Pneumoccus – cultural characteristics


Pneumoccus bacteria demonstrating capsular swelling using quellung reaction

Pneumoccus grow only in enriched media. (blood agar, glucose broth)

  • aerobes, facultative anaerobes
  • optimal temperature – 37C (25-42C)
  • optimal pH – 7.8 (6.5-8.3)
  • increased growth in 5-10% CO2

Blood agar – 18 hours incubation

  • small colonies (0.5-1mm)
  • glistening
  • dome shaped
  • surrounded by green ring (alpha hemolysis similar to S.viridans)

Blood agar – prolonged incubation

  • flat with raised edges
  • central umbonation
  • concentric rings formed (carrom coin appearance or Draughtsman appearance)
  • mucoid colonies formed with capsule forming strains (types 3,7)

Blood agar – anaerobic conditions

  • colonies surrounded by clear ring of hemolysis (beta hemolysis by oxygen labile hemolysin)

Liquid media (glucose broth)

  • uniform turbidiy

Other features

  • undergo autolysis due to intracellular enzymes
  • autolysis increased by surface active agents such bile salts (chenodeoxy cholate), sodium lauryl sulphate
  • autolysis not present in heat killed oranisms 

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Carrom coin appearance

Appearance of pneumococcus colonies after prolonged incubation in blood agar - with concentric rings and central umbonation - also called Draughtsman...