Colonies on Blood Agar
1 mm in Diameter, Round, Domed and
Surrounded by a Zone of α-Haemolysis.
On Prolonged Incubation:
Some Strains > Mucoid Colonies.
In Broth > Short Chains or Isolated Cocci.
Soluble in Bile.
Sensitive to Optochin (Ethylhydrocuprein
Capsular Polysacharide > Antiphagocytic.
– Repeated Subculturing in the Presence of
Specific Anticapsular Antibody Results in NonCapsulated Strains.
Non-Capsulated Strains > Avirulent >
"S" Colonies >> Virulent.
Capsule Can Be Demonstrated by:
1. "Quelling Reaction" or “Capsular Swelling
2. Addition of India Ink:
Pneumococcal Infections of the
Causes Disease of the Middle Ear,
Paranasal Sinuses, Mastoides and the
Meningitis, Endocarditis and
i. Should Show a Predominance of Pus Cells Rather
Than Squamous Epithelial Cells of Buccal Origin.
ii. The Specimen is Then Homogenized by an Agent
CSF Deposit: From Cases of Meningitis.
Blood: Patients with Pneumococcal
Pneumonia and Meningitis.
2. Isolation and Identification:
Incubate in 5-10% CO2/
α - Haemolytic Colonies
Susceptibility to Optochin
Sensitive >> Strep. Pneumoniae
Resistant >> Strep. viridans