Streptococcal Serology

Terry Kotrla

Introduction

• Gram-positive• Beta hemolytic• Spherical, ovoid

or lancet shaped• Pairs or chains

Divided into Serotypes or groups

• Two major outer proteins M and T• Eighteen interior proteins knows as

Lancefield grouping• Streptococcus pyogenes belong to

Lancefield group A• M protein chief virulent factor

Numerous Exoantigens

• Exoantigens are produced and excreted and include:– Streptolysin O– Dnase– Hyaluronidase– Nicotinamide Adenine Dinucleotidase – Streptokinase

• Patients react to exoantigens by producing antibodies

Characteristics

• Two major sites of infection– Upper respiratory tract– Skin

• If infections left untreated can lead to post-streptococcal sequelae– Acute glomerulonephritis– Rheumatic fever

Upper Respiratory

• Sore Throat • Tonsillar exudate• Fever• Chills• 20% school

children carriers

Skin

• Impetigo– Lesions on

extremities– Commonly on face– Pustular and

crusty

Suppurative Complications

• Suppurate -To generate pus; as, a boil or abscess suppurates.

• Erysipelas• Necrotizing fasciitis• Scarlet fever

Erysipelas– Infection involves the dermis and lymphatics

and is a more superficial subcutaneous infection of the skin than cellulitis.

– characterized by intense erythema, induration and a sharply demarcated border.

Necrotizing Fasciitis

Scarlet Fever

• Strep bacteria produces a toxin that causes a rash

• Sandpapery• Peels

Non-Suppurative

• Inflammatory response elsewhere in the body.

• Damaging sequelae to strep infection– Rheumatic Fever– Post-Streptococcal glomerulonephritis

Rheumatic Fever• Delayed consequence of an untreated

upper respiratory infection with group A streptococci

• Causes serious, debilitating damage to the heart.

• Associated with large amount of M protein and a capsule

• Due to immune response against Strep antigens similar to heart antigens.

Rheumatic Fever

This is the heart of a 44 year old woman who had rheumatic fever and had been treated for congestive heart failure for about one year.

Poststreptococcal glomerulonephritis

• Follows strep infection of skin or pharynx

• Characterized by damage to glomeruli of kidneys

• Deposition of Ag-Ab complexes, activation of complement.

• Inflammatory response causes damage.

Poststreptococcal glomerulonephritis

• Most common in children 2-12• Symptoms:

– Hematuria– Proteinuria– Edema– hypertension

Poststreptococcal glomerulonephritis• The scattered capillary wall granular

deposits in acute poststreptococcal glomerulonephritis also stain for complement (immunofluorescence with antibody to C3)

Laboratory Testing

• Culture and identification• Rapid Strep Tests from throat swab• Detection of Streptococcal

antibodies• Anti-Streptolysin O (ASO) titer