Streptococcal growth and toxin production in vivo

Streptococcal growth in vivo was studied with inoculated micropore filter chambers which were implanted into the peritoneal cavities of mice. Eight of nine group A strains and one group B strain grew in vivo, achieving concentrations of 10(7) to 10(9) CFU/ml in the chambers. Experiments with the Richards strain showed that the number of viable organisms remained high at 5 and 8 weeks after infection. The use of specific inhibitors and appropriate toxin-negative strains demonstrated that both cytolytic toxins produced by group A streptococci, streptolysin S and streptolysin O, were present in the culture fluids harvested from the chambers. This finding represents the first evidence that streptolysin S is produced in vivo. The host response to streptococci growing in vivo was examined by following the increase in serum antistreptolysin O levels. The response was first detected 2 weeks after chamber implantation and appeared to be maximal after 5 weeks. In addition, the production of antibody to streptococcal cell surface antigens was demonstrated indirectly with fluorescein-labeled anti-mouse immunoglobulin G.