Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 10, 1999
Publication Date: N/A
Interpretive Summary: Bordetella bronchiseptica causes swine atrophic rhinitis and pneumonia, tracheobronchitis in dogs, and bronchopneumonia in many species, including rabbits, guinea pigs, cats, and horses. Atrophic rhinitis and pneumonia are extremely costly to the swine production industry worldwide. The lack of a simple and reliable typing system for classification of B. bronchiseptica isolates has hampered efforts to understand how this organism is spread within and between herds. In a previous report we demonstrated that a technique known as ribotyping, which reveals variations in the DNA of different isolates, could be used to classify strains of B. bronchiseptica obtained from different hosts. In this study, we report modifications to the original ribotyping procedure that allow the detection of even more subtle differences between isolates. The modified ribotyping technique was applied to an additional 101 previously uncharacterized pig, rabbit, and dog B. bronchiseptica isolates from Hungary. Swine strains circulating in Hungary appear to be identical to those circulating in other parts of the world. However, some unique strains not previously seen were identified from rabbits and dogs. The ability to detect additional differences between isolates of B. bronchiseptica will permit a better understanding of how this organism is spread between different hosts, resulting in more effective prevention and control measures.
It was reported previously that ribotype patterns generated with PvuII and a probe derived from the Escherichia coli rrnB gene could be used to differentiate isolates of Bordetella bronchiseptica (Register, K. B. et al., 1997. Use of ribotyping to distinguish B. bronchiseptica isolates. Int. J. Syst. Bacteriol. 47, 678-683). Here we report modifications to the eprocedure that permit detection in the formerly characterized isolates of an additional 8 fragments with homology to rrnB. Ribotypes were redefined to include these fragments. Although this modification did not permit the detection of novel ribotypes from the previously characterized isolates, it did result in a more accurate reclassification of 5 of them. It was hypothesized that the additional fragments could form the basis for novel ribotypes in future analyses, and this was supported by the subsequent evaluation of 101 previously un characterized pig, rabbit, and dog B. bronchiseptica isolates from Hungary. A total of 6 different patterns wer detected from this group, including 2 not previously seen that were designated ribotypes 17 and 18. The profile of ribotype 17 includes a novel fragment not associated with any other ribotype. A subset of the fragments constituting ribotype 18, essential for its differentiation from other ribotypes, is only detectable under the modified conditions reported here. Hungarian swine isolates are highly clonal, since 98.2% were identified as ribotype 3. Similarly, 83.7% of rabbit isolates from Hungary are also ribotype 3. Cluster analysis revealed that despite the existence of numerous ribotypes, B. bronchiseptica isolates display limited heterogeneity. The ability to detect additional ribotypes strengthens the usefulness of ribotyping as an epidemiologic tool.