Relationship between intracellular survival in macrophages and pathogenicity of Streptococcus suis type 2 isolates.
Naturally-occurring Streptococcus suis type 2 meningitis affects pigs and man; experimental models of the disease have also been established in pigs and mice. A sustained, high-level bacteraemia is an important phase preceding the development of S. suis type 2 meningitis. The main cellular clearance mechanism for circulating bacteria is the resident hepatic and splenic macrophages. The interaction between various isolates of S. suis type 2 and murine macrophages was investigated to determine whether there were differences in the outcome of the interaction that would reflect observed differences in pathogenicity. Phagocytosed non-pathogenic isolates were killed whereas intracellular pathogenic organisms survived and replicated within phagosomes in the absence of anti-S. suis type 2 antibody and complement. The addition of anti-S. suis type 2 antibody and complement to macrophages containing ingested pathogenic organisms resulted in inactivation of the intracellular bacteria. Thus whilst the pathogenicity of S. suis type 2 isolates may be related to an ability to survive within macrophages, immunity to S. suis type 2 meningitis may result from anti-S. suis type 2 antibody preventing pathogenic organisms surviving within macrophages.
Department of Clinical Veterinary Medicine, University of Cambridge, U.K.
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Williams
D000165:Acridine Orange; D000818:Animals; D000907:Antibodies, Bacterial; D002470:Cell Survival; D015169:Colony Count, Microbial; D006801:Humans; D007106:Immune Sera; D066298:In Vitro Techniques; D008264:Macrophages / Q000382:microbiology*; D008581:Meningitis / Q000276:immunology*; D010529:Peritoneal Cavity / Q000382:microbiology; D010587:Phagocytosis; D011817:Rabbits; D012680:Sensitivity and Specificity; D013291:Streptococcus / Q000276:immunology / Q000472:pathogenicity* / Q000648:ultrastructure; D013552:Swine
D000907:Antibodies, Bacterial; D007106:Immune Sera; D000165:Acridine Orange