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Questions and Answers
Which organism is bacitracin resistant?
Which organism is bacitracin resistant?
What type of hemolysis is exhibited by beta hemolytic streptococci?
What type of hemolysis is exhibited by beta hemolytic streptococci?
What does a positive result in the hippurate hydrolysis test indicate?
What does a positive result in the hippurate hydrolysis test indicate?
Which characteristic is NOT true regarding Streptococcus species?
Which characteristic is NOT true regarding Streptococcus species?
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Which test is used to measure ASO antibody titer?
Which test is used to measure ASO antibody titer?
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What is the primary classification method used for differentiating streptococci based on their hemolytic properties?
What is the primary classification method used for differentiating streptococci based on their hemolytic properties?
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What is indicated by a lack of hemolysis in the Antistreptolysin O test?
What is indicated by a lack of hemolysis in the Antistreptolysin O test?
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What is the principal enzyme detected in the PYR test?
What is the principal enzyme detected in the PYR test?
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Which of the following statements is true about Streptococcus pyogenes?
Which of the following statements is true about Streptococcus pyogenes?
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What is the significance of an arrowhead of hemolysis in the CAMP test?
What is the significance of an arrowhead of hemolysis in the CAMP test?
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Which Lancefield group is primarily associated with human infections?
Which Lancefield group is primarily associated with human infections?
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What type of bacteria are Streptococcus classified as on the Gram reaction scale?
What type of bacteria are Streptococcus classified as on the Gram reaction scale?
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Which grouping is used for classifying streptococci based on specific antigens?
Which grouping is used for classifying streptococci based on specific antigens?
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What reagent is used to detect the product of the hippurate hydrolysis test?
What reagent is used to detect the product of the hippurate hydrolysis test?
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Which of the following is a characteristic of Streptococcus bacteria?
Which of the following is a characteristic of Streptococcus bacteria?
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What distinguishes alpha hemolytic streptococci from other types?
What distinguishes alpha hemolytic streptococci from other types?
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What is the primary cause of rheumatic fever?
What is the primary cause of rheumatic fever?
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Which of the following is a common laboratory method to diagnose S.agalactiae?
Which of the following is a common laboratory method to diagnose S.agalactiae?
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What is notable about the growth characteristics of S.agalactiae?
What is notable about the growth characteristics of S.agalactiae?
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What type of hemolysis is produced by both S.pyogenes and S.agalactiae on blood agar?
What type of hemolysis is produced by both S.pyogenes and S.agalactiae on blood agar?
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In rheumatic fever, which tissue is primarily affected by damage due to the autoimmune reaction?
In rheumatic fever, which tissue is primarily affected by damage due to the autoimmune reaction?
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What characterizes the colonial morphology of S.pyogenes on a culture medium?
What characterizes the colonial morphology of S.pyogenes on a culture medium?
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What is the result of the catalase test for S.pyogenes?
What is the result of the catalase test for S.pyogenes?
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During which stage of life is S.agalactiae most dangerous to individuals?
During which stage of life is S.agalactiae most dangerous to individuals?
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What is the most significant virulence factor of S.pyogenes that aids in colonization and escaping phagocytosis?
What is the most significant virulence factor of S.pyogenes that aids in colonization and escaping phagocytosis?
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Which condition is primarily characterized by a bright red rash and pharyngitis in children aged 5-15 years?
Which condition is primarily characterized by a bright red rash and pharyngitis in children aged 5-15 years?
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Which extracellular enzyme produced by S.pyogenes facilitates the digestion of fibrin clots?
Which extracellular enzyme produced by S.pyogenes facilitates the digestion of fibrin clots?
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What type of infections can occur weeks after a local infection with S.pyogenes, primarily due to immunologic responses?
What type of infections can occur weeks after a local infection with S.pyogenes, primarily due to immunologic responses?
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Which of the following is NOT a symptom of pharyngitis caused by S.pyogenes?
Which of the following is NOT a symptom of pharyngitis caused by S.pyogenes?
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What is the role of lipoteichoic acids in the pathogenicity of S.pyogenes?
What is the role of lipoteichoic acids in the pathogenicity of S.pyogenes?
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Which extracellular toxin from S.pyogenes is known to be oxygen labile and induces specific antibody formation?
Which extracellular toxin from S.pyogenes is known to be oxygen labile and induces specific antibody formation?
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What is the main consequence of S.pyogenes infections in the endometrium following delivery or abortion?
What is the main consequence of S.pyogenes infections in the endometrium following delivery or abortion?
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Study Notes
Streptococcus
- Streptococcus is a genus of Gram-positive bacteria
- "Coiled berry" describes the characteristic chain-like arrangement of bacteria
- General characteristics include:
- Gram-positive cocci (spherical bacteria)
- Form chains or pairs
- Non-motile, non-spore-forming
- Some are encapsulated
- Facultative anaerobes (can survive with or without oxygen)
- Fastidious (require specific nutrients)
- Catalase-negative (cannot produce the enzyme catalase)
Classification of Streptococci
-
Classification by hemolysis on blood agar (brown classification):
- Beta-hemolytic: Complete hemolysis, surrounding the colonies, due to streptolysin
- Alpha-hemolytic: Partial hemolysis, surrounding the colonies, with a green-brown color due to methemoglobin
- Gamma/non-hemolytic: No hemolysis
-
Classification by Lancefield grouping:
- Streptococci produce specific carbohydrates (C carbohydrate) antigens in the cell wall
- Identified using specific antisera (blood serum containing antibodies)
- Divided into 21 groups (A-H and K-V)
- Some groups (A, B, C, D, and G) are frequently associated with human infections
Streptococcus pyogenes (Group A)
-
General characteristics:
- Gram-positive cocci in chains
- Non-motile, non-spore-forming
- Some strains are encapsulated
- Aerobic and facultative anaerobic
- Temperature range of 22-42°C, optimum at 35-37°C
- Fastidious
- Catalase-negative
-
Normal habitat:
- Found in water, dust, vegetation, milk and milk products
- Part of the upper respiratory tract (URT) normal flora
-
Virulence factors:
- Adherence factors (mediate colonization): M protein, lipoteichoic acids, F protein
- Extracellular enzymes: Streptokinase, Hyaluronidase, DNases
- Extracellular toxins: Streptolysins (O and S), Erythrogenic toxin
Streptococcus agalactiae (Group B)
-
General characteristics:
- Gram-positive cocci in chains
- Non-motile
- Non-spore-forming
- Some strains are encapsulated
- Aerobic and facultative anaerobic
- Temperature range of 22-42°C, optimum at 35-37°C
- Non-fastidious
- Habitat: colonizes the genital tract of 10-30% of pregnant women; can be transferred to infants during delivery
Pathogenicity
- Different diseases can be caused, depending on the species, namely:
- Pharyngitis (strep throat)
- Scarlet fever
- Puerperal fever.
- Acute glomerulonephritis (kidney disease)
- Rheumatic fever
Laboratory Diagnosis
-
Specimen collection: Depends on the site of infection (throat swab, blood, vaginal swab, CSF)
-
Biochemical tests:
- Catalase test (negative for Streptococcus)
- Bacitracin sensitivity test (to differentiate S. pyogenes and S. agalactiae)
- Lancefield grouping (serological test for identification of specific serotypes)
- Pyrrolidonyl arylamidase (PYR) test
- Hippurate hydrolysis test
- CAMP test
-
Culture characteristics:
- Aerobic and facultative anaerobic
- Required temperature range
- Media types (blood agar, nutrient agar, etc.)
-
Antimicrobial sensitivity:
- Streptococcus pyogenes is sensitive to penicillin and erythromycin.
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Description
This quiz covers the essential characteristics and classification of Streptococcus bacteria. Learn about their morphology, classification methods, and different types based on hemolysis and Lancefield grouping. Test your knowledge on Gram-positive cocci and their specific traits.
