Streptococci With Pics (1)

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Streptococci With Pics (1)

  1. 1. STREPTOCOCCI ELIZABETH P. QUILES, M.D., FPASMAP DEPARTMENT OF MICROBIOLOGY OUR LADY OF FATIMA UNIVERSITY COLLEGE OF MEDICINE
  2. 2. CHARACTERISTICS <ul><li>Gram positive cocci, in pairs or chains </li></ul><ul><li>Catalase negative </li></ul><ul><li>Facultative anaerobes </li></ul><ul><li>Complex nutritional requirements (blood or serum enriched medium) </li></ul><ul><li>Ferment carbohydrates with formation of lactic acid </li></ul>
  3. 3. CLASSIFICATION <ul><li>1. Clinical – pyogenic, oral, enteric </li></ul><ul><li>2. Serologic  Lancefield Classification - </li></ul><ul><li>based on group specific cell wall carbohydrate </li></ul><ul><li>3. Hemolysis </li></ul><ul><li>a. alpha – incomplete hemolysis </li></ul><ul><li>b. beta – complete hemolysis </li></ul><ul><li>c. gamma – no hemolysis </li></ul>
  4. 4. LANCEFIELD CLASSIFICATION <ul><li>Group A – rhamnose-N-acetylglucosamine </li></ul><ul><li>Group B – rhamnose-glucosamine polysaccharide </li></ul><ul><li>Group C –rhamnose-N-acetylglucosamine </li></ul><ul><li>Group D – glycerol teichoic acid containing alanine & glucose </li></ul><ul><li>Group F – glucopyrasonyl-N- acetylgalactosamine </li></ul>
  5. 5. CLASSIFICATION TABLE Alpha, Gamma S. salivarius, S. sanguis, etc VIRIDANS Alpha S. pneumoniae - -do- S. milleri G Alpha, Beta, Gamma S. milleri F Alpha, Gamma Alpha, Beta, Gamma S. bovis S. faecalis D Beta S. equimilis C Beta, Alpha, Gamma S. agalactiae B Beta S. pyogenes A HEMOLYTIC PATTERN BIOCHEMICAL SEROLOGIC
  6. 6. PRESUMPTIVE IDENTIFICATION OF STREPTOCOCCI + - - - - R S Pneumococcus - - - - - R R (var) Viridans - - + + + - - + - - R R R R Grp D S. faecalis S. bovis - - + + - R R S. agalactiae - - - - - S R S. pyogenes Lysis bile Growth Bile NaCl Hydrolysis hippurate esculin Susceptibility A P Organism
  7. 7. Group A Streptococcus (S. pyogenes) <ul><li>Structure: </li></ul><ul><li>1. Capsule – hyaluronic acid </li></ul><ul><li>2. Cell wall </li></ul><ul><li> a. protein antigens M,T,R </li></ul><ul><li>M protein  major virulence factor </li></ul><ul><li>T & R protein  no role in the virulence </li></ul>
  8. 8. <ul><li>b. group specific carbohydrates – rhamnose-N-acetylglucosamine </li></ul><ul><li>3. Pili  consists partly of M protein & covered with lipoteichoic acid  for attachment </li></ul>
  9. 9. VIRULENCE FACTORS <ul><li>Capsule – non-immunogenic </li></ul><ul><li>M protein – hair-like projections on the cell wall </li></ul><ul><li>- major virulence factor </li></ul><ul><li>- promotes adherence </li></ul><ul><li>- antiphagocytic </li></ul><ul><li>- anticomplement </li></ul><ul><li>- type specific </li></ul>
  10. 10. <ul><li>3. Lipoteichoic acid – for adherence </li></ul><ul><li>4. Erythrogenic toxin – pyrogenic exotoxins A,B,C </li></ul><ul><li>- responsible for the rash of Scarlet fever </li></ul><ul><li>5. Streptolysin O – lyses WBC, platelets, RBC </li></ul><ul><li>- immunogenic </li></ul><ul><li>6. Streptolysin S – non-immunogenic </li></ul><ul><li> - responsible for the hemolytic zones around colonies </li></ul>
  11. 11. <ul><li>7. Streptokinase (fibrinolysin) – lyze blood clots  plasminogen  plasmin  digest fibrin & other proteins </li></ul><ul><li>- facilitates spread of infection </li></ul><ul><li>- used in the treatment of pulmonary emboli & coronary artery & venous thromboses </li></ul>
  12. 12. <ul><li>8. DNAse (streptodornase) – depolymerizes cell-free DNA in purulent materials </li></ul><ul><li>9. Hyaluronidase – spreading factor </li></ul><ul><li>- splits hyaluronic acid </li></ul><ul><li>streptodornase & streptokinase  used in enzymatic debridement  liquefy exudates & facilitate removal of pus & necrotic tissue  antibiotics gain better access </li></ul>
  13. 13. CLINICAL SYNDROMES <ul><li>A. Suppurative Infections </li></ul><ul><li>1. Skin Infections </li></ul><ul><li>a. impetigo – superficial blisters covered with pus or honey–colored crust </li></ul><ul><li>b. erysipelas – acute superficial cellulitis of the skin with lymphatic involvement </li></ul>
  14. 14. <ul><li>2. Pharyngitis – most common infection </li></ul><ul><ul><li>nasopharyngitis, tonsillitis, purulent exudates, cervical lymphadenopathy & high fever </li></ul></ul><ul><li>3. Sepsis –follows infection of traumatic or surgical wounds </li></ul><ul><li>4. Puerperal Fever – occurs ffg delivery </li></ul><ul><li>5. Acute Endocarditis – occurs in previously deformed heart valves </li></ul>
  15. 15. <ul><li>6. Scarlet fever – a complication of pharyngitis if the causative agent is capable of producing erythrogenic toxin </li></ul><ul><ul><li>initial symptoms of pharyngitis, diffuse erythematous rash with sparing of the palms & soles </li></ul></ul><ul><ul><li>Circumoral pallor </li></ul></ul><ul><ul><li>“ strawberry tongue” </li></ul></ul>
  16. 16. <ul><li>7. Pneumonia – rapidly progressive & severe </li></ul><ul><li>most commonly a sequela to viral infections like influenza or measles </li></ul>
  17. 17. <ul><li>B. Non-suppurative sequelae </li></ul><ul><li>1. Rheumatic fever – associated with M types causing URI & skin infections </li></ul><ul><ul><li>fever, malaise, migratory nonsuppurative polyarthritis, evidence of inflammation of the heart </li></ul></ul><ul><ul><li>carditis  leads to thickened & deformed valves & to small perivascular granulomas in the myocardium ( Aschoff bodies ) </li></ul></ul>
  18. 18. <ul><li>2. Acute Glomerulonephritis – associated with M types producing URI & skin infections </li></ul><ul><li>particularly associated with types 12, 4, 2 & 49 which are nephritogenic </li></ul><ul><li>initiated by ag-ab complexes on the glomerular basement membrane </li></ul><ul><li>hematuria, proteinuria, edema & hypertension </li></ul>
  19. 19. Strawberry Tongue Impetigo
  20. 20. scarlatiniform rash
  21. 21. DIAGNOSIS <ul><li>Microscopy </li></ul><ul><li>Culture – Bacitracin Test (Taxo-A) </li></ul><ul><li>Antigen detection tests – Enzyme-linked immunosorbent assay (ELISA) or agglutination tests </li></ul><ul><li>Antibody detection </li></ul><ul><ul><li>ASO titer – for respiratory disease </li></ul></ul><ul><ul><li>antiDNAse & antihyaluronidase – for skin infections </li></ul></ul>
  22. 22. TREATMENT <ul><li>Penicillin G – drug of choice </li></ul><ul><li>Erythromycin </li></ul><ul><li>Antistreptococcal chemoprophylaxis in persons who have suffered an acute attack of rheumatic fever  Penicillin G 1.2 M units IM every 3-4 weeks or daily oral penicillin or oral sulfonamide </li></ul>
  23. 23. GROUP B STREPTOCOCCI (S. agalactiae) <ul><li>Cell wall  rhamnose-glucosamine polysaccharide </li></ul><ul><li>Colonize the URT, lower GIT & vagina </li></ul><ul><li>Serotypes Ia, Ib, II & III – account for most human infections </li></ul>
  24. 24. CLINICAL SYNDROMES <ul><li>Early-Onset Neonatal Disease – can occur in utero, at birth or during the 1 st 5 days of life </li></ul><ul><ul><li>may occur as bacteremia, meningitis or pneumonia </li></ul></ul>
  25. 25. <ul><li>2. Late-Onset Neonatal Disease – in older infants from exogenous sources </li></ul><ul><ul><li>Bacteremia with meningitis </li></ul></ul><ul><li>3. Post-partum Sepsis – as endometritis or wound infection with bacteremia </li></ul>
  26. 26. STREPTOCOCCUS PNEUMONIAE <ul><li>Also known as Pneumococcus or Diplococcus pneumoniae </li></ul><ul><li>Gram (+) cocci, in pairs or short chains </li></ul><ul><li>Lancet-shaped </li></ul><ul><li>May or may not be encapsulated </li></ul><ul><li>Normal inhabitant of the upper respiratory tract </li></ul>
  27. 27. STRUCTURE <ul><li>Capsule – complex polysaccharides </li></ul><ul><ul><li>Serologically typable (84 serotypes) </li></ul></ul><ul><ul><li>Immunogenic  principal determinant of immunity </li></ul></ul><ul><li>Teichoic acid </li></ul>
  28. 28. VIRULENCE FACTORS <ul><li>Capsule - antiphagocytic </li></ul><ul><li>Pneumolysin - hemolysin </li></ul><ul><li>Purpura-producing principle – responsible for dermal hemorrhages </li></ul><ul><li>Neuraminidase – spreading factor </li></ul><ul><li>Amidase – autolysin & for cell division </li></ul>
  29. 29. EPIDEMIOLOGY <ul><li>Common inhabitant of the nasopharynx of healthy individuals </li></ul><ul><li>Most common cause of bacterial pneumonia & meningitis above 5 years old & in adults </li></ul><ul><li>One of the two most common causes of acute sinusitis & otitis media </li></ul>
  30. 30. CLINICAL SYNDROMES <ul><li>1. Pneumonia </li></ul><ul><ul><li>MOT: aspiration of endogenous oral organisms thru droplets </li></ul></ul><ul><ul><li>Cough, blood-tinged or rusty colored sputum & sharp pleural pain </li></ul></ul><ul><ul><li>Generally localized in the lower lobes of the lungs  lobar pneumonia </li></ul></ul><ul><ul><li>May also occur as bronchopneumonia </li></ul></ul>
  31. 31. <ul><li>2. Sinusitis & otitis media – preceded by viral infection of the URT </li></ul><ul><li>3. Meningitis – follows bacteremia, infections of the ear & sinuses or head trauma </li></ul><ul><li>4. Bacteremia – associated with pneumococcal pneumonia & meningitis </li></ul>
  32. 32. DIAGNOSIS <ul><li>1. Microscopy </li></ul><ul><li>2. Capsule swelling test  Quellung rxn </li></ul><ul><li>3. Culture </li></ul><ul><ul><li>Optochin test (Taxo-P) </li></ul></ul><ul><ul><li>Biochemical test </li></ul></ul><ul><ul><li>Autolysin activated by bile </li></ul></ul><ul><li>4. Serologic tests – immunofluorescence & Latex (detects capsular polypeptides) </li></ul>
  33. 33. TREATMENT <ul><li>Penicillin – drug of choice </li></ul><ul><li>Alternate drugs  Erythromycin, chloramphenicol, cephalosporins </li></ul><ul><li>Severe infections with Penicillin resistance  Vancomycin, Imipenem, 3 rd generation cephalosporins </li></ul>
  34. 34. GROUP D STREPTOCOCCUS (ENTEROCOCCUS) <ul><li>Grown in 6.5% NaCl </li></ul><ul><li>Hydrolyze esculin in the presence of bile </li></ul><ul><li>E. faecalis  most common cause of human infections </li></ul><ul><li>Normal flora of GIT & URT </li></ul>
  35. 35. INFECTIONS <ul><li>UTI – in hospitalized patients with in- dwelling catheters & receiving broad spectrum antibiotics </li></ul><ul><li>Intra-abdominal abscess </li></ul><ul><li>Wound infection </li></ul><ul><li>Endocarditis </li></ul><ul><li>Pulmonary infections in children </li></ul>
  36. 36. TREATMENT <ul><li>Aminoglycosides combined with cell wall active antibiotics (Penicillin, ampicillin, vancomycin) </li></ul>
  37. 37. thank you

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