Streptococcus Pyogenes Virulence Factors Quiz: Test Your Knowledge

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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?

To act as an immunological mask Signup and view all the answers

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

H. influenzae type b Signup and view all the answers

What is the function of streptokinase in Streptococcus pyogenes?

To dissolve fibrin in clots Signup and view all the answers

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

Degrades secretory IgA Signup and view all the answers

Which type of H. influenzae is the most pathogenic?

Type b Signup and view all the answers

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

Both a and b Signup and view all the answers

What is the primary function of pili in Pseudomonas aeruginosa?

To adhere to host cells Signup and view all the answers

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

To identify the requirement of both X and V factors Signup and view all the answers

What is the characteristic of streptolysin O?

It is oxygen labile Signup and view all the answers

What is the characteristic lesion seen in scarlet fever?

A 'strawberry' tongue Signup and view all the answers

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

Cross-reactivity between streptococcal M proteins and human tissues Signup and view all the answers

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

Scarlet fever Signup and view all the answers

What is the treatment for scarlet fever?

Antitoxin serum Signup and view all the answers

What is the effect of pyocyanin on host cells?

It damages the cilia and causes cell death Signup and view all the answers

Which of the following is a characteristic of Corynebacterium diphtheriae?

Gram positive rods, Non-spore-forming Signup and view all the answers

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

Blood culture Signup and view all the answers

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

To prevent streptococcal infections Signup and view all the answers

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

Formation of adherent biofilm Signup and view all the answers

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

It is an opportunistic pathogen Signup and view all the answers

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

It poses a significant threat to public health Signup and view all the answers

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

They have a compromised host defense Signup and view all the answers

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

A serpentine cordlike pattern Signup and view all the answers

What is the primary mechanism of Mycobacterium tuberculosis pathogenicity?

Survival and multiplication within macrophages Signup and view all the answers

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

High lipid content of the cell wall Signup and view all the answers

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

Cell-mediated immunity Signup and view all the answers

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

Airborne transmission through inhalation of respiratory aerosol Signup and view all the answers

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

Defect in cell-mediated immunity 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.

Streptococcus Pyogenes Virulence Factors