Group B Streptococci Overview
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Group B Streptococci Overview

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Questions and Answers

Which virulence factor is crucial for Group A streptococci to establish infection by enhancing adherence to damaged epithelial barriers?

  • Capsular polysaccharide
  • M-protein (correct)
  • Teichoic acid
  • Lipid A

    • What is the primary laboratory test used to differentiate pneumococcal pneumonia from other bacterial pneumonias?

  • Blood agar incubation
  • Bile solubility test
  • Optochin sensitivity test (correct)
  • Gram staining

    • Which of the following conditions is most commonly associated with infections caused by Staphylococcus aureus rather than Streptococcus pneumoniae?

  • Bacterial meningitis
  • Aspiration pneumonia
  • Osteomyelitis (correct)
  • Sinusitis

    • What virulence mechanism is primarily associated with Group B streptococci?

    <p>Capsule polysaccharide</p> Signup and view all the answers

    What is the significance of the Lancefield Grouping in diagnosing enterococci infections?

    <p>Identifying the species of the infection</p> Signup and view all the answers

    Which serotypes of Group B streptococci are most commonly associated with colonization and disease?

    <p>Types Ia and III to V</p> Signup and view all the answers

    In the context of sinusitis and otitis media, which bacteria are most frequently implicated in these infections?

    <p>Streptococcus pneumoniae</p> Signup and view all the answers

    What is the common clinical infection associated with Streptococcus mutans?

    <p>Dental caries</p> Signup and view all the answers

    Which of the following is NOT a consequence of infection with Group C streptococci?

    <p>Hemolytic anemia</p> Signup and view all the answers

    What type of bacterium is Streptococcus pneumoniae classified as?

    <p>Alpha-hemolytic streptococci</p> Signup and view all the answers

    Which virulence factor is primarily responsible for the adhesion of Group B streptococci to host tissues?

    <p>Surface proteins - adhesins</p> Signup and view all the answers

    Which group of streptococci is associated with both upper respiratory tract infections and endocarditis?

    <p>Group G streptococci</p> Signup and view all the answers

    What characteristic differentiates alpha-hemolytic streptococci from beta-hemolytic streptococci?

    <p>Type of hemolysin produced</p> Signup and view all the answers

    What virulence factor is encoded by the emm gene in streptococci?

    <p>M protein</p> Signup and view all the answers

    Which of the following best describes the clinical symptoms associated with pneumococcal pneumonia?

    <p>Productive cough, pleuritic chest pain, and fever</p> Signup and view all the answers

    What is the most common causative organism for pneumococcal meningitis?

    <p>Streptococcus pneumoniae</p> Signup and view all the answers

    Which statement is true regarding the pathogenicity of Enterococci?

    <p>They have a broad spectrum of antibiotic resistance.</p> Signup and view all the answers

    What is a primary clinical manifestation of sinusitis caused by streptococci?

    <p>Facial pain and purulent nasal discharge</p> Signup and view all the answers

    Which group of streptococci is typically associated with beta-haemolysis?

    <p>Group A and Group B</p> Signup and view all the answers

    Which of the following describes the Lancefield classification?

    <p>Based on the structure of the bacterial cell wall antigens</p> Signup and view all the answers

    In which haemolytic pattern does Streptococcus pneumoniae typically present?

    <p>Alpha haemolysis</p> Signup and view all the answers

    Which of the following statements is true about beta-haemolytic streptococci?

    <p>They can be classified using Lancefield grouping.</p> Signup and view all the answers

    What is the characteristic Gram stain appearance of Streptococcus pyogenes?

    <p>Gram-positive cocci in chains</p> Signup and view all the answers

    What role do M-proteins play in the virulence of Group A beta-haemolytic streptococci?

    <p>They mediate attachment to host cells and prevent phagocytosis.</p> Signup and view all the answers

    Which cytolysin is associated with pyrogenic effects and responsible for causing rash and fever?

    <p>Streptolysin O</p> Signup and view all the answers

    Which structural component of Group A beta-haemolytic streptococci helps resist phagocytosis?

    <p>Capsule</p> Signup and view all the answers

    What mechanism allows Group A beta-haemolytic streptococci to enhance their spread in host tissues?

    <p>Secreting hyaluronidase, which breaks down tissue barriers.</p> Signup and view all the answers

    Which of the following describes a common symptom associated with pharyngitis caused by Group A beta-haemolytic streptococci?

    <p>Sore throat and fever</p> Signup and view all the answers

    How do streptokinases contribute to the pathogenicity of Group A beta-haemolytic streptococci?

    <p>By breaking down blood clots, facilitating spread of infection.</p> Signup and view all the answers

    Which condition is NOT typically associated with infections caused by Group A beta-haemolytic streptococci?

    <p>Bacterial meningitis</p> Signup and view all the answers

    What factor is most important in regulating the transient colonization of Group A beta-haemolytic streptococci in the oropharynx?

    <p>Acquired immunity and competition from other organisms</p> Signup and view all the answers

    What is the primary way Group A beta-haemolytic streptococci gain entry into the host?

    <p>Via droplet spread and direct contact.</p> Signup and view all the answers

    What type of clinical infection is characterized by severe infection of the skin and subcutaneous tissues, potentially leading to systemic complications?

    <p>Necrotizing fasciitis</p> Signup and view all the answers

    Study Notes

    Group B Streptococci

    • May be carried in the throat.
    • Important cause of neonatal sepsis.
    • Colonization in neonates usually occurs via the mother's genital tract.
    • Risk factors for neonatal colonization:
      • Maternal colonization.
      • Premature delivery or premature rupture of membranes.
      • Prolonged labor.
      • Low birth rate.
      • Intra-partum fever.

    Group B Streptococci: Irish Epidemiology

    • Started collecting data in Ireland in 2019.
    • Number of isolates increased from 176 in 2019 to 102 in 2020.
    • Percent of isolates with Erythromycin resistance increased from 41.9% to 31.9% in 2020.

    Group B Streptococci: Virulence Mechanisms

    • Have different serotypes based on capsular polysaccharides.
    • Types Ia, III to V are most commonly associated with colonization and disease.
    • Produce haemolysins, hyaluronidase, and surface proteins (adhesins).

    Other Beta-Hemolytic Streptococci

    • Can cause similar diseases as Group A streptococcus but without the immunological complications.
    • Group C streptococci can cause:
      • Puerperal fever.
      • Tonsillitis.
      • Wound sepsis.
    • Group G streptococci can cause:
      • Upper respiratory tract infections.
      • Endocarditis.

    Alpha-Hemolytic Streptococci

    • Include "viridans" streptococci and Streptococcus pneumonia.

    "Viridans" Streptococci

    • Commonly found in the oropharynx, Gastrointestinal tract, and Genitourinary tract.
    • Most lack Lancefield antigens except S.bovis (Group D).
    • Common "viridans" streptococci include:
      • S.sanguis
      • S.mitis
      • S.mutans.
    • S.bovis (Group D) can cause infective endocarditis.
    • S.mutans can cause dental caries.

    Hemolytic Patterns of Streptococci

    • Alpha-hemolytic: Reduce Hb and cause a greenish discoloration of blood agar.
    • Beta-hemolytic: Lyse blood cells and cause complete clearing of blood agar.
    • Gamma-hemolytic: No change in blood agar.

    Lancefield Classification of Streptococci

    • A serological system for grouping streptococci.
    • Based on specific antigens present in their cell walls.
    • Groups A-G are of the most clinical significance.
    • Basis of test: antibody/antigen reaction.
    • Positive test: agglutination.

    Clinical Case 1

    • A 10 year old male presents to his GP with a sore throat.

    Clinical Case 1: Examination

    • Examination shows swollen, erythematous tonsils with exudate.
    • Cervical lymph nodes are swollen and tender.

    Clinical Case 1: Likely Diagnosis

    • Pharyngitis.

    Clinical Case 1: Throat Swab Culture

    • Gram-positive cocci in chains.

    Clinical Case 1: Cause of Infection

    • Streptococcus pyogenes.

    Streptococcus pyogenes (Group A Beta-Hemolytic)

    • Possesses the Lancefield group A antigen.
    • Commonly colonizes oropharynx of children and young adults.
    • Colonization is transient.
    • Influenced by acquired immunity and competition from other organisms in the oropharynx.
    • Major cause of bacterial pharyngitis.

    Group A Streptococci: Irish Epidemiology

    • Invasive group A strep is a notifiable disease.

    Group A Beta-Hemolytic Streptococci: Virulence Mechanisms

    • Structural components include:
      • Capsule: resists phagocytosis.
      • Cell wall: peptidoglycan can activate the alternative complement pathway.
    • M-proteins:
      • Over 80 types, mediate attachment to cells, anti-phagocytic.
      • Major virulence factors - some types associated with greater severity of disease.
    • M-like proteins: bind IgG and IgM.
    • Cytolysins:
      • Streptolysin O/S: exotoxins.
      • Streptolysin S: exotoxins.
    • Hyaluronidase: tissue destruction, allowing the spread of infection.
    • Leucocidin: produced by both antigen-presenting cells and T lymphocytes.
    • Hemolysins.
    • Streptokinase.

    Pathogenesis of Group A Beta-Hemolytic Streptococci

    • Droplet spread.
    • Direct contact.
    • Colonizes the oropharynx.
    • Invades epithelial cells.
    • M-proteins and capsule aid in evading the immune system.
    • Exotoxins, haemolysins, hyaluronidase, leucocidin, and streptokinase cause damage to host cells.

    Clinical Infections of Group A Beta-Hemolytic Streptococci

    • Suppurative infections:
      • Pharyngitis.
      • Scarlet fever.
      • Erysipelas, cellulitis, necrotizing fasciitis.
      • Intra-abdominal infections.
    • Prolonged hospitalization, especially in the ICU.

    Infective Endocarditis

    • Turbulent blood flow through the heart provides a surface for bacteria to attach.
    • Bacteria enter the blood usually after a procedure that damages epithelial barriers.
    • Bacteria attach to damaged valves and form vegetations.

    Anaerobic Streptococcus (Peptostreptococcus)

    • Over 25% of anaerobes found in clinical specimens.
    • Colonize the oral cavity, GI tract, GU tract, and skin.
    • Infections include:
      • Aspiration pneumonia.
      • Sinusitis and brain abscess.
      • Intra-abdominal abscesses.
      • Pelvic infections.

    General Aspects of Diagnosis of Streptococcal Infections

    • Clinical suspicion based on clinical features.
    • Appropriate samples are sent to the laboratory based on the site of infection:
      • Blood (if invasive disease is suspected).
      • CSF (meningitis).
      • Urine.
      • Throat swab (pharyngitis).
    • Laboratory tests:
      • Gram stain on sterile site sample (blood, CSF, pus).
      • Culture (takes 24-48 hours): samples incubated aerobically and anaerobically.
        • Blood agar (for haemolysis).
        • MacConkey agar (for enterococci).

    Laboratory Diagnosis of Streptococcal Infections

    • Identification:
      • Lancefield grouping.
      • Bacitracin susceptibility (GAS).
      • Optochin sensitivity (pneumococcus).
      • Bile solubility (enterococci).
    • Serology: detect a recent Group A infection in suspected rheumatic fever and glomerulonephritis.
    • PCR: blood, CSF.
    • Urinary antigen (for pneumococcus).

    Streptococcus pyogenes Lab Diagnosis

    • Gram-positive cocci in chains.
    • Beta-hemolytic.
    • Catalase-negative.
    • Group A.
    • Bacitracin susceptible.

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    Description

    This quiz covers essential information about Group B Streptococci, including its role in neonatal sepsis, epidemiological data from Ireland, and its virulence mechanisms. Learn about risk factors, serotypes, and the importance of maternal colonization.

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