Nosocomial Infections Quiz
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Questions and Answers

What is the primary mechanism by which methicillin-resistant Staphylococcus aureus (MRSA) strains exhibit resistance to beta-lactam antibiotics?

  • Prevention of antibiotic entry into the bacterial cell by altering cell membrane permeability.
  • Modification of the antibiotic target site, involving the PBP2a protein. (correct)
  • Enzymatic inactivation of beta-lactam antibiotics through beta-lactamase production.
  • Active efflux of beta-lactam antibiotics from the bacterial cell.

    • Which structural component of the bacterial cell wall is the target of both beta-lactam and glycopeptide antibiotics like vancomycin?

  • Mycolic acid
  • Peptidoglycan (correct)
  • Lipopolysaccharide
  • Teichoic acid

    • What modification in the peptidoglycan precursor is characteristic of Vancomycin-Resistant Staphylococcus aureus (VRSA) strains?

  • Replacement of D-Alanine with D-Lactate in the D-Ala-D-Ala peptide. (correct)
  • Substitution of D-Alanine with L-Alanine in the D-Ala-D-Ala peptide.
  • Insertion of an additional Alanine residue in the D-Ala-D-Ala peptide.
  • Deletion of both Alanine residues from the D-Ala-D-Ala peptide sequence.

    • What mobile genetic element is responsible for introducing mecA gene into Staphylococcus aureus, leading to methicillin resistance?

    <p>SCCmec (C)</p> Signup and view all the answers

    Which of the following best describes the trend in Staphylococcus aureus antibiotic resistance over time, as described in the text?

    <p>An initial resistance to beta-lactams, followed by resistance to beta-lactam resistant drugs and then to glycopeptides like vancomycin. (D)</p> Signup and view all the answers

    In addition to target modification and enzymatic inactivation, what is another mechanism employed by Staphylococcus aureus to resist antibiotics, exemplified by fluoroquinolone resistance?

    <p>Active efflux (D)</p> Signup and view all the answers

    What is a common initial treatment option for infections caused by methicillin-sensitive Staphylococcus aureus (MSSA) strains?

    <p>Oxacillin (D)</p> Signup and view all the answers

    What is a significant consequence of the increasing prevalence of highly drug-resistant Staphylococcus aureus strains like VRSA and VISA?

    <p>Increased challenges in effectively treating <em>S. aureus</em> infections and limited treatment options. (D)</p> Signup and view all the answers

    What are nosocomial infections also known as?

    <p>Hospital-acquired infections (HAI) (A)</p> Signup and view all the answers

    Approximately how many patients acquire infections after care within the NHS in England each year?

    <p>300,000 (B)</p> Signup and view all the answers

    What is the approximate annual cost burden of HAIs to the NHS?

    <p>£1 billion (A)</p> Signup and view all the answers

    In developing countries, what proportion of hospitalized patients acquire at least one HAI?

    <p>1 in 10 (C)</p> Signup and view all the answers

    What characteristic distinguishes Staphylococcus aureus from other pathogenic staphylococci?

    <p>Its production of coagulase (A)</p> Signup and view all the answers

    Where is Staphylococcus aureus commonly found in carriers?

    <p>In the nares and on the skin (C)</p> Signup and view all the answers

    When does Staphylococcus aureus typically cause an infection?

    <p>When the skin barrier is breached (D)</p> Signup and view all the answers

    What is one of the first steps in a Staphylococcus aureus infection?

    <p>Adhesion to the host epithelium (C)</p> Signup and view all the answers

    What is the primary role of adhesins like Fnbp and clumping factor A in Staphylococcus aureus pathogenesis?

    <p>Mediating the attachment of bacteria to host cell surfaces. (C)</p> Signup and view all the answers

    Which of the following accurately describes the sequence of events following a breach in the epithelial layer during a Staphylococcus aureus infection?

    <p>Tissue invasion, recruitment of macrophages and neutrophils, and subsequent abscess formation. (C)</p> Signup and view all the answers

    Neutrophils utilize various mechanisms to combat Staphylococcus aureus infections. Which of the following is a mechanism employed by neutrophils?

    <p>Production of reactive oxygen species (ROS) to induce oxidative damage. (D)</p> Signup and view all the answers

    What is a defining characteristic of Staphylococcus aureus biofilms that contributes to the difficulty in treating these infections?

    <p>Limited penetration of antibiotics through the extracellular matrix of the biofilm. (C)</p> Signup and view all the answers

    Staphylococcus aureus is described as a facultatively intracellular pathogen. What does this characteristic imply about its survival strategy?

    <p>It has the ability to survive and replicate both inside and outside of host cells. (C)</p> Signup and view all the answers

    Which of the following factors makes intracellular Staphylococcus aureus infections challenging to treat with antibiotics?

    <p>Limited antibiotic penetration into host cells to reach intracellular bacteria. (C)</p> Signup and view all the answers

    Among the infections listed, which is specifically mentioned as being associated with Staphylococcus aureus infection of the heart valves?

    <p>Infectious endocarditis (B)</p> Signup and view all the answers

    Why is Staphylococcus aureus infection considered a significant financial burden on healthcare systems worldwide?

    <p>As a result of its ability to cause a wide range of infections and increasing antibiotic resistance. (C)</p> Signup and view all the answers

    Which of the following components of S. aureus facilitates its attachment to host cells?

    <p>Adhesins (C)</p> Signup and view all the answers

    S. aureus can only survive outside of host cells.

    <p>False (B)</p> Signup and view all the answers

    What type of infection can S. aureus cause in the heart valves?

    <p>Infectious endocarditis</p> Signup and view all the answers

    S. aureus can penetrate deeper tissues when there's a breach in the ______ layer.

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

    Match the infection with the affected body part:

    <p>Osteomyelitis = Bone and joint Skin and soft tissues infections (SSTI) = Skin Pneumonia = Lungs Bacteremia = Blood</p> Signup and view all the answers

    What is a major challenge in treating S.aureus biofilm infections?

    <p>Poor antibiotic penetration into biofilms (B)</p> Signup and view all the answers

    Neutrophils use reactive oxygen species (ROS) to kill S.aureus.

    <p>True (A)</p> Signup and view all the answers

    What medical term is used for the presence of bacteria in the blood?

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

    Staphylococcus aureus is an obligate anaerobe.

    <p>False (B)</p> Signup and view all the answers

    What characteristic pigment gives Staphylococcus aureus its species name 'aureus'?

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

    Staphylococcus aureus is part of the human microbiota and can be found in the ______ and on the skin.

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

    Match the infection type with its place of origin:

    <p>Nosocomial infection = Hospital Community acquired infection = Community HAI = Healthcare Facility</p> Signup and view all the answers

    What enzyme does S. aureus produce that differentiates it from other staphylococci?

    <p>Coagulase (B)</p> Signup and view all the answers

    What is the estimated annual cost of HAIs to the NHS in England?

    <p>£1 billion</p> Signup and view all the answers

    HAIs are only caused by bacterial pathogens.

    <p>False (B)</p> Signup and view all the answers

    Which antibiotic is used to treat MRSA infections?

    <p>Vancomycin (A)</p> Signup and view all the answers

    VRSA strains are completely resistant to vancomycin.

    <p>True (A)</p> Signup and view all the answers

    What gene is responsible for encoding PBP2a, the protein that confers resistance to beta-lactam antibiotics in MRSA?

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

    Beta-lactam antibiotics target ______ binding proteins (PBPs) involved in bacterial cell wall synthesis.

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

    Match the S. aureus strain with its resistance profile:

    <p>MSSA = Sensitive to methicillin MRSA = Resistant to methicillin VRSA = Resistant to vancomycin VISA = Intermediate resistance to vancomycin</p> Signup and view all the answers

    What percentage of MRSA bacteraemia cases in the UK (2018-2019) resulted 30-day mortality?

    <p>~26% (D)</p> Signup and view all the answers

    S. aureus infections are becoming easier to treat due to new antibiotics.

    <p>False (B)</p> Signup and view all the answers

    Besides target modification and enzymatic drug inactivation, name one other mechanism of antibiotic resistance commonly employed by S. aureus.

    <p>Active drug efflux</p> Signup and view all the answers

    Flashcards

    Adhesins

    Proteins aiding bacterial attachment to host cells.

    S. aureus invasion

    Penetration of S. aureus when epithelial barriers are breached.

    Neutrophils

    Immune cells that phagocytose bacteria to kill them.

    Biofilm

    Bacterial communities bound by an extracellular matrix.

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    Intracellular survival

    Ability of S. aureus to live within host cells.

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    Healthcare-associated infections

    Infections caused by pathogens like S. aureus in medical settings.

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    Common S. aureus infections

    Includes skin infections, pneumonia, and endocarditis.

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    Antibiotic resistance

    S. aureus's ability to resist multiple antibiotics.

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    Nosocomial Infections

    Infections originating in a hospital or healthcare facility.

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    Community Acquired Infections

    Infections contracted outside of a hospital, in the community.

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    Impact of HAIs in England

    300,000 patients a year acquire infections, costing £1 billion to the NHS.

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    Risk Factors for HAIs

    Associated with medical devices or surgical wounds.

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    Staphylococcus aureus

    A Gram-positive coccus seen in grape-like clusters, causes HAIs.

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    Coagulase Positive

    S.aureus produces coagulase, differentiating it from coagulase-negative staphylococci.

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    Facultative Anaerobe

    S.aureus can survive with or without oxygen.

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    Infection Processes of S.aureus

    Key processes include adhesion, tissue invasion, and biofilm formation.

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    Beta-lactamases

    Enzymes produced by bacteria that inactivate beta-lactam antibiotics like penicillin.

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    MRSA

    Methicillin-resistant Staphylococcus aureus, a strain of bacteria resistant to methicillin and related antibiotics.

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    VISA

    Vancomycin intermediate resistant Staphylococcus aureus, strains with reduced sensitivity to vancomycin.

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    VRSA

    Vancomycin resistant Staphylococcus aureus, strains completely resistant to vancomycin.

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    SCCmec

    Mobile genetic element that carries the mecA gene in MRSA, conferring antibiotic resistance.

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    PBP2a

    Variant form of penicillin-binding protein in MRSA that is resistant to beta-lactam antibiotics.

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    D-Ala-D-Ala

    Specific peptides blocked by vancomycin during peptidoglycan synthesis in bacteria.

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    MSSA

    Methicillin-sensitive Staphylococcus aureus strains that react to penicillin derivatives.

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    Fibrinogen binding proteins (Fnbp)

    Adhesins that bind to integrin receptors on host cells.

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    Macrophages

    Immune cells that ingest and destroy pathogens at the infection site.

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    Reactive oxygen species (ROS)

    Molecules produced by neutrophils to destroy bacteria.

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    Abscess formation

    Localized collection of pus due to immune response to infection.

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    Biofilm on medical devices

    Aggregation of bacteria on surfaces, complicating treatment due to resistance.

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    Intracellular replication

    The ability of S. aureus to reproduce inside host cells.

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    Skin and soft tissue infections (SSTI)

    Common infections caused by S. aureus affecting skin or soft tissue.

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    Endocarditis

    Infection of the heart valves caused by S. aureus.

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    HAI Statistics

    300,000 yearly infections in England costing £1 billion.

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    Colonization of S. aureus

    S. aureus lives on skin and nares of up to 30% of people.

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    Infection trigger for S. aureus

    Occurs when skin barrier is breached, allowing invasion.

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    Resistance in S. aureus

    Some strains show high resistance to antibiotics, complicating treatment.

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    Impact of HAIs in developing countries

    1 in 10 hospitalized patients acquire an HAI.

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    Key infection processes of S. aureus

    Include adhesion, invasion, and biofilm formation.

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    Community Associated MRSA (CA-MRSA)

    Strains of MRSA acquired in the community, not in hospitals.

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    Hospital Acquired MRSA (HA-MRSA)

    Strains of MRSA that originate in hospital settings.

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    VISA and VRSA

    Strains of S.aureus resistant to vancomycin, with VISA being intermediate and VRSA being fully resistant.

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    S.aureus resistance mechanisms

    Includes drug target modification, enzymatic inactivation, and active drug efflux.

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    Peptidoglycan

    A key component of the Gram-positive bacterial cell wall made of sugars and amino acids.

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    mecA gene

    Gene in MRSA encoding PBP2a, which is resistant to beta-lactams.

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    Penicillin-binding proteins (PBPs)

    Proteins essential for peptidoglycan synthesis targeted by beta-lactam antibiotics.

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    Study Notes

    Nosocomial Infections (HAIs)

    • Nosocomial infections, also known as healthcare-associated infections (HAIs), are infections acquired in a hospital or healthcare facility after admission. They are distinct from infections present at the time of admission.
    • In England, approximately 300,000 patients acquire healthcare-associated infections annually within the NHS, placing a significant cost burden of about £1 billion per year.
    • In developing countries, one in ten hospitalized patients acquires at least one HAI.
    • HAIs are commonly linked to medical devices or surgical wounds, ranging from catheter-related infections to bloodstream infections from ventilators.

    Types of Bacterial Pathogens

    • HAIs can be caused by various bacterial, viral, and other pathogens.
    • Common antibiotic-resistant bacteria associated with HAIs include Acinetobacter baumannii, ESBL-producing Enterobacteriaceae, Staphylococcus aureus, and Clostridium difficile.

    Staphylococcus aureus (S. aureus)

    • S. aureus is a Gram-positive coccus, appearing in clusters.
    • It is named "aureus" due to its golden pigment.
    • It produces coagulase, an enzyme contributing to blood clotting, and distinguishing it from other staphylococci.
    • S. aureus is a facultative anaerobe—meaning it can survive with or without oxygen.
    • It is a member of the human microbiota, found in the noses and skin of up to 30% of the population. These individuals are carriers of S. aureus.
    • S. aureus can cause various infections due to its ability to produce toxins and enzymes that allow it to colonize and invade tissue. These include lipase, nucleases, and alpha toxin

    S. aureus Adhesion and Invasion

    • S. aureus adheres to host tissue (skin, mucosa) via specific surface proteins, enabling colonization.
    • Invasion into deeper tissues occurs when barriers are breached, allowing S. aureus to penetrate deeper tissue layers.
    • Tissue macrophages and neutrophils respond to infection through processes like phagocytosis and the formation of neutrophil extracellular traps (NETs).

    S. aureus Biofilms

    • S. aureus forms biofilms—aggregates of bacteria bound together by an extracellular matrix—on tissues and medical devices.
    • Biofilm infections are challenging to treat effectively due to antibiotic impermeability.

    Intracellular Survival of S. aureus

    • Some S. aureus strains can survive and multiply inside host cells, particularly immune cells like macrophages.

    S. aureus Infections and Associated Issues

    • S. aureus infections cause a wide variety of illnesses, ranging from minor skin abscesses to life-threatening conditions such as endocarditis.
    • S. aureus strains have developed resistance to various antibiotics, including beta-lactams and vancomycin.
    • Methicillin-resistant Staphylococcus aureus (MRSA) were responsible for 12,878 cases of bacteremia in the UK between 2018 and 2019, with a mortality rate of approximately 26% within 30 days of infection.
    • S. aureus can cause recurrent infections, which are common in prosthetic joint infections and skin and soft tissue infections due to persistence in tissues.

    Treatment and Prevention of S. aureus Infections

    • Treatment of S. aureus infections, particularly resistant strains, is challenging.
    • Treatment strategies depend on the sensitivity of the S. aureus strain to different antibiotics. Common treatment regimens include penicillin derivatives (e.g., oxacillin) for methicillin-sensitive strains and vancomycin for methicillin-resistant strains (MRSA).
    • Hospital infection control measures are crucial, including hand hygiene, general cleanliness, wound care, and use of personal protective equipment.

    Recurrent Infections

    • Recurrence rates of S. aureus infections are high, often attributed to bacteria surviving inside biofilms or cells, leading to persistence and reemergence of infection.
    • Infections are often recurrent due to the bacteria persisting in tissues within biofilms or inside cells.
    • Daptomycin and linezolid are often used to treat S. aureus infections, particularly when dealing with SSTI and MRSA infections.

    Transmission of S. aureus

    • S. aureus can be transmitted endogenously (within the patient) through colonization, or exogenously through person-to-person contact or spread via equipment/surfaces.
    • S. aureus can spread via the environment through skin dust which can be transmitted through skin scales or dust causing exogenous spread.

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    Description

    Test your knowledge about nosocomial infections and their impact on healthcare. This quiz covers the types of bacterial pathogens associated with healthcare-associated infections (HAIs), their prevalence, and the importance of antibiotic resistance. Dive into the details of these infections and challenge yourself!

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