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Which virulence factor is crucial for Group A streptococci to establish infection by enhancing adherence to damaged epithelial barriers?
Which virulence factor is crucial for Group A streptococci to establish infection by enhancing adherence to damaged epithelial barriers?
What is the primary laboratory test used to differentiate pneumococcal pneumonia from other bacterial pneumonias?
What is the primary laboratory test used to differentiate pneumococcal pneumonia from other bacterial pneumonias?
Which of the following conditions is most commonly associated with infections caused by Staphylococcus aureus rather than Streptococcus pneumoniae?
Which of the following conditions is most commonly associated with infections caused by Staphylococcus aureus rather than Streptococcus pneumoniae?
What virulence mechanism is primarily associated with Group B streptococci?
What virulence mechanism is primarily associated with Group B streptococci?
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What is the significance of the Lancefield Grouping in diagnosing enterococci infections?
What is the significance of the Lancefield Grouping in diagnosing enterococci infections?
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Which serotypes of Group B streptococci are most commonly associated with colonization and disease?
Which serotypes of Group B streptococci are most commonly associated with colonization and disease?
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In the context of sinusitis and otitis media, which bacteria are most frequently implicated in these infections?
In the context of sinusitis and otitis media, which bacteria are most frequently implicated in these infections?
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What is the common clinical infection associated with Streptococcus mutans?
What is the common clinical infection associated with Streptococcus mutans?
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Which of the following is NOT a consequence of infection with Group C streptococci?
Which of the following is NOT a consequence of infection with Group C streptococci?
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What type of bacterium is Streptococcus pneumoniae classified as?
What type of bacterium is Streptococcus pneumoniae classified as?
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Which virulence factor is primarily responsible for the adhesion of Group B streptococci to host tissues?
Which virulence factor is primarily responsible for the adhesion of Group B streptococci to host tissues?
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Which group of streptococci is associated with both upper respiratory tract infections and endocarditis?
Which group of streptococci is associated with both upper respiratory tract infections and endocarditis?
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What characteristic differentiates alpha-hemolytic streptococci from beta-hemolytic streptococci?
What characteristic differentiates alpha-hemolytic streptococci from beta-hemolytic streptococci?
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What virulence factor is encoded by the emm gene in streptococci?
What virulence factor is encoded by the emm gene in streptococci?
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Which of the following best describes the clinical symptoms associated with pneumococcal pneumonia?
Which of the following best describes the clinical symptoms associated with pneumococcal pneumonia?
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What is the most common causative organism for pneumococcal meningitis?
What is the most common causative organism for pneumococcal meningitis?
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Which statement is true regarding the pathogenicity of Enterococci?
Which statement is true regarding the pathogenicity of Enterococci?
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What is a primary clinical manifestation of sinusitis caused by streptococci?
What is a primary clinical manifestation of sinusitis caused by streptococci?
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Which group of streptococci is typically associated with beta-haemolysis?
Which group of streptococci is typically associated with beta-haemolysis?
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Which of the following describes the Lancefield classification?
Which of the following describes the Lancefield classification?
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In which haemolytic pattern does Streptococcus pneumoniae typically present?
In which haemolytic pattern does Streptococcus pneumoniae typically present?
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Which of the following statements is true about beta-haemolytic streptococci?
Which of the following statements is true about beta-haemolytic streptococci?
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What is the characteristic Gram stain appearance of Streptococcus pyogenes?
What is the characteristic Gram stain appearance of Streptococcus pyogenes?
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What role do M-proteins play in the virulence of Group A beta-haemolytic streptococci?
What role do M-proteins play in the virulence of Group A beta-haemolytic streptococci?
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Which cytolysin is associated with pyrogenic effects and responsible for causing rash and fever?
Which cytolysin is associated with pyrogenic effects and responsible for causing rash and fever?
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Which structural component of Group A beta-haemolytic streptococci helps resist phagocytosis?
Which structural component of Group A beta-haemolytic streptococci helps resist phagocytosis?
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What mechanism allows Group A beta-haemolytic streptococci to enhance their spread in host tissues?
What mechanism allows Group A beta-haemolytic streptococci to enhance their spread in host tissues?
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Which of the following describes a common symptom associated with pharyngitis caused by Group A beta-haemolytic streptococci?
Which of the following describes a common symptom associated with pharyngitis caused by Group A beta-haemolytic streptococci?
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How do streptokinases contribute to the pathogenicity of Group A beta-haemolytic streptococci?
How do streptokinases contribute to the pathogenicity of Group A beta-haemolytic streptococci?
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Which condition is NOT typically associated with infections caused by Group A beta-haemolytic streptococci?
Which condition is NOT typically associated with infections caused by Group A beta-haemolytic streptococci?
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What factor is most important in regulating the transient colonization of Group A beta-haemolytic streptococci in the oropharynx?
What factor is most important in regulating the transient colonization of Group A beta-haemolytic streptococci in the oropharynx?
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What is the primary way Group A beta-haemolytic streptococci gain entry into the host?
What is the primary way Group A beta-haemolytic streptococci gain entry into the host?
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What type of clinical infection is characterized by severe infection of the skin and subcutaneous tissues, potentially leading to systemic complications?
What type of clinical infection is characterized by severe infection of the skin and subcutaneous tissues, potentially leading to systemic complications?
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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.
