Molecular and serological characterization of Riemerella isolates associated with poultry in Australia

A total of 62 isolates of Riemerella-like organisms, originally isolated from Australian poultry (10 from chickens, 46 from ducks, five from unknown hosts and one vaccine strain), were included in this study. On the basis of two published polymerase chain reaction (PCR) assays that are reported to be specific for Riemerella anatipestifer, 51 of the isolates were identified as R. anatipestifer. Forty-six of these isolates had a detailed history and were sourced from ducks, while five were of unknown origin. The 11 remaining isolates failed to yield a positive reaction in either PCR with 10 originating from chickens and one from a duck. Amplification and sequencing of the 16S rRNA gene of these isolates identified the duck isolate as Moraxella lacunta. Phylogenetic analysis of the 10 chicken isolates identified one as R. columbina and the remaining nine isolates as Riemerella-like taxon 2. The 51 Australian R. anatipestifer isolates were assigned by gel diffusion test to serovars 1 (26 isolates), 6 (seven isolates), 8 (five isolates), 9 (two isolates), 13 (one isolate) and 14 (one isolate) while nine isolates gave no reaction to any antiserum. A commercial system was used to perform DNA fingerprinting using rep-PCR analysis, which revealed different clusters with a lack of a clear relationship between the clusters and the serovars.