Genetic Diversity of Ornithobacterium rhinotracheale Isolated from Chickens and Turkeys in the United States.

Ornithobacterium rhinotracheale (ORT) is an important bacterial pathogen of great economic significance to poultry production. This bacterium causes severe disease in chickens and turkeys worldwide. The objective of this study was to characterize ORT isolates from two different geographic locations in the United States by multilocus sequence typing (MLST). A total of 60 isolates were included in this study; 36 from California and 24 from Minnesota. All 60 isolates were confirmed to be ORT by PCR that targeted the 16S rRNA gene. The results of MLST revealed eight different sequence types (ST) of ORT. Out of these, four were novel and were assigned numbers ST-32, ST-33, ST-34, and ST-35. ST-1 was the predominant sequence type among all isolates followed by ST-9 and ST-8. Only one isolate was identified as ST-2. No significant variation was seen in STs in ORT isolated from different years. In turkeys, 76.3% (29/38) of isolates belonged to ST-1 and 7.9% (3/38) to ST-8. Of the chicken isolates, 72.2% (13/18) belonged to ST-1 and 16.6% (3/18) to ST-9. Isolates from both states showed low genetic variability. Of the 32 isolates from California, 24 (75%) were identified as ST-1 and 4 (12.5%) were identified as ST-9. The most prevalent sequence type was ST-1 (17/24) followed by ST-8 (3/24) in Minnesota. Three isolates from turkeys in Minnesota belonged to the same ST (ST-8) as the already known ORT strain RefO, which isolated from a rook in Germany in 2000. Whether this sequence type had evolved from wild birds could not be ascertained in this study.

Correction: Molecular Characterization of the Recently Emerged Poultry Pathogen Ornithobacterium rhinotracheale by Multilocus Sequence Typing.

[This corrects the article DOI: 10.1371/journal.pone.0148158.].

Molecular Characterization of the Recently Emerged Poultry Pathogen Ornithobacterium rhinotracheale by Multilocus Sequence Typing.

Ornithobacterium rhinotracheale (ORT) is an economically important bacterial pathogen of turkeys and chickens worldwide. Since its first detection, a variety of typing methods have been used to gain basic knowledge about the bacterial population structure, an issue that still needs to be addressed. Serological characterization revealed at least 18 different serotypes (A-R) with ORT of serotype A to be predominate among poultry. This study aimed to establish a multilocus sequence typing (MLST) scheme for ORT that could easily be used by other laboratories and allows for worldwide comparison of sequence data. For this purpose, 87 ORT strains from different poultry hosts, geographical origins, years of isolation and serotypes were included in the analysis to identify correlations. Fourteen different sequence types (ST) were found. The most common ST1 was identified in 40 ORT strains from turkeys and chickens on 4 continents and in 3 different European countries. Together with ST9, both STs represented over three quarters (77%) of ORT strains used in the MLST analysis and included strains of frequently cross-reacting ORT serotypes A, E and I. Nine STs were only represented by one ORT strain and might indicate possible avian host, disease or serotype-specific relationships. In contrast, discrepancies between serotype and phylogenetic relatedness were clearly demonstrated by ORT strains that belonged to identical serotypes but differed in their ST. The overall identified low genetic diversity among strains isolated from turkeys and chickens independent of host and geographical origins suggests that ORT has only recently been introduced into domestic poultry and dispersed worldwide.

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

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.