20 Questions
Which component anchors the peptidoglycan to the cytoplasmic membrane in Gram-Positive bacterial cell walls?
Lipoteichoic acids
What type of stain is used for difficult staining in water-based dyes for Mycobacterium?
Acid-fast stain
Which bacteria retain crystal violet dye and appear purple in the Gram stain?
Bacillus
Which bacteria occur in grapelike clusters and are nonmotile?
Staphylococcus
Which bacteria are normal members of every human's microbiota and can be opportunistic pathogens?
Staphylococcus
Which bacterium is responsible for causing necrotizing fasciitis?
Streptococcus pyogenes
What is the most common site of Group B Streptococcus colonization in adults?
Gastrointestinal tract
Which species of Streptococcus is responsible for causing pus-filled abscesses and pharyngitis?
Streptococcus equisimilis
Which type of Streptococci lacks group-specific carbohydrates and does not form distinct groups using the Lancefield system?
Alpha-hemolytic Streptococci
Which bacterium is commonly found in the mouths and pharynges of most humans and can cause pneumonia?
Streptococcus pneumoniae
What are the two common disease-causing species of Staphylococcus?
Staphylococcus aureus and Staphylococcus epidermidis
What size are Staphylococcus bacteria in diameter?
1-5 microns
Which enzyme produced by S. aureus enables it to spread between cells?
Hyaluronidase
What do lipases produced by Staphylococcus digest, allowing it to grow on skin and in oil glands?
Lipids
Which syndrome is associated with Staphylococcus growth, fever, vomiting, rash, low blood pressure, and multiorgan failure?
Toxic-shock syndrome
Which bacterial strain is known for being resistant to multiple antibiotics?
Vancomycin-resistant Staphylococcus aureus (VRSA)
Which bacteria are common causes of pneumonia and can lead to empyema?
Streptococcus pneumoniae
What is a significant human pathogen categorized based on Lancefield's classification?
Streptococcus pyogenes
What is a complication of pharyngitis caused by Streptococcus pyogenes?
Scarlet fever
What is a rare but severe complication of bacteriaemia caused by Streptococcus pyogenes, characterized by organ failure, shock, and a 40% mortality rate?
Streptococcal toxic-shock syndrome
Study Notes
- Aureus, epidermidis, and other bacteria can cause bacteriaemia, which is the presence of bacteria in the blood. Half of these infections are nosocomial, meaning they occur in hospitals and are often linked to surgical wounds or medical devices.
- Staphylococcus aureus and Streptococcus species are significant causes of bacteriaemia. Endocarditis, a damage to the heart lining, is a severe complication of bacteriaemia and has a 50% mortality rate.
- Pneumonia, an inflammation of the lungs, can lead to empyema, where pus fills the lungs. Staphylococcus aureus and Streptococcus pneumoniae are common causes of pneumonia.
- Osteomyelitis, an inflammation of the bone and bone marrow, can be caused by various bacteria, including Staphylococcus aureus and Streptococcus.
- Urinary tract infections are common in young women and can be caused by various bacteria, including strains of Escherichia coli.
- Staphylococcus aureus is diagnosed by identifying gram-positive bacteria in grapelike arrangements. Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Staphylococcus aureus (VRSA) are emerging strains that are resistant to multiple antibiotics.
- Prevention of staphylococcal infections includes hand antisepsis and proper wound cleansing.
- Streptococcus species, particularly Streptococcus pyogenes, are facultative anaerobes, catalase-negative cocci arranged in pairs or chains. They are often categorized based on Lancefield's classification and are significant human pathogens.
- Streptococcus pyogenes, also known as Group A Streptococcus, has a large zone of beta-hemolysis in a 24-hour culture on blood agar. They have structural components to evade phagocytosis, including M proteins, hyaluronic acid capsules, streptokinases, and deoxyribonucleases.
- Streptococcus pyogenes uses various mechanisms to cause disease, including the production of pyrogenic or erythrogenic toxins and lysing red and white blood cells and platelets.
- Streptococcus pyogenes can infect the pharynx or skin, causing diseases such as pharyngitis ("strep throat"), scarlet fever, pyoderma, erysipelas, and streptococcal toxic-shock syndrome.
- Pharyngitis, caused by Streptococcus pyogenes, is characterized by red, swollen, purulent abscesses on the tonsils. Scarlet fever, a complication of pharyngitis, can cause a chest rash and is caused by pyrogenic toxins released by lysogenized strains.
- Pyoderma and erysipelas are caused by Streptococcus pyogenes and are characterized by localized pus-filled lesions and inflammation of lymph nodes, respectively.
- Streptococcal toxic-shock syndrome is a rare but severe complication of bacteriaemia caused by Streptococcus pyogenes. It can cause organ failure, shock, and death (40%). Necrotizing fasciitis, another complication of bacteriaemia caused by Streptococcus, is characterized by the spread of streptococci along the fascia and the secretion of enzymes and toxins that destroy tissue (50%).
Test your knowledge on staphylococcus infections, including bacteremia, endocarditis, pneumonia, osteomyelitis, and urinary tract infections. Learn about diagnosis, treatment, and prevention methods for these infections.
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