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Questions and Answers
What is the characteristic feature of the lactic acid bacteria?
What is the characteristic feature of the lactic acid bacteria?
- They are spore-forming bacteria
- They ferment sugars with the formation of lactic acid as one of the major products (correct)
- They are gram-negative bacteria
- They have a high GC content
What is the significance of the coagulase test in Staphylococcus aureus?
What is the significance of the coagulase test in Staphylococcus aureus?
- It is an indication of the organism's ability to form spores
- It helps to identify Staphylococcus aureus from other Staphylococcus species (correct)
- It determines the presence of catalase
- It shows the ability of the organism to break down blood
What is the characteristic feature of Staphylococcus aureus that distinguishes it from Streptococcus?
What is the characteristic feature of Staphylococcus aureus that distinguishes it from Streptococcus?
- It is catalase-positive (correct)
- It is a gram-negative bacterium
- It is a spore-forming bacterium
- It is catalase-negative
What is the common habitat of Staphylococcus aureus?
What is the common habitat of Staphylococcus aureus?
What is the mechanism of action of coagulase in Staphylococcus aureus?
What is the mechanism of action of coagulase in Staphylococcus aureus?
What is the disease caused by Staphylococcus aureus in immunocompromised patients?
What is the disease caused by Staphylococcus aureus in immunocompromised patients?
What is the characteristic arrangement of Staphylococcus aureus cells?
What is the characteristic arrangement of Staphylococcus aureus cells?
What is the percentage of G+C content in Staphylococcus aureus?
What is the percentage of G+C content in Staphylococcus aureus?
What is the primary mechanism by which Staphylococcus aureus invades subcutaneous tissue?
What is the primary mechanism by which Staphylococcus aureus invades subcutaneous tissue?
What is the typical source of Staphylococcus aureus in hospital-acquired infections?
What is the typical source of Staphylococcus aureus in hospital-acquired infections?
What is the purpose of the fibrin barrier in Staphylococcus aureus infections?
What is the purpose of the fibrin barrier in Staphylococcus aureus infections?
What is the primary cause of scalded skin syndrome?
What is the primary cause of scalded skin syndrome?
What is the typical age range of individuals affected by scalded skin syndrome?
What is the typical age range of individuals affected by scalded skin syndrome?
What is the primary route of bacterial entry in hematogenous osteomyelitis?
What is the primary route of bacterial entry in hematogenous osteomyelitis?
What is the typical outcome of scalded skin syndrome?
What is the typical outcome of scalded skin syndrome?
What is the primary role of coagulase in Staphylococcus aureus infections?
What is the primary role of coagulase in Staphylococcus aureus infections?
What is the role of lipases in the invasion of subcutaneous tissue?
What is the role of lipases in the invasion of subcutaneous tissue?
What is the result of the toxins released by the organism in the subcutaneous tissue?
What is the result of the toxins released by the organism in the subcutaneous tissue?
What is the role of coagulase in the formation of abscesses?
What is the role of coagulase in the formation of abscesses?
What is the effect of exfoliatin on the skin?
What is the effect of exfoliatin on the skin?
What is the role of leukocidin in the pathogenesis of the disease?
What is the role of leukocidin in the pathogenesis of the disease?
What is the effect of TSST-1 on the host?
What is the effect of TSST-1 on the host?
What is the role of fibrolysin in the invasion of tissues?
What is the role of fibrolysin in the invasion of tissues?
What is the characteristic of Panton-Valentine leukocidin?
What is the characteristic of Panton-Valentine leukocidin?
What is the function of fibrolysin in Staphylococcus aureus?
What is the function of fibrolysin in Staphylococcus aureus?
What is the characteristic of enterotoxins A, B, and D?
What is the characteristic of enterotoxins A, B, and D?
What is the mechanism of action of TSST-1?
What is the mechanism of action of TSST-1?
Why are many MRSA strains resistant to multiple antibiotics?
Why are many MRSA strains resistant to multiple antibiotics?
What is the function of hemolysins in Staphylococcus aureus?
What is the function of hemolysins in Staphylococcus aureus?
What is the current treatment for MRSA infections?
What is the current treatment for MRSA infections?
What is the function of leukocidin in Staphylococcus aureus?
What is the function of leukocidin in Staphylococcus aureus?
Why are Staphylococcus aureus infections difficult to treat?
Why are Staphylococcus aureus infections difficult to treat?
What is the primary concern associated with the isolation of a VRSA strain from a dialysis patient with a foot ulcer in Detroit?
What is the primary concern associated with the isolation of a VRSA strain from a dialysis patient with a foot ulcer in Detroit?
What is a common characteristic of individuals who have acquired C-MRSA?
What is a common characteristic of individuals who have acquired C-MRSA?
What is the primary difference between Staphylococcus aureus and Staphylococcus epidermidis?
What is the primary difference between Staphylococcus aureus and Staphylococcus epidermidis?
What is the most common source of Staphylococcus epidermidis infections?
What is the most common source of Staphylococcus epidermidis infections?
What is the primary concern associated with the spread of C-MRSA?
What is the primary concern associated with the spread of C-MRSA?
What is the significance of the VRSA strain isolated from a dialysis patient with a foot ulcer in Detroit?
What is the significance of the VRSA strain isolated from a dialysis patient with a foot ulcer in Detroit?
Staphylococcus aureus can cause pneumonia and septicaemia in immunocompromised patients.
Staphylococcus aureus can cause pneumonia and septicaemia in immunocompromised patients.
Impetigo is a skin infection caused by Staphylococcus aureus.
Impetigo is a skin infection caused by Staphylococcus aureus.
All Staphylococcus aureus strains are coagulase positive.
All Staphylococcus aureus strains are coagulase positive.
Osteomyelitis is a type of skin infection caused by Staphylococcus aureus.
Osteomyelitis is a type of skin infection caused by Staphylococcus aureus.
Scalded skin syndrome is a toxin-mediated disease caused by Staphylococcus aureus.
Scalded skin syndrome is a toxin-mediated disease caused by Staphylococcus aureus.
Lactic acid is a byproduct of sugar fermentation in Staphylococcus aureus.
Lactic acid is a byproduct of sugar fermentation in Staphylococcus aureus.
Staphylococcus aureus can cause septic arthritis in older individuals.
Staphylococcus aureus can cause septic arthritis in older individuals.
Staphylococcus aureus is a gram-negative bacterium.
Staphylococcus aureus is a gram-negative bacterium.
Streptomyces is a type of gram-positive, non-spore forming bacteria.
Streptomyces is a type of gram-positive, non-spore forming bacteria.
Coagulase is produced by all strains of Staphylococcus aureus.
Coagulase is produced by all strains of Staphylococcus aureus.
Staphylococcus aureus can be transmitted by hospital personnel.
Staphylococcus aureus can be transmitted by hospital personnel.
Mycoplasma is a type of gram-positive, non-spore forming bacteria.
Mycoplasma is a type of gram-positive, non-spore forming bacteria.
Lipases are not involved in the invasion of subcutaneous tissue by Staphylococcus aureus.
Lipases are not involved in the invasion of subcutaneous tissue by Staphylococcus aureus.
All Corynebacteria are gram-negative bacteria.
All Corynebacteria are gram-negative bacteria.
Staphylococcus aureus is typically found in the nose and skin of healthy individuals.
Staphylococcus aureus is typically found in the nose and skin of healthy individuals.
Staphylococcus aureus causes pneumonia and septicaemia in immunocompromised patients.
Staphylococcus aureus causes pneumonia and septicaemia in immunocompromised patients.
Lipases aid in the invasion of subcutaneous tissue by Staphylococcus aureus.
Lipases aid in the invasion of subcutaneous tissue by Staphylococcus aureus.
Coagulase is involved in the formation of a fibrin barrier during Staphylococcus aureus infections.
Coagulase is involved in the formation of a fibrin barrier during Staphylococcus aureus infections.
Panton-Valentine leukocidin is produced by all strains of Staphylococcus aureus.
Panton-Valentine leukocidin is produced by all strains of Staphylococcus aureus.
Enterotoxins A, B, and D are heat-labile.
Enterotoxins A, B, and D are heat-labile.
TSST-1 is a type of hemolysin.
TSST-1 is a type of hemolysin.
Fibrolysin is involved in the formation of a fibrin barrier during Staphylococcus aureus infections.
Fibrolysin is involved in the formation of a fibrin barrier during Staphylococcus aureus infections.
Exfoliatin is a type of leukocidin.
Exfoliatin is a type of leukocidin.
Staphylococcus aureus infections are typically acquired through skin lesions.
Staphylococcus aureus infections are typically acquired through skin lesions.
Leukocidin is a toxin that damages only erythrocytes.
Leukocidin is a toxin that damages only erythrocytes.
Exfoliatin is a plasmid-encoded toxin that produces a strong immune response.
Exfoliatin is a plasmid-encoded toxin that produces a strong immune response.
TSST-1 is a heat-labile toxin that causes severe diarrhoea and vomiting.
TSST-1 is a heat-labile toxin that causes severe diarrhoea and vomiting.
Methicillin-resistant Staphylococcus aureus (MRSA) is typically sensitive to penicillin.
Methicillin-resistant Staphylococcus aureus (MRSA) is typically sensitive to penicillin.
Vancomycin is a beta-lactam antibiotic that is effective against MRSA.
Vancomycin is a beta-lactam antibiotic that is effective against MRSA.
Staphylococcus aureus is typically found in the environment and not on human skin.
Staphylococcus aureus is typically found in the environment and not on human skin.
Food poisoning caused by Staphylococcus aureus is usually treated with antibiotics.
Food poisoning caused by Staphylococcus aureus is usually treated with antibiotics.
Hemolysins are toxins that only damage macrophages.
Hemolysins are toxins that only damage macrophages.
The patient from Detroit who was infected with VRSA had not been recently hospitalized.
The patient from Detroit who was infected with VRSA had not been recently hospitalized.
Coagulase-negative Staphylococcus epidermidis is a major component of skin flora.
Coagulase-negative Staphylococcus epidermidis is a major component of skin flora.
C-MRSA is typically seen in people who have been recently hospitalized.
C-MRSA is typically seen in people who have been recently hospitalized.
Staphylococcus epidermidis is a common cause of opportunistic infections.
Staphylococcus epidermidis is a common cause of opportunistic infections.
The VRSA strain isolated from the patient in Detroit acquired resistance genes from a vancomycin-resistant E. coli strain.
The VRSA strain isolated from the patient in Detroit acquired resistance genes from a vancomycin-resistant E. coli strain.
Most cases of C-MRSA in the UK have been seen in injecting drug users.
Most cases of C-MRSA in the UK have been seen in injecting drug users.
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Study Notes
Gram-Positive Bacteria
- Firmicutes (Low GC) and Actinobacteria (High GC) are two categories of gram-positive bacteria
- Non-spore forming bacteria include Lactic Acid Bacteria (Streptococcus, Lactobacillus, etc.), Nocardia, Corynebacteria, Mycobacteria, and Mycoplasma
- Spore-forming bacteria include Clostridium and Bacillus
Staphylococcus
- Gram-positive, non-motile cocci (>30 species)
- Facultative anaerobes capable of fermentation and respiration
- Ferment sugars with lactic acid as a major product
- G + C content (30-40%) similar to Lactic Acid Bacteria
- Less restrictive growth requirements
- Grape-like clusters of cocci (Staphyle - Greek for "bunch of grapes")
Staphylococcus aureus
- Catalase positive (distinguishes from Streptococcus)
- Coagulase positive (distinguishes from S. epidermidis and Micrococcus)
- Causes plasma to clot by converting fibrinogen to fibrin
- Beta-hemolysis on blood agar
- Part of normal flora - skin and nose
- Causes pneumonia and septicemia in newborns and immunocompromised patients
- Causes skin infections, impetigo, furuncles, and carbuncles
- Causes septic arthritis, osteomyelitis, and endocarditis
Staphylococcal Infections
- Scalded Skin Syndrome (SSSS) - toxin produced by phage group 2 S. aureus
- Initial infection in mouth, nasal cavities, throat, or umbilicus
- Lytic toxin (exfoliatin A or B) affects skin at remote sites, leading to desquamation
- Mostly affects young children, especially neonates
- Heals within weeks
Pathogenicity
- Hemolysins - lyse erythrocytes and damage various cell types
- Leukocidin - toxin acts on polymorphonuclear leukocytes and macrophages
- Exfoliatin - plasmid-encoded skin toxin causing wrinkling and peeling of epidermis
- Enterotoxins A, B, and D - exotoxins causing food poisoning (severe diarrhea and vomiting)
- Heat-stable and resistant to boiling
- TSST-1 - superantigen stimulating T-cells to activate macrophages, releasing TNF and causing shock
- Lipases - lipid-hydrolyzing enzymes allowing invasion of tissues
- Fibrolysin - dissolves fibrin clots, enabling spread
- Extracellular coagulase - may be involved in forming fibrin wall of abscess
Panton-Valentine Leukocidin (PVL)
- Produced by strains carrying lukF and lukS genes on a phage
- Associated with community-acquired infections in the young and healthy
- Acts with other leukocidins to lyse host cell membranes, leading to invasive soft tissue infections
Food Poisoning
- Caused by ingestion of preformed toxin from contaminated food
- Toxin is heat-stable and resistant to boiling
- Onset and recovery occur within a few hours
- Inhibits water absorption, leading to explosive diarrhea
- Not a human infection, but a toxin-mediated illness
Staphylococcus aureus Treatment and Resistance
- Produces penicillinase (β-lactamases)
- Usually sensitive to synthetic penicillins (e.g., oxacillin, methicillin)
- Methicillin-resistant S. aureus (MRSA) strains produce altered penicillin-binding proteins and penicillinase
- MRSA strains are resistant to multiple antibiotics, but can be treated with vancomycin
- Community-acquired MRSA (C-MRSA) strains are becoming increasingly prevalent
Staphylococcus epidermidis
- Non-hemolytic, coagulase-negative staphylococcus
- Major component of skin flora, also found in gut and respiratory tract
- Opportunistic infections, less common than S. aureus
- Major cause of nosocomial infections (e.g., catheters, shunts, and prosthetic heart valves)
Gram-Positive Bacteria
- Firmicutes (Low GC) and Actinobacteria (High GC) are two categories of gram-positive bacteria
- Non-spore forming bacteria include Lactic Acid Bacteria (Streptococcus, Lactobacillus, etc.), Nocardia, Corynebacteria, Mycobacteria, and Mycoplasma
- Spore-forming bacteria include Clostridium and Bacillus
Staphylococcus
- Gram-positive, non-motile cocci (>30 species)
- Facultative anaerobes capable of fermentation and respiration
- Ferment sugars with lactic acid as a major product
- G + C content (30-40%) similar to Lactic Acid Bacteria
- Less restrictive growth requirements
- Grape-like clusters of cocci (Staphyle - Greek for "bunch of grapes")
Staphylococcus aureus
- Catalase positive (distinguishes from Streptococcus)
- Coagulase positive (distinguishes from S. epidermidis and Micrococcus)
- Causes plasma to clot by converting fibrinogen to fibrin
- Beta-hemolysis on blood agar
- Part of normal flora - skin and nose
- Causes pneumonia and septicemia in newborns and immunocompromised patients
- Causes skin infections, impetigo, furuncles, and carbuncles
- Causes septic arthritis, osteomyelitis, and endocarditis
Staphylococcal Infections
- Scalded Skin Syndrome (SSSS) - toxin produced by phage group 2 S. aureus
- Initial infection in mouth, nasal cavities, throat, or umbilicus
- Lytic toxin (exfoliatin A or B) affects skin at remote sites, leading to desquamation
- Mostly affects young children, especially neonates
- Heals within weeks
Pathogenicity
- Hemolysins - lyse erythrocytes and damage various cell types
- Leukocidin - toxin acts on polymorphonuclear leukocytes and macrophages
- Exfoliatin - plasmid-encoded skin toxin causing wrinkling and peeling of epidermis
- Enterotoxins A, B, and D - exotoxins causing food poisoning (severe diarrhea and vomiting)
- Heat-stable and resistant to boiling
- TSST-1 - superantigen stimulating T-cells to activate macrophages, releasing TNF and causing shock
- Lipases - lipid-hydrolyzing enzymes allowing invasion of tissues
- Fibrolysin - dissolves fibrin clots, enabling spread
- Extracellular coagulase - may be involved in forming fibrin wall of abscess
Panton-Valentine Leukocidin (PVL)
- Produced by strains carrying lukF and lukS genes on a phage
- Associated with community-acquired infections in the young and healthy
- Acts with other leukocidins to lyse host cell membranes, leading to invasive soft tissue infections
Food Poisoning
- Caused by ingestion of preformed toxin from contaminated food
- Toxin is heat-stable and resistant to boiling
- Onset and recovery occur within a few hours
- Inhibits water absorption, leading to explosive diarrhea
- Not a human infection, but a toxin-mediated illness
Staphylococcus aureus Treatment and Resistance
- Produces penicillinase (β-lactamases)
- Usually sensitive to synthetic penicillins (e.g., oxacillin, methicillin)
- Methicillin-resistant S. aureus (MRSA) strains produce altered penicillin-binding proteins and penicillinase
- MRSA strains are resistant to multiple antibiotics, but can be treated with vancomycin
- Community-acquired MRSA (C-MRSA) strains are becoming increasingly prevalent
Staphylococcus epidermidis
- Non-hemolytic, coagulase-negative staphylococcus
- Major component of skin flora, also found in gut and respiratory tract
- Opportunistic infections, less common than S. aureus
- Major cause of nosocomial infections (e.g., catheters, shunts, and prosthetic heart valves)
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