Comparative virulence and genomic analysis of streptococcus suis isolates

Authors: Nicholson, Tracy; WAACK, URSULA - Orise Fellow; Anderson, Tavis; Bayles, Darrell; ZAIA, SAM - University Of Texas At San Antonio; GOERTZ, ISAIAH - University Of Texas At San Antonio; EPPINGER, MARK - University Of Texas At San Antonio; Hau, Samantha; Brockmeier, Susan; Shore, Sarah

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2020
Publication Date: 1/26/2021
Citation: Nicholson, T.L., Waack, U., Anderson, T.K., Bayles, D.O., Zaia, S.R., Goertz, I., Eppinger, M., Hau, S.J., Brockmeier, S., Shore, S. 2021. Comparative virulence and genomic analysis of streptococcus suis isolates. Frontiers in Microbiology. 11. Article 620843. https://doi.org/10.3389/fmicb.2020.620843.
DOI: https://doi.org/10.3389/fmicb.2020.620843

Interpretive Summary: Streptococcus suis is a bacterial swine pathogen causing substantial economic and health burdens to the pork industry. Mechanisms used by S. suis to colonize and cause disease remain unknown and vaccines and/or intervention strategies currently do not exist. Studies addressing virulence mechanisms used by S. suis have been complicated because different isolates can cause a spectrum of disease outcomes ranging from lethal systemic disease to asymptomatic carriage. The objectives of this study were to perform comparative genomic analyses of S. suis isolates that exhibit different pathogenic capacities to identify genomic attributes associated with virulent phenotypes. This study identified regions of difference between the genome sequences of highly virulent and nonvirulent isolates. This information can be directly used to design improved vaccines and therapeutic interventions to eradicate S. suis from swine herds that do not rely on antimicrobial use.

Technical Abstract: Streptococcus suis is a zoonotic bacterial swine pathogen causing substantial economic and health burdens to the pork industry. Mechanisms used by S. suis to colonize and cause disease remain unknown and vaccines and/or intervention strategies currently do not exist. Studies addressing virulence mechanisms used by S. suis have been complicated because different isolates can cause a spectrum of disease outcomes ranging from lethal systemic disease to asymptomatic carriage. The objectives of this study were to evaluate the virulence capacity of nine US S. suis isolates following intranasal challenge in swine and then perform comparative genomic analyses to identify genomic attributes that could be associated with swine-virulent phenotypes. Our analysis revealed a high degree of genetic variability among some of the isolates along with the identification of a plasmid encoded bacteriocin locus. Several integrative and conjugative/ mobilizable elements (ICEs/ IMEs) within the S. suis genomes were identified, some of which contained antimicrobial resistance (AMR) genes. Overall, there was no correlation between a variety of functional characteristics evaluated in this report, such as genome size and attributes, serotype, sequence type (ST), in vitro virulence-associated phenotypes and the capacity to cause disease in swine. No correlation between a variety of functional characteristics, such as genome size, serotype, sequence type (ST), in vitro virulence-associated phenotypes and the capacity to cause disease in swine was identified. Differences among the predicted protein coding sequences between highly virulent and nonvirulent isolates were identified. Collectively, this report provides a framework for future allelic replacement and/or functional genomic studies investigating genetic elements underlying the spectrum of disease outcomes caused by S. suis isolates.