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Partial characterization of plasmids from rabbit isolates of Pasteurella multocida
R Gunther1, P J Manning, J E Bouma
1Department of Laboratory Medicine and Pathology, University of Minnesota Medical School, Minneapolis 55455.
Abstract:
Plasmids have not been reported for isolates of Pasteurella multocida from rabbits. We assayed 28 isolates of rabbit P. multocida for plasmids and sought to determine whether or not plasmid presence correlated with clinical or pathologic findings, serotype, toxin production, possession of pili, or biochemical characteristics. Fourteen isolates bore a single 1.6 Md (covalently closed circular form in 0.7% agarose gels) plasmid. An additional isolate had two plasmids which migrated as a closely-spaced doublet, centered around 1.6 Md. Eleven isolates appeared to have identical plasmids, according to Hae III and Hinf I digests. The apparent linear size of this common plasmid in 2% agarose gels was 2.1 Md, as calculated from the sums of the sizes of Hae III or Hinf I digestion fragments. Linearization of the common plasmid with Msp I produced an apparent size of 2.5 Md in 0.7% agarose gels. No correlations between presence of the common plasmid and somatic serotype, toxigenicity, presence of pili, antimicrobial resistance, selected biochemical characteristics, anatomic site from which the bacteria were cultured, or disease status of the host were found.
Insights
Plasmids were detected in Pasteurella multocida rabbit isolates, with a common plasmid found in eleven strains. However, plasmid presence did not correlate with any clinical, pathological, or bacterial characteristics examined.
Area of Science:
- Veterinary Microbiology
- Bacterial Genetics
Background:
- Plasmids are extrachromosomal DNA elements that can confer advantageous traits to bacteria.
- Previous studies have not reported the presence of plasmids in Pasteurella multocida isolates from rabbits.
Purpose of the Study:
- To investigate the presence of plasmids in rabbit Pasteurella multocida isolates.
- To determine if plasmid presence correlates with specific clinical, pathological, or genotypic characteristics.
Main Methods:
- Assaying 28 rabbit Pasteurella multocida isolates for plasmid DNA using agarose gel electrophoresis.
- Characterizing plasmid size and restriction fragment patterns (Hae III, Hinf I, Msp I).
- Correlating plasmid presence with serotype, toxin production, pili, biochemical tests, and host disease status.
Main Results:
- Plasmids were detected in 15 out of 28 isolates.
- A common plasmid of approximately 2.1 Md (linearized) was identified in 11 isolates.
- No significant correlations were found between plasmid presence and the evaluated characteristics.
Conclusions:
- Plasmids can be present in rabbit Pasteurella multocida, contrary to previous reports.
- The common plasmid identified does not appear to be associated with virulence factors or specific disease presentations in rabbits.