Notes on Streptococcus

  >   Rahul's Noteblog   >   Notes on Bacteriology   >   Notes on Streptococcus

General Streptococcus Notes

• Gram-positive bacteria that produce lactic acid as end-product of their fermentative metabolism.

• They may grow in O2, but can only ferment.

• Cocci shaped and grow in chains of variable lengths.

• Inhabit the oral cavity and throat.

• Streptococcus pyogenes causes pharyngitis (sore throat) and other diseases.

Genus: Streptococcus.

• Gram +; cocci/pairs of cocci; catalase -.


• Beta = clear; alpha = partial (green); gamma = non-hemolytic.


Streptococcus pneumoniae.


Streptococcus pyogenes.

Streptococcus pyogenes:

• Beta-hemolytic; bacitracin sensitive.

• Beta-hemolytic; inhibited by bacitracin on blood agar.

• Found in human throat and skin; spread by respiratory droplets and direct contact.

• Causes infections such as strep throat, scarlet fever (due to pyrogenic exotoxin), and other conditions.

• Also causes wound infection and even death.

• Also causes necrotizing faciitis or "flesh eating disease."

• Beta-hemolytic, Gram-positive, chain-forming coccus with Lancefield group A cell wall polysaccharide.

• Causes sore throat.

• Produces enzymes that cause blood cell lyses.

• Colonies are surrounded by beta-hemolytic streptococci.

• Causes scarlet fever, acute glomerlonephiritis, acute rheumatic fever and cholera.


• Hyaluronic acid capsule and M-protein inhibit phagocytosis.

• M12 strains cause acute glomerulonephritis.


• Streptolysins O and Streptococcus.

Spreading factors:

• Streptokinase, streptococcal DNAse, hyaluronidase.

Exotoxins A-C:

• Fever and rash; inhibit clearnance of endotoxin.


• Acute (suppurative/pus-forming) Pharyngitis, scarlet fever, pyoderma/impetigo.

• Non-suppurative: rheumatic fever and acute glomerulonephritis.

Lab tests:

• Strep throat: rapid antigen test.

• Rheumatic fever: ASO titer.


• Beta-lactum drugs or erythromycin.

Streptococcus agalactiae:

• group B Streptococci.

• Beta-hemolytic; bacitracin resistant on blood agar; Group B.

• Catalase -;

• CAMP test +;


Found in vagina.


• Capsule, beta-hemolysin, and CAMP factor.


• Neonatal septicemia and meningitis.


• Ampicillin with cefotaxime or gentamicin. Treat mom before delivery.

Streptococcus pneumoniae:

• Alpha-hemolytic, optochin sensitive in blood agar, Gram +, lysed by bile.

• Human upper respiratory tract.


• Respiratory droplets.

Causes pneumonia:

• Predisposed by: CHF, alcoholism, COPD, asplenia.


• IgA protease: colonization.

• Teichoic acid: attachment.

• Polysaccharide capsule inhibits phagocytosis.

• Quellung reaction +.

• Pneumolysin damages respiratory epithelium.

• Meningitis confirmation: use latex agglutination test.


• Bacterial pneumonia, meningitis, otitis media and sinusitis in children.


• Penicillin G.

Viridians streptococci.

• Alpha-hemolytic; optochin resistant.

• Found in human oropharynx.


• Dental caries, infective endocarditis.


• Dextran/biofilm mediated adherence.


• Penicillin G with aminoglycoside for endocarditis.

Other Types of Streptococcus

• Streptococcus agalactiae: found in the gut and female urogenital tract.

• Streptococcus mutans: found in the oral cavity; leads to tooth decay.

• Streptococcus pneumoniae: causes pneumonia.

• Streptococcus thermophilus: found in dairy products; used in yogurt production.

Additional Readings:

Basic Bacteriology

1. Bacterial Locations and Toxins
2. Growth Medias and Oxygen Requirements
3. Staphylococus
4. Streptococcus
5. Enterococcus
6. Bacillus
7. Listeria
8. Corynebacterium
9. Actinomyces
10. Nocadria
11. Mycobacterium
12. Clostridium
13. Neisseria
14. Pseudomonas
15. Legionella
16. Bordetella
17. Francisella
18. Brucella
19. Campylobacter
20. Escherichia
21. Shigella
22. Klebsiella
23. Salmonella
24. Yersinia
25. Proteus
26. Vibrio
27. Pasteurella
28. Haemophilus
29. Bacteriodes and Prevotella
30. Treponema
31. Borrelia
32. Rickettsia
33. Coxiella
34. Ehrlichia
35. Chlamydia
36. Mycoplasma
37. What is an ELEK's Test?
38. Causes of Orchitis
39. What is Leprosy?
40. What is Folliculitis?
41. What is Botulism?
42. How to interpret PPD (Purified Protein Derivative) results?
43. Prenatal Infections

Related Topics

1. Bacterial vs viral infections

Medical Images

Useful Medical Images & Diagrams (link opens in a new window)

Random Pages:

What is Time? How To Optimize Your Web Server
Video of me playing Yanni`s "Nightingale" Notes on Lymphoid Tissue
Notes on Back and Nervous System What is Folliculitis?
Notes on Gluconeogenesis CHADS2 Score for Atrial Fibrillation Stroke Risk
Significance of Measuring Albumin while with Calcium Levels Notes on Endocrine Pancreas
Notes on Basic Gastrointestinal Physiology What is Time?
Review of Delta Roma Imperiale Fountain Pen What is an ELEK`s Test?
Why did I decide to become a doctor? Medical School Admissions Essay Video: Titanic Piano Theme: The Portrait
Corporate Failure: The Enron Case My Experience during the Iraqi Invasion of Kuwait
USMLE Blood Lab Values Regulation of Heart Rate by Autonomic Nervous System
Images of Antibodies Video of me playing Hagood Hardy`s "The Homecoming"
Notes on Lymphoid Tissue Differentiation and Anatomy of a Blastocyst
Notes on Cell Components Notes on Nervous Tissue
Voices from Hell: My Experience in Mussoorie, India Video of Cardiology Examination in a Clinical Setting

Please Do Not Reproduce This Page

This page is written by Rahul Gladwin. Please do not duplicate the contents of this page in whole or part, in any form, without prior written permission.