Streptococcus pyogenes and Staphylococcus aureus

Abstract

Introduction Gram-positive bacteria are common commensal bacteria of the skin and mucosal surfaces that can cause disease with clearly defined clinical syndromes. Streptococci are usually penicillin sensitive, while staphylococci are often penicillin resistant. The epidemiology of streptococcal and staphylococcal disease, and in particular patterns of antibiotic sensitivity are not well described across Africa (Lubell et al ., 2010; Reddy et al ., 2010). Streptococcal infections The streptococci are a group of 30 species of bacteria. These are usefully divided according to the appearance of their colonies on blood agar plates. Colonies with a surrounding green pigmented zone (described as alpha-haemolysis) are Streptococcus pneumoniae or one of the large groups of Streptococcus viridans , which are common oral and nasopharyngeal flora only occasionally causing severe disease. Non-haemolytic streptococci are rarely pathogenic. Streptococcal colonies with a surrounding zone of complete haemolysis (clear appearance) are called beta-haemolytic streptococci. These are serologically classified into groups A to H and K to V. Of these, Group A beta-haemolytic streptococci (also known as Streptococcus pyogenes ) are by far the most important in causing human disease, and form the subject of this chapter. Some Group B streptococci may cause puerperal sepsis and neonatal infections (including meningitis) in Africa, and Groups C, D and G organisms may cause upper respiratory infections, urinary infections and endocarditis.