Pneumococcus vs Viridans streptococci- 12 Major Differences

Differences between Pneumococcus and Viridans streptococci

Streptococcus pneumoniae can be differentiated from Viridans streptococci by various features:

S.N. Properties Pneumococcus Viridans streptococci
1 Morphology Lanceolate or flame-shaped Round/oval
2 Arrangement Gram-positive cocci in pairs Gram-positive cocci in long chains
3 Capsule Present Absent
4 On blood agar Draughtsman or carom coin colony Convex shaped colony
5 Liquid medium Uniform turbidity Granular turbidity
6 Bile solubility Soluble in bile Insoluble in bile
7 Inulin fermentation Fermenter Non-fermenter
8 Optochin Sensitive Resistant
9 Mice Pathogenicity Pathogenic Non-pathogenic
10 Quellung Test Positive Negative
11 Hemolysis Alpha-hemolytic (under aerobic conditions) or Beta-hemolytic (under anaerobic conditions) Alpha hemolytic or non-hemolytic
12 Pathogenesis Causes pneumonia Causes mainly oral infections


  1. Apurba Sankar Sastry and Sandhya Bhat K. 2018. Review of Microbiology and Immunology. Sixth Edition. Jaypee Brothers Medical Publishers (P) Ltd.
  2. Suzuki N, Seki M, Nakano Y, Kiyoura Y, Maeno M, Yamashita Y. 2005. Discrimination of Streptococcus pneumoniae from viridans group streptococci by genomic subtractive hybridization. J Clin Microbiol. 43(9):4528–4534. doi:10.1128/JCM.43.9.4528-4534.2005.

Differences between Pneumococcus and Viridans streptococci

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