Streptococcus pyogenes.
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a. Acute pharyngitis is usually caused by viral infections. Strep. pyogenes is the cause in up to 50% of children aged 4-13 years but in <30% of cases in other age groups. Other bacterial causes of pharyngitis include gonococcus, diphtheria and Arcanobacterium haemolyticum.
b. Asymptomatic carriage occurs in about 10% of children. Bacterial numbers are generally small. Risk of systemic spread and of acute rheumatic fever is generally very low in such cases.
c. Strep. pyogenes septicaemia has a mortality of about 50%. Severe Strep. pyogenes infections (bacteraemia, septic shock like syndrome and necrotising fasciitis) as a group are now more common than meningococcal septicaemia.
d. Complications of pharyngeal infection include: otitis media, suppurative cervical adenitis, quinsy, acute rheumatic fever and acute post infectious glomerulonephritis.
