A 47-year-old man suddenly develops high fever and hypotension. He has a generalized erythematous macular rash, and over the next day, develops gangrene of his left leg. Which of the following is the most likely organism?

Streptococcus group A can cause a toxic shock-like syndrome, and has been increasing in frequency in North America. Streptococcal toxic shock-like syndrome was so named because of its similarity to staphylococcal toxic shock syndrome. The illness includes fever, hypotension, renal impairment, and the respiratory distress syndrome. It is usually caused by strains that produce exotoxin. It may be associated with localized infection as well; the most common associated infection is a soft tissue infection such as necrotizing fasciitis. The mortality is high (up to 30%), usually secondary to shock and respiratory failure. The rapid progression of the disease and its high mortality demand early recognition and aggressive treatment. Management includes fluid resuscitation, pressor agents, mechanical ventilation, antibodies, and, if necrotizing fasciitis is present, surgical debridement.