Unlocking the Secrets of Streptococcus suis Infections

Overview

This research has improved our understanding of Streptococcus suis (S. suis), a bacterial pathogen affecting pigs and causing significant economic losses. By using advanced genomic methods and field studies, the project investigated the genetic diversity of S. suis, its impact on pig microbiota, and its role in disease development. The findings will help develop better disease management strategies, inform vaccination efforts, and address antimicrobial resistance, ultimately improving swine health and industry practices.

Application

Poljak’s research on S. suis identifies factors that contribute to the pathogen progressing from harmless colonization to severe systemic infections in pigs. These findings have the potential to improve disease prediction, vaccine development, and tailored control strategies, enhancing animal welfare while reducing the need for antibiotic interventions for fighting the disease.

Challenge

Livestock diseases present significant threats to both animal welfare and the agricultural industry. When left unmanaged, these diseases can result in substantial economic losses due to decreased livestock populations. One such disease is Streptococcus suis (S. suis), a bacterial infection that is both economically important and endemic to Canadian and global swine populations. S. suis is a common pathogen that can cause high morbidity and mortality in pigs, leading to compromised animal welfare and financial setbacks for producers. Given the widespread prevalence of S. suis in swine operations across Ontario and the range of associated risks, there is a critical need for better understanding of this pathogen. This knowledge is essential for improving disease management strategies and supporting both animal health and the broader livestock industry. In particular, a better understanding of the relative importance of host, pathogen, and environmental factors is needed to explain differences between symptomatic and asymptomatic pigs, and to determine whether these differences are crucial for developing effective intervention strategies.

Did You Know?

S. suis is a pervasive bacterial pathogen found in pigs, though only certain pigs show signs of infection. Poljak’s research demonstrates that the host pig’s microbiota, virulence-associated factors, antimicrobial resistance, and genetic variations of S. suis influence what pigs get sick.

Research

The research led by Dr. Zvonimir Poljak investigated the features related to S. suis in pigs, combining various factors to determine their importance and predictive ability. The research used advanced methods to identify characteristics of uncategorizable isolates and important genome features related to the disease. By leveraging genomic sequencing, microbiota analysis, and machine learning, the study identified critical bacterial, host, and environmental factors linked to the disease. Polijak’s project is a part of a broader research program aimed at understanding of the manifestations of S. suis in swine populations to inform vaccination development, policy interventions, and future research in the field of molecular epidemiology.

Veterinarian doctor with tablet examining pigs at pig farm.

Results

The team conducted three field studies on genetic and microbial variation of S. suis across swine farms in Southern Ontario. The research looked at both healthy and diseased pigs, including probable cases. By sampling the upper respiratory tract, the team found that untypable strains, bacteria strains that cannot be identified as any of the known serotypes (strain categories) of the disease, coexisted alongside identifiable strains within the same pigs, revealing significant genetic diversity. While studying the tonsil microbiota, they discovered that although overall Streptococcus levels stayed consistent between healthy and sick pigs, the broader microbial community showed distinct patterns between groups, suggesting the local microbiome plays a crucial role in determining infection outcomes. Using whole-genome sequencing, the final study identified specific serotypes and virulence genes linked to systemic infections. Most alarming was the discovery of antimicrobial resistance genes in virtually all samples, pointing to potentially serious challenges in future treatment approaches.

Impact

This work on S. suis significantly improves our current understanding of factors related to S. suis infection in pigs, with the understanding that the disease can be present in healthy pigs without causing signs of infection. Characterizing virulence genes, host microbiota, bacteria serotypes, and other factors will have both direct and indirect impacts on disease control strategies for S. suis. It will help identify whether certain genetic features, such as those associated with the bacteria’s ability to cause disease, are more likely to be present in S. suis found in diseased animals compared to healthy ones. Poljak team’s work contributes to the larger effort among researchers to better understand and manage this important pathogen, leading to more effective disease control and prevention strategies in the swine industry.

Learn More

Aradanas, M., Poljak, Z., Fittipaldi, N., Ricker, N., & Farzan, A. (2021). Serotypes, Virulence-Associated Factors, and Antimicrobial Resistance of Streptococcus suis Isolates Recovered From Sick and Healthy Pigs Determined by Whole-Genome Sequencing. Frontiers in Veterinary Science, 8, 742345. https://doi.org/10.3389/fvets.2021.742345

Denich, L., Farzan, A., Friendship, R., Arndt, E., Ricker, N., Gottschalk, M., & Poljak, Z. (2021). Study of the relationship between untypable and typable isolates of Streptococcus suis recovered from clinically ill and healthy nursery pigs. Veterinary Microbiology, 257, 109064. https://doi.org/10.1016/j.vetmic.2021.109064

Niazy, M., Hill, S., Nadeem, K., Ricker, N., & Farzan, A. (2022). Compositional analysis of the tonsil microbiota in relationship to Streptococcus suis disease in nursery pigs in Ontario. Animal Microbiome, 4(1), 10. https://doi.org/10.1186/s42523-022-00162-3

Managing Agri-Food Pathogens

Unlocking the Secrets of Streptococcus suis Infections

Overview

Application

Challenge

Did You Know?

Research

Results

Impact

Learn More

Principal Investigator

Zvonimir Poljak

Collaborators

Students

Partners

Research funding for Food from Thought is provided in part by the Canada First Research Excellence Fund

Research

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University of Guelph