lab no 5

Lab no (5) Streptococcus pneumonia e
• Fastidious, lancet-shaped gram positive diplococcic.
• Possess a capsule of polysaccharide that permits typing with specific antisera.
• Found as a normal flora in the upper respiratory tract.


Antigenic structure :
Capsular poly saccharides: pathogenicity determinant with anti- phagocytic property. There are more than 80 serotypes of the bacteria based on capsular typing.


Identified by capsular swelling test ( quelling reaction)
C substance: cell wall associated antigen .
Protein M antigen .
IgA, protease: enzyme which cleaved IgA.

Clinical features
.labor pneumonia, meningitis, endocarditis,
. otitis media , septic arthritis, Sinusitis, bacteremia

Laboratory Diagnosis:
Specimen : sputum, blood, cerebrospinal fluid, ear discharge and sinus drainage.
Smear: lancet-shaped gram positive diplococcic.
Culture: grow best in chocolate agar media in CO2 enriched atmosphere.
• Shows ? –hemolytic, draughts man colony. Appearance: Sunken centre colony due to spontaneous autolysis of older bacteria.
• Young colonies resemble dew-drops due to capsule.
• Bile soluble, ferment inulin.
• Optochin sensitive.
Serological test :
Quelling reaction:
Procedure :
Mix specific serotype of S. pneumonia ( fresh specimen) with specific anti- polysaccharides serum of the same serotype or with polyvalent anti-serum on a slide.
. look for the appearance of capsule swelling under the 100x objective microscope.
Treatment :
Amoxicillin , Chloramphenicol, and third generation Cephalosporins
Prevention and control : pneumococcal conjugate vaccine : immunization of individuals with type specific polysaccharides vaccine.
Biochemical reaction to diagnose streptococci
. Bile solubility test.
. Litmus milk reduction test .
. CAMP test
. Bacitracin test.
Optochin test.