Staging of the baboon response to group A streptococci administered intramuscularly: A descriptive study of the clinical symptoms and clinical chemical response patterns

Group A streptococcal infections, ranging from necrotizing fasciitis and my ositis to toxic shock syndrome, have increased over the last 10 years, We d eveloped the first primate model of necrotizing fasciitis and myositis. Thi rteen baboons were inoculated intramuscularly with group A streptococci (GA S). Eleven animals survived for greater than or equal to 11 days before sac rifice, and two animals died within 2 days. The site of inoculation of the survivors exhibited an intense neutrophilic influx (stage I), followed by a lymphoplasmacytic influx (stages II and III). This was accompanied by the appearance of markers of an acute and then a chronic systemic inflammatory response. In contrast, the site of inoculation of the two nonsurvivors exhi bited intravascular aggregates of neutrophils at its margin with no influx of neutrophils and with extensive bacterial colonization. We conclude that GAS inoculation induces a local and systemic acute neutrophilia followed by a chronic lymphoplasmacytic response; failure, initially, of neutrophilic influx into the site of inoculation predisposes to systemic GAS sepsis and death; and this three-stage primate model approximates the human disease.