for mbbs 2nd prof

1. PNEUMOCOCCUS
Pneumococci are normal commensals of the upper respiratory tract. They are important
pathogens of pneumonia and otitis media in children.
MORPHOLOGY –
- Gram + ve cocci arranged in pairs (diplococci)
- 1 micro meter
- Capsulated
- Non motile
- Non sporing
CULTURE –
- They grow only in enriched media especially supplement with blood.
- Aerobes and facultative anaerobes
- Temp. – 25 – 42 degree
- PH – 6.5 – 8.3
- Colony – small (0.5 – 1 mm), dome shaped, greenish discolouration (alpha haemolysis
around them)
- On prolonged incubation – draughtsman appearance
BIOCHEMICAL REACTIONS –
- Ferment several sugar with production of acid only.
- Fermentation is tested in Hiss’s serum water.
- Fermentation of inulin differentiate pneumococci from streptococci.
- Bile solubility test – pneumococci soluble in bile.
- Optochin sensitivity test - +ve
- Catalase – negative
- Oxidase - negative
ANTIGENIC STRUCTURE –
- Capsule polysaccharide
- M – protein
- Cell wall carbohydrate

2. TOXINS –
Haemolysin & Leucocidin – pneumococci produce an oxygen labile intracellular Haemolysin &
Leucocidin. The virulence of pneumococci is dependent upon its capsule which prevents or
inhibits phagocytosis.
Pneumolysin – a toxin produced by pneumococci is another virulence factor. It has cytotoxic
and complement activating properties. It is immunogenic.
PATHOGENESIS –
A. Lobar pneumonia
B. Bronchopneumonia
C. Meningitis
D. Other infections
- Empyema
- Sinusitis
- Pericarditis
- Otitis media
- Conjunctivitis
- Peritonitis
- Suppurative arthritis
LAB DIAGNOSIS –
- Specimens – sputum, CSF, Blood
- Collection and transport – collected in sterile container
- Direct microscopy & antigen detection – capsular polysaccharide
- Culture, morphology, colony & staining – see above
- Biochemical reaction – see above
- Antibiotic sensitivity test