Antimicrobial Therapy Overview
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Questions and Answers

What is the primary characteristic that qualifies a compound as an antibiotic?

  • It can be lab-made.
  • It can harm human cells.
  • It is produced by microorganisms. (correct)
  • It can inhibit viral replication.

    • Why is selective toxicity important in antimicrobial therapy?

  • It eliminates all types of microorganisms equally.
  • It allows targeting of microbes without harming the host's cells. (correct)
  • It ensures that drugs are more affordable.
  • It increases the broad-spectrum activity of drugs.

    • Which of the following drugs disrupts bacterial cell wall synthesis?

  • Aminoglycosides
  • Fluoroquinolones
  • Penicillin (correct)
  • Sulfonamides

    • What is the role of sulfonamides in antimicrobial therapy?

    <p>They inhibit an enzyme critical for bacterial survival.</p> Signup and view all the answers

    What distinguishes narrow-spectrum antibiotics from broad-spectrum antibiotics?

    <p>Narrow-spectrum antibiotics target specific types of bacteria.</p> Signup and view all the answers

    Which statement is true regarding protein synthesis in bacterial versus mammalian cells?

    <p>Antibiotics can selectively disrupt bacterial protein synthesis.</p> Signup and view all the answers

    Which of the following describes a broad-spectrum antibiotic?

    <p>Effective against both Gram-positive and Gram-negative bacteria.</p> Signup and view all the answers

    Which antimicrobial category includes drugs like acyclovir and interferon-alpha?

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

    What is a characteristic effect of bacterial lysis caused by antibiotics?

    <p>Cell wall disruption leads to osmotic imbalance.</p> Signup and view all the answers

    What distinguishes the activity of aminoglycosides from that of penicillin?

    <p>Aminoglycosides inhibit protein synthesis, while penicillin does not.</p> Signup and view all the answers

    What is a reason for using antibiotic combinations in treating severe infections?

    <p>To provide wide antimicrobial coverage while awaiting identification</p> Signup and view all the answers

    In which situation is the combination of antibiotics most beneficial?

    <p>In a neutropenic host with unknown etiology</p> Signup and view all the answers

    What is one potential benefit of combining antibiotics?

    <p>Enhanced antibacterial action than what one drug can achieve alone</p> Signup and view all the answers

    How does antibiotic combination therapy help in the prevention of drug resistance?

    <p>By suppressing the emergence of resistant bacteria through varied mechanisms</p> Signup and view all the answers

    What is the disadvantage of using a bacteriostatic drug like tetracycline with a bactericidal drug like penicillin?

    <p>They may result in suboptimal effectiveness when combined</p> Signup and view all the answers

    Why is the compatibility of infectious microbes important in treatment?

    <p>To administer treatment suitable for mixed infections</p> Signup and view all the answers

    Which combination example reduces toxicity in treatment?

    <p>Flucytosine with amphotericin B</p> Signup and view all the answers

    What is a key consideration when using antibiotics in treatments for TB?

    <p>Combination therapies are crucial to prevent drug resistance</p> Signup and view all the answers

    Which mechanism allows bacteria to resist the effects of certain antibiotics by altering their target molecules?

    <p>Alteration of drug target molecules</p> Signup and view all the answers

    What does the NDM-1 gene primarily confer resistance against?

    <p>All β-lactam antibiotics</p> Signup and view all the answers

    How is spontaneous mutation in bacteria best described in terms of drug resistance?

    <p>It randomly changes the bacterium's DNA, conferring resistance to a single drug.</p> Signup and view all the answers

    Which type of antibiotic is most likely to promote bacterial resistance due to its broad-spectrum activity?

    <p>Broad-spectrum antibiotics</p> Signup and view all the answers

    What is a significant consequence of antibiotic-induced alteration of normal flora?

    <p>It reduces overall bacterial diversity.</p> Signup and view all the answers

    What is an example of an antagonistic compound produced by microbes that can lead to drug resistance?

    <p>Increased PABA</p> Signup and view all the answers

    How does conjugation contribute to antibiotic resistance in bacteria?

    <p>It facilitates the transfer of resistance genes between bacteria.</p> Signup and view all the answers

    What is the primary risk associated with superinfections during antibiotic therapy?

    <p>They arise from the inhibition of normal flora, allowing new infections to take hold.</p> Signup and view all the answers

    Which of the following statement correctly describes the relationship between antibiotics and drug resistance?

    <p>Antibiotics create conditions that allow resistant microbes to thrive.</p> Signup and view all the answers

    What role does the NDM-1 gene play in bacterial resistance?

    <p>It produces an enzyme that inactivates β-lactam antibiotics.</p> Signup and view all the answers

    What causes Methicillin-resistant Staphylococcus aureus (MRSA) to be resistant to antibiotics?

    <p>Altered penicillin-binding proteins</p> Signup and view all the answers

    What is the primary treatment for healthcare-associated MRSA (HCA-MRSA) infections?

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

    How are the properties of individual penicillins determined?

    <p>By alterations to the common nucleus</p> Signup and view all the answers

    What type of infections do community-associated MRSA (CA-MRSA) primarily cause?

    <p>Mild infections of skin and soft tissues</p> Signup and view all the answers

    What is a key characteristic of the beta-lactam ring in penicillins?

    <p>It is essential for the antibacterial actions of penicillins.</p> Signup and view all the answers

    Which of the following is an example of a penicillinase-resistant narrow spectrum penicillin?

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

    What is a common method of transmission for community-associated MRSA (CA-MRSA) infections?

    <p>Direct contact with infected surfaces</p> Signup and view all the answers

    What percentage of Staphylococcus aureus strains are currently resistant to penicillin?

    <p>80%</p> Signup and view all the answers

    What is the consequence of administering a dosage of antibiotics that is too low?

    <p>Increased risk of adverse effects without therapeutic benefit</p> Signup and view all the answers

    What role does surgical drainage play in antimicrobial therapy?

    <p>It promotes antimicrobial effects by cleansing tissue and exudate</p> Signup and view all the answers

    Why are penicillin and other beta-lactams considered bactericidal?

    <p>They destroy the cell wall leading to bacterial lysis during growth</p> Signup and view all the answers

    Which of the following actions does penicillin NOT perform to weaken the bacterial cell wall?

    <p>Production of penicillin-binding proteins</p> Signup and view all the answers

    What is one mechanism of bacterial resistance to penicillin?

    <p>Production of penicillin-binding proteins with low affinity for penicillin</p> Signup and view all the answers

    How does the structure of the gram-negative bacterial cell envelope contribute to penicillin's efficacy?

    <p>It comprises three layers which makes it more resistant to penicillin</p> Signup and view all the answers

    What is a primary adverse effect associated with beta-lactam antibiotics, particularly penicillins?

    <p>Allergic reactions</p> Signup and view all the answers

    What is the role of penicillinases in bacterial resistance?

    <p>They cleave the beta-lactam ring structure of penicillin</p> Signup and view all the answers

    Why are penicillins generally considered safe for humans?

    <p>Humans do not possess bacterial cell walls</p> Signup and view all the answers

    What is a common outcome when monitoring antimicrobial therapy effectiveness?

    <p>Resolution of signs such as fever and improvement of breath sounds</p> Signup and view all the answers

    Study Notes

    Antimicrobial Therapy

    • Antibiotics are chemicals produced by microbes that can harm other microbes.
    • Antimicrobials are any agents, natural or synthetic, that can suppress or kill microbes.
    • Selective Toxicity: The ability of a drug to target specific microbial cells without harming other cells.
    • Achieving Selective Toxicity:
      • Targeting microbial processes that don't occur in mammals, such as disruption of the bacterial cell wall.
      • Inhibiting bacterial enzymes unique to bacteria, like sulfonamides that inhibit folic acid synthesis.
      • Disrupting bacterial protein synthesis through differences in bacterial ribosomes.
    • Antibiotic Classification:
      • Broad Spectrum: Effective against a wide range of bacteria.
      • Narrow Spectrum: Effective against a limited range of bacteria.
      • Antibacterial Drugs: Treat bacterial infections.
        • Narrow Spectrum Examples: Penicillin G, Vancomycin, Erythromycin, Clindamycin, Aminoglycosides, Isoniazid, Rifampin, Ethambutol, Pyrazinamide
        • Broad Spectrum Examples: Ampicillin, Cephalosporins (3rd Generation), Trimethoprim, Carbapenems, Sulfonamides, Fluoroquinolones
      • Antiviral Drugs: Treat viral infections.
        • HIV Examples: Reverse Transcriptase Inhibitors, Protease Inhibitors, Fusion Inhibitors, Integrase Inhibitors, CCR5 Antagonists
        • Flu Examples: Adamantanes, Neuraminidase Inhibitors
        • Other Examples: Acyclovir, Ribavirin, Interferon-alpha
      • Antifungal Drugs: Treat fungal infections.
        • Examples: Polyene Antibiotics, Azoles, Echinocandins (Caspofungin)

    Mechanisms of Antibiotic Resistance

    • Inability to reach the target: The drug cannot enter the cell or reach the Target (e.g., gram-negative bacteria, where the outer membrane prevents entry).
    • Drug Inactivation: Bacteria produce enzymes that inactivate the drug (e.g., beta-lactamases that degrade penicillin).
    • Alteration of Drug Target Molecules: Mutations in the bacterial target molecule (e.g., ribosomes) prevent drug binding.
    • Antagonist Production: Bacteria produce compounds that interfere with the drug's action.
    • Drug Efflux Pumps: Bacterial pumps actively remove the drug from the cell.

    Acquisition of Resistance

    • Spontaneous Mutation: Random changes in the bacterial DNA, conferring resistance to a specific drug.
    • Conjugation: Transfer of extrachromosomal DNA (plasmids) containing resistance genes from one bacterium to another, often between different species. This can lead to multidrug resistance (MDR).
    • Increased Antibiotic use: Promotes the selection of drug-resistant bacteria.
      • Broad-spectrum antibiotics eliminate more competitors, potentially leading to increased resistance.
      • Antibiotic use increases the chance of resistance in both pathogens and normal flora, which can then transfer resistance to pathogens.
      • Hospital-acquired infections (HAIs) are often highly resistant.

    Superinfection

    • New infection that arises during treatment of a primary infection, often caused by the suppression of normal flora.
    • Example: Trimethoprim-sulfamethoxazole can cause superinfection by disturbing the balance of bacteria in the gut.

    Indications for Combination Therapy

    • Severe Infection: Where the cause is unknown, a combination of drugs with a broad spectrum provides initial coverage.
    • Mixed Infections: When multiple organisms with different drug susceptibilities are involved.
    • Preventing Resistance: Combination therapy can prevent the development of resistance, particularly in treating tuberculosis.
    • Decreased Toxicity: Combining drugs can reduce the toxicity of individual drugs.
    • Enhanced Antibacterial Action: Some drugs act synergistically, leading to greater potency when combined.

    Monitoring Antimicrobial Therapy

    • Clinical Outcomes: Monitor patient signs and symptoms (e.g., fever, respiratory improvement)
    • Laboratory Tests: Monitor the growth of bacteria in cultures.
    • Serum Drug Levels: Monitor to ensure adequate dosage and avoid toxicity.

    Penicillin: A Cell Wall Weakening Drug

    • Penicillins belong to the beta-lactam family, containing a beta-lactam ring.
    • They weaken the bacterial cell wall, leading to cell lysis and death.
    • Their primary adverse effect is allergic reactions.
    • Mechanism of Action:
      • Inhibits transpeptidases: Enzymes involved in cell wall synthesis.
      • Activates autolysins: Enzymes that break down the cell wall.
      • Targets penicillin-binding proteins (PBPs): Binding to PBPs on the bacterial cell membrane disrupts cell wall synthesis.
      • Bactericidal: Works against actively dividing bacteria.

    Mechanisms of Penicillin Resistance

    • Inhibition of Penicillin Reach to the Target: Some bacteria have outer membrane barriers that prevent penicillin from reaching the PBPs.
    • Beta-lactamases: Enzymes that break the beta-lactam ring, rendering penicillin inactive.
    • Altered Penicillin Binding Proteins (PBPs): Some bacteria have PBPs with low affinity for penicillin, making them resistant.
    • Methicillin-Resistant Staphylococcus aureus (MRSA): Resistant due to low affinity PBPs.

    Penicillin Chemistry

    • All penicillins are derived from the common nucleus 6-aminopenicillanic acid.
    • The beta-lactam ring is essential for antibacterial activity.
    • Modifications to the nucleus result in different properties:
      • Affinity for PBPs.
      • Resistance to beta-lactamases
      • Ability to penetrate gram-negative membranes.
      • Resistance to stomach acid.
      • Pharmacokinetic properties.

    Penicillin Classification

    • Narrow Spectrum Penicillin: Penicillinase-sensitive: (Penicillin G, V) Effective against Streptococcus spp., Neisseria, Anaerobes.
    • Narrow Spectrum Penicillin: Penicillinase-resistant: (Dicloxacillin, Nafcillin) Effective against Staphylococcus spp.

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    Week 7 Basic Principles of Antimicrobial Therapy 2024 PDF

    Description

    This quiz explores antimicrobial therapy, focusing on antibiotics and antimicrobials. It highlights the concept of selective toxicity and the classification of antibiotics based on their spectrum of activity. Test your knowledge on how these agents work and the differences between broad and narrow-spectrum antibiotics.

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