Prior infection with Bordetella bronchiseptica enhanced colonization but not disease with Streptococcus suis

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

Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/30/2023
Publication Date: 8/1/2023
Citation: Hau, S.J., Nielsen, D.W., Brockmeier, S.L. 2023. Prior infection with Bordetella bronchiseptica enhanced colonization but not disease with Streptococcus suis. Veterinary Microbiology. 284:109841. https://doi.org/10.1016/j.vetmic.2023.109841.
DOI: https://doi.org/10.1016/j.vetmic.2023.109841

Interpretive Summary: Bordetella bronchiseptica (B. bronchiseptica) is a bacterium that causes pneumonia in pigs. It also contributes to complex respiratory infections called porcine respiratory disease complex. B. bronchiseptica increases the severity of infections with viruses and bacteria. It can also increase the presence of other bacteria in the respiratory tract. Colonization is the first step toward bacterial infection. Increased colonization due to B. bronchiseptica infection could increase disease with other bacteria. B. bronchiseptica is commonly isolated from piglets around weaning. Weaning is stressful for the animals due to diet change and transport. Stressors can also increase the likelihood of disease with other pathogens, such as Streptococcus suis (S. suis). S. suis is a common swine pathogen. It contributes to porcine respiratory disease complex and causes systemic diseases including arthritis, meningitis, polyserositis, and septicemia. B. bronchiseptica and S. suis interact in laboratory models with B. bronchiseptica increasing colonization of respiratory tissues. B. bronchiseptica may also increase tissue damage and promote S. suis disease in susceptible populations. The goal of this study was to understand how B. bronchiseptica impacts S. suis colonization and disease in pigs. We used two models: normal pigs and cesarean derived, colostrum deprived (CDCD) pigs. Pigs were exposed to B. bronchiseptica, S. suis, or both. S. suis disease was not increased by coinfection with B. bronchiseptica. Nasal colonization with S. suis was increased by B. bronchiseptica infection. Coinfection had no impact on B. bronchiseptica nasal colonization, but it did decrease tracheal and lung colonization. Though coinfection did not increase S. suis disease, it did increase colonization. Increased colonization may contribute to increased disease when animals are stressed or immunocompromised, such as at weaning.

Technical Abstract: Bordetella bronchiseptica and Streptococcus suis are widely distributed swine pathogens. B. bronchiseptica is a primary pathogen and causes atrophic rhinitis and bronchopneumonia. S. suis is a contributing agent to porcine respiratory disease complex and causes systemic diseases including arthritis, meningitis, polyserositis, and septicemia. Colonization with B. bronchiseptica has been associated with increased colonization by other pathogenic bacteria and increased disease severity with viral and bacterial pathogens. It has also been shown to predispose cesarean derived, colostrum deprived (CDCD) piglets to S. suis systemic disease. Here, we evaluated the role of B. bronchiseptica colonization on S. suis colonization, dissemination, and disease in one study using conventional pigs and another using CDCD pigs. Pigs were challenged with S. suis, B. bronciseptica, or B. bronchiseptica followed by S. suis. S. suis disease was not increased in either study for animals pre-inoculated with B. bronchiseptica. Nasal colonization with S. suis was increased in coinfected animals, while B. bronchiseptica colonization was slightly reduced. Lower respiratory tract colonization with B. bronchiseptica also tended to be higher in monoinfected animals than coinfected animals. Though increased S. suis disease was not seen in coinfected pigs, there is evidence that B. bronchiseptica can increase colonization with S. suis, which may contribute to elevated disease when animals are stressed or immunocompromised.