GROUP A STREPTOCOCCAL INFECTIONS
ESSENTIALS OF DIAGNOSIS & TYPICAL FEATURES
Group A streptococci (GAS) are common gram-positive bacteria producing a wide variety of clinical illnesses, including acute pharyngitis, impetigo, cellulitis, and scarlet fever, the generalized illness caused by strains that elaborate erythrogenic toxin. GAS can also cause pneumonia, septic arthritis, osteomyelitis, meningitis, and other less common infections. GAS infections may also produce nonsuppurative sequelae (rheumatic fever and acute glomerulonephritis).
The cell walls of streptococci contain both carbohydrate and protein antigens. The C-carbohydrate antigen determines the group, and the M- or T-protein antigens determine the specific type. In most strains, the M protein appears to confer virulence, and antibodies developed against the M protein are protective against reinfection with that type.
Almost all GAS are β-hemolytic. These organisms may be carried without symptoms on the skin and in the pharynx, rectum, and vagina. All GAS are sensitive to penicillin. Resistance to erythromycin is common in some countries and has increased in the United States.
GAS pharyngitis usually occurs after contact with respiratory secretions of a person infected with GAS. Crowding facilitates spread of GAS and outbreaks of pharyngitis and impetigo can be seen. Prompt recognition and institution of antibiotics may decrease spread. Treatment with antibiotics prevents acute rheumatic fever.
1. Respiratory infections
A. Infancy and early childhood (age < 3 years)
The onset is insidious, with mild symptoms (low-grade fever, serous nasal discharge, and pallor). Otitis media is common. Exudative pharyngitis and cervical adenitis are uncommon in this age group.
Onset is sudden, with fever and marked malaise and often with repeated vomiting. The pharynx is sore and edematous, and generally there is tonsillar exudate. Anterior cervical lymph nodes are tender and enlarged. Small petechiae are frequently seen on the soft palate. In scarlet fever, the skin is diffusely erythematous and appears sunburned and roughened (sandpaper rash). The rash is most intense in the axillae, groin, and on the abdomen and trunk. It blanches except in the skin folds, which do not blanch and are pigmented (Pastia sign). The rash usually appears 24 hours after the onset of fever and rapidly spreads over the next 1–2 days. Desquamation begins on the face at the end of the first week and becomes generalized by the third week. Early in the course of infection, ...