Mucin model for group B type III streptococcal infection in mice.

An experimental murine infection was established by the intraperitoneal injection of a log-phase culture of a laboratory reference strain of Streptococcus agalactiae, Lancefield group B, type III (strain SS620), suspended in sterile hog gastric mucin. The enhancement of streptococcal virulence was measured by a significantly increased mortality in outbred ICR Swiss mice. An inbred C57BL6 strain of mice was resistant to the mucin-bacterial combination. Mucin, treated with Desferal to chelate the iron, did not lose the capacity to enhance the virulence of group B, type III streptococci in ICR Swiss mice. Iron-dextran was not a suitable substitute for mucin and failed to enhance the virulence of group B, type III streptococci. The results of these studies indicate that iron is not the resistance-lowering factor in this group B, type III streptococci-mucin model.