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8/10/2019 Ser Unit4notePart3Strep

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Unit 4

Part 3 Streptococcal Serology

Terry Kotrla, MS, MT(ASCP)BB


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Introduction

Gram-positive

Beta hemolytic

Spherical, ovoid or

lancet shaped Pairs or chains


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Divided into Serotypes or groups

Two major outer proteins M and T

Interior proteins divided into 20 defined

groups known as Lancefield groupings A-H

and K-T.

Streptococcus pyogenesbelong to Lancefield

group A

M protein chief virulent factor


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Numerous Exoantigens

Exoantigens are produced and excreted and

include:

Streptolysin O

Dnase Hyaluronidase

Nicotinamide Adenine Dinucleotidase

Streptokinase

Patients react to exoantigens by producingantibodies


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Streptococcus pyogenes

Organism found only in man.

Leading cause of oropharyngitis which may

lead to serious complications (sequelae)

Rheumatic fever

Acute glomerulonephritis

Culture and rapid screening tests detect early

infection.


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Characteristics

Two major sites of infection

Upper respiratory tract

Skin


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Skin

Pyoderma or Impetigo

Lesions on extremities

Commonly on face

Pustular and crusty


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SuppurativeComplications

Suppurate -To generate pus; as, a boil or

abscess suppurates.

Erysipelas

Cellulitis

Necrotizing fasciitis

Scarlet fever

Puerperal sepsis


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Erysipelas Erysipelas produces a rash that is red, slightly swollen, with

very defined borders (well demarcated), warm, and tender

to the touch.

In this photograph, the right cheek is involved. There may

be symptoms that affect the entire body (systemic)

including fever and chills.


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Cellulitis

Diffuse inflammation of connective tissue with

severe inflammation of dermal and subcutaneous

layers of skin.

Skin on face or lower leg most common site, but canoccur anywhere on body.


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Necrotizing Fasciitisrare infection of deeperlayers of skin and subcutaneous tissue


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Scarlet Fever

Strawberry tongue

Strep bacteriaproduces a toxin

that causes a rash Appears 12-48 hours

after fever

Sandpapery

Peels


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Suppurative Complications

Septic arthritis

Acute bacterial endocarditis

Meningitis

Toxic shock-like syndrome


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Non-Suppurative Complications

Inflammatory response elsewhere in the

body.

Damaging sequelae to strep infection

Rheumatic Fever

Post-Streptococcal glomerulonephritis


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Rheumatic Fever

Due to immune response against Strep

antigens similar to heart antigens.

Inflammation of the mitral valve the most

serious.

Thirty to 60% of patients suffer permanent

disability.


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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.


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Poststreptococcal glomerulonephritis

Follows strep infection of skin or pharynx.

Occurs about 10 days following initial

infection.

Characterized by damage to glomeruli of

kidneys.

Inflammatory response causes damage.


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Post-Streptococcal Glomerulonephritis

Deposition of Ag-Ab complexes, activation of

complement.

Complement activated resulting in

hypocomplementemia.

Renal function impaired due to reduction in

glomerular filtration rate, results in edema

and hypertension. Renal failure not typical.


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Most common in children 2-12

Symptoms:

Hematuria

Proteinuria

Edema

hypertension


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The scattered capillary wall granular deposits in

acute poststreptococcal glomerulonephritis also

stain for complement (immunofluorescence with

antibody to C3)


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Laboratory Testing

Culture and identification

Rapid Strep Tests from throat swab

Detection of Streptococcal antibodies

Anti-Streptolysin O (ASO) titer

DNA probes


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Detection of Streptococcal Antibodies

Most useful in Streptococcal sequelae

Organisms elaborate more than 20 exotoxins

that may invoke antibody response.

Most useful antibodies are:

Anti-Streptolysin O (ASO)

Anti-DNase B

Anti-NADase Anti-Hyaluronidates


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Detection of Streptococcal Antibodies

Serological evidence of disease is based on

elevated or rising titer of Streptococcal

antibodies.

Four fold (2 tube dilution) rise in titer isconsidered clinically significant.


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Anti-Streptolysin O (ASO) titer

Two of the toxins produced are Streptolysin S,

which is oxygen stable, nonantigenic and

Streptolysin O (SLO), which is oxygen labile and

antigenic.

SLO is a hemolysin which is toxic to many tissues,

including heart and kidneys.

Evokes an antibody response (anti-SLO) which

neutralizes the hemolytic action of SLO. Specific for ASO, it does not test for antibodies to

any other Streptococcal exotoxins.


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Anti-DNase B Testing

May appear earlier than ASO.

Increased sensitivity for detection of

glomerulonephritis preceded by streptococcal

skin infections.

Macro- and micro-titer, ELISA and

neutralization techniques are available.

Neutralization technique has advantage ofstability of reagents.


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DNA Probes

Sensitive and specific

Takes less time, hours versus days

Many methods developed but principle the

same.

PCR

Add specific primers (probes) with tag

Tag gives off signal, ie, fluorescence


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The End

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