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Streptococcal Diseases

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  1. Streptococcal Diseases Streptococcus pyogenes

  2. Streptococcus pyogenesPyogenes means pus producing • One of the most important pathogens • Gram positive cocci in chains • Lancefield Serological Group A • Beta Hemolytic on blood agar

  3. Gram Stain of S. pyogenes

  4. Hemolysis on Blood Agar Plates • Alpha hemolysis-organism excretes hemolysins which partially break down rbc (incomplete hemolysis) thus a greenish zone appears around colony. S. pneumoniae • Beta hemolysis-organisms excretes potent hemoysins which completely lyse rbc (complete hemolysis) thus a clear zone appears around colony. S. pyogenes

  5. S.pyogenes S. pneumonia Beta hemolysis Alpha hemolysis

  6. Diseases caused by S. pyogenes • Strep throat • Impetigo • Erysipelas • Cellulitis • Invasive Strep A infections • Necrotizing fasciitis • Myositis • Toxic shock-like syndrome

  7. Erysipelas • Acute infection and imflammation of the dermal layer of skin. • Painful red patches which enlarge and thicken • Treatment -penicillin or erythromycin

  8. Erysipelas

  9. Strep Throat • Most common of all Strep diseases • Spread by saliva or nasal secretions • Incubation period 2-4 days • Sore throat, slight fever (101) • Important to treat immediately to avoid post strep diseases

  10. Diagnosis and treatment of Strep Throat • Tell tale symptoms are slight fever associated with sore throat and visual of pus in back of throat • Quick diagnostic tests (Molecular) available but must be confirmed by throat swab and growth on blood agar (beta hemolysis)

  11. Diagnosis and treatment of Strep Throat • If the strain of S. pyogenes is lysogenic for a particular phage which expresses an erythrogenic toxin the result is Scarlet fever • Rash appears and characteristic is the strawberry colored tongue

  12. Strawberry Tongue

  13. Treatment of Strep • Penicillin G or Erythromycin are drugs of choice • Although the disease is self-limiting it is important to treat immediately to avoid post strep complications

  14. Poststreptococcal diseases • Rheumatic Fever-autoimmune disease involving heart valves,joints, nervous system. Follows a strep throat • Acute glomerulonehritis or Bright’s Disease-inflamatory disease of renal glomeruli and structures involved in blood filter of kidney. Due to deposition of Ag/Ab complexes

  15. Rheumatic Fever • Most common cause of permanent heart valve damage in children • Exact cause not yet known but there appears to be some antibody cross reactivity between the cell wall of S. pyogenes and heart muscle

  16. Rheumatic Fever • Diagnosis is based on symptoms and is difficult • Occurs most frequently between ages of 6 and 15 • US it is about 0.05% of pop having strep infections • 100x more frequent in tropical countries

  17. Rheumatic Fever • Treatment is via salicylates (aspirin derivatives) and corticosteroids to decrease inflammation and fever.

  18. Glomerular Nephritis • Diagnosis based on history of Strep throat and clinical findings. • Symptoms include fever, malaise,edema, hypertension and blood or protein in urine • Occurs in 0.5% of those having strep throat.

  19. Glomerular NephritisTreatment and Recovery • Penicillin or erythromycin to eradicate and residual strep infection • 80-90% of cases recover with bed rest lasting for months • Kidney damage in the remainder is often permanent resulting in chronic glomerular nephritis

  20. Streptococcus Pneumonia • Caused by infection with Streptococcus pneumoniae • Gram positive, alpha hemolytic, not of lancefield serotype A • Often part of normal flora of respiratory track and becomes infective once hosts resistance is lowered. Classified as an endogenous infection.

  21. Strep Pneumonia

  22. Strep Pneumonia S. pneumoniae Alpha hemolysis

  23. Strep pneumonia • Predisposing factors: upper respiratory viral infection, diabetes, alcoholism • 60-80% of all pneumonias

  24. Strep Pneumonia

  25. Cause of strep pneumonia • Primary virulence factor is the capsular polysaccharide which protects the organism against phagocytosis • Pathogenesis is due to rapid growth of bacteria in alveolar spaces

  26. Symptoms of Strep Pneumonia • Onset abrupt • Chest pains • Chills • Labored breathing

  27. Diagnosis of Strep pneumonia • Chest Xray • Culture and staining • Biochemical tests of isolated organism

  28. Treatment of Strep Pneumonia • Typically treated with Penicillin G cefotaxime, oflaxacin or for those allergic to penicillins can be treated with erythromycin or tetracycline • Pneumococcal vaccine (Pneumovax 23 or Pnu-immune 23) is available for the elderly

  29. Staphylococcal infections • One of the most common of all infections • Staphylococcus are divided into pathogens and non pathogens based on possession of the enzyme coagulase • Coagulase + are usually S. aureus and pathogenic • Coagulase - are organisms like S. epidermidis are less invasive

  30. Diseases of Staphylococcus

  31. Toxic Shock Syndrome • Most in women using superabsorbant tampons • Staphylococcus aureus-Gram positive cocci • Low blood pressure, fever, diarrhea, skin rash can be fatal

  32. Toxic Shock Syndrome • Symptoms mainly caused by toxic shock syndrome toxin 1(TSST1) • Several other enterotoxins also involved

  33. Staph skin infections • Most common cause of acne, boils, furuncle and cabuncles • Treatment can be difficult because of antibiotic resistance.Usually can be treated with methicillin, cephalosporins,or vancomycin • Methicillin resistant strains=MRSA

  34. Staph skin infections Furuncle (infected hair follicle Deep folliculitis superficialfolliculitis Carbuncle Multiple abcesses Around many hair follicles Scalded skin syndrome Staph impetigo

  35. Scalded Skin Syndrome • Due to strains of S. aureus containing a special toxin-exfoliatin

  36. Diagnosis • Culture and stain-gram positive in grape-like clusters • Catalase and coagulase tests • DNA fingerprinting

  37. S. aureus