بسم الله الرحمن الرحيم

Streptococcus pneumoniaeProf. Khalifa Sifaw Ghenghesh

Diplococcus pneumoniae or Pneumococcus

Gram +ve Coccus, Encapsulated, Occur in Pairs with Broad Ends Opposed.

Requires Enriched Media for Growth.

Growth Enhanced by 0.1% Glucose and 5-10% CO2.

Streptococcus pneumoniae

Colonies on Blood Agar

1 mm in Diameter, Round, Domed and

Surrounded by a Zone of -Haemolysis.

On Prolonged Incubation:

"Draughtsman" Colonies.

Some Strains > Mucoid Colonies.

In Broth > Short Chains or Isolated Cocci.

Soluble in Bile.

Sensitive to Optochin (Ethylhydrocuprein Hydrochloride).

VIRULENCE FACTORS Capsular Polysacharide > Antiphagocytic.

– Repeated Subculturing in the Presence of Specific Anticapsular Antibody Results in Non-Capsulated Strains.

Non-Capsulated Strains > Avirulent >

"R" Colonies. "S" Colonies >> Virulent.

Capsule Can Be Demonstrated by:

1. "Quelling Reaction" or “Capsular Swelling Test”:

2. Addition of India Ink:

CLINICAL INFECTION Pneumococcal Infections of the

Respiratory Tract.

Causes Disease of the Middle Ear, Paranasal Sinuses, Mastoides and the Lung Paranchyma.

Meningitis, Endocarditis and Peritonitis.

Pneumococcal Bacteraemia.

Pneumococcal Meningitis

LABORATORY DIAGNOSIS

1. Specimens: Sputum: 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

(e.g. N-Acetylcysteine).

CSF Deposit: From Cases of Meningitis.

Blood: Patients with Pneumococcal

Pneumonia and Meningitis.

2. Isolation and Identification:Gram Stain BA

Incubate in 5-10% CO2/

Overnight

- Haemolytic Colonies

Susceptibility to Optochin

Sensitive >> Strep. Pneumoniae

Resistant >> Strep. viridans

TREATMENT Penicillins, Cephalosporins, Erythromycin,

Tetracycline, Clindamycin, Vancomycin and Ciprofloxacin.

Resistance:

Streptococcus viridans