Staphylococcus-Streptococcus-Enterococcus

1. Staphylococcus-Streptococcus-Enterococcus

2. Gr + cocci ~ 21 genera • Common features • Spherical shape • Gram stain reaction • Absence of endospores • Catalase activity subdividing • Catalase positive genera Staphylococcus Micrococcus Stomatococcus Alloiococcus • Catalase negative genera Streptococcus Enterococcus

3. Staphylococcus • Gram positive • Grow pattern cluster of grapes single cells, pairs, short chains • Nonmotile • Aerobic or facultatively anaerobic • Catalase-positive • Grow in 10 % NaCl medium @ 18-40 o C

4. S. aureus S. epidermidis S. saprophyticus S. capitis S. haemolyticus Produce coagulase Coagulase negative staphylococcus Most common Staph. causing diseases

5. Micrococcus • Can be confused with CN staphs • Differ in that, they grow only aerobically • Resistant to lizostafin and furazolidone • Isolation of micrococcus in clinical samples • Contamination ?

6. Stomatococcus mucilaginosus Only species in this genus Infection in the immunocompromised host Alloiococcus otitidis Only species in this genus Aerobic Gr + Disease?? Stomatococcus Alloiococcus

7. Staphylococcus and their diseases • S. aureus • Toxin-mediated • Food poisoning • Toxic shock syndrome, scalded skin syndrome • Cutaneous • Impetigo • Folliculitis • Furuncles • Carbuncles, wound infections

8. Staphylococcus and their diseases • S. aureus • Others • Bacteremia • Endocarditis, • Pneumoniae • Empyema • Osteomyelitis • Septic arthritis

9. Staphylococcus and their diseases • S. epidermidis • Bacteremia • Endocarditis, • Surgical wounds • Urinary tract infections • Opportunistic infections of catheters, shunts, prostetic devices and peritoneal dialysates

10. Staphylococcus and their diseases • S. saprophyticus • Urinary tract infections • Opportunistic infections • Resistant to novobiocin

11. Staphylococcus/physiology & structure • Capsule • Peptidoglycan • Teichoic acids • Protein A • Coagulase and other sutface proteins • Cytoplasmic membrane

12. Staphylococcus/capsule • Loose-fitting • Polysaccharide layer (slime layer) • In vitro rare

13. Staphylococcus/peptidoglycan • Half of the cell wall • More rigide compared to Gr negatives • Endotoxin-like activity • Endogenous pyrogenes • Activation of complement • Production of int-1 from monocytes • Aggregation of polymorphonuclears

14. Staphylococcus/teichoic acids • Teichoic & lipoteichoic acid • Polysaccharide A in S. aureus • Polysaccharide B in S. epidermidis • Mediate the attachment of staphs to mucosal surfaces • Poor immunogens (except when bound to peptidoglycan)

15. Staphylococcus/protein A • The surface of most S. aureus is coated with protein A (not CNS) • Affinity to bind Fc receptor of IgG1, IgG2 & IgG4 prevents the antibody-mediated immune clearence of the bacteria

16. Staphylococcus/coagulase & other surface proteins • S. aureus clumping factor (bound coagulase) • Collagen-binding protein adherence to • Elastin-binding protein host tissues • Fibronectin-binding protein

17. Staphylococcus/pathogenesis & immunity • Toxins & • Enzymes

18. Staphylococcus/toxins • Alpha toxin • Beta toxin • Delta toxin • Gamma toxin & Panton-Valentine Leukocidin • Exfoliative toxins • Enterotoxins • Toxic shock syndrome toxin-1

19. Staphylococcus/toxins a Toxin important mediator of tissue damage in staphylococcal diseases toxic for many cells (erythrocytes, leukocytes, hepatocytes,..) produced by most strains of S. aureus

20. Staphylococcus/toxins b Toxin sphingomyelinase C toxic for many cells role in tissue destruction & abscess formation produced by most strains of S. aureus

21. Staphylococcus/toxins d Toxin wide spectrum of cytolytic activity detergent-like activity produced by most strains of S. aureus

22. Staphylococcus/toxins g Toxin & Panton-Valentine Leukocidin composed of two polypeptide chains toxic for many cells

23. Staphylococcus/toxins Exfoliative toxins staphylococcal scalded skin syndrome (SSSS) exfoliative dermatitis two types: ETA & ETB produced by 5 to 10 % of all S. aureus strains

24. Staphylococcus/toxins Enterotoxins 8 serologically distinct enterotoxins exist (A-E, G-I) stable to heating resistant to gastric & jejunal enzymes produced by 30 to 50 % of all S. aureus strains are superantigens

25. Staphylococcus/toxins Toxic shock syndrome toxin-1 heat & proteolysis resistant all S. aureus responsible for menstruation-associated TSS produce TSST-1 50 % of the strains responsible for other forms of TSS produce TSST-1 superantigens

26. Staphylococcus/enzymes • Coagulase • Catalase • Hyaluronidase • Fibrinolysin • Lipases • Nuclease • Penicillinase

27. Staphylococcus/enzymes • Coagulase • S. aureus • 2 forms • Bound • free

28. Staphylococcus/enzymes • Catalase • “All staphylococci produce catalase” • H2O2 (toxic) H2O O2

29. Staphylococcus/enzymes • Hyaluronidase • Hydrolyzes hyaluronic acids facilitates the spread of S. aureus in tissues • > 90 % of S. aureus produce hyaluronidase

30. Staphylococcus/enzymes • Fibrinolysine • Staphylokinase • All S. aureus • Dissolve fibrine clots

31. Staphylococcus/enzymes • Lipases • All S. aureus & 30 % of the CNS produce several different lipases • Nuclease • A marker for S. aureus • Penicillinase (b-lactamase)

32. Staphylococcus/IDENTIFICATION • Microscopy • Culture: • Nutritionally enriched agar media with sheep blood • Selective agar media for S. aureus with 7.5 % NaCl + mannitol • Aerobic and anaerobic • Large, smooth colonies • Identification • Positive coagulase, heat-stable nuclease, alkaline phosphatase, mannitol ferment. S. aureus

33. Streptococcus • Gram positive • Grow pattern pairs, chains • Most species are facultatively anaerobes • Some grow only in atmosphere enhanced with CO2 • Nutritional requirements are complex • Blood, serum • “Catalase-negative”

34. Streptococcus • Classification is complicated • 3 different schemes are used • Lancefield groupings according to serologic properties (A-H, K-M, O-V) • Hemolytic patterns: b, a & g hemolysis • Biochemical properties

35. S. pyogenes (group A) Pharyngitis, scarlet fever, pyoderma, erysipelas, cellulitis, necrotizing fasciitis, streptococcal toxic shock syndrome, bacteremia, rheumatic fever, glomerulonephritis Streptococci and their diseases

36. S. agalactiae (group B) Neonatal infections (meningitis, pneumoniae, bacteremia) Urinary tract infections Amnionitis, Endometritis Wound infections Streptococci and their diseases

37. Streptococcus pyogenes/physiology & structure • Spherical cocci • Form short (clinical specimen) or long chains (liquid media) • Grow on enriched blood agar media • White colonies 1-2 mm with large zones of b-hemolysis • Encapsulated strains mucoid • Basic structure in the cell wall is peptidoglycan as Staphs group spec. Ag

38. Streptococcus pyogenes/physiology & structure • Group specific carbohydrate • Within the cell wall • 10 % of the dry weight • Is used to classify group A streptococci and distinguish them from others

39. Streptococcus pyogenes/physiology & structure • Type specific proteins • M protein major type-specific protein associated with virulent streptococci • 2 polypeptide chains • Highly conserved among all ggroup A streptococci • Responsible for the antigenic variability >80 serotypes • T protein (trypsin-resistant) secondary • Usefull when bacteria fail to express the M protein

40. Streptococcus pyogenes/physiology & structure • Other cell surface components • M-like proteins • Lipoteichoic acid • F protein • Capsule (hyaluronic acid)

41. Streptococcus pyogenes/Pathogenesis&Immunity • Virulence of S. pyogenes • The ability of the bacteria • to adhere to the surface of the host cells • Invade into the epithelial cells • Avoid opsonization & phagocytosis • Produce a variety of toxins & enzymes

42. Streptococcus pyogenes/Pathogenesis&Immunity • Pyrogenic exotoxins (Streptococcal pyrogenic exotoxin, Spes) • Produced by lysogenic strains • Superantigens • Responsible for the streptococcal toxic shock syndrome

43. Streptococcus pyogenes/Pathogenesis&Immunity • Streptolysin S & O • Streptolysine S lyse erythrocytes leukocytes platelets responsible for b-hem. • Streptolysine O lyse erythrocytes leukocytes platelets antibodies are formed against ASO test

44. Streptococcus pyogenes/Pathogenesis&Immunity • Streptokinases • A & B • Lyse blood clots • Used in medicine • Deoxyribonucleases • A to D • Depolymerase free DNA in pus reduce viscosity • C5a peptidase • Hyaluronidase,diphosphopyridine nucleotidase

45. Streptococcus pyogenes/IDENTIFICATION • Microscopy • Culture: • Proper collection of throat swab specimen • Nutritionally enriched agar media with sheep blood • Selective media (media with “bactrim”) • Identification • Table 23-4

46. Streptococcus agalactiae (Group B) • The only species that carries the group B antigen • physiology & structure • Gr + cocci • Short or long chains (indistinguishable from S. pyogenes) • Buttery colonies, narrow zone of b-hem. • Subdividing • The B antigen group specific • Capsular polysaccharides type-specific • C protein (surface protein)

47. Streptococcus agalactiae/IDENTIFICATION • Microscopy • Culture: • Readily grow on a nutritionally enriched medium • Large colonies • b-hemolysis may be absent selective broth medium with antibiotics • Identification • Preliminary identification (+) CAMP test, hydrolysis of hippurate

48. Other beta-hemolytic streptococci • Group C, F and G are most commonly associated with human disease • 2 species of particular importance • S. anginosus • S. dysgalactiae

49. Viridans Streptococci • a-hemolytic and nonhemolytic streptococci • Produce green pigment on blood agar media • Require complex media supplemented with blood products and inc. @ 5-10 % CO2 atmsp.

50. Streptococcus pneumoniae • Encapsulated, Gr + coccus • Lancet-shaped cells, in pairs or short chains • a-hemolytic • Can grow only on enriched media (with blood products) • Catalase (-) • Capsule, classified accr. to polysaccharides • 90 serotypes • Capsular polysaccharides are used in vaccines • Teichoic acid C polysaccharide (CRP)