Characterization of Atypical Hemolytic Ornithobacterium rhinotracheale Isolates and Comparison with the Normal Non-Hemolytic Phenotype

dc.contributor.authorWalters, Jessica Nicoleen
dc.contributor.committeechairPierson, Frank Williamen
dc.contributor.committeememberMcElroy, Audreyen
dc.contributor.committeememberEvans, Roberten
dc.contributor.committeememberSriranganathan, Nammalwaren
dc.contributor.committeememberLeRoith, Tanyaen
dc.contributor.departmentVeterinary Medical Sciencesen
dc.date.accessioned2017-04-06T15:44:09Zen
dc.date.adate2014-12-02en
dc.date.available2017-04-06T15:44:09Zen
dc.date.issued2014-10-24en
dc.date.rdate2016-10-18en
dc.date.sdate2014-11-06en
dc.description.abstractOrnithobacterium rhinotracheale (ORT) is a Gram-negative bacterium that causes respiratory disease in poultry characterized by rhinitis, tracheitis, and pneumonia with mortality averaging 2-3%. In the Shenandoah Valley of Virginia, the seroprevalence for ORT among turkey flocks as determined by enzyme-linked immunosorbent assay (ELISA) was found to be 70.9% (n=175). Additionally, the seroprevalence for hemorrhagic enteritis virus (vaccine induced), Bordetella avium, and paramyxovirus-1 was 100%, 74.8%, and 6.3% respectively. No significant interactions were detected. The type strain of ORT is characteristically non-hemolytic at least for 96 hours at 37°C on Columbia Blood Agar. In recent years, atypical isolates that rapidly produce hemolysis have been isolated with increasing frequency. A variety of in vitro tests were used to determine differences between representative isolates of the hemolytic (H) and non-hemolytic (NH) phenotypes. Findings suggest that the H isolate contains a 4 kb plasmid similar to that found in Reimerella anatipestifer. No plasmid was found in the NH isolate. Differences in growth characteristics and resistance to tetracyclines were also noted. No differences in proteins, biochemical characteristics or 16S rRNA sequences were found, the latter serving as confirmation that the isolates were both ORT. Embryo inoculation was used to assess virulence. No significant differences were observed and most embryos survived through to the day of hatch (pip) despite the fact that ORT could be re-isolated. In turkey poults however, the H phenotype did appear less virulent. A significant depression in weight gain was noted for birds inoculated intratracheally with the NH isolate at 7 days post-inoculation (dpi). NH inoculates also had significantly higher antibody levels on ELISA at 14 and 21 dpi and histopathological lesion scores for lung at 7, 14, and 21 dpi. The NH isolate could be re-isolated from NH-inoculated poults through 21 dpi; whereas the H isolate could only be re-isolated through 14 dpi. In conclusion, there are numerous differences between the NH and H isolates found in the field with the H isolate appearing less virulent and as such, making it a potential vaccine candidate. The phenotypic difference appears to correlate with this, but may not suffice to explain it.en
dc.description.degreePh. D.en
dc.identifier.otheretd-11062014-155425en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-11062014-155425/en
dc.identifier.urihttp://hdl.handle.net/10919/77251en
dc.language.isoen_USen
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectOrnithobacterium rhinotrachealeen
dc.subjecthemolysisen
dc.subjectELISAen
dc.subjectplasmiden
dc.subjectturkeysen
dc.titleCharacterization of Atypical Hemolytic Ornithobacterium rhinotracheale Isolates and Comparison with the Normal Non-Hemolytic Phenotypeen
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplineVeterinary Medical Sciencesen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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