1. ‫بسم ا الرحمن الرحيم‬
GENUS:
STREPTOCOCCUS
Prof. Khalifa Sifaw Ghenghesh

2. The Majority are Facultative Anaerobes.
G +v Cocci Arranged in Chains,
Some are Capsulated.
Catalase:
On Blood Agar:
1. β-Haemolytic Streptococci
(Strep. pyogenes)
2. α-Haemolytic Streptococci
(Strep. pneumoniae)
3. Non-Haemolytic Streptococci
(Strep. Faecalis = Enterococcus
faecalis).

3. A photomicrograph of Streptococcus spp.

4. Streptococcus pyogenes
Lancefield Grouping
> Haemolytic Streptococci by Serology > >
Groups A-H & K-V.
Group A = Strep. Pyogenes
Griffith Types
Lancefield Group A > by Specific
Sera >> Types M, T, & R.
Type M > 60 Serotypes > Type 1, Type 2,
Etc..

5. VIRULENCE FACTORS
A. Structural Components:> M-Protein >
B. Extraceluular Products:
Erythrogenic Toxins:
> In Experimental Animals: Pyrogenicity,
Cytotoxicity, Immunosuppresion, etc.
Streptolysin O and Streptolysin S: Lysis RBCs.
Streptokinase (Fibrinolysin):
> Prevents the formation of an effective fibrin barrier
Deoxyribonucleases (DNases):
Hyalorunidase:

6. CLINICAL INFECTIONS
Acute Sore Throat
Impetigo
Erysipelas
Scarlet Fever
Rheumatic Fever
Acute Glomerulonephritis.

7. Inflammation of the oropharynx and petechiae, or
small red spots on the soft palate caused by
Streptococcus group A

8. LABORATORY DIAGNOSIS:
A. By Direct Isolation & Identification:
1. Specimens:
i. Throat Swabs > Patients with Sore
Throat
(Tonsillitis and /or Pharyngitis).
ii. Throat and Nasal Swabs > Carriers
(Outbreaks of Sore Throat or Scarlet Fever).

9. 2. Culture:
> 2 Blood agar plates
> If β - Haemolytic
> Bacitracin sensitivity test
> Sensitive >> Group A Streptococci.
3. Confirmation:
> Lancefield's Serogrouping
(Commercial Kits).

10. B. By Examination of Patient's Sera for
Rising Titre of Antibodies to Streptococcal
Antigens (e.g. RF or AGN):
1. Specimens:
> Two Serum Samples are Collected in the
Acute and Convalescent Stages.
2. Test:
> The Antistreptolysin-O (ASO) Test.
TREATMENT:
S. Pyogenes > Penicillin G or Erythromycin

11. GROUP B STREPTOCOCCI
Strep. agalactiae
> A major Streptococcal Pathogen in
Neonates and the Young Infants.
1. Early-Onset Infection:> Septicaemia
2. Late-Onset Infection:
> Purulent Meningitis
> Infection in Adults:
GROUP D STREPTOCOCCI:
Enterococcus faecalis