., 1995. Phenotypic characterisation of Pasteurella multocida isolates from Australian poultry. Vet. Microbiol., 47, 281-286.]. Six of the seven biovars, including biovar 3, were identified as P. multocida subsp. multocida, 124 isolates in total. One other biovar, consisting of thirteen isolates, was identified as P. multocida subsp. gallicida. Within the six biovars that were identified as P. multocida subsp. multocida, biovars 12, 13 and 14 represented unusual biochemical variants. The nine isolates assigned to biovar 12 appeared to be lactose positive variants of P. multocida subsp. multocida. The three isolates in biovar 13 appeared to be ornithine decarboxylase (ODC) negative variants of P. multocida subsp. multocida. The single isolate in biovar 14 appeared to be an ODC negative, lactose positive variant of P. multocida subsp. multocida.