Bacitracin Susceptibility Test- Principle, Procedure, Results, Uses

Bacitracin Susceptibility Test- Principle, Procedure and Result Interpretation

What is Bacitracin Susceptibility Test? Bacitracin susceptibility test is one of the antimicrobial disk tests for the identification of group A Streptococci from other β-hemolytic Streptococci. Antimicrobial susceptibility tests are mostly performed for the differentiation of different species of a particular genus. Antimicrobial disks are used to determine the susceptibility of bacteria to particular antibiotics. Bacitracin is a bactericidal drug …

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Biochemical Test of Bacteria

Biochemical Test of Bacteria

Biochemical reactions are very important in the identification of bacterial isolates and in the identification of different bacterial species. These tests depend on the presence of certain enzymes, such as catalase, oxidase, urease, gelatinase, etc., produced by the bacteria. Different bacteria produce varying spectra of enzymes. For example, some enzymes are necessary for the bacterium’s individual metabolism, and some facilitate …

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Biochemical Test of Streptococcus pyogenes

Biochemical Test of Streptococcus pyogenes

Biochemical Test of Streptococcus pyogenes Characteristics Properties (Streptococcus pyogenes) CAMP Negative (-ve) Capsule Capsulated Catalase Negative (-ve) Gram Staining Positive (+ve) Hemolysis Beta Motility Non-Motile OF (Oxidative-Fermentative) Fac. Anaerobes PYR Positive (+ve) Shape Cocci Spore Non-Sporing Urease Negative (-ve) VP (Voges Proskauer) Negative (-ve) 6.5% NaCl Growth Negative (-ve) Fermentation of Adonitol Negative (-ve) Arabinose Negative (-ve) Arabitol Negative (-ve) …

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Laboratory diagnosis of Streptococcus pyogenes

Laboratory diagnosis of Streptococcus pyogenes

1. Specimens Throat swab Pus Cerebrospinal fluid Blood Serum for antibody determinant 2. Smear Gram staining Purple color cocci in chain arrangement Not to be confused with Viridans Streptococci from throat swab sample since both have same appreance 3. Culture Culture on blood agar Addition of bacitracin in inoculum: S pyogenes are sensitive to bacitracin Colonial appearance: Grayish white, transparent …

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Clinical manifestation and Pathogenesis of Streptococcus pyogenes

Clinical manifestation and Pathogenesis of Streptococcus pyogenes

Virulence factors of Streptococcus pyogenes A. Antigenic structure M protein: rod like coiled structure with two major structural classes; Class I and Class II ;major virulence factor;resist phagocytosis and intracellular killing by polymorphonuclear leukocytes in the absence of antibodies. B. Toxins and enzymes Streptokinase It is also called as fibrinolysin. It transforms the plasminogen of human plasma into plasmin, an …

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Habitat and Morphology of Streptococcus pyogenes

Habitat and Morphology of Streptococcus pyogenes

Habitat of Streptococcus pyogenes They are found in throat and skin of human. They are commensals of upper respiratory tract. Carrier rate of S. pyogenes in the respiratory tract is only few in adults, over 10% in children attending kindergarten. Opportunistic pathogens May survive in dust for some times. Morphology of Streptococcus pyogenes Gram +ve bacteria Spherical or oval cocci in …

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