Carbohydrate Availability Regulates Virulence Gene Expression in Streptococcus suis

Abstract

Streptococcus suis is a major bacterial pathogen of young pigs causing worldwide economic problems for the pig industry. S. suis is also an emerging pathogen of humans. Colonization of porcine oropharynx by S. suis is considered to be a high risk factor for invasive disease. In the oropharyngeal cavity, where glucose is rapidly absorbed but dietary α-glucans persist, there is a profound effect of carbohydrate availability on the expression of virulence genes. Nineteen predicted or confirmed S. suis virulence genes that promote adhesion to and invasion of epithelial cells were expressed at higher levels when S. suis was supplied with the α-glucan starch/pullulan compared to glucose as the single carbon source. Additionally the production of suilysin, a toxin that damages epithelial cells, was increased more than ten-fold when glucose levels were low and S. suis was growing on pullulan. Based on biochemical, bioinformatics and in vitro and in vivo gene expression studies, we developed a biological model that postulates the effect of carbon catabolite repression on expression of virulence genes in the mucosa, organs and blood. This research increases our understanding of S. suis virulence mechanisms and has important implications for the design of future control strategies including the development of anti-infective strategies by modulating animal feed composition.

Evaluation of Galleria mellonella larvae for studying the virulence of Streptococcus suis

“…This might be due to higher expression of suilysin, the pore-forming toxin produced by most pathogenic strains of S. suis , which is carbon catabolite repressed by glucose when grown in vitro [44]. …”

Initial steps of the pathogenesis of the infection caused byStreptococcus suis: fighting against nonspecific defenses

“…More precisely, catabolite control protein A (CcpA) has been shown to modulate the expression of virulence features, including CPS, under conditions of high glucose availability . It has also been proposed that at the porcine upper oropharyngeal niche, the high ratio of starch to glucose promotes a significant change on S. suis gene transcription, including those putatively involved in epithelial cell interactions . Again, more studies on the role of the environment on a possible down‐regulation of the CPS and/or up‐regulation of the expression of adhesins, with a consequent increase of adhesion to epithelial cells, should be done to confirm such hypotheses.…”

“…The decreased lethality and the absence of bacterial blood loads of pigs after intranasal experimental infection with the Δiga mutant strain suggested that mucosal IgA would play a crucial role in resistance to S. suis invasion of mucosal barriers and dissemination in the naïve host . In addition, an association between in vitro up‐regulation of the iga gene expression and the increase in adhesion/invasion of pig tracheal epithelial cells has recently been observed . However, in healthy animals, the presence of specific or cross‐reactive IgA against S. suis, which might explain the lack of virulence of such a mutant, has not been tested.…”

“…In the particular case of gut‐associated lymphoid tissue (or GALT, which is also part of the MALT), no changes in leukocyte populations in the lymphoepithelium, in lamina propria or in mesenteric lymph nodes have been observed after intestinal experimental infection of pigs with S. suis , even if bacteria is detected in the draining lymph nodes . It is still not clear if the innate immune system play a role in controlling S. suis infection at the gastrointestinal environment.…”

Enterococcus faecalis Uses a Phosphotransferase System Permease and a Host Colonization-Related ABC Transporter for Maltodextrin Uptake

“…The link between carbohydrate utilization and virulence has been studied in pathogens, like group A streptococci (GAS), or more recently in Streptococcus suis using transcriptome analyses or mouse oropharynx colonization experiments (1,31). The combined results demonstrate that maltodextrin acquisition is likely to be a key factor in the ability of GAS to successfully infect the oropharynx.…”