STREPTOCOCCUS & ENTEROCOCCUS

2. STREPTOCOCCUS & ENTEROCOCCUS

3. REVIEW • Bacterial Cell Morphology • Gram Stain • Cytoplasmic (plasma) membrane • Cell wall structure • Bacterial cell shapes

5. Common Cell Membrane

6. Gram-Positive Cell Wall

7. Peptidoglycan Gram-Negative Gram-Positive

8. Gram-Positive Cell Wall Teichoic Acid

9. Gram-Negative Cell Wall

10. Gram-Negative Cell Wall

15. Genus Streptococcus • Commensals or Parasites of man & animals • or • Saprophytesof decaying matter • Morphology • Gram-Positive Cocci in Pairs or Chains

16. Gram-Positive Streptococcus

17. Genus Streptococcus • Physiology & Metabolism • Facultative Anaerobes • Fastidious Growth Requirements • Fermentative Metabolism of Carbohydrates: • Lactic acid, ethanol, acetate endproducts produced; No gas • Catalase Negative (2H2O2 ---> O2 + 2H2O) • Separation of streptococci from staphylococci • Oxidase Negative (oxidoreductase oxidizes substrate w/ O2) • Beta, Alpha, or GammaHemolysis on blood agar

21. Genus Streptococcus • Rebecca Lancefield • Developed useful serogrouping system • Classification of beta-hemolytic streptococci by group-specific cell wall carbohydrate (CHO) antigen • As of 1992, Serogroups A to H and K to V • Groups A, B, C, D, and G are most • comonly associated with human disease • Viridans streptococci and • Streptococcus pneumoniaehave • no group-specific antigen

22. Antigenic Structure • Streptococcus pyogenes (Group A) • Lancefield Group-specific antigen(C polysaccharide) • Complex polysaccharide in cell wall • Proteins: Two major classes, M & T antigens • Two minor classes, R & F • M-Protein: Type-specific antigen • Fimbriae-like, hairy extensions • Resistant to heat and acid • Trypsin Sensitive • Specific adherence by lipoteichoic acid and M-protein • (LTA-M) complexes

24. Antigenic Structure • Streptococcus pyogenes (Group A) • Lancefield Group-specific antigen(C polysaccharide) • Complex polysaccharide in cell wall • Proteins: Two major classes, M & T antigens • Two minor classes, R & F • M-Protein: Type-specific antigen • Fimbriae-like, hairy extensions • Resistant to heat and acid • Trypsin Sensitive • Specific adherence by lipoteichoic acid and M-protein (LTA-M) complexes • T Antigens (not virulence factor) • Resistant to trypsin, heat and acid; • Adjunct to M-typing; Routine surveillance • Others

25. Antigenic Structure (cont.) • Streptococcus pyogenes (Group A) • Capsular Polysaccharide: • Hyaluronic acid • Not present in all strains • Same as host hyaluronic acid (cartilage,skin etc) • Nonimmunogenic • Antiphagocytic • Hyaluronidase (cell wall division) during late growth • Lipoteichoic Acid

26. Lancefield Serogroup Classification of Beta-Hemolytic Streptococci Important in Human Disease • Group A Streptococci: • Streptococcus pyogenes • One of Most Important Human Pathogens • Suppurative Diseases: • Pharyngitis; Scarlet Fever; • Cutaneous & Soft Tissue Infections • Systemic Disease • Non-Suppurative Sequelae:ARF,RHD,AG

27. Streptococcus pyogenes (Phase Contrast)

28. Lancefield Serogroup Classification of Beta-Hemolytic Streptococci Important in Human Disease (cont.) • Group B Streptococci: • Streptococcus agalactiae • Neonatal disease & obstetric complications • Systemic, Cutaneous, UTI's

29. Streptococcus agalactiae

30. Lancefield Classification of Beta-Hemolytic Streptococci (cont.) • Group C Streptococci: Pharyngitis • Enterococcus& Group D Streptococci • Genitourinary Tract Infections (UTIs) • Endocarditis • Group G Streptococci: • S.anginosus-milleri grp; Streptococcus spp. • Pharyngitis • Non-Lancefield Group Streptococci • Viridans Streptococci • Dental Caries: Streptococcus mutans • Streptococcus sanguis; Streptococcus salivarius; Streptococcus mitis • Streptococcus pneumoniae

31. Major Human Diseases of • Beta-Hemolytic Streptococci • Group A Streptococcus (S. pyogenes): • Diverse group of acute suppurative (pus-forming) & nonsuppurative diseases • Suppurative Streptococcal Diseases • Pharyngitis (& tonsilitis): • Scarlet fever: Complication of streptococcal pharyngitis when infecting strain is lysogenized; Frequently develop scarletina rash on upper chest spreading to extremities • Cutaneous & Soft Tissue Infxns. • Pyoderma(Impetigo: contagious pyoderma with superficial yellow weeping lesions) • Erysipelas: Acute superficial cellulitis of skin with lymphatic involvement; face and lower extremities, skin and subcutaneous tissues

32. Erysipelas NOTE: • erythema • bullae

33. Major Human Diseases of • Beta-Hemolytic Streptococci (cont.) • Group A Streptococcus (S. pyogenes) • Suppurative Streptococcal Diseases • Cutaneous & Soft Tissue Infxns(cont.) • Cellulitis: Involvement of deeper subcutaneous tissues; Deeper invasion with systemic symptoms • Necrotizing fasciitis: (a.k.a., “flesh-eating bacteria”): Infection deep in subcutaneous tissues that spreads along fascial planes, destroying muscle and fat; Initially cellulitis followed by bullae (fluid filled blisters; bulla is singular), gangrene, systemic toxicity, multiorgan failure and mortality in more than 50% of patients • Wound Infections

34. Suppurative Streptococcal Diseases Group A Streptococcus(cont.) • Other Suppurative Diseases • Puerperal & neonatal sepsis • Lymphangitis: Inflammation of lymphatic vessel(s) • Pneumonia • Systemic Disease • Streptococcal Toxic Shock • Syndrome (TSS):Multisystem toxicity following soft tissue infection progressing to shock and organ failure (not to be confused with Staphylococcal Toxic Shock Syndrome where hyperabsorbent tampons have been identified as an important risk factor) • Bacteremia

35. Group A Streptococcal Diseases (cont.) • Nonsuppurative Sequelae • Post-infection complications of Group A streptococcal disease; Serious complications in pre-antibiotic era; still important in developing countries • Acute rheumatic fever (ARF): • Inflammation of heart, joints, blood vessels, sub-cutaneous tissues • Rheumatic heart disease(RHD): • Chronic, progressive heart valve damage • Acute glomerulonephritis(AG): • Acute inflammation of renal (kidney) glomeruli • Foodborne Disease

36. Epidemiology of Acute Streptococcal Infection • Predilection for upper respiratory tract or skin • Group A commonly colonize oropharynx of healthy children • M-types of strains colonizing throat differ from those on skin • Rapidly killed after phagocytosis, but cell walls not digested and may lead to chronic inflammatory lesions • Pharyngitis transmitted by droplets from respiratory secretions • Crowding increases risk (e.g., classrooms, day care facilities) Pyodermatransmitted by direct contact with infectious lesions

37. Nonsuppurative Sequelae of Acute Group A Streptococcal Infection • Acute Rheumatic Fever (ARF) • Inflammatory reaction characterized by arthritis, carditis, chorea (disorder of CNS with involuntary spastic movements), erythema marginatum (skin redness with defined margin), or subcutaneous nodules • Within 2-3 weeks followingpharyngitis • Epidemic pharyngitis: ARF in as many as 3% • Sporadic pharyngitis: ARF in 1 per 1000 • Morbidity & mortality linked to subsequent disease of heart valve (Rheumatic Heart Disease) • Poorly understood pathogenesis with several proposed theories including cross-reactivity of heart tissues & strep AGNs • ?? (Type ??hypersensitivity, exotoxins, direct invasion) II

38. NonsuppurativeSequelae of Acute Group A Streptococcal Infection (cont.) • Acute Glomerulonephritis • Follows either respiratory (pharyngitis) or cutaneous(pyoderma) streptococcal infection • Associated with well-defined group of M-types • Incidence varies from <1% to 10-15% • Most often seen in children manifesting as dark, smoky urine with RBC's, RBC casts, white blood cells, depressed serum complement, decreased glomerular filtration rate • Latent period: 1-2 weeks after skin infection and 2-3 weeks after pharyngitis • Granular accumulations of immunoglobulin due to deposition of immune complexes within the kidney • (Type ?? Hypersensitivity) III

40. Determinants of Pathogenicity • Cellular Virulence Factors • Capsule • Antiphagocytic; Nonspecific adherence • Hyaluronic acid (polysaccharide) mimics animal tissue • Lipoteichoic Acid • Cytotoxic for wide variety of cells • Adherence: Complexes with M protein (LTA-M) and binds to fibronectin on epithelial cells • M-Protein • LTA-M protein is adhesin • Antiphagocytic • Inhibitsalternate C’ pathway and opsonization • M-like Proteins: bind IgM and IgG • FProtein: mediates adherence

41. Extracellular Virulence Factors • Exotoxins: • Streptolysin O (SLO): • Hemolytic and Cytolytic • Prototype of oxygen-labile and thiol-activated cytolytic exotoxins (e.g., Streptococcus, Bacillus, Clostridium, Listeria) • Lytic for variety of cells: bind to cholesterol-containing membranes and form arc- or ring- shaped oligomers that make cell leaky (RBC's, WBC’s, PMN's, platelets, etc.) • Causes sub-surface hemolysis on BAP • Stimulate release of lysosomal enzymes • SLO titer indicates recent infection (300-500 in pediatric populations)

42. Extracellellular Virulence Factors (cont.) • Exotoxins (cont.): • Streptolysin S (SLS): • Hemolytic and Cytolytic • Oxygen stable, non-antigenic • Lytic for red and white blood cells and wall-less forms (protoplast, L- forms) • Causes surface hemolysis on BAP • Lysogeny: Lysogenized bacteriophages play key role in directing synthesis of various Group A streptococcal enzymes and toxins • Pyrogenic Exotoxin (erythrogenic toxin) • Phage-associated muralysins (lyse cell walls) produced by both Groups A and C

43. Extracellular Virulence Factors (cont.) • Exotoxins (cont): • Pyrogenic (Erythrogenic) Exotoxins(Types A, B &C) • Produced by more than 90% of Grp A strep • Lysogeny: Structural gene is carried by temperate bacteriophage, as is the case with diphtheria toxin • Mediate pyrogenicity (fever) • Causes scarlet fever (scarletiniform) rash • Increase susceptibility to endotoxic shock • Type C toxin increases permeability of blood-brain barrier • Enhance DTH • Mitogenic for T lymphocytes (cause cell division), myocardial and hepatic necrosis, decrease in antibody synthesis • Immunomodulators (superantigens): stimulate T cells to release cytokines • Cardiohepatic toxin

44. Extracellular Virulence Factors (cont.) • Enzymes: • Nucleases:Four antigenic types (A,B,C,D) • Facilitate liquefication of pus generating growth substrates • Nucleases A, C have DNase activity • Nucleases B, D also have RNase activity • Streptokinases: Two different forms • Lyse blood clots: catalyze conversion of plasminogen to plasmin, leading to digestion of fibrin • C5a Peptidase: destroys C’ chemotactic signals (C5a) • Hyaluronidase: hydrolyzes hyaluronic acid • Others:Proteinase, NADase, ATPase, phosphatase, etc.

45. Lab Identification of • S. pyogenes (Group A) • Primary culture by pour or streak plate • Domed,grayish/opalescent colonies • Encapsulated cells produce mucoid colonies • Beta-hemolytic • Zone several times greater than diameter of colony

46. TSA S. pyogenes

47. Lab Identification of S. pyogenes (Group A) (cont.) • Catalase Negative: Differentiates from Staphylococcus • Bacitracin test: presumptively distinguishing between Group • A beta-hemolytic streptococci (bacitracin POS) and other beta-hemolytic streptococci that are isolated from pharyngeal swabs (95% sensitivity for Grp A strep) • Rapid Identification Tests: • Based on extraction of Group A carbohydrate directly from throat swabs • ELISA, Coagglutination, Fluorescent Antibody

49. Group B Streptococcus • Streptococcus agalactiae

50. Group B Streptococcal Infections