Unit 4
Part 3 Streptococcal Serology
Terry Kotrla, MS, MT(ASCP)BB
Introduction
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Gram-positive
Beta hemolytic
Spherical, ovoid or
lancet shaped
Pairs or chains
Divided into Serotypes or groups
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Two major outer proteins M and T
Interior proteins divided into 20 defined
groups known as Lancefield groupings A-H
and K-T.
Streptococcus pyogenes belong to Lancefield
group A
M protein chief virulent factor
Numerous Exoantigens
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Exoantigens are produced and excreted and
include:
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Streptolysin O
Dnase
Hyaluronidase
Nicotinamide Adenine Dinucleotidase
Streptokinase
Patients react to exoantigens by producing
antibodies
Streptococcus pyogenes
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Organism found only in man.
Leading cause of oropharyngitis which may
lead to serious complications (sequelae)
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Rheumatic fever
Acute glomerulonephritis
Culture and rapid screening tests detect early
infection.
Characteristics
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Two major sites of infection
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Upper respiratory tract
Skin
Upper Respiratory
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Sore Throat
Tonsillar exudate
Fever
Chills
Headache
20% school children
carriers
Skin
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Pyoderma or Impetigo
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Lesions on extremities
Commonly on face
Pustular and crusty
Suppurative Complications
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Suppurate -To generate pus; as, a boil or
abscess suppurates.
Erysipelas
Cellulitis
Necrotizing fasciitis
Scarlet fever
Puerperal sepsis
Erysipelas
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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.
Cellulitis
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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 can
occur anywhere on body.
Necrotizing Fasciitis – rare infection of deeper
layers of skin and subcutaneous tissue
Scarlet Fever
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Strawberry tongue
Strep bacteria
produces a toxin
that causes a rash
Appears 12-48 hours
after fever
Sandpapery
Peels
Suppurative Complications
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Septic arthritis
Acute bacterial endocarditis
Meningitis
Toxic shock-like syndrome
Non-Suppurative Complications
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Inflammatory response elsewhere in the
body.
Damaging sequelae to strep infection
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Rheumatic Fever
Post-Streptococcal glomerulonephritis
Rheumatic Fever
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Only certain serotypes involved.
Delayed consequence of an untreated upper
respiratory infection with group A streptococci in 23% of population.
Not well understood.
Symptoms occur 20 days after sore throat.
Causes serious, debilitating damage to the heart.
Associated with large amount of M protein and a
capsule
Rheumatic Fever
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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.
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
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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.
Post-Streptococcal Glomerulonephritis
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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.
Poststreptococcal glomerulonephritis
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Most common in children 2-12
Symptoms:
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Hematuria
Proteinuria
Edema
hypertension
Poststreptococcal glomerulonephritis
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The scattered capillary wall granular deposits in
acute poststreptococcal glomerulonephritis also
stain for complement (immunofluorescence with
antibody to C3)
Laboratory Testing
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Culture and identification
Rapid Strep Tests from throat swab
Detection of Streptococcal antibodies
Anti-Streptolysin O (ASO) titer
DNA probes
Rapid Strep Tests from throat swab
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Antigen from a swab is extracted.
Test extracted antigens using ELISA or latex
agglutination.
If negative perform C&S.
Detection of Streptococcal Antibodies
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Most useful in Streptococcal sequelae
Organisms elaborate more than 20 exotoxins
that may invoke antibody response.
Most useful antibodies are:
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Anti-Streptolysin O (ASO)
Anti-DNase B
Anti-NADase
Anti-Hyaluronidates
Detection of Streptococcal Antibodies
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Serological evidence of disease is based on
elevated or rising titer of Streptococcal
antibodies.
Four fold (2 tube dilution) rise in titer is
considered clinically significant.
Anti-Streptolysin O (ASO) titer
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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.
Anti-DNase B Testing
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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 of
stability of reagents.
DNA Probes
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Sensitive and specific
Takes less time, hours versus days
Many methods developed but principle the
same.
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PCR
Add specific primers (probes) with tag
Tag gives off signal, ie, fluorescence
The End