Microbiology: Gram Positive Bacteria
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Questions and Answers

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?

  • 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?

  • 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?

    <p>Skin and nose</p> Signup and view all the answers

    What is the mechanism of action of coagulase in Staphylococcus aureus?

    <p>It converts fibrinogen to fibrin</p> Signup and view all the answers

    What is the disease caused by Staphylococcus aureus in immunocompromised patients?

    <p>All of the above</p> Signup and view all the answers

    What is the characteristic arrangement of Staphylococcus aureus cells?

    <p>Grape-like clusters</p> Signup and view all the answers

    What is the percentage of G+C content in Staphylococcus aureus?

    <p>30-40%</p> Signup and view all the answers

    What is the primary mechanism by which Staphylococcus aureus invades subcutaneous tissue?

    <p>With the aid of lipases</p> Signup and view all the answers

    What is the typical source of Staphylococcus aureus in hospital-acquired infections?

    <p>Patients</p> Signup and view all the answers

    What is the purpose of the fibrin barrier in Staphylococcus aureus infections?

    <p>To trap white blood cells</p> Signup and view all the answers

    What is the primary cause of scalded skin syndrome?

    <p>A toxin produced by phage group 2 Staphylococcus aureus</p> Signup and view all the answers

    What is the typical age range of individuals affected by scalded skin syndrome?

    <p>Young children and neonates</p> Signup and view all the answers

    What is the primary route of bacterial entry in hematogenous osteomyelitis?

    <p>Through the bloodstream</p> Signup and view all the answers

    What is the typical outcome of scalded skin syndrome?

    <p>Healing within a few weeks</p> Signup and view all the answers

    What is the primary role of coagulase in Staphylococcus aureus infections?

    <p>To form a fibrin barrier</p> Signup and view all the answers

    What is the role of lipases in the invasion of subcutaneous tissue?

    <p>To aid the organism in invading subcutaneous tissue</p> Signup and view all the answers

    What is the result of the toxins released by the organism in the subcutaneous tissue?

    <p>Killing of cells and production of pus</p> Signup and view all the answers

    What is the role of coagulase in the formation of abscesses?

    <p>It forms a fibrin wall around the abscess</p> Signup and view all the answers

    What is the effect of exfoliatin on the skin?

    <p>It produces wrinkling and peeling of the epidermis</p> Signup and view all the answers

    What is the role of leukocidin in the pathogenesis of the disease?

    <p>It acts on polymorphonuclear leukocytes and macrophages</p> Signup and view all the answers

    What is the effect of TSST-1 on the host?

    <p>It stimulates T-cells to activate macrophages</p> Signup and view all the answers

    What is the role of fibrolysin in the invasion of tissues?

    <p>It dissolves fibrin clots</p> Signup and view all the answers

    What is the characteristic of Panton-Valentine leukocidin?

    <p>It is produced by strains carrying the lukF and lukS genes on a phage</p> Signup and view all the answers

    What is the function of fibrolysin in Staphylococcus aureus?

    <p>To dissolve fibrin clots</p> Signup and view all the answers

    What is the characteristic of enterotoxins A, B, and D?

    <p>They are exotoxins that cause severe diarrhoea and vomiting</p> Signup and view all the answers

    What is the mechanism of action of TSST-1?

    <p>It stimulates T-cells to release TNF, leading to shock</p> Signup and view all the answers

    Why are many MRSA strains resistant to multiple antibiotics?

    <p>Due to production of altered penicillin-binding proteins and penicillinase</p> Signup and view all the answers

    What is the function of hemolysins in Staphylococcus aureus?

    <p>To lyse erythrocytes</p> Signup and view all the answers

    What is the current treatment for MRSA infections?

    <p>Vancomycin</p> Signup and view all the answers

    What is the function of leukocidin in Staphylococcus aureus?

    <p>To act on polymorphonuclear leukocytes and macrophages</p> Signup and view all the answers

    Why are Staphylococcus aureus infections difficult to treat?

    <p>Due to the production of altered penicillin-binding proteins and penicillinase</p> Signup and view all the answers

    What is the primary concern associated with the isolation of a VRSA strain from a dialysis patient with a foot ulcer in Detroit?

    <p>The transfer of resistance genes from E. faecalis to other bacteria</p> Signup and view all the answers

    What is a common characteristic of individuals who have acquired C-MRSA?

    <p>Engagement in high-risk activities such as injecting drug use</p> Signup and view all the answers

    What is the primary difference between Staphylococcus aureus and Staphylococcus epidermidis?

    <p>The production of coagulase</p> Signup and view all the answers

    What is the most common source of Staphylococcus epidermidis infections?

    <p>Contaminated medical devices such as catheters and prosthetic heart valves</p> Signup and view all the answers

    What is the primary concern associated with the spread of C-MRSA?

    <p>The potential for C-MRSA to spread in the community through high-risk activities</p> Signup and view all the answers

    What is the significance of the VRSA strain isolated from a dialysis patient with a foot ulcer in Detroit?

    <p>It is a warning sign for the potential transfer of resistance genes to other bacteria</p> Signup and view all the answers

    Staphylococcus aureus can cause pneumonia and septicaemia in immunocompromised patients.

    <p>True</p> Signup and view all the answers

    Impetigo is a skin infection caused by Staphylococcus aureus.

    <p>True</p> Signup and view all the answers

    All Staphylococcus aureus strains are coagulase positive.

    <p>False</p> Signup and view all the answers

    Osteomyelitis is a type of skin infection caused by Staphylococcus aureus.

    <p>False</p> Signup and view all the answers

    Scalded skin syndrome is a toxin-mediated disease caused by Staphylococcus aureus.

    <p>True</p> Signup and view all the answers

    Lactic acid is a byproduct of sugar fermentation in Staphylococcus aureus.

    <p>True</p> Signup and view all the answers

    Staphylococcus aureus can cause septic arthritis in older individuals.

    <p>True</p> Signup and view all the answers

    Staphylococcus aureus is a gram-negative bacterium.

    <p>False</p> Signup and view all the answers

    Streptomyces is a type of gram-positive, non-spore forming bacteria.

    <p>False</p> Signup and view all the answers

    Coagulase is produced by all strains of Staphylococcus aureus.

    <p>False</p> Signup and view all the answers

    Staphylococcus aureus can be transmitted by hospital personnel.

    <p>True</p> Signup and view all the answers

    Mycoplasma is a type of gram-positive, non-spore forming bacteria.

    <p>True</p> Signup and view all the answers

    Lipases are not involved in the invasion of subcutaneous tissue by Staphylococcus aureus.

    <p>False</p> Signup and view all the answers

    All Corynebacteria are gram-negative bacteria.

    <p>False</p> Signup and view all the answers

    Staphylococcus aureus is typically found in the nose and skin of healthy individuals.

    <p>True</p> Signup and view all the answers

    Staphylococcus aureus causes pneumonia and septicaemia in immunocompromised patients.

    <p>True</p> Signup and view all the answers

    Lipases aid in the invasion of subcutaneous tissue by Staphylococcus aureus.

    <p>True</p> Signup and view all the answers

    Coagulase is involved in the formation of a fibrin barrier during Staphylococcus aureus infections.

    <p>True</p> Signup and view all the answers

    Panton-Valentine leukocidin is produced by all strains of Staphylococcus aureus.

    <p>False</p> Signup and view all the answers

    Enterotoxins A, B, and D are heat-labile.

    <p>False</p> Signup and view all the answers

    TSST-1 is a type of hemolysin.

    <p>False</p> Signup and view all the answers

    Fibrolysin is involved in the formation of a fibrin barrier during Staphylococcus aureus infections.

    <p>False</p> Signup and view all the answers

    Exfoliatin is a type of leukocidin.

    <p>False</p> Signup and view all the answers

    Staphylococcus aureus infections are typically acquired through skin lesions.

    <p>True</p> Signup and view all the answers

    Leukocidin is a toxin that damages only erythrocytes.

    <p>False</p> Signup and view all the answers

    Exfoliatin is a plasmid-encoded toxin that produces a strong immune response.

    <p>False</p> Signup and view all the answers

    TSST-1 is a heat-labile toxin that causes severe diarrhoea and vomiting.

    <p>False</p> Signup and view all the answers

    Methicillin-resistant Staphylococcus aureus (MRSA) is typically sensitive to penicillin.

    <p>False</p> Signup and view all the answers

    Vancomycin is a beta-lactam antibiotic that is effective against MRSA.

    <p>False</p> Signup and view all the answers

    Staphylococcus aureus is typically found in the environment and not on human skin.

    <p>False</p> Signup and view all the answers

    Food poisoning caused by Staphylococcus aureus is usually treated with antibiotics.

    <p>False</p> Signup and view all the answers

    Hemolysins are toxins that only damage macrophages.

    <p>False</p> Signup and view all the answers

    The patient from Detroit who was infected with VRSA had not been recently hospitalized.

    <p>True</p> Signup and view all the answers

    Coagulase-negative Staphylococcus epidermidis is a major component of skin flora.

    <p>True</p> Signup and view all the answers

    C-MRSA is typically seen in people who have been recently hospitalized.

    <p>False</p> Signup and view all the answers

    Staphylococcus epidermidis is a common cause of opportunistic infections.

    <p>True</p> Signup and view all the answers

    The VRSA strain isolated from the patient in Detroit acquired resistance genes from a vancomycin-resistant E. coli strain.

    <p>False</p> Signup and view all the answers

    Most cases of C-MRSA in the UK have been seen in injecting drug users.

    <p>True</p> Signup and view all the answers

    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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    Lecture 2 Staphylococcus 2023 PDF

    Description

    Quiz covering the different types of gram positive bacteria, including Staphylococcus, Streptococcus, and Lactobacillus. Topics include Firmicutes, Actinobacteria, and Bacillus.

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