ASO

Antistreptolysin O

It is an antibody directed against the antigen, streptolysin O.

Streptolysin O

• s a hemolysin.

• It is an example of an extracellular product important in the pathogenesis of disease and the serologic diagnosis of streptococcal infection.

Todd (1932)

Streptolysin-O was discovered by?

• bacterial pharyngitis

• childhood impetigo

Group A Streptococci is a major cause of?

Pyrogenic exotoxins A, B, and C

are responsible for the rash seen in scarlet fever and appear to contribute to pathogenicity.

M protein

• is a major virulence factor.

• It acts to inhibit phagocytosis and limits the deposition of C3 on the bacterial surface.

Pharyngitis

• It's a sore throat.

• There is swelling and redness of the pharynx.

• There are small red spots or petechiae on the soft palate of the patient.

Streptococcal Pyoderma/Impetigo

• A skin infection characterized by vesicular lesions on the extremities.

• It starts off as a lesion.

• As the lesion becomes pustular, if there is presence of a yellow discharge, it is called the pus.

• It dries up, and then later on becomes crusted

• Upper respiratory tract

• Skin

Major site of infection

• Pharyngitis or Sore Throat

• Necrotizing fasciitis

• Streptococcal Toxic Shock Syndrome

• Streptococcal Pyoderma or Impetigo

Clinical manifestations of Streptococcus pyogenes

Human

Reservoir of S. pyogenes

Scarlet fever

• It features a bright red rash that covers most of the body.

• It starts off on the neck and the face, then goes to the throat, then to the extremities.

• The red rash is actually due to the erythrogenic toxins produced by Streptococcus pyogenes.

1. Acute Rheumatic Fever

2. Post-Streptococcal Glomerulonephritis

Group A streptococci sequelae consist of:

Acute Rheumatic Fever

• Occurs only after upper respiratory tract infection

• Fever and pain caused by inflammation in the joints, and inflammation of the heart.

• The mechanism behind ARF is autoimmunity.

1-3 weeks

latency period of acute rheumatic fever

Post-streptococcal glomerulonephritis

• Follow infection of either the skin or the pharynx.

• Most common in children between the ages of 2 & 12.

• The mechanism is similar to autoimmunity.

• Deposition of antibody-streptococcal antigen complexes in kidney resulting in glomeruli damage.

Hemolysins

are substances or extracellular products that damage RBCs, polymorphonuclear cells, and platelets.

• Streptolysin O

• Streptolysin S

Two very important hemolysins are:

Streptolysin O

• Oxygen labile

• Antigenic

• Causes subsurface hemolysis.

Streptolysin S

• Oxygen stable

• Non-antigenic

• Responsible for the characteristic beta hemolysis on the blood agar.

Passive Agglutination

Principle

Stabilized Streptolysin O

What is coated in polystyrene latex?

Anti-streptolysin O

What is being detected?

• Polystyrene

• Bentonite

• Charcoal

• RBC

Carrier particles:

ASO latex reagent

• White latex particles with SLO (Stabilized Streptolysin O)

• 0.95 g/L sodium azide

• 200 mmol/L ammonium chloride

• pH 8.2

Control serum positive

Human serum containing ASO >200 IU/mL

Control serum negative

Human serum containing ASO <200 IU/mL