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:

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.

References

  • HRODEK, Otto – VAVŘINEC, Jan, et al. Pediatrics. 1. edition. Galén, 2002. ISBN 80-7262-178-5.
  • ŠAŠINKA, Miroslav – ŠAGÁT, Tibor – KOVÁCS, László, et al. Pediatrics. 2. edition. Herba, 2007. ISBN 978-80-89171-49-1.