20 Questions
Which of the following options are catalase-negative Gram-positive spherical or oval cocci, that grow well on blood agar, and are lactic acid bacteria?
Lactobacilli
Staphylococcus aureus is:
Coagulase positive
The microorganism that causes tonsillitis and pharyngitis, scarlet fever, otitis media, and impetigo is:
Streptococcus pyogenes
Which of the following options are not catalase-negative Gram-positive spherical or oval cocci?
Staphylococci
Which of the following is true about Streptococcus mutans?
It is a cariogenic bacteria
What is the characteristic hemolytic reaction of Streptococcus?
β-haemolysis wide, clear, translucent zone of complete haemolysis
What is the family classification of Streptococcus?
Streptococcaceae
What is the characteristic size of Gram-positive spherical or oval cocci of Streptococcus?
0.7-0.9 µm in diameter
Which of the following is a characteristic of Staphylococci?
Arranged in grape-like clusters
Which of the following is a characteristic of Streptococci mutans group bacteria?
Major agents of dental caries
Which of the following is a characteristic of Lancefield group A?
Contains Streptococcus pyogenes
Which of the following bacteria is associated with endodontic treatment failure?
Enterococcus faecalis
Which bacteria is a common pathogen causing localized skin and serious systemic infections?
Staphylococcus aureus
Which bacteria is associated with catheter-related tract sepsis, artificial joints, and urinary infections?
Staphylococcus epidermidis
Which of the following bacteria causes neonatal meningitis and sepsis?
Streptococcus agalactiae
Which of the following bacteria is a normal constituent of microbiota?
Enterococcus faecalis
Which of the following bacteria spreads by contact and is associated with catheter-related tract sepsis, artificial joints, and urinary infections?
Staphylococcus epidermidis
Which of the following bacteria causes infections like tonsillitis, pharyngitis, and rheumatic fever?
Streptococcus pyogenes
Which of the following bacteria is a major agent of dental caries?
Streptococcus mutans
Which of the following bacteria can be classified by the degree of haemolysis on blood agar and the cell wall carbohydrate antigens into Lancefield groups?
Streptococci
Study Notes
Bacterial Classification and Characteristics
- Streptococci are Gram-positive bacteria, appearing as spherical or oval cocci in chains and pairs.
- Streptococci can be classified by the degree of haemolysis on blood agar and the cell wall carbohydrate antigens into Lancefield groups.
- Lancefield group A contains Streptococcus pyogenes, causing infections like tonsillitis, pharyngitis, and rheumatic fever.
- Oral streptococci are a mixed group, typically showing α-haemolysis on blood agar, and can be divided into four main species groups.
- The mutans group bacteria are major agents of dental caries.
- Staphylococci resemble streptococci in appearance but are arranged in grape-like clusters and are all catalase-positive.
- Staphylococcus aureus is a common pathogen causing localized skin and serious systemic infections, producing numerous toxins and enzymes as virulence factors.
- Antibiotic resistance in staphylococci has led to the emergence of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Staphylococcus aureus (VRSA).
- Streptococcus pyogenes causes a number of infections, including scarlet fever, otitis media, and impetigo.
- Streptococcus agalactiae causes neonatal meningitis and sepsis.
- Enterococcus faecalis is a normal constituent of microbiota and is associated with endodontic treatment failure.
- Staphylococcus epidermidis spreads by contact and is associated with catheter-related tract sepsis, artificial joints, and urinary infections.
Test your knowledge of bacterial classification and characteristics with this quiz. Learn about the different groups of streptococci and their associated infections, as well as the characteristics and impact of staphylococci, including antibiotic resistance and pathogenicity.
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