Multilocus sequence typing of Ornithobacterium rhinotracheale isolated from pigeons and birds of prey revealed new insights into its population structure

Abstract

The sudden emergence of Ornithobacterium rhinotracheale (ORT) in commercially raised poultry species and its presence in non-galliform birds raise important epidemiological issues about the role of interspecies transmission. In the present study, 21 ORT strains isolated from pigeons and from birds of prey were analyzed using the recently established multilocus sequence typing (MLST) scheme. Results were compared to MLST sequence data available from ORT strains isolated mainly from turkeys and chickens, but also single strains from pheasant, guineafowl and rook. The pigeon-derived ORT strains (n=11) were closely related amongst themselves representing their own cluster distant from ORT strains of non-columbiform avian hosts. ORT strains isolated from birds of prey (n=10) revealed a higher genetic heterogeneity that corresponded well to their host family relationships but grouped within the two mainly poultry-based clusters. None of these strains had a sequence type identical to strains investigated previously. However, three strains isolated from common kestrels and a single strain from a turkey vulture shared one or two out of seven gene loci, respectively, with strains of turkey and chicken origin. The MLST results of ORT isolated from pigeons and birds of prey likely reflect evolutionary bacterial host adaptations but might also indicate a potential for interspecies transmission. Definite conclusions should be drawn carefully as so far a few strains from non-galliform birds were analyzed by MLST. By extending the number of ORT isolates and the range of potential avian hosts, the MLST database can provide a valuable resource in understanding transmission dynamics.

Phylogenetic relationship of Ornithobacterium rhinotracheale isolated from poultry and diverse avian hosts based on 16S rRNA and rpoB gene analyses

“…The structure of the phylogenetic tree (Fig. 1), however, was largely comparable to MLST results [16]. The majority of O. rhinotracheale strains were arranged in one cluster and separated from two subsets of three strains each isolated from poultry (family Phasianidae) or birds of prey (family Accipitridae), respectively.…”

“…Sixty-five strains previously identified as O. rhinotracheale were used for genetic analyses (Table 1), including 51 strains that were already investigated by MLST and represent the 31 sequence types (ST) as described by Thieme et al [3, 16], and six additional strains isolated from turkeys in Portugal (present study). Eight strains were identified only genetically from swab samples of different birds of prey and corvid species [20].…”

“…Over the past few decades, the host range of birds infected by O. rhinotracheale or carrying the bacterium in their respiratory tract has constantly increased [16]. The presence of O. rhinotracheale in apparently healthy, captive and free-ranging non-galliform species raises important epidemiological and taxonomic questions for a better understanding of its diversity, ecology and transmission cycles.…”

“…The presence of O. rhinotracheale in apparently healthy, captive and free-ranging non-galliform species raises important epidemiological and taxonomic questions for a better understanding of its diversity, ecology and transmission cycles. Multilocus sequence typing (MLST) recently established by Thieme et al [3, 16] not only revealed specific phylogenetic relationships in non-galliform birds such as pigeons and birds of prey, but also identified few strains from turkeys and chickens that clearly differed from the main poultry cluster. The aim of the present study was to introduce partial rpoB gene sequencing for O. rhinotracheale into routine diagnostics to differentiate strains isolated from poultry and more diverse avian hosts and to compare the results with those from 16S rRNA gene and MLST analyses.…”

Phylogenetic relationship of <i>Ornithobacterium rhinotracheale</i> strains

“…It is clear that this strain represents significant new diversity that has not been previously recognized and association with antigenic and pathogenic traits need to be studied. This reference strain was included in a multilocus sequence typing (MLST) analysis that included seven housekeeping genes, and showed the most nucleotide polymorphisms [ 15 , 16 ]. Two distinct phylogenetic clusters were identified in the phylogenetic tree generated from MLST sequences and reference strain ORV 94084 K858 of serovar F of O. rhinotracheale was allocated, along with other two strains, to cluster A and differed considerably from the vast majority of O. rhinotracheale strains included in that study [ 16 ].…”