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STAPHYLOCOCCI and Streptococcus

MSc. Sarah Ahmed

* STAPHYLOCOCCI

Gram positive Facultative anaerobes Grape like-clusters Catalase positive Major components of normal flora skin nares

2- Catalase test Positive by bubble formation

3- Coagulase test

Streptococcus

Staphylococcus

Species

Lancefield Group
Typical Hemolysis
Important Lab Characteristics
Streptococcus pyogenes
A
Beta
Bacitracin sensitivePYR Test positive


B
Beta
Bacitracin resistantHippurate utilizedCAMP test positive
S. pneumoniae
Not groupable
Alpha
Bile solubleInhibited by optochin
Viridans group
Not groupable
Alpha
Not bile solubleNot inhibited by optochin

Identification Schema

Schema to differentiate Group A and B from other b-hemolytic streptococci

Biochemical Identification

Susceptibility testsBacitracin (0.04 units) or “A” disk Identifies Group A streptococci Group A streptococcus is susceptible to “A” disk (left)

Biochemical Identification

Christie-Atkins, Munch-Petersen (CAMP) test Detects the production of enhanced hemolysis that occurs when b-lysin and the hemolysins of Group B streptococci come in contact
Group B streptococci showing the classical “arrow-shaped hemolysis near the staphylococcus streak

Identification Schema

Schema to differentiate S. pneumoniae from other a-hemolytic streptococci

Biochemical Identification

Susceptibility testOptochin “P” diskDifferentiates S. pneumoniae from other alpha-hemolytic streptococci (Viridans group)Bile solubility testS pneumoniae lyses in a suspension of sodium deoxycholate while other viridans streptococci do not lyse

Identification Schema

Schema to differentiate Enterococcus and Group D streptococci from other nonhemolytic streptococci

Biochemical Identification

PYR hydrolysis Substrate L-pyrrolidonyl-b-napthlyamide (PYR) is hydrolyzed by Group A Streptococci and Enterococcus sp. As specific as 6.5% NaCl broth for Enterococcus sp. More specific than Bacitracin for Group A streptococci
PYR test for Group A streptococci and enterococci. Both are positive for this test (right); left is a negative result

Biochemical Identification

Bile Esculin hydrolysis Ability to grow in 40% bile and hydrolyze Esculin are features of streptococci that possess Group D antigen Growth in 6.5% NaCl broth Differentiates Group D streptococci from enterococci
Both Group D streptococci and enterococci produce a positive (left) bile Esculin hydrolysis test.

THE END