Difference between Streptococcus Pneumoniae and Streptococcus Viridans

Category: Microbiology.

Disclaimer: the treatment offered here is for medical professional’s note and not a prescription for a specific patient. Don’t take medicines without a doctor’s prescription. Incorrect medication can cause severe health issues and even death.

Remember that S. Pneumonia is a single species while S. Viridans is a large group of species.

Category S. Pneumoniae S. Viridans
Morphology Lancet shaped Elongated, oval, or rounded
Capsule Present Absent
Quellung Test Positive Negative
Gram Stain Gram positive Gram positive
Bile Solubility Soluble Insoluble
Optochin Sensitivity Sensitive Resistant
Hemolysis Beta hemolytic Alpha Hemolytic or non hemolytic
Lancefiled Class None None
Important Diseases C-MOPS.
Otitis Media
Subacute infective endocarditis (SBE)
Dental Carries
Liver and Brain Abscesses
Treatment Penicillin (resistance is common 40%
or more patient are resistant)
Ceftriaxone (not in children < 2 years)
Cefotoxime in children < 2y
SBE (S. Viridans)
IV Benzyl Penicillin
1.2 g 6 times daily
4 weeksIV Gentamicin
1 mg/Kg 3 times daily
2 to 4 weeks
Mind the penicillin allergies.


Here is a visual mnemonic for you. Can you find the two pathogens?