Podcast
Questions and Answers
What is the primary function of the polysaccharide capsule of S. agalactiae?
What is the primary function of the polysaccharide capsule of S. agalactiae?
Which of the following tests is used to identify Group B Streptococci?
Which of the following tests is used to identify Group B Streptococci?
Which disease is primarily associated with Group D Streptococci?
Which disease is primarily associated with Group D Streptococci?
In which environment is Group B Streptococci typically found?
In which environment is Group B Streptococci typically found?
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What morphology and arrangement do Gram-positive S. agalactiae display?
What morphology and arrangement do Gram-positive S. agalactiae display?
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Which of the following is a characteristic culture requirement for S. agalactiae?
Which of the following is a characteristic culture requirement for S. agalactiae?
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What is a common serological test for identifying the capsule of S. agalactiae?
What is a common serological test for identifying the capsule of S. agalactiae?
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Which of the following diseases is least likely associated with S. agalactiae?
Which of the following diseases is least likely associated with S. agalactiae?
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What is a characteristic clinical feature of scarlet fever?
What is a characteristic clinical feature of scarlet fever?
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Which of the following infections are classified as suppurative infections?
Which of the following infections are classified as suppurative infections?
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What type of test is primarily used for diagnosing pharyngitis?
What type of test is primarily used for diagnosing pharyngitis?
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What is an important aspect of the culture requirements for growing S. pyogenes?
What is an important aspect of the culture requirements for growing S. pyogenes?
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Which of the following tests can differentiate S. pyogenes from other beta-hemolytic streptococci?
Which of the following tests can differentiate S. pyogenes from other beta-hemolytic streptococci?
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Which condition can result as a post-streptococcal sequelae?
Which condition can result as a post-streptococcal sequelae?
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What is the main characteristic of erysipelas as an invasive infection?
What is the main characteristic of erysipelas as an invasive infection?
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What pathological mechanism is thought to contribute to post-streptococcal conditions?
What pathological mechanism is thought to contribute to post-streptococcal conditions?
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What indicates a positive reaction when testing for Streptococcus pyogenes?
What indicates a positive reaction when testing for Streptococcus pyogenes?
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What is the principle behind the Schultz-Charlton reaction?
What is the principle behind the Schultz-Charlton reaction?
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If an individual has a positive Dick test result, what is expected to be observed?
If an individual has a positive Dick test result, what is expected to be observed?
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What indicates an immune response in the Dick test?
What indicates an immune response in the Dick test?
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What does a significant titer level of Anti-streptolysin O (ASO) indicate?
What does a significant titer level of Anti-streptolysin O (ASO) indicate?
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Which of the following is NOT a specific test used for diagnosis of rheumatic fever?
Which of the following is NOT a specific test used for diagnosis of rheumatic fever?
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What is a characteristic of the pseudo-reaction in the Dick test?
What is a characteristic of the pseudo-reaction in the Dick test?
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Why is no vaccine currently available for rheumatic fever?
Why is no vaccine currently available for rheumatic fever?
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Which classification is used to differentiate types of hemolysis in streptococci?
Which classification is used to differentiate types of hemolysis in streptococci?
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What is the arrangement of streptococci bacteria?
What is the arrangement of streptococci bacteria?
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Which of the following streptococci are classified as β-hemolytic?
Which of the following streptococci are classified as β-hemolytic?
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What is a key virulence factor associated with S. pyogens?
What is a key virulence factor associated with S. pyogens?
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Which enzyme produced by streptococci is responsible for lysis of fibrin?
Which enzyme produced by streptococci is responsible for lysis of fibrin?
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What type of hemolysin is Streptolysin O classified as?
What type of hemolysin is Streptolysin O classified as?
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Which characteristic is NOT typical of streptococci?
Which characteristic is NOT typical of streptococci?
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Which of the following statements best describes the capsule of S. pyogens?
Which of the following statements best describes the capsule of S. pyogens?
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What characteristic appearance do colonies of the organism on blood agar show?
What characteristic appearance do colonies of the organism on blood agar show?
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What biochemical reaction differentiates S. pneumoniae from S. viridans?
What biochemical reaction differentiates S. pneumoniae from S. viridans?
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What type of reaction occurs when specific polyvalent antibodies are added to S. pneumoniae?
What type of reaction occurs when specific polyvalent antibodies are added to S. pneumoniae?
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Which group of individuals is most recommended to receive the pneumococcal vaccine?
Which group of individuals is most recommended to receive the pneumococcal vaccine?
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What characteristic distinguishes S. pneumoniae in terms of pathogenicity in mice?
What characteristic distinguishes S. pneumoniae in terms of pathogenicity in mice?
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What is the Gram stain morphology of S. pneumoniae?
What is the Gram stain morphology of S. pneumoniae?
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What is a common predisposing factor for bacterial endocarditis caused by S. viridans?
What is a common predisposing factor for bacterial endocarditis caused by S. viridans?
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How does S. pneumoniae behave in terms of optochin sensitivity compared to S. viridans?
How does S. pneumoniae behave in terms of optochin sensitivity compared to S. viridans?
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Which clinical feature is associated with scarlet fever?
Which clinical feature is associated with scarlet fever?
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What type of infections fall under suppurative infections caused by S. pyogenes?
What type of infections fall under suppurative infections caused by S. pyogenes?
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How does one identify S. pyogenes in culture?
How does one identify S. pyogenes in culture?
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Which condition is a recognized post-streptococcal sequelae?
Which condition is a recognized post-streptococcal sequelae?
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What mechanism is thought to contribute to post-streptococcal diseases?
What mechanism is thought to contribute to post-streptococcal diseases?
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What is the significance of the bacitracin sensitivity test for S. pyogenes?
What is the significance of the bacitracin sensitivity test for S. pyogenes?
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What characterizes the clinical presentation of streptococcal toxic shock-like syndrome?
What characterizes the clinical presentation of streptococcal toxic shock-like syndrome?
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What timing is observed for the onset of post-streptococcal sequelae?
What timing is observed for the onset of post-streptococcal sequelae?
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What is the main reason the polysaccharide capsule of S. agalactiae is considered a virulence factor?
What is the main reason the polysaccharide capsule of S. agalactiae is considered a virulence factor?
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Which of the following is NOT true about the CAMP test related to S. agalactiae?
Which of the following is NOT true about the CAMP test related to S. agalactiae?
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What differentiates Group D Streptococci from Group B Streptococci in culture characteristics?
What differentiates Group D Streptococci from Group B Streptococci in culture characteristics?
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Which infection is predominantly caused by Group B Streptococci?
Which infection is predominantly caused by Group B Streptococci?
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What type of bacteria does the Quellung reaction specifically test for?
What type of bacteria does the Quellung reaction specifically test for?
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What culture condition is ideal for growing S. agalactiae?
What culture condition is ideal for growing S. agalactiae?
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The presence of which of the following indicates faecal pollution in water?
The presence of which of the following indicates faecal pollution in water?
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What is a significant indicator of susceptibility in a Dick test for scarlet fever?
What is a significant indicator of susceptibility in a Dick test for scarlet fever?
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What is one primary function of M-proteins in Streptococcus pyogenes?
What is one primary function of M-proteins in Streptococcus pyogenes?
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What is the importance of the capsular swelling reaction in identification?
What is the importance of the capsular swelling reaction in identification?
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Which test assesses susceptibility to scarlet fever through the irritation caused by erythrogenic toxin?
Which test assesses susceptibility to scarlet fever through the irritation caused by erythrogenic toxin?
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What defines a pseudo-reaction in the Dick test?
What defines a pseudo-reaction in the Dick test?
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Which of the following is an enzyme produced by streptococci that acts as a spreading factor?
Which of the following is an enzyme produced by streptococci that acts as a spreading factor?
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What does a significant titer level of Anti-streptolysin O (ASO) greater than 200 Todd units indicate?
What does a significant titer level of Anti-streptolysin O (ASO) greater than 200 Todd units indicate?
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What characterizes Streptolysin O in terms of its reaction to oxygen?
What characterizes Streptolysin O in terms of its reaction to oxygen?
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Which laboratory finding can be classified as a non-specific test for rheumatic fever?
Which laboratory finding can be classified as a non-specific test for rheumatic fever?
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Which characteristic differentiates α-hemolytic streptococci from β-hemolytic streptococci?
Which characteristic differentiates α-hemolytic streptococci from β-hemolytic streptococci?
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In the Schultz-Charlton reaction, what is the principle behind the disappearance of the rash?
In the Schultz-Charlton reaction, what is the principle behind the disappearance of the rash?
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Which group of streptococci is known for its association with the highest number of surface protein variants?
Which group of streptococci is known for its association with the highest number of surface protein variants?
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In terms of biological classification, what does the Lancefield classification system use to differentiate streptococci species?
In terms of biological classification, what does the Lancefield classification system use to differentiate streptococci species?
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What does high levels of C-reactive protein (CRP) indicate in a clinical setting?
What does high levels of C-reactive protein (CRP) indicate in a clinical setting?
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What is the primary specimen type used for the diagnosis of scarlet fever?
What is the primary specimen type used for the diagnosis of scarlet fever?
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What is a common feature of capsulated streptococci in terms of their immune evasion?
What is a common feature of capsulated streptococci in terms of their immune evasion?
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Which of the following streptococci is classified as non-typable based on hemolysis?
Which of the following streptococci is classified as non-typable based on hemolysis?
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What is the appearance of colonies of S. pneumoniae on blood agar?
What is the appearance of colonies of S. pneumoniae on blood agar?
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Which biochemical characteristic can be used to differentiate S. pneumoniae from S. viridans?
Which biochemical characteristic can be used to differentiate S. pneumoniae from S. viridans?
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What does a positive Quellung reaction indicate?
What does a positive Quellung reaction indicate?
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What is the pathogenicity of S. pneumoniae in mice upon intraperitoneal injection?
What is the pathogenicity of S. pneumoniae in mice upon intraperitoneal injection?
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Which group of individuals is commonly recommended to receive the pneumococcal vaccine?
Which group of individuals is commonly recommended to receive the pneumococcal vaccine?
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Which of the following conditions is S. viridans specifically associated with?
Which of the following conditions is S. viridans specifically associated with?
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What is the morphology of S. pneumoniae when observed under a Gram stain?
What is the morphology of S. pneumoniae when observed under a Gram stain?
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How does S. pneumoniae react to optochin sensitivity compared to S. viridans?
How does S. pneumoniae react to optochin sensitivity compared to S. viridans?
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Study Notes
Group B Streptococci (Streptococcus agalactiae)
- Found in normal vaginal, oral, and gastric flora
- Causes neonatal septicemia, pneumonia, meningitis
- CAMP test positive, bacitracin resistant
Group D Streptococci (Streptococcus faecalis) (Enterococci)
- Present in the gastrointestinal tract
- Considered an indicator of fecal pollution in water
- Causes urinary tract infections, wound infections
- Bile esculin hydrolysis test: positive
Streptococcus agalactiae (Group B Streptococci) Morphology and Characteristics
- Gram-positive, lancet-shaped cocci
- Arranged in diplococci
- Non-motile
- Non-spore-forming
-
Capsulated:
- The capsule appears as unstained halos around the cocci.
- Main virulence factor: The polysaccharide capsule resists phagocytosis.
- Serotyping: Classified into ≥ 80 serotypes based on the antigenic structure of the capsule.
- Detection: Can be detected by a serological test (Quellung reaction = capsular swelling reaction)
Streptococcus agalactiae (Group B Streptococci) Diseases
- Most frequent cause: Pneumonia and its complications, including bacteremia, meningitis, septic arthritis, and endocarditis.
- Common cause: Sinusitis, acute otitis media, and conjunctivitis.
Streptococcus agalactiae (Group B Streptococci) Samples
- Sputum
Streptococcus agalactiae (Group B Streptococci) Culture
-
Culture requirements:
- Oxygen: Facultative anaerobes
- Temperature: Optimum growth at 37°C
- Carbon Dioxide: Grow in normal CO2 concentration, but grow better in excess CO2.
-
Culture media:
- Ordinary media: Cannot grow on it.
Streptococcus pyogenes (Group A Streptococci) Morphology and Characteristics
- Gram-positive cocci
- Arranged in chains or pairs
- Facultative anaerobes
- Non-motile
- Non-spore-forming
- Capsulated
-
Cell Wall:
- Carbohydrate (c) antigen: Used for Lancefield classification (Group A = S. pyogenes)
-
Protein antigens: M, R, and T-proteins
- M-proteins: > 50 types of S.pyogenes, important virulence factors
- R & T-proteins: Used as epidemiologic markers, no role in virulence
Streptococcus pyogenes (Group A Streptococci) Capsule
- Non-antigenic
- Composed of hyaluronic acid, similar to host connective tissue
Streptococcus pyogenes (Group A Streptococci) Virulence Factors:
-
Cell Wall Associated Proteins and Polymers:
- M-protein and Lipoteichoic acid: Adherence to cells, inhibit phagocytosis.
- M-protein and hyaluronic acid capsule: Inhibits phagocytosis
-
Enzymes:
- Streptokinase: Lysis of fibrin
- Streptodornase: Lysis of nucleic acid
- Hyaluronidase: Spreading factor that digests hyaluronic acid
-
Toxins:
- Streptolysin S: Oxygen-stable, non-antigenic hemolysin.
-
Streptolysin O: Oxygen-labile, antigenic hemolysin.
- Antibodies to Streptolysin O are used in the diagnosis of streptococcal diseases.
Streptococcus pyogenes (Group A Streptococci) Exotoxins
-
Erythrogenic toxin:
- Causes the rash of scarlet fever.
- Associated with a toxic shock-like syndrome.
Streptococcus pyogenes (Group A Streptococci) Diseases
-
Suppurative Infections:
- Respiratory infections: Tonsillitis, sinusitis, otitis media, and pneumonia.
- Skin infections: Superficial (impetigo) or deep (cellulitis).
- Invasive infections: Bacteremia, osteomyelitis, wound infections, meningitis, endocarditis, puerperal sepsis, and erysipelas.
-
Toxogenic Diseases:
- Streptococcal toxic shock-like syndrome (STSS): Similar to Staphylococcal TSS.
- Scarlet fever: Affects children; clinical picture includes fever, skin rash, and stomatitis (strawberry tongue).
-
Post-Streptococcal Sequelae:
- Definition: Infections can cause sequelae, such as acute rheumatic fever and acute glomerulonephritis.
- Timing: Begin 1-3 weeks after an acute streptococcal illness.
- Pathogenesis: Poorly understood, but thought to be immune-mediated (autoimmune response).
Streptococcus pyogenes (Group A Streptococci) Diagnosis
-
Diagnosis of suppurative infection:
-
Samples:
- Blood: Puerperal sepsis, erysipelas, endocarditis, bacteremia.
- Throat swab: Pharyngitis, scarlet fever.
- Sputum: Pneumonia.
-
Samples:
-
Gram Stain:
- Direct film stained with Gram stain for characteristic morphology.
-
Culture:
-
Culture requirements:
- Oxygen: Facultative anaerobes.
- Temperature: 37°C
- Carbon Dioxide: Grow in normal atmospheric CO2 concentration, but 10% CO2 enhances growth.
-
Culture media:
- Ordinary media: Cannot grow on it.
- Enriched media: Grow on blood agar, colonies are small (pinpoint), translucent, and surrounded by zones of β-hemolysis.
-
Culture requirements:
-
Identification of Growth (Biochemical Reactions):
- Film stained by Gram stain: Shows morphology.
- Catalase negative: Differentiates from Staphylococci.
- Bacitracin sensitivity: Sensitive (distinguishes from other beta-hemolytic streptococci which are bacitracin resistant).
- Specific identification of S. pyogenes: By reaction with specific antibodies.
Streptococcus pyogenes (Group A Streptococci) Serology
- Clumping of latex particles indicates it is a Lancefield group A Streptococcus (Streptococcus pyogenes).
Streptococcus pyogenes (Group A Streptococci) Diagnosis of Scarlet Fever
- Specimen: Throat swab, examined as mentioned above.
-
Schultz-Charlton reaction:
- Principle: Neutralization of the toxin with specific antitoxins.
- Procedure: Injection of antierythrogenic toxin into a rash; rash disappears within 6-12 hours.
-
Dick test (Test of Susceptibility):
- Uses: To assess susceptibility to scarlet fever.
- Principle: Erythrogenic toxin is irritating and causes a local reaction when injected intradermally, unless neutralized by specific antitoxin.
-
Method:
- 0.1 ml of toxin is injected intradermally into one forearm (test arm).
- The same amount of heated toxin (detoxified) is injected into the other forearm (control arm). Read results within 4-7 days.
-
Interpretation:
- Positive test (susceptible): Redness and swelling in the test arm that reaches maximum after 4-7 days and disappears gradually. No reaction in the control arm.
- Negative test (immune): No reaction on both arms.
- Pseudo-reaction (hypersensitivity): Reaction appears and disappears in both arms at the same time.
Streptococcus pyogenes (Group A Streptococci) Diagnosis of Rheumatic Fever
-
Clinical:
- Clinical picture and history of preceding streptococcal infections.
- Elevated C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR).
-
Non-specific tests:
- CRP is a non-specific protein that appears in serum during active rheumatic fever and other inflammatory conditions.
-
Specific tests:
-
Anti-streptolysin O (ASO):
- Purpose: To determine the titer of antibodies to streptolysin O toxin.
- Significance: A titer of 200 or more Todd units is significant.
- Other tests: Anti-DNase, anti-hyaluronidase, anti-streptokinase.
-
Anti-streptolysin O (ASO):
- Vaccine: Currently, no vaccine is available.
Streptococcus pneumoniae Morphology and Characteristics
- Habitat: Normal oral flora.
- Gram stain: Gram-positive cocci arranged in pairs or short chains.
-
Morphology:
- Non-spore-forming.
- Non-motile
- Non-capsulated.
-
Culture:
- Produces α-hemolytic small colonies on blood agar.
- Resistant to optochin
- Not bile soluble.
Streptococcus pneumoniae Diseases
-
Bacterial endocarditis:
- Especially if heart valves are damaged by previous rheumatic fever or congenital heart disease.
- Dental manipulation associated with transient bacteremia is a common predisposing factor.
Streptococcus pneumoniae vs. Streptococcus viridans: Characteristics and Comparisons
Characteristic | Streptococcus pneumoniae | Streptococcus viridans |
---|---|---|
Inulin fermentation | Positive | Negative |
Bile solubility | Soluble | Not soluble |
Optochin sensitivity | Sensitive | Resistant |
Capsule and Quelling | Positive (Quelling reaction) | Negative |
Mice Pathogenicity | Pathogenic | Non-pathogenic |
Rheumatic Endocarditis | Subacute Bacterial Endocarditis | Acute Ulcerative Endocarditis |
Post-Streptococcal Infections
- Group A beta-hemolytic streptococci: Causes post-streptococcal infections (e.g., rheumatic fever, glomerulonephritis).
- Streptococcus viridans: Associated with subacute bacterial endocarditis.
- Streptococcus pyogenes: Causes acute ulcerative endocarditis.
- Streptococcus faecalis: Not associated with endocarditis.
- *Important Note- ** There may be a few additional details that are not fully fleshed out here, but this provides a comprehensive overview of the key information contained in the text, as requested.
Group B Streptococci (Streptococcus agalactiae)
- Normal vaginal, oral, and gastric flora
- Causes: neonatal septicemia, pneumonia, meningitis
- CAMP test positive
- Bacitracin resistant
- Gram-positive lancet-shaped cocci
- Diplococci
- Non-motile
- Non-spore forming
- Capsulated (appears as unstained halos around cocci)
- Main virulence factor: polysaccharide capsule (resists phagocytosis)
- Classified into 80 serotypes based on capsule antigenic structure
- Can be detected by the Quellung reaction (capsular swelling reaction)
- Frequent cause of pneumonia and complications like bacteremia, meningitis, septic arthritis, and endocarditis
- Also causes sinusitis, acute otitis media, and conjunctivitis
- Grows in normal CO2 concentration, but better in excess CO2
-
Culture Media:
- Cannot grow on ordinary media
- Grown on enriched media (blood agar)
Group D Streptococci (Streptococcus Faecalis) (Enterococci)
- Present in the GIT
- Considered an indication of fecal pollution of water
- Causes: urinary tract infections, wound infections
- Bile esculin hydrolysis test: positive
Streptococcal Infections
- Classified into 18 different sero-groups (A → U) based on carbohydrate antigen (C-antigen) on cell wall
- Streptococcus pyogenes (Group A)
- Streptococcus agalactia (Group B)
Streptococcus pyogenes (Group A)
-
Gram-positive cocci arranged in long chains
-
Non-motile, non-spore forming
-
Capsulated
-
Virulence Factors:
-
Cell Wall Associated Proteins and Polymers:
- M protein & Lipoteichoic acid: Adherence to cells, inhibit phagocytosis
- M protein & Hyaluronic Acid Capsule: Inhibit phagocytosis
-
Enzymes:
- Streptokinase: Lysis of fibrin
- Streptodornase: Lysis of nucleic acid
- Hyaluronidase: Spreading factor (digests hyaluronic acid)
-
Toxins:
- Streptolysin S: Oxygen-stable, non-antigenic, hemolysin
- Streptolysin O: Oxygen-labile, antigenic hemolysin (antibodies to streptolysin O used in diagnosis of streptococcal diseases)
- Erythrogenic toxin: Causes the rash of scarlet fever and has been associated with toxic shock-like syndrome
-
Cell Wall Associated Proteins and Polymers:
-
Diseases:
-
Suppurative Infections:
- Respiratory Infections: Tonsillitis, sinusitis, otitis media, pneumonia
- Skin Infections: Superficial (impetigo) or deep (cellulitis)
- Invasive Infections: Bacteremia, osteomyelitis, wound infections, meningitis, endocarditis, puerperal sepsis, erysipelas
-
Toxogenic Diseases:
- Streptococcal Toxic Shock-like Syndrome (TSS): Similar to staphylococcal TSS
- Scarlet fever: Affects children, causing fever, skin rash, and stomatitis (strawberry tongue)
-
Post-streptococcal Sequelae:
- Occur 1–3 weeks after a streptococcal illness
- Mechanism: Immune-mediated (e.g., antibodies produced during infection cross-react with host tissues)
-
Examples:
- Acute rheumatic fever
- Acute glomerulonephritis
-
Suppurative Infections:
Streptococcus pneumoniae (Pneumococcus)
-
Gram-positive cocci arranged in pairs or short chains
-
Non-motile, non-spore forming, and non-capsulated
-
α-hemolytic (small colonies on blood agar)
-
Resistant to optochin and not bile-soluble
-
Causes: Pneumonia, bacteremia, meningitis, otitis media
-
Specific Identification:
- Film stained by Gram stain to show morphology
- Biochemical reactions: Ferment inulin, bile-soluble
- Sensitive to optochin
- Pathogenicity to mice: Intraperitoneal injection of culture into mice leads to death within 18–48 hours due to septicemia
- Capsular swelling reaction (Quellung reaction): Swelling of the capsule after addition of specific polyvalent antibodies
-
Vaccination:
- Pneumococcal Vaccine: Contains capsular material from 23 pathogenic strains
- Recommended for young children, elderly, and debilitated persons
Streptococcus viridans
- Gram-positive cocci
- Non-spore forming
- Non-motile
- Produces α-hemolytic small colonies on blood agar
- Resistant to optochin (distinguishes it from S. pneumoniae)
- Bile insoluble
- Considered normal oral flora
- Causes:
- Dental caries
- Bacterial endocarditis (especially if heart valves have been damaged by rheumatic fever or congenital heart disease)
Differentiating Streptococci
Streptococcus pneumoniae | Streptococcus viridans | |
---|---|---|
Inulin Fermentation | Positive | Negative |
Bile Solubility | Soluble | Not soluble |
Optochin Sensitivity | Sensitive | Resistant |
Capsule & Quellung Reaction | Positive | Negative |
Mice Pathogenicity | Pathogenic | Non pathogenic |
Endocarditis | Subacute bacterial endocarditis | Acute ulcerative endocarditis |
Diagnosis of Streptococcal Infections
Diagnosis of Suppurative Infection
-
Samples:
- Blood: Puerperal sepsis, erysipelas, endocarditis, bacteremia
- Throat swab: Pharyngitis, scarlet fever
- Sputum: Pneumonia
-
Gram Staining:
- Direct film stained for characteristic morphology
-
Culture:
- Requirements: Facultative anaerobes, optimum temperature 37°C, normal atmospheric CO2 concentration (10% CO2 enhances growth)
- Media: Cannot grow on ordinary media, grows on blood agar (small, translucent colonies surrounded by zones of β-hemolysis)
-
Identification:
- Film stained with Gram stain to show morphology
- Biochemical reactions: Catalase negative
- Bacitracin sensitivity: Sensitive (differentiates from other β-hemolytic streptococci, which are resistant)
- Specific identification of S. pyogenes: Reaction with specific antibodies
- Serology: Latex agglutination test (Clumping of latex particles in the "A" circle indicates Group A)
Diagnosis of Scarlet Fever
- Specimen: Throat swab
-
Schultz-Charlton Reaction
- Principle: Neutralization of erythrogenic toxin with specific antitoxin
- Procedure: Injection of antierythrogenic toxin into the rash causes rash disappearance within 6–12 hours.
-
Dick Test (Test of Susceptibility)
- Uses: Assess susceptibility to scarlet fever
- Principle: Erythrogenic toxin is irritating and causes a local reaction when injected intradermally unless neutralized by specific antitoxin
- Method: 0.1 ml of toxin intradermally in one forearm (test arm); same amount of heated (detoxified) toxin in the other forearm (control arm)
-
Interpretation:
- Positive Test: Redness and swelling in the test arm that reaches maximum after 4–7 days and disappears gradually; No reaction in the control arm
- Negative Test: No reaction in both arms
- Pseudo-reaction (hypersensitivity): Reaction appears and disappears in both arms simultaneously
Diagnosis of Rheumatic Fever
- Clinical Picture and History: History of preceding streptococcal infections
-
Non-specific Tests:
- C-reactive protein (CRP): Increased in active rheumatic fever as well as inflammatory conditions
- ESR: Elevated
-
Specific Tests:
- Increase in the titer of:
- Anti-streptolysin O (ASO): Used to determine the titer of antibodies to streptolysin O toxin ( titer of 200 or more Todd units is significant)
- Anti-DNase
- Anti-hyaluronidase
- Anti-streptokinase
- Increase in the titer of:
- No vaccine is currently available for streptococcal infections.
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