Streptococcus bacteria in microbiology

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  1. STREPTOCOCCUS
     Rivolta-Isolate pus forming organism in
    chain from horse,
     Rebecca-Lancefield classification
     Pasteur-Pus due to streptococci
    Morphology
    ➢ Gram-positive cocci arranged in long chains,
    ➢ Size-1.0 micrometer , Non-spore-forming, Non motile
    ➢ Facultative anaerobes,
    ➢ Catalase – Negative
    ➢ KOH, Oxidase – Negative
    ➢ Fastidious and require enriched media
    (1) Classification on Base of Hemolysis
    ➢ In 1903 J.H. Brown grouped streptococci by their ability to lyse
    RBCs
    ❖Beta hemolysis( ): complete haemolysis (Most pathogenic)
    ❖Alpha hemolysis ( ): is partial or incomplete haemolysis
    resulting in an opaque greenish-brown zone
    around colonies,
    ❖Gamma hemolysis ( ): no haemolysis
    ( S.faecalis/Enterococcus)
    (2) Sherman Classification of streptococcus
    ➢ Sherman in the early 1900s placed the streps in “physiologic”
    groups via physiological differences.
    ❖ “pyogenic” group (to form pus): contained most of the
    pathogenic penicillin sensitive beta hemolytic species, usually
    isolated from pus.
    ❖ The bile tolerant penicillin resistant “gut” bacteria:
    removed from the genus Streptococcus and later becoming the
    genus Enterococcus
    ❖ The alpha hemolytic bile and penicillin sensitive
    streptococci :which are normal microbiota of the oral cavity
    several species are included here including S. mutans and Lancefield Capillary Precipitation download free