Streptococcus Pyogenes Virulence Factors
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Questions and Answers

What is the primary function of fibronectin-binding protein in Streptococcus pyogenes?

  • To break down fibrin in clots
  • To resist phagocytosis
  • To degrade DNA
  • To promote adherence to epithelial cells (correct)

    • Which of the following is NOT a function of M protein in Streptococcus pyogenes?

  • Degrading DNA (correct)
  • Resisting phagocytosis
  • Promoting adherence to epithelial cells
  • Breaking down C5a complement

    • What is the major virulence factor of H. influenzae?

  • IgA protease
  • Outer membrane
  • Tracheobronchitis
  • Polysaccharide capsule (correct)

    • What is the function of hyaluronic acid capsule in Streptococcus pyogenes?

    <p>To act as an immunological mask</p> Signup and view all the answers

    What is the most common cause of epiglottitis in young children?

    <p>H. influenzae type b</p> Signup and view all the answers

    What is the function of streptokinase in Streptococcus pyogenes?

    <p>To dissolve fibrin in clots</p> Signup and view all the answers

    What is the function of IgA protease in H. influenzae?

    <p>Degrades secretory IgA</p> Signup and view all the answers

    Which type of H. influenzae is the most pathogenic?

    <p>Type b</p> Signup and view all the answers

    What is the name of the vaccine used to prevent H. influenzae type b infection?

    <p>Both a and b</p> Signup and view all the answers

    What is the primary function of pili in Pseudomonas aeruginosa?

    <p>To adhere to host cells</p> Signup and view all the answers

    What is the purpose of the X&V factor test in H. influenzae?

    <p>To identify the requirement of both X and V factors</p> Signup and view all the answers

    What is the characteristic of streptolysin O?

    <p>It is oxygen labile</p> Signup and view all the answers

    What is the characteristic lesion seen in scarlet fever?

    <p>A 'strawberry' tongue</p> Signup and view all the answers

    What is the cause of inflammation in post-streptococcal diseases?

    <p>Cross-reactivity between streptococcal M proteins and human tissues</p> Signup and view all the answers

    Which of the following diseases is caused by Streptococcus pyogenes that produce erythrogenic toxin?

    <p>Scarlet fever</p> Signup and view all the answers

    What is the treatment for scarlet fever?

    <p>Antitoxin serum</p> Signup and view all the answers

    What is the effect of pyocyanin on host cells?

    <p>It damages the cilia and causes cell death</p> Signup and view all the answers

    Which of the following is a characteristic of Corynebacterium diphtheriae?

    <p>Gram positive rods, Non-spore-forming</p> Signup and view all the answers

    Which of the following is not a diagnostic laboratory test for streptococcal infections?

    <p>Blood culture</p> Signup and view all the answers

    What is the purpose of giving long acting penicillin in prevention?

    <p>To prevent streptococcal infections</p> Signup and view all the answers

    Which of the following is a characteristic of mucoid strains of P. aeruginosa?

    <p>Formation of adherent biofilm</p> Signup and view all the answers

    What is the primary reason why P. aeruginosa is an important cause of nosocomial infections?

    <p>It is an opportunistic pathogen</p> Signup and view all the answers

    What is the significance of multiple drug resistance in P. aeruginosa?

    <p>It poses a significant threat to public health</p> Signup and view all the answers

    What is the common characteristic of individuals who are susceptible to P. aeruginosa infections?

    <p>They have a compromised host defense</p> Signup and view all the answers

    What is the characteristic growth pattern of virulent Mycobacterium tuberculosis strains?

    <p>A serpentine cordlike pattern</p> Signup and view all the answers

    What is the primary mechanism of Mycobacterium tuberculosis pathogenicity?

    <p>Survival and multiplication within macrophages</p> Signup and view all the answers

    Which of the following is a factor that contributes to the resistance of Mycobacterium tuberculosis to antibiotics?

    <p>High lipid content of the cell wall</p> Signup and view all the answers

    What is the primary mechanism of immune protection against Mycobacterium tuberculosis?

    <p>Cell-mediated immunity</p> Signup and view all the answers

    What is the primary route of transmission of Mycobacterium tuberculosis in humans?

    <p>Airborne transmission through inhalation of respiratory aerosol</p> Signup and view all the answers

    What is the primary reason why patients with AIDS are more susceptible to disseminated tuberculosis?

    <p>Defect in cell-mediated immunity</p> Signup and view all the answers

    Study Notes

    Pseudomonas Aeruginosa

    • Virulence factors:
    • Pili (fimbriae)
    • Endotoxin (Lipopolysaccharide): causes septic shock
    • Exotoxin A: inhibits protein synthesis and causes tissue necrosis
    • Extracellular enzymes: facilitate invasion into the blood
    • Pyocyanin: damages cilia and causes cell death
    • Alginate (glycocalyx): forms adherent biofilm, protecting from antibodies, complement, and antibiotics
    • Broad antibiotic resistance: intrinsic and acquired

    Medical Importance of P. Aeruginosa

    • Flourishes in simple aqueous solutions, withstands disinfectants
    • Causes nosocomial infections
    • Opportunistic pathogen that infects:
    • Those with destroyed skin host defenses (e.g., extensive burns)
    • Those with chronic respiratory disease (e.g., cystic fibrosis)
    • Immunocompromised individuals
    • Those with medical devices (e.g., catheters, ventilators, I.V lines)
    • One of the top antimicrobial resistance threats worldwide (MDR)

    Clinical Findings

    • Respiratory infections:
    • Hospital-acquired pneumonia (especially ventilator-associated pneumonia and in cystic fibrosis patients)
    • External ear infections:
    • Malignant otitis externa (especially in diabetics)
    • Swimmer’s ear
    • Eye infections:
    • Corneal ulcer (frequently associated with contact lens use)
    • Skin infections

    Scarlet Fever

    • Caused by Streptococci
    • Characterized by:
    • Fever
    • Sore throat
    • Scarlet erythematous rash
    • “Strawberry” tongue

    Post-Streptococcal Diseases

    • Caused by autoantibodies against Streptococcal M proteins that cross-react with human tissues
    • Occur weeks after a local infection with group A Streptococci
    • Include:
    • Acute Rheumatic fever (follows pharyngitis)
    • Acute Glomerulonephritis (follows skin infections rather than pharyngitis)

    Diagnostic Laboratory Tests

    • Throat swab
    • Gram-stained smears
    • Culture: on blood agar, β-hemolytic colonies, catalase negative, and bacitracin sensitive
    • Antigen detection tests: ELISA or agglutination tests for rapid antigen detection
    • ASO test: for diagnosis of post-streptococcal diseases, ASO titers high soon after infection

    Treatment of Scarlet Fever

    • Antitoxin serum
    • Shortens the course of the disease and prevents rash

    Prevention

    • Rheumatic fever can be prevented by adequate treatment of strept.pharyngitis for 10 days
    • Prevention of streptococcal infections (usually with long-acting penicillin) in persons who have had rheumatic fever

    Corynebacterium Diphtheriae

    • Gram-positive rods, non-spore-forming

    Mycobacterium Tuberculosis

    • Obligate aerobe
    • Slow growers, growth appears after 4-6 weeks
    • Virulence factors:
    • High lipid content of cell wall (Mycolic acids)
    • Cord factor: virulent strains grow in a characteristic “Serpentine” cordlike pattern
    • Inhibit phago-lysosomal fusion
    • Resistance and sensitivity:
    • Highly resistant to dryness, chemicals, and many acids and alkalis
    • Killed by sunlight, UV rays, 5% phenol, heat (60°C for 20 min), and pasteurization

    Pathogenesis

    • Tubercle bacilli do not contain or produce toxins
    • Pathogenicity depends on the fact that the organism survives and multiplies in macrophages, preventing phago-lysosomal fusion
    • Intracellular organism

    Immunity Against Tuberculosis

    • Cell-mediated immunity (CMI) (Delayed-type = type IV hypersensitivity) (Granuloma formation)
    • Patients deficient in cellular immunity, such as AIDS patients, are more susceptible to disseminated (miliary) tuberculosis

    Group A, Beta-Haemolytic Streptococci (Streptococcus Pyogenes)

    • Virulence factors:
    • Adherence factors: promotes adherence to epithelial cells
    • Anti-phagocytic factors:
      • M protein: major virulence factor that resists phagocytosis
      • Hyaluronic acid capsule: acts as an immunological mask
      • C5a peptidase: breaks down C5a complement
    • Spreading factors:
      • Streptokinase (Fibrinolysin): dissolves fibrin in clots
      • Streptodornase (Deoxynuclease): degrades DNA
      • Hyaluronidase
    • Toxins:
      • Streptolysins (Hemolysins): pore-forming cytotoxin
      • Pyrogenic exotoxins: cause the rash in scarlet fever

    Diseases Caused by Streptococcus Pyogenes

    • Streptococcal pharyngitis (Strep throat): acute follicular tonsillitis
    • Scarlet fever: caused by streptococci that produce erythrogenic toxin (strains of S. pyogenes)

    Haemophilus Influenzae

    • Virulence factors:
    • Polysaccharide capsule: major virulence factor, classify capsulated strains into 6 types (a-f)
    • Outer membrane: ↓↓ mucociliary clearance → colonization
    • IgA protease: degrades secretory IgA
    • Pathogenicity:
    • Capsulated types (invasive) particularly type b (Hib) cause:
      • Epiglottitis: life-threatening disease of young children that can obstruct the airway
      • Bacteremia, meningitis, septic arthritis
    • Non-capsulated (non-typable) strains:
      • Otitis media and sinusitis
      • Tracheobronchitis and pneumonia in adults and elderly in the presence of predisposing factors

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    Description

    Test your knowledge on the virulence factors of Streptococcus Pyogenes, including adherence factors, anti-phagocytic factors, and more. Learn about the different types of M protein, lipoteichoic acids, and hyaluronic acid capsule. Identify the mechanisms that help this bacteria resist phagocytosis and evade the immune system.

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