Unit 4 Part 3 Streptococcal Serology

1. Unit 4Part 3 Streptococcal Serology Terry Kotrla, MS, MT(ASCP)BB

2. Introduction • Gram-positive • Beta hemolytic • Spherical, ovoid or lancet shaped • Pairs or chains

3. 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

4. Numerous Exoantigens • Exoantigens are produced and excreted and include: • Streptolysin O • Dnase • Hyaluronidase • Nicotinamide Adenine Dinucleotidase • Streptokinase • Patients react to exoantigens by producing antibodies

5. 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.

6. Characteristics • Two major sites of infection • Upper respiratory tract • Skin

7. Upper Respiratory • Sore Throat • Tonsillar exudate • Fever • Chills • Headache • 20% school children carriers

8. Skin • Pyoderma or Impetigo • Lesions on extremities • Commonly on face • Pustular and crusty

9. Suppurative Complications • Suppurate -To generate pus; as, a boil or abscess suppurates. • Erysipelas • Cellulitis • Necrotizing fasciitis • Scarlet fever • Puerperal sepsis

10. 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.

11. 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.

12. Necrotizing Fasciitis – rare infection of deeper layers of skin and subcutaneous tissue

13. Scarlet Fever • Strawberry tongue • Strep bacteria produces a toxin that causes a rash • Appears 12-48 hours after fever • Sandpapery • Peels

14. Suppurative Complications • Septic arthritis • Acute bacterial endocarditis • Meningitis • Toxic shock-like syndrome

15. Non-Suppurative Complications • Inflammatory response elsewhere in the body. • Damaging sequelae to strep infection • Rheumatic Fever • Post-Streptococcal glomerulonephritis

16. 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

17. 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.

18. 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.

19. 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.

20. 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.

21. Poststreptococcal glomerulonephritis • Most common in children 2-12 • Symptoms: • Hematuria • Proteinuria • Edema • hypertension

22. Poststreptococcal glomerulonephritis • The scattered capillary wall granular deposits in acute poststreptococcal glomerulonephritis also stain for complement (immunofluorescence with antibody to C3)

23. Laboratory Testing • Culture and identification • Rapid Strep Tests from throat swab • Detection of Streptococcal antibodies • Anti-Streptolysin O (ASO) titer • DNA probes

24. 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.

25. 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

26. 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.

27. 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.

28. 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.

29. 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

30. The End