The molecular epidemiology of four outbreaks of porcine pasteurellosis

Biochemical profiles, restriction endonuclease analysis (REA) and ribotypin g were used to investigate a total of 38 Pasteurella multocida isolates fro m four separate outbreaks of pasteurellosis in Australian piggeries. Six is olates were obtained from Outbreak 1, 16 from Outbreak 1 and eight each fro m outbreaks 3 and 4. Outbreaks 1 and 2 were cases of pneumonic pasteurellos is while outbreaks 3 and 4 involved systemic pasteurellosis. Biochemical ch aracterisation established that a number of different types of P. multocida were present in outbreaks 1 and 3 while outbreaks 2 and 4 were associated with a single type of P. multocida. Outbreaks 1 and 3 yielded isolates of P . multocida that belonged to the subspecies multocida and gallicida, with t he subspecies multocida isolates being identified as biovar 3 (6 in total) or 12 (1 in total) and the subspecies gallicida isolates (7 in total) being identified as biovar 8. All 24 isolates from outbreaks 2 and 3 belonged to the subspecies multocida and were all biovar 3, REA and ribotyping showed that, in outbreaks 1 and 3, there were three different types of P. multocid a in each outbreak with no common strains between the outbreaks. The molecu lar methods showed that only a single strain of P, multocida was associated with outbreaks 2 and 4, although the outbreaks were associated with strain s that differed in REA profiles but shared a ribotype profile. This study h as shown that both, systemic and pneumonic pasteurellosis can be associated with either a single strain or multiple strains of P. multocida. The resul ts also indicate that the molecular typing methods of REA and ribotyping ar e superior to biochemical characterisation for epidemiological investigatio n of porcine pasteurellosis. (C) 2000 Elsevier Science B.V. All rights rese rved.