Toxicity of group B Streptococcus agalactiae in adult rats.

Several strains of group B Streptococcus agalactiae were found to be lethal for young adult rats. When bacteria were heat killed and then injected intraperitoneally into rats, rapid death (14 to 18 h) of the rats occurred, characterized by labored breathing, hemolyzed serum, hemoglobinuria, and subungual hemorrhages. Sections of tissues from these rats failed to reveal the cause of death. Rats injected with toxic or nontoxic strains of group B S. agalactiae had reduced numbers of circulating leukocytes and low serum C3 levels in comparison with those in control rats. The toxic strains of group B S. agalactiae induced dramatic decreases in platelet numbers, and in plasma fibrinogen levels as well, suggesting that the toxicity was due to disruption of the coagulation system. Rapid death in the absence of infection suggests that group B S. agalactiae may have a cell-associated toxin that induces these changes. Such a toxin may be a contributory factor in the high mortality rate associated with group B streptococcal infections of the human neonate.