Genotypic diversity of Pasteurella multocida isolates from pigs and poultry in Australia.

OBJECTIVE: To investigate the genotype and diversity of Pasteurella multocida present in pig herds and to determine the extent of overlap with isolates from poultry flocks in Australia.

METHODS: A total of 43 isolates from pigs from different farms and regions of Australia were used in this study. A diverse collection of 41 poultry isolates, with 31 being previously characterised, was also used. The pig isolates and 10 poultry isolates were identified by species-specific PCR assay, serotyped by the Heddleston scheme and genotyped by a multiplex PCR based on the lipopolysaccharide (LPS) outer core biosynthesis locus, repetitive element PCR fingerprinting (rep-PCR) and multilocus sequence typing (MLST), with the latter being used on a subset of the isolates based on the rep-PCR results.

RESULTS: Only 4 out of 8 recognised LPS genotypes were found in the pig isolates, with each isolate assigned to an LPS genotype. In contrast, 77% of the isolates were non-typable or cross-reacting in the Heddleston serotyping scheme. The rep-PCR analysis recognised 20 patterns, yet only 16 sequence types (STs) were found and 4 were new STs. There were 5 STs (STs 7, 11, 20, 24 and 58) shared among the pig and poultry isolates.

CONCLUSIONS: Although only limited numbers of isolates have been examined, there is evidence of a sharing of genotypes between Australian pigs and chickens. These findings have major implication for biosecurity measures with regard to minimising both direct (e.g. animal to animal) and in-direct (e.g. shared staff or cross-visitors) contact between poultry and pigs.