Group A streptococcal infection

Streptococcal infections are among the most common bacterial infections. Streptococci are obligately pathogenic, facultative pathogenic and saprophytic micoorganisms. We classify them according to the degree of hemolysis – α-hemolytic (incomplete, partial hemolysis on agar) and β-hemolytic (complete, complete hemolysis), according to the serological differentiation of capsular antigen C into A and B.

Group A streptococci are the cause of 90% of streptococcal infections. Bacteria produce a number of toxins: erythrogenic toxin, streptolysin O a streptolysin S (causes hemolysis and is toxic to myocardial fibers and hepatocytes), streptokinase (fibrinolysis), hyaluronidase (invasive factor of streptococci), etc. Against some toxins, Ig is formed that can be used in diagnostics – ASLO (antistreptolysin O) – they decrease in a few weeks after infection. Group A streptococci cause various diseases: – skin and mucous membrane involvement, protracted seropurulent rhinitis, scarlet fever, impetigo, tonsillopharyngitis in young children.

The most common infections caused by group A streptococci include:
 * angina pectoris
 * scarlet fever
 * erysipelas
 * impetigo contagiosa

Complications of angina and scarlet fever

 * Multiple submandibular nodes, retrotonsillar, paratonsillar abscess, otitis, mastoitis, sinusitis,
 * more rarely – bacteremia, metastatic foci – purulent arthritis, endocarditis, meningitis, brain abscess, osteomyelitis and mediastinitis. Transfer of infection to the mediastinum is a rare but very dangerous complication with a high mortality rate.
 * without therapy – risk of late complications – rheumatic fever or glomerulonephritis.

Rheumatic fever

 * Most often after group A streptococci, 1-4 weeks after infection (in about 3% of those infected),
 * the course of the original infection may be inapparent (without obvious symptoms),
 * acute immunologically conditioned multisystemic inflammation,
 * often affects the heart – chronic changes in the valves,
 * main manifestations: migrating polyarthritis, pancarditis, subcutaneous nodules, erythema marginatum and Sydenham's chorea – st. Welcome, chorea minor (neurological disorder – unconscious untargeted rapid movements),
 * secondary symptoms: secondary symptoms – fever, joint pain, increased CRP…,
 * diagnosis: Jones criteria – history of streptococcal infection, presence of at least two manifest main or secondary symptoms,
 * pathogenesis: hypersensitivity reaction, Ig against M protein of streptococci cross-react with glycoproteins of heart muscle, joints etc.,
 * relapses.

Complications of streptococcal skin infections

 * Rarely, septic complications, possibly also glomerulonephritis,
 * rheumatic fever rarely,
 * acute glomerulonephritis.

Related articles

 * Genus Streptococcus: Streptococcus pyogenes
 * Streptococcus agalactiae
 * Streptococcus pneumoniae
 * Streptococcus mutans
 * Streptococcal infections: Group A streptococcal infections
 * Feber
 * Angina fever
 * Erysipelas
 * Impetigo
 * Infections caused by viridating streptococci
 * Complications and treatment of streptococcal infections
 * Rheumatic fever