Microbiology lec4

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Microbiology lec4

  1. 1. Medical Microbiology Lecture 3 Dr. Saleh M Y OTH PhD Medical Molecular Biotechnology and Infectious Diseases 02/10/2010 IMS - MSU Systemic Bactreiology
  2. 2. STREPTOCOCCI Systemic Bactreiology
  3. 3. Words must to be known <ul><li>Group A streptococcus (S. pyogenes ) </li></ul><ul><li>Lancefield groups </li></ul><ul><li>Hemolysis (alpha, beta, gamma) </li></ul><ul><li>Bacitracin susceptibility test </li></ul><ul><li>M, T, R proteins </li></ul><ul><li>Streptolysins O and S </li></ul><ul><li>F protein/lipoteichoic acid </li></ul><ul><li>Rheumatic fever/carditis/arthritis </li></ul><ul><li>Glomerulonephritis </li></ul><ul><li>Scarlet fever </li></ul><ul><li>Toxic shock-like syndrome/bacteremia </li></ul><ul><li>“ Flesh-eating bacteria” </li></ul><ul><li>Pyrogenic toxin </li></ul><ul><li>Erythrogenic toxin </li></ul><ul><li>Group B streptococcus ( S.agalactiae ) </li></ul><ul><li>Neonatal septicemia/meningitis </li></ul><ul><li>CAMP test </li></ul><ul><li>Hippurate hydrolysis test </li></ul><ul><li>Group D streptococcus </li></ul><ul><li>Urinary tract infection/ endocarditis </li></ul><ul><li>Bile-esculin test </li></ul><ul><li>Enterococci </li></ul><ul><li>Non-enterococci </li></ul><ul><li>Large colony </li></ul><ul><li>Minute colony </li></ul><ul><li>Viridans streptococci </li></ul><ul><li>Dental caries/endocarditis </li></ul>
  4. 4. Streptococcus pyogenes During the infection, this bacteria produce pus <ul><li>- One of the most important pathogens </li></ul><ul><li>- Gram positive cocci in chains </li></ul><ul><li>- Lancefield Serological Group A </li></ul><ul><li>- Beta Hemolytic on blood agar </li></ul>
  5. 5. Gram Stain of S. pyogenes Streptcoccus pyogenes S. agalactia S. peumoniae
  6. 6. Hemolysis on Blood Agar Plates <ul><li>Beta hemolysis -organisms excretes potent hemoysins which completely lyse RBCs (complete hemolysis) thus a clear zone appears around colony. S. pyogenes </li></ul><ul><li>Alpha hemolysis -organism excretes hemolysins which partially break down rbc (incomplete hemolysis) thus a greenish zone appears around colony. S. pneumoniae </li></ul>
  7. 7. S.pyogenes S. pneumonia Beta hemolysis Alpha hemolysis
  8. 8. <ul><li>Streptococci </li></ul><ul><ul><li>facultative anaerobe </li></ul></ul><ul><ul><li>Gram-positive </li></ul></ul><ul><ul><li>chains or pairs </li></ul></ul><ul><ul><li>catalase negative </li></ul></ul><ul><li>(staphylococci are catalase positive) </li></ul>Streptococcus in chains (Gram stain)
  9. 9. <ul><li>Streptococci </li></ul><ul><ul><li>Lancefield groups </li></ul></ul><ul><ul><ul><li>one or more species per group </li></ul></ul></ul><ul><ul><ul><li>carbohydrate antigens </li></ul></ul></ul>
  10. 10. Groupable streptococci <ul><li>1- A, B and D </li></ul><ul><ul><li>frequent </li></ul></ul><ul><li>2- C, G, F </li></ul><ul><ul><li>less frequent </li></ul></ul>
  11. 11. Non-groupable <ul><li>1- S. pneumoniae </li></ul><ul><ul><li>pneumonia </li></ul></ul><ul><li>2- viridans streptococci </li></ul><ul><ul><li>e.g. S. mutans </li></ul></ul><ul><ul><ul><li>dental caries </li></ul></ul></ul>
  12. 12. hemolysis reaction - sheep blood agar <ul><li>a- (beta- β ) </li></ul><ul><ul><li>complete clearing </li></ul></ul><ul><ul><li>A and B </li></ul></ul><ul><li>b- (alpha- α ) </li></ul><ul><ul><li>partial hemolysis </li></ul></ul><ul><ul><ul><li>green color </li></ul></ul></ul><ul><li>c- (gamma- δ ) </li></ul><ul><ul><li>no lysis </li></ul></ul>White colonies
  13. 13. Hemolysis <ul><li>1- Groups A an B </li></ul><ul><ul><li>β -hemolysis </li></ul></ul><ul><li>2- Group D </li></ul><ul><li>α or δ -hemolysis </li></ul><ul><li>3- S. pneumoniae and S. viridans </li></ul><ul><ul><li>α -hemolysis </li></ul></ul>
  14. 14. hemolysis reaction + one characteristic presumptive identification
  15. 15. Group A streptococcus ( S. pyogenes ) Group A streptococcal infections affect all ages peak incidence at 5-15 years of age
  16. 16. S. pyogenes – suppurative <ul><li>1- non-invasive </li></ul><ul><ul><li>- pharyngitis </li></ul></ul><ul><ul><li>- skin infection, impetigo </li></ul></ul><ul><li>2- invasive bacteremia </li></ul><ul><ul><li>- toxic shock-like syndrome </li></ul></ul><ul><ul><li>- &quot;flesh eating&quot; bacteria </li></ul></ul><ul><ul><li>- pyrogenic toxin </li></ul></ul>
  17. 17. Pyrogenic toxin <ul><li>Streptococcus pyogenes and Staphylococcus aureus express pyrogenic toxin superantigens (PTSAgs) that are associated with toxic shock syndrome (TSS) and staphylococcal food poisoning (SFP). </li></ul><ul><li>Most PTSAgs cause TSS in deep-tissue infections, whereas only TSS toxin 1 (TSST-1) is associated with menstrual, vaginal TSS. </li></ul><ul><li>In contrast, SFP has been linked only with staphylococcal enterotoxins (SEs). </li></ul>
  18. 18. Pyrogenic toxin … <ul><li>Because of the differential abilities of PTSAgs to cause systemic or localized symptoms in a site-dependent manner, these toxins have abilities to cross mucosal barriers. </li></ul><ul><li>The activity of three PTSAgs when delivered orally , vaginally , or intravenously to rabbits and orally to monkeys in some experimental studies. </li></ul>
  19. 19. Pyrogenic toxin <ul><li>1- superantigen </li></ul><ul><li>2- T cell mitogen </li></ul><ul><li>3- activates immune system </li></ul>
  20. 20. Scarlet fever - rash - erythrogenic toxin
  21. 22. non-suppurative <ul><li>rheumatic fever </li></ul><ul><ul><li>- inflammatory disease </li></ul></ul><ul><ul><li>- life threatening </li></ul></ul><ul><ul><li>- chronic sequalae </li></ul></ul><ul><ul><ul><li>fever </li></ul></ul></ul><ul><ul><ul><li>heart </li></ul></ul></ul><ul><ul><ul><li>joints </li></ul></ul></ul><ul><ul><ul><ul><li>rheumatic NOT rheumatoid arthritis </li></ul></ul></ul></ul>Rheumatic fever is an inflammatory disease that occurs following a Group A streptococcal infection, (such as strep throat or scarlet fever). Believed to be caused by antibody cross-reactivity that can involve the heart, joints, skin, and brain, the illness typically develops two to three weeks after a streptococcal infection. Acute rheumatic fever commonly appears in children between the ages of 5 and 15, with only 20% of first-time attacks occurring in adults. The illness is so named because of its similarity in presentation to rheumatism.
  22. 23. Rheumatic fever -etiology <ul><li>M protein </li></ul><ul><ul><li>cross-reacts heart myosin </li></ul></ul><ul><ul><li>autoimmunity </li></ul></ul><ul><li>Cell wall antigens </li></ul><ul><ul><li>poorly digested in vivo </li></ul></ul><ul><ul><li>persist indefinitely </li></ul></ul>
  23. 24. Rheumatic fever <ul><li>Penicillin </li></ul><ul><ul><li>terminates pharyngitis </li></ul></ul><ul><ul><li>decreases carditis </li></ul></ul>
  24. 25. Acute glomerulonephritis immune complex disease of kidney
  25. 26. Major pathogenesis factors <ul><li>lipoteichoic acid /F protein </li></ul><ul><ul><li>fimbriae </li></ul></ul><ul><ul><li>binds to epithelial cells </li></ul></ul><ul><li>M protein </li></ul><ul><ul><li>anti-phagocytic </li></ul></ul>
  26. 27. S. pyogenes fibronectin lipoteichoic acid/F-protein epithelial cells
  27. 28. M protein M protein fibrinogen peptidoglycan IgG Complement IMMUNE NON-IMMUNE r r r r r r
  28. 29. M protein <ul><li>major target </li></ul><ul><ul><li>natural immunity </li></ul></ul><ul><li>strain variation </li></ul><ul><ul><li>antigenicity </li></ul></ul><ul><li>re-infection </li></ul><ul><ul><li>occurs with different strain </li></ul></ul>
  29. 30. Capsules <ul><li>Anti-phagocytic </li></ul><ul><ul><li>mucoid strains </li></ul></ul>
  30. 31. Isolation and identification <ul><li>β - hemolytic colonies </li></ul><ul><ul><li>bacitracin inhibits growth </li></ul></ul><ul><li>β - hemolytic colonies </li></ul><ul><ul><li>group A antigen </li></ul></ul>Bacitracin is a mixture of related cyclic polypeptides produced by organisms of the licheniformis group of Bacillus subtilis var Tracy, isolation of which was first reported in 1945. As a toxic and difficult-to-use antibiotic , bacitracin does not work well orally. However, it is very effective topically, and is a common ingredient of eye and skin antibiotic preparations. Its action is on gram-positive cell walls. It can cause contact dermititis due to allergic sensitivity to it.
  31. 32. Β - hemolysis <ul><li>hemolysin O </li></ul><ul><ul><li>sensitive oxygen </li></ul></ul><ul><li>hemolysin S </li></ul><ul><ul><li>insensitive oxygen </li></ul></ul>
  32. 33. Modern Rapid “Strep” Test Throat swab extract (+/- streptococcal antigen) Antibody Liposome + - Streptococcal antigen
  33. 34. Post-infectious diagnosis (serology) <ul><li>antibodies to streptolysin O </li></ul><ul><li>important if delayed clinical sequelae occur </li></ul>
  34. 35. Traditional serotyping of proteins: - M - T - R Typing Modern: - Sequencing of M protein gene
  35. 36. Group B streptococcus <ul><li>neonatal meningitis </li></ul><ul><li>septicemia </li></ul><ul><li>transmission </li></ul><ul><ul><li>vaginal flora </li></ul></ul>
  36. 37. Group B streptococcus - identification <ul><li> hemolysis </li></ul><ul><li>hippurate hydrolysis </li></ul><ul><li>CAMP reaction </li></ul><ul><ul><li>increases  hemolysis of S. aureus </li></ul></ul>
  37. 38. Group D streptococcus <ul><li>Growth on bile esculin agar </li></ul><ul><ul><li>black precipitate </li></ul></ul><ul><li>6.5% saline </li></ul><ul><li>grow </li></ul><ul><ul><li>enterococci </li></ul></ul><ul><li>no growth </li></ul><ul><ul><li>non-enterococci </li></ul></ul>
  38. 39. Enterococci <ul><li>distantly related to other streptococci </li></ul><ul><li>genus Enterococcus </li></ul><ul><li>gut flora </li></ul><ul><ul><li>urinary tract infection </li></ul></ul><ul><ul><ul><li>fecal contamination </li></ul></ul></ul><ul><ul><li>opportunistic infections </li></ul></ul><ul><ul><ul><li>particularly endocarditis </li></ul></ul></ul><ul><li>most common E. (S.) faecalis </li></ul>
  39. 40. Enterococci <ul><li>resistant to many antibiotics </li></ul><ul><ul><li>including vancomycin </li></ul></ul><ul><ul><ul><li>terminal D-ala replaced by D-lactate </li></ul></ul></ul>
  40. 41. Minute colony streptococci <ul><li>Various groups/hemolysis (e.g. group A) </li></ul><ul><ul><li>genetically distinct </li></ul></ul><ul><ul><ul><li>from large colony (e.g. S. pyogenes) </li></ul></ul></ul><ul><ul><li>no rheumatic fever </li></ul></ul>Large colony Minute colony
  41. 42. Viridans streptococci <ul><li>diverse species </li></ul><ul><li>oral </li></ul><ul><li>dental caries </li></ul><ul><li> hemolytic and negative for other tests </li></ul><ul><li>non-groupable. </li></ul><ul><li>includes S. mutans </li></ul><ul><ul><li>endocarditis </li></ul></ul><ul><ul><li>tooth extraction </li></ul></ul>

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