Podcast
Questions and Answers
What was observed in the presence of hydrochloric acid regarding depolymerized DNA?
What was observed in the presence of hydrochloric acid regarding depolymerized DNA?
- A zone of clearing around the colonies (correct)
- No observable change
- Formation of a cloudy precipitate
- Thicker, polymerized DNA structure
What type of bacteria was identified from the throat culture?
What type of bacteria was identified from the throat culture?
- Gram-positive cocci in clusters
- Gram-negative cocci in pairs
- Gram-positive cocci in long chains (correct)
- Gram-positive bacilli
What kind of agar is used to indicate the hydrolysis of DNA?
What kind of agar is used to indicate the hydrolysis of DNA?
- Blood agar
- Nutrient agar
- Modified DNAse agar (correct)
- Methylene blue agar
Which characteristic best describes the organism examined in the culture?
Which characteristic best describes the organism examined in the culture?
Which observation supports the presence of polymerized DNA in the culture?
Which observation supports the presence of polymerized DNA in the culture?
Which species is classified under Lancefield Group A?
Which species is classified under Lancefield Group A?
What type of hemolysis is associated with S.agalactiae?
What type of hemolysis is associated with S.agalactiae?
What infections are commonly associated with S.pyogenes?
What infections are commonly associated with S.pyogenes?
Which species is usually associated with γ-hemolysis?
Which species is usually associated with γ-hemolysis?
What type of infections are commonly caused by S.bovis?
What type of infections are commonly caused by S.bovis?
What is a characteristic feature of the viridans group streptococci?
What is a characteristic feature of the viridans group streptococci?
Which species does NOT belong to the Lancefield classification?
Which species does NOT belong to the Lancefield classification?
What type of agar may have methyl green as an indicator?
What type of agar may have methyl green as an indicator?
Which hemolytic pattern indicates complete lysis of RBCs?
Which hemolytic pattern indicates complete lysis of RBCs?
What does growth in a 6.5% sodium chloride solution indicate?
What does growth in a 6.5% sodium chloride solution indicate?
What is the appearance of α-hemolytic streptococci on blood agar?
What is the appearance of α-hemolytic streptococci on blood agar?
If an isolate shows no growth in a 6.5% sodium chloride solution, what is it likely to be?
If an isolate shows no growth in a 6.5% sodium chloride solution, what is it likely to be?
What procedure is used to test for β-hemolytic streptococci?
What procedure is used to test for β-hemolytic streptococci?
What type of hemolysis does not lyse RBCs?
What type of hemolysis does not lyse RBCs?
Which type of streptococci is resistant to optochin?
Which type of streptococci is resistant to optochin?
How is non-hemolytic characterized in terms of RBC lysis?
How is non-hemolytic characterized in terms of RBC lysis?
What is the main virulence factor of Streptococcus pyrogenes?
What is the main virulence factor of Streptococcus pyrogenes?
Which enzyme acts as a plasminogen activator in Streptococcus pyrogenes?
Which enzyme acts as a plasminogen activator in Streptococcus pyrogenes?
What role does hyaluronidase play for Streptococcus pyrogenes?
What role does hyaluronidase play for Streptococcus pyrogenes?
What is the function of pyrogenic exotoxin in Streptococcus pyrogenes?
What is the function of pyrogenic exotoxin in Streptococcus pyrogenes?
What is the difference between Streptolysin O and Streptolysin S?
What is the difference between Streptolysin O and Streptolysin S?
What complication can arise from mimicry between streptococcal M protein and cardiac myosin?
What complication can arise from mimicry between streptococcal M protein and cardiac myosin?
Which factor reduces the host immune response in Streptococcus pyrogenes?
Which factor reduces the host immune response in Streptococcus pyrogenes?
What symptoms did the patient experience after being diagnosed with strep throat?
What symptoms did the patient experience after being diagnosed with strep throat?
What does a positive reaction in the Antistreptolysin O test indicate?
What does a positive reaction in the Antistreptolysin O test indicate?
How long after a streptococcal infection do antistreptolysin O levels typically rise?
How long after a streptococcal infection do antistreptolysin O levels typically rise?
Why is the Antistreptolysin O test performed?
Why is the Antistreptolysin O test performed?
What is the first step in the ASO tube testing procedure?
What is the first step in the ASO tube testing procedure?
In Tube 1 of the ASO testing, what is the dilution ratio used?
In Tube 1 of the ASO testing, what is the dilution ratio used?
What can elevated antistreptolysin O levels indicate in a patient?
What can elevated antistreptolysin O levels indicate in a patient?
What happens when streptococcal antigens remain in circulation after treatment?
What happens when streptococcal antigens remain in circulation after treatment?
Which of the following conditions can the ASO test help diagnose?
Which of the following conditions can the ASO test help diagnose?
Study Notes
Identifying Cocci
- Catalase negative cocci can be identified by analyzing their hemolytic patterns on blood agar plates.
- Viridans streptococci are resistant to optochin.
- Enterococci can grow in 6.5% sodium chloride solution.
- Streptococcus bovis is non-hemolytic and cannot grow in a highly salinic solution.
Hemolytic Patterns
- β-hemolytic: indicates complete lysis of red blood cells (RBCs), seen as a clear zone around the colonies.
- α-hemolytic: partial lysis of RBCs, producing a greenish discoloration around the colonies.
- γ-hemolytic: no lysis of RBCs, no change in the surrounding medium.
Lancefield’s Grouping
- A serological method for classifying streptococci into groups.
- Based on the presence of polysaccharides or sugars, and teichoic acid antigens in the bacterial cell wall.
- Streptococci are designated by letter based on their group.
Streptococcus pyogenes
- A β-hemolytic streptococcus associated with various suppurative infections.
- Virulence factors:
- Protein M: limits phagocytosis, prevents complement fixation, mediates adhesion to host cells.
- DNAse: reduces host immune response, allows bacteria to use nucleic acids as a nutrient source.
- Streptokinase: converts plasminogen to plasmin, allowing lysis of fibrin and bacterial metastasis.
- Hyaluronidase: spreading factor, allows bacterial dissemination through tissue.
- Pyrogenic exotoxin: superantigen, causes Streptococcal Toxic Shock Syndrome.
- Streptolysin: causes tissue death by inducing release of lysosomal contents after ingestion by phagocytes.
- Streptolysin O: immunogenic, oxygen labile.
- Streptolysin S: non-immunogenic, oxygen stable.
Antistreptolysin O (ASO) Testing
- ASO is a specific neutralizing antibody produced against streptolysin O of S.pyogenes.
- Levels rise 1-3 weeks after an infection (not useful for diagnosing acute streptococcal infection).
- Utilized for diagnosing post-streptococcal conditions like glomerulonephritis, rheumatic fever, rheumatic heart disease, and bacterial endocarditis.
ASO Tube Testing (Semi-Quantitative, Neutralization Test)
- Serial dilutions of patient serum are made in test tubes.
- A positive reaction displays fine flocculation (agglutination) within 2-3 minutes.
- A negative reaction shows no agglutination.
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Description
This quiz covers the identification of cocci bacteria, focusing on their hemolytic patterns on blood agar and classification through Lancefield's grouping. Learn about the characteristics of various streptococci and their significance in microbiology.
