Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/26/2002
Publication Date: N/A
Technical Abstract: Previous studies demonstrated sequence heterogeneity within and surrounding the region 1 and 2 repeats of the B. bronchiseptica pertactin gene prn. Since pertactin appears to be a protective immunogen in swine, vaccine efficacy may be enhanced by inclusion of pertactin variants matching those most frequently identified in field isolates. However, very few swine isolates have been characterized by pertactin type. The DNA sequence of prn regions 1 and 2 was determined for 25 B. bronchiseptica isolates, acquired during the 1990's, from swine with respiratory disease. Predicted amino acid sequences were compared to the previously reported prn types of 3 strains used in commercial vaccines for atrophic rhinitis, designated A, B, or C. Four prn types were identified from the swine isolates examined. Seventy-six percent of isolates (19/25) possess type 1-3a / 2-7a. Type 1- 4a / 2-6a accounted for 16% (4/25) of isolates, while types 1-3a / 2-8e and d1-5b / 2-8d each accounted for 4% (1/25). Type 1-3a / 2-8e has not been previously reported. Only vaccine strain A possessed the prn type found most frequently in swine field isolates. The types found in vaccine strains B and C were not present in any of the swine isolates examined. Two prn variants appear to predominate within recent B. bronchiseptica swine isolates, although others circulate at lower frequencies. The results presented are consistent with the concept of vaccine-driven evolution of prn variants in swine, as has been described for Bordetella pertussis in humans. A total of 17 B. bronchiseptica prn variants have now been reported. This degree of polymorphism suggests that a variety of selective pressures may underlie the emergence of pertactin variants in B. bronchiseptica.