Coinfection with Bordetella bronchiseptica does not enhance disease with Streptococcus suis

Authors: Hau, Samantha; NIELSEN, DANIEL - Oak Ridge Institute For Science And Education (ORISE); BROCKMEIER, SUSAN - Retired ARS Employee

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Introduction Bordetella bronchiseptica and Streptococcus suis are widely distributed swine pathogens that contribute to post-weaning morbidity and mortality. B. bronchiseptica is a primary pathogen that causes atrophic rhinitis and bronchopneumonia (1). S. suis is a contributing agent to porcine respiratory disease complex and causes systemic diseases including arthritis, meningitis, polyserositis, and septicemia (2). B. bronchiseptica can enhance colonization with pathogenic bacteria, such as Pasteurella multocida, Glaesserella parasuis, and S. suis. It also has been shown to increase severity of viral and bacterial infections by causing increased tissue damage and increased release of pro-inflammatory cytokines (3-5). When animals are commingled post-weaning, B. bronchiseptica can rapidly disseminate to naïve animals. This may enhance colonization with other bacterial pathogens and increase the prevalence of disease within the herd. To better understand the interaction between B. bronchiseptica and S. suis and determine if B. bronchiseptica is contributing to the development of S. suis disease post-weaning, we evaluated coinfection in conventional and cesarean derived, colostrum deprived (CDCD) pigs. Materials and Methods Two studies were performed: study one evaluated coinfection in conventional pigs and study two evaluated coinfection in CDCD pigs. For study one, 47 pigs were divided into four groups: B. bronchiseptica challenged (n=12), S. suis challenged (n=12), B. bronchseptica and S. suis coinfection (n=12), and non-infected (n=11). Conventional pigs in study one were challenged with a highly virulent S. suis isolate 7 days after B. bronchiseptica inoculation. Necropsies were performed on day 7 and 21 post-challenge with S. suis to evaluate systemic lesions and distribution of S. suis. For study two, 30 CDCD pigs were divided into three groups: B. bronciseptica challenged (n=6), S. suis challenged (n=12), and B. bronchiseptica and S. suis coinfection (n=12). CDCD pigs in study two were challenged with a less virulent S. suis isolate 7 days after B. bronchiseptica inoculation. For study two, all animals were necropsied 14 days post-challenge with S. suis. In both studies, colonization was assessed every other day for the first week post-challenge and weekly thereafter. Serum was collected on day 0 and at necropsy to evaluate antibody titers. Results Study one revealed increased nasal colonization with S. suis in animals inoculated with B. bronchiseptica. No conventional animals developed systemic disease with S. suis during the study period and no evidence of systemic disease or systemic distribution of S. suis was found at necropsy. Similarly, study two found increased S. suis colonization in coinfected animals. There was no statistical increase in S. suis disease; however, three animals developed clinical S. suis: one in the S. suis infected group and two in the coinfected group. Antibody titers to B. bronchiseptica were higher for animals inoculated with B. bronchiseptica, but S. suis titers were similar between groups. Discussion Infection with B. bronchiseptica caused increased colonization with S. suis but did not enhance systemic disease. However, increased colonization may contribute to disease when animals are stressed or immunocompromised, such as during commingling at weaning.