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Streptococcus suis and group B Streptococcus differ in their interactions with murine macrophages
M A Segura1, P Cléroux, M Gottschalk
1Groupe de Recherche sur les Maladies Infectieuses du Porc, Faculté de Médecine Vétérinaire, Université de Montréal, Qué, Canada.
Abstract:
Streptococcus suis type 2 and group B Streptococcus type III (GBS) are important encapsulated bacterial species causing meningitis. In the present study we compared quantitatively the uptake and intracellular survival of S. suis type 2 and GBS type III with murine macrophages in non-opsonic conditions. The role of the capsule of both pathogens was also studied using previously obtained unencapsulated isogenic mutants. Encapsulated S. suis wild-type strain was practically not phagocytosed, while the unencapsulated mutant was easily ingested by macrophages. On the other hand, the well encapsulated GBS strain and its unencapsulated mutant were both phagocytosed in large numbers. Even if S. suis unencapsulated mutant showed a higher uptake rate than the parental strain, this value was always markedly lower than the numbers of ingested GBS strains. In addition, the intracellular survival of encapsulated and unencapsulated GBS strains was significantly higher than that of S. suis strains. These results suggest that interactions between GBS type III and S. suis type 2 with murine macrophages as well as the role of the capsule as an antiphagocytic factor are different for the two bacterial pathogens.
Insights
Streptococcus suis and group B Streptococcus (GBS) interact differently with macrophages. GBS is readily phagocytosed regardless of its capsule, unlike S. suis, where the capsule hinders ingestion.
Area of Science:
- Bacteriology
- Immunology
- Cell Biology
Background:
- Streptococcus suis type 2 and group B Streptococcus type III (GBS) are significant encapsulated bacterial pathogens responsible for meningitis.
- Understanding their interaction with host immune cells is crucial for developing effective treatments.
Purpose of the Study:
- To quantitatively compare the phagocytosis and intracellular survival of S. suis type 2 and GBS type III by murine macrophages under non-opsonic conditions.
- To investigate the role of the capsule in the interaction of these pathogens with macrophages.
Main Methods:
- Quantitative comparison of uptake and intracellular survival of encapsulated and unencapsulated strains of S. suis type 2 and GBS type III with murine macrophages.
- Utilized non-opsonic conditions to assess inherent bacterial-macrophage interactions.
Main Results:
- Encapsulated S. suis type 2 was poorly phagocytosed, while its unencapsulated mutant showed increased uptake.
- Both encapsulated and unencapsulated GBS type III strains were phagocytosed in large numbers.
- Intracellular survival was significantly higher for both GBS strains compared to S. suis strains.
- The capsule played a differential role as an antiphagocytic factor between the two species.
Conclusions:
- The interaction mechanisms of GBS type III and S. suis type 2 with murine macrophages differ significantly.
- The bacterial capsule serves as an antiphagocytic factor, but its effectiveness varies between S. suis and GBS.