unit 4 part 3 streptococcal serology terry kotrla, ms, mt(ascp)bb
TRANSCRIPT
Unit 4Part 3 Streptococcal Serology
Terry Kotrla, MS, MT(ASCP)BB
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 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
Exoantigens are produced and excreted and include: Streptolysin O Dnase Hyaluronidase Nicotinamide Adenine Dinucleotidase Streptokinase
Patients react to exoantigens by producing antibodies
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.
Characteristics
Two major sites of infection Upper respiratory tract Skin
Upper Respiratory
Sore Throat Tonsillar exudate Fever Chills Headache 20% school children
carriers
Skin
Pyoderma or Impetigo Lesions on extremities Commonly on face Pustular and crusty
Suppurative Complications
Suppurate -To generate pus; as, a boil or abscess suppurates.
Erysipelas Cellulitis Necrotizing fasciitis Scarlet fever Puerperal sepsis
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.
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 can occur anywhere on body.
Necrotizing Fasciitis – rare infection of deeper layers of skin and subcutaneous tissue
Scarlet Fever
Strawberry tongue Strep bacteria
produces a toxin that causes a rash
Appears 12-48 hours after fever
Sandpapery Peels
Suppurative Complications
Septic arthritis Acute bacterial endocarditis Meningitis Toxic shock-like syndrome
Non-Suppurative Complications Inflammatory response elsewhere in the
body. Damaging sequelae to strep infection
Rheumatic Fever Post-Streptococcal glomerulonephritis
Rheumatic Fever
Only certain serotypes involved. Delayed consequence of an untreated upper
respiratory infection with group A streptococci in 2-3% 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
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 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 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 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 DNA probes
Rapid Strep Tests from throat swab Antigen from a swab is extracted. Test extracted antigens using ELISA or latex
agglutination. If negative perform C&S.
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
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 is considered clinically significant.
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.
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 of stability of reagents.
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
The End