10 Questions
What is the suspected diagnosis of the first case based on the physical examination and laboratory results?
Acute follicular tonsillitis
What is the likely cause of the patient's symptoms in the second case?
Streptococcus pyogenes
What is the purpose of performing a RADT (Rapid Antigen Detection Test) in the first case?
To confirm the diagnosis of Streptococcus pyogenes
What is the significance of the patient's history of repetitive attacks of acute follicular tonsillitis in the second case?
It suggests a diagnosis of rheumatic fever
What is the likely diagnosis of the second case based on the patient's symptoms and laboratory results?
Rheumatic fever
What is the purpose of performing a microscopical examination of the patient's throat or tonsillar region in the first case?
To confirm the diagnosis of Streptococcus pyogenes
What is the significance of the patient's ECG and Echo results in the second case?
They suggest a diagnosis of heart block
What is the likely cause of the patient's elevated CRP and ESR in the first case?
Streptococcus pyogenes infection
What is the purpose of performing a culture on blood agar in the first case?
To confirm the diagnosis of Streptococcus pyogenes
What is the proper management of the second case?
Antibiotic therapy and bed rest
Study Notes
Streptococci
- Gram-positive cocci, arranged in chains (except S. pneumoniae, which is arranged in pairs)
- Non-capsulated (except S. pneumoniae and a few other exceptions)
- Non-motile, non-spore forming, and fastidious organisms
Classification of Streptococci
- Facultative anaerobes
- Alpha-hemolytic: partial hemolysis (e.g., viridans streptococci, S. pneumoniae)
- Beta-hemolytic: complete hemolysis (e.g., S. pyogenes)
- Gamma-hemolytic: no hemolysis (e.g., S. faecalis)
Alpha-Hemolytic Streptococci
- S. pneumoniae (Pneumococci)
- Viridans streptococci (opportunistic pathogens of low virulence)
- S. mitis group
- S. mutans group
- S. bovis group
Streptococcus pneumoniae (Pneumococci)
- Polysaccharide capsule is an important virulence factor
- Alpha-hemolytic on blood agar
- Optochin sensitive
- Causes lobar pneumonia, meningitis, and subacute bacterial endocarditis
Beta-Hemolytic Streptococci
- S. pyogenes
- Causes acute follicular tonsillitis, pharyngitis, scarlet fever, acute bacterial endocarditis, and post-streptococcal diseases (e.g., acute glomerulonephritis, rheumatic fever)
- Direct detection of S. pyogenes antigens from throat swabs is possible by RADT (rapid antigen detection tests)
- Diagnosis:
- Microscopical examination: Gram-positive cocci, chains (non-motile, non-spore forming, non-capsulated)
- Culture characteristics: beta hemolysis on blood agar
- Antistreptolysin O Titer (ASOT): measures antibodies against streptolysin O produced by S. pyogenes
Antistreptolysin O Titer (ASOT)
- Principle: streptolysin O (antigen) + RBCs + patient serum (ASO)
- Positive reaction: no hemolysis
- Titre: 1/highest dilution showing positive results (no hemolysis)
- Diagnostic titer >200 Todd
Case Studies
- Case 1: suspected diagnosis of acute follicular tonsillitis, caused by Streptococcus pyogenes
- Case 2: suspected diagnosis of rheumatic fever, caused by Streptococcus pyogenes
Test your knowledge of Streptococci, a type of Gram-positive bacteria, including their classification, characteristics, and types such as alpha, beta, and gamma hemolytic Streptococci. Learn about their diagnosis, arrangement, and other important features.
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