Invasive group a streptococcal disease: epidemiology, pathogenesis and management

Invasive group A streptococcal infections are uncommon, although serious, infections with high case fatality rates. Periodic resurgences in invasive group A streptococcal infections in industrialized countries have been reported from the 1980s onwards, with current estimates of incidence in these countries of approximately 3-4 per 100 000 population. Infants, pregnant women and the elderly are at increased risk of invasive group A streptococcal infection. The group A streptococcus has an array of virulence factors that underpin its invasive capacity and, in approximately 10% of cases, superantigen toxins produced by the bacteria stimulate a large proportion of T cells, leading to streptococcal toxic shock syndrome. Given the rapid clinical progression, effective management of invasive group A streptococcal infections hinges on early recognition of the disease and prompt initiation of supportive care (often intensive care) together with antibacterial therapy. In cases of toxic shock syndrome, it is often difficult to distinguish between streptococcal and staphylococcal infection before cultures become available and so antibacterial choice must include coverage of both of these organisms. In addition, clindamycin is an important adjunctive antibacterial because of its anti-toxin effects and excellent tissue penetration. Early institution of intravenous immunoglobulin therapy should be considered in cases of toxic shock syndrome and severe invasive infection, including necrotizing fasciitis. Early surgical debridement of necrotic tissue is also an important part of management in cases of necrotizing fasciitis.