Streptococcus pyogenes = Lancefield Group A

Taxonomy
Family: Streptococcaceae

Natural habitats
Colonizes the human throat and skin and has developed complex virulence mechanism to avoid host defenses.

Clinical significance
The upper respiratory tract and skin lesions serve as primary focal sites of infections and principal reservoirs of transmission.

They can cause superficial or deep infections due to toxin-mediated and immunologically mediated mechanisms of disease.

S. pyogenes is the most common cause of bacterial pharyngitis and impetigo.

In the past, S. pyogenes was a common cause of childbed fever of puerperal sepsis.

They are responsible for deep or invasive infections, especially bacteremia, sepsis, deep soft tissue infections, such as erysipelas, cellulitis, and necrotizing fasciitis.

Less common myositis, osteomyelitis, septic arthritis, pneumonia, meningitis, endocarditis, pericarditis, and severe neonatal infections following intrapartum transmission.