Streptococcus

Streptococcus

Streptococci are gram positive cocci mainly in chains and pneumococcal in pairs.

Classification of Streptococcus:

 According to hemolytic properties Streptococcus three types:

1.  α- hemolytic .Ex: Streptococcus …. S.viridunce

2.β- hemolytic .Ex: strep –pyogenes …Strep.agalactiae

3.δ –hemolytic. Ex: strep-bovis………Strep.faeculis

Anatomy or structure:

Cell of streptococcus composed of

(a)    Cytoplasm &

(b)   Cytoplasm membrane.

Outer part of cytoplasmic membrane is cell wall.

This cell wall has three antigenic layers—

1. Protein layer-M,T,&R. protein
2. Carbohydrate layer.
3. Mucopeptide layer.

Outer part of cell wall is capsule.

Habitat: Streptococcus mainly found in throat and nose.

Morphology of Streptococcus:

Shape : spherical or oval.

Size : I µm in diameter.

Arrange: In chain

Flagella: Absent

Spore : Absent

Capsule : May be capsulated.

Motility : Non –motile.

Staining: They are gram positive cocci.

Cultural character of Streptococcus:

1. Aerobic and facultative anaerobes.
2. Optimum Ph : 7.4 to 7.6
3. Optimum temperature :37°C

Growth characters:

(a)    Blood agar: colonies are circular, convex& semi-transparent.

(b)   Loffler ‘s serum –slope: Grow rapidly & tend to be confluent.

(c)    Glucose broth : granular deposit forms at the bottom . Chain formation is promoted.

(d)   Bile inhibits the growth ,  therefore no growth in bile containing media.

Pathogen city of Streptococcus:

Pathogen city depend on 3 protein ,specially M-protein, the streptococcus which has these protein are highly pathogenic.