Impact of Escherichia coli vaccine on parent stock mortality, first week mortality of broilers and population diversity of E. coli in vaccinated flocks.

In the present investigation 20,000 broiler parents were vaccinated during rearing with Nobilis Escherichia coli vaccine and were placed in two out of four identical houses, with the remaining two houses on the same farm accommodating 20,000 unvaccinated control birds. During the production period a total of 335 dead birds (including 171 vaccinated and 164 control birds) randomly selected from the four houses were subjected to post-mortem examination. Although the overall mortality between the vaccinated and control flocks did not differ, mortality due to E. coli infections made up only 8.2% in vaccinated birds compared with 24.6% in unvaccinated birds. All E. coli isolates recovered from internal organs were assigned to the same phylogenetic group (B2), but a major genetic diversity was outlined by multilocus sequence typing. Only a single isolate was demonstrated to harbour a gene encoding the P-fimbriae variant F11, a key component of the Nobilis vaccine. Significant differences in average first week mortality, calculated average weight at 38 days and food conversion rate among broiler flocks originating from vaccinated and control birds, respectively, were not found. Further investigations are needed to explain the protection observed and the impact on the genetic diversity of E. coli.

Characterization of Pasteurellaceae-like bacteria isolated from clinically affected psittacine birds.

AIMS: The aim of the present investigation was to identify and characterize Pasteurella-like isolates obtained from clinically affected psittacine birds. METHODS AND RESULTS: A total of 37 isolates from psittacine birds tentatively classified with the family Pasteurellaceae were characterized phenotypically. The genetic relationship was investigated by sequencing of partial rpoB and 16S rRNA genes for selected isolates. The results obtained were compared with the data from 16 reference strains. Nine isolates were identified as Gallibacterium spp., 16 as Volucribacter spp. or Volucribacter-like, while 11 isolates were classified as taxon 44 of Bisgaard. A single isolate was identified as Pasteurella multocida. CONCLUSIONS: Characterization of Pasteurellaceae by traditional methods is often inconclusive because of inconsistent reactions and phenotypic diversity. For the same reason, genotyping is essential to allow proper classification as demonstrated in the present study. SIGNIFICANCE AND IMPACT OF THE STUDY: Limited information exists on the isolation and significance of Pasteurellaceae associated with clinically affected psittacine birds showing signs of digestive and/or respiratory disorders. The present investigations demonstrated that these organisms are widely distributed among clinically affected birds, but isolation of these taxa cannot be unambiguously correlated with the symptoms observed.