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Genotypic, phenotypic, and biological characteristics of Moraxella bovis
Abstract:
Several isolates of Moraxella bovis obtained from cattle with infectious bovine keratoconjunctivitis killed monocytes and macrophages in vitro and carried 3 to 5 plasmids. Cloned and noncloned M bovis isolates readily induced the disease, killed the phagocytes in vitro, and carried 3 plasmids. Moraxella bovis isolates of low in vivo virulence carried 5 plasmids and did not kill phagocytes to the extent that isolates with 3 plasmids did. The possible implications of these findings in the pathogenesis of infectious bovine keratoconjunctivitis are discussed. Also, a classification of M bovis colonies into rough or smooth varieties according to their staining characteristics with crystal violet is suggested.
Insights
Moraxella bovis isolates from cattle with infectious bovine keratoconjunctivitis killed phagocytes. Isolates with 3 plasmids were more virulent than those with 5 plasmids, suggesting a role in disease pathogenesis.
Area of Science:
- Veterinary Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- Infectious bovine keratoconjunctivitis (IBK) is a significant ocular disease in cattle.
- Moraxella bovis is the primary bacterial agent associated with IBK.
- The virulence factors and genetic basis of M. bovis pathogenicity are not fully understood.
Purpose of the Study:
- To investigate the relationship between plasmid content and virulence of Moraxella bovis isolates.
- To assess the in vitro killing of phagocytes by different M. bovis isolates.
- To explore potential classification methods for M. bovis colonies based on virulence.
Main Methods:
- Isolation and characterization of Moraxella bovis from cattle with IBK.
- In vitro assays to evaluate the cytotoxic effects of M. bovis on monocytes and macrophages.
- Plasmid profiling of M. bovis isolates using molecular techniques.
- Assessment of M. bovis virulence in vivo.
- Colony staining with crystal violet for classification.
Main Results:
- M. bovis isolates from IBK-affected cattle exhibited varying degrees of virulence.
- Isolates with 3 plasmids were found to readily induce disease and kill phagocytes in vitro.
- Isolates with 5 plasmids showed lower in vitro phagocyte-killing activity and reduced in vivo virulence.
- A correlation between plasmid number and M. bovis pathogenicity was observed.
Conclusions:
- Plasmid content, specifically the number of plasmids, appears to be associated with the virulence of Moraxella bovis.
- The ability to kill monocytes and macrophages in vitro may serve as an indicator of M. bovis pathogenicity.
- Findings suggest potential implications for understanding IBK pathogenesis and classifying M. bovis strains.