Laboratory Diagnosis of Streptococcus pyogenes (group A streptococci)

Excerpt

Historically, Streptococcus pyogenes (group A streptococci) was first cultured and identified as the cause of erysipelas by Friedrich Fehleisen in 1883, and it received its species designation from Rosenbach in 1884. Today, laboratory diagnosis of group A streptococcal infections still largely relies on culturing bacteria from clinical specimens. To detect streptococci in clinical samples (and especially S. pyogenes), the material is most often cultured on blood agar plates, which facilitates an easy preliminary screen for β-hemolytic colonies. Subsequent confirmation of suspicious colonies as S. pyogenes can be achieved by several easy, rapidly performed laboratory tests that are still widely applied in clinical microbiology, despite the increasing use of automated identification systems. In contrast to the diagnosis of acute S. pyogenes infections, the diagnosis of poststreptococcal diseases, such as glomerulonephritis, acute rheumatic fever, and cerebral disorders relies on the determination of specific antibodies. For epidemiological studies and outbreak investigations, different typing methods have been developed. In addition to classical serology based typing methods, well-established molecular typing systems are available, which provide large databases of already characterized strains. This chapter will try to give a comprehensive overview of classical microbiology and serology tests, molecular methods, automated systems, as well as both molecular and conventional typing methods that are used for the identification and characterization of S. pyogenes.