بسم الله الرحمن الرحيم

GENUS: STREPTOCOCCUS

Prof. Khalifa Sifaw Ghenghesh

The Majority are Facultative Anaerobes. G +v Cocci Arranged in Chains,

Some are Capsulated. Catalase: On Blood Agar:1. -Haemolytic Streptococci

(Strep. pyogenes)

2. -Haemolytic Streptococci

(Strep. pneumoniae)

3. Non-Haemolytic Streptococci(Strep. Faecalis = Enterococcus faecalis).

A photomicrograph of Streptococcus spp.

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..

VIRULENCE FACTORSA. 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:

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

Inflammation of the oropharynx and petechiae, or small red spots on the soft palate caused by

Streptococcus group A

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).

2. Culture:> 2 Blood agar plates

> If - Haemolytic

> Bacitracin sensitivity test

> Sensitive >> Group A Streptococci.

3. Confirmation:

> Lancefield's Serogrouping

(Commercial Kits).

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

GROUP B STREPTOCOCCI Strep. agalactiae > A major Streptococcal Pathogen in

Neonates and the Young Infants.1. Early-Onset Infection:> Septicaemia2. Late-Onset Infection:

> Purulent Meningitis

> Infection in Adults:

GROUP D STREPTOCOCCI: Enterococcus faecalis