Antimicrobials and Their Mechanisms
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Which class of antimicrobials is primarily time dependent and includes agents such as B-lactam antibiotics?

  • Tetracycline (correct)
  • Aminoglycosides
  • Macrolides
  • Fluoroquinolone

    • What mechanism of action do beta lactams mainly utilize to inhibit bacterial growth?

  • Interference with protein synthesis
  • Disruption of cellular metabolism
  • Inhibition of cell wall peptidoglycan synthesis (correct)
  • Inhibition of nucleic acid synthesis

    • Which of the following is not a beta lactam antibiotic?

  • Monobactam
  • Cephalosporin
  • Penicillin
  • Macrolide (correct)

    • Which of the following is true about aminopenicillins in relation to gastric pH?

    <p>They remain effective despite the gastric pH.</p> Signup and view all the answers

    Which of the following agents is categorized as bactericidal and concentration dependent?

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

    What is the primary mechanism by which beta-lactam antibiotics exhibit their antibacterial effect?

    <p>Inhibiting cell wall synthesis</p> Signup and view all the answers

    Which statement accurately describes beta-lactamase inhibitors like clavulanic acid?

    <p>They mainly assist in overcoming resistance from bacteria producing specific beta-lactamases.</p> Signup and view all the answers

    Which of the following statements about aminoglycosides is correct?

    <p>Aminoglycosides, in particular gentamicin, are ineffective against intracellular pathogens.</p> Signup and view all the answers

    What is the primary route of elimination for beta-lactam antibiotics?

    <p>Renal excretion as unchanged drug</p> Signup and view all the answers

    Which of the following combinations is known to be synergistic when used together?

    <p>Cell wall synthesis inhibitor and gentamicin</p> Signup and view all the answers

    What is the primary reason mycoplasma exhibits intrinsic resistance?

    <p>It lacks a cell wall.</p> Signup and view all the answers

    Which generation of cephalosporins includes cefazolin?

    <p>First generation</p> Signup and view all the answers

    What is a common side effect associated with cephalosporins, similar to Penicillin G?

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

    In which type of animals is cefpodoxime primarily absorbed when administered orally?

    <p>Dogs, cats, and horse neonates</p> Signup and view all the answers

    Which of the following organisms is known to show resistance to first-generation cephalosporins?

    <p>Rhodococcus equi</p> Signup and view all the answers

    What is the mechanism by which cephalosporins are eliminated from the body?

    <p>Renal excretion</p> Signup and view all the answers

    Which side effect is specific to injection of ceftiofur?

    <p>Injection site inflammation</p> Signup and view all the answers

    What class of bacteria do cephalosporins primarily target in terms of their activity spectrum?

    <p>Both gram-positive and gram-negative bacteria</p> Signup and view all the answers

    Which of the following antibiotics is considered a narrow-spectrum agent primarily effective against gram positive bacteria and anaerobes?

    <p>Penicillin G</p> Signup and view all the answers

    What is a noted side effect associated with the use of Procaine penicillin G when administered intravenously?

    <p>CNS stimulation</p> Signup and view all the answers

    Which of the following is true regarding the bioavailability of amoxicillin compared to ampicillin?

    <p>Amoxicillin is not affected by food.</p> Signup and view all the answers

    Which organisms are classified as gram negative that can be treated with sodium ampicillin-sulbactam?

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

    What is a key pharmacokinetic characteristic of penicillin G when administered intramuscularly?

    <p>Absorption can vary significantly depending on the injection site</p> Signup and view all the answers

    Which statement about the clinical indications for penicillin is accurate?

    <p>It is a first-line agent for treating septic pneumonia.</p> Signup and view all the answers

    What describes the route of elimination for penicillin?

    <p>Renal excretion of unchanged drug</p> Signup and view all the answers

    Which of the following anaerobes is specifically mentioned as being susceptible to treatment with penicillin?

    <p>Bacteroides fragilis</p> Signup and view all the answers

    What are the primary routes of elimination for drugs affecting the meninges?

    <p>Renal excretion via glomerular filtration</p> Signup and view all the answers

    Which antibiotic is known for having a broad spectrum of activity, particularly against Gram-positive and Gram-negative bacteria?

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

    Which bacterial genus is intrinsically resistant to antibiotics due to the lack of a cell wall?

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

    What is a notable feature of antistaphylococcal penicillin in relation to Gram-negative bacteria?

    <p>Used as indicators of multi-drug resistance</p> Signup and view all the answers

    Which formulation is commonly associated with antistaphylococcal penicillin?

    <p>Intramammary infusion</p> Signup and view all the answers

    What is the primary drug interaction concern when using beta-lactams with aminoglycosides?

    <p>Formation of precipitates</p> Signup and view all the answers

    Which Gram-negative bacteria is known to exhibit some resistance to penicillins?

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

    What is a characteristic of the absorption of antipseudomonal penicillin when administered orally?

    <p>Carbenicillin is the only one sufficiently absorbed</p> Signup and view all the answers

    What is the mechanism of action of aminoglycosides?

    <p>Bind to 30s ribosomal subunit</p> Signup and view all the answers

    Which of the following is an intrinsic resistance characteristic of mycoplasma?

    <p>Lack of cell wall</p> Signup and view all the answers

    Which penem is known to be nephrotoxic and has the potential to cause seizures when administered rapidly?

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

    Which class of antibiotics is recommended to avoid in veterinary medicine?

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

    What is the primary reason for the narrow spectrum activity of aminoglycosides?

    <p>Dependence on aerobic conditions for uptake</p> Signup and view all the answers

    What adverse effect is associated with the use of aminoglycosides in veterinary medicine?

    <p>Renal failure and ototoxicity</p> Signup and view all the answers

    Which of the following antibiotics is characterized by a broad spectrum of activity against G-, G+, and mycoplasma?

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

    What factor significantly influences the efficacy of aminoglycosides in the presence of purulent debris?

    <p>The acidic environment impact on drug stability</p> Signup and view all the answers

    Which resistance mechanism is commonly observed due to the extensive use of tetracyclines?

    <p>Plasmid-mediated resistance</p> Signup and view all the answers

    What is primarily responsible for the renal accumulation and resultant toxicity of aminoglycosides?

    <p>Active transport into renal tubular cells</p> Signup and view all the answers

    Study Notes

    Antimicrobials

    • Various classes of antimicrobials are available, each with unique mechanisms of action.
    • Antimicrobials can be classified as bacteriostatic or bactericidal, depending on their effect on bacterial growth.
      • Bactericidal agents kill bacteria.
      • Bacteriostatic agents inhibit bacterial growth.

    Bactericidal vs Bacteriostatic

    • Concentration-dependent antimicrobials: their effectiveness increases with increasing concentration, examples are Aminoglycosides, Fluroquinolone, Nitroimidazoles, Polymyxin (F, NAP)
    • Time-dependent antimicrobials: their effectiveness depends on the duration of exposure, examples are B-lactam, Ansamycin, Glycopeptides (BAG)

    Beta-Lactams

    • Beta-lactams are a class of antibiotics that inhibit bacterial cell wall synthesis.
    • Beta-lactamase inhibitors can overcome bacterial resistance mechanisms preventing degradation of beta lactam ring.
    • Examples include Penicillin, Aminopenicillin, Antistaphylococcal Penicillin, Antipseudomonal Penicillin, Cephalosporins, Penems and Monobactams
    • Chemistry: Major target for bacterial resistance mechanisms, gastric pH deactivates most beta lactams except aminopenicillins and some cephalosporins.
    • MOA: Inhibits penicillin binding protein (PBP) - synthesis of bacterial cell wall peptidoglycan
    • Acetylaticon of transpeptidase
    • Effective against rapidly multiplying organisms.
    • Poor membrane penetration: little use for intracellular pathogens.
    • Susceptibility G+ > G- except aminopenicillin, extended spectrum penicillins, cephalosporins, penem, monobactams

    General Info

    • Resistance: Bacteria produce beta-lactamases that hydrolyze the beta-lactam ring.
    • Synergistic effects: Can be used alongside aminoglycosides and other beta-lactams
      • Should not be used with bacteriostatic antimicrobials.

    Beta-Lactamase Inhibitor

    • Amoxicillin-clavulanic acid - commonly used for humans and animals; different ratios for human/vet formulations.

    • Spectrum of activity: Very little antibacterial properties; inhibits bacterial beta lactamases, inactivation of penicillinase and some cephalosporinases. Does not inactivate all G- beta lactamases.

    • Clinical indications: Treatment of sepsis in small animals or foals

    Penicillin

    • Chemistry: Weak acid, hydrolyzed in an acidic environment.
    • Time dependent: Very narrow spectrum; mostly effective against gram + and anaerobes
    • PK (Pharmacokinetics): Oral penicillin V; IM/SQ quickly absorbed. Concentration in muscle tissue depends on injection site. Distribution in ECF, may not reach therapeutic concentrations in some locations. Short half-life if IV, or long acting for slow release
    • PD (Pharmacodynamics): Narrow spectrum of activity, gram+ and anaerobes

    Aminopenicillin

    • Amoxicillin: 2x bioavailability of penicillin, higher in neonates than older foals.
    • PK: PO, absorbed with and without food; good bioavailability of ampicillin IM or SQ
    • PD: Broad spectrum; G+ and G-; especially amoxicillin.
    • Clinical indications: UTI, respiratory disease, superficial bacterial infections

    Antistaphylococcal Penicillin

    • Spectrum of activity: Narrow spectrum of activity targeting G+
    • Resistance: Resistant to beta-lactamases of Staphylococcus spp.
    • Clinical indications: Superficial bacterial folliculitis in dogs, intramammary infections for mastitis in dairy cows.

    Antipseudomonal Penicillin

    • Spectrum of activity: Narrow spectrum targeting G- and anaerobes
    • Clinical indications: Severe gram-negative bacterial infections in small animals and foals.
    • Absorption: PO – Carbenicillin only absorbed, Ticarcillin & Piperacillin must be injected

    Cephalosporins

    • Generations: 1st and 2nd generation, 3rd & 4th generation; 1st gen - good against anaerobes
    • Spectrum of activity: Broad spectrum, gram + and gram -
    • Clinical indications: Alternatives to penicillin (staph & strep); mastitis in dairy cattle, metritis; good activity against anaerobes; peritonitis
    • Absorption/Distribution/Elimination: Variable based on generation, with some having longer half-life.

    Penems, Monobactams

    • Clinical indications: Last resort drugs in human medicine.
    • Absorption/Distribution/Elimination: Variable based on specific antibiotic.
    • Spectrum of activity: Broad spectrum, gram-negative bacteria (gram + only for Monobactams)

    Aminoglycoside & Aminocyclitols

    • Mechanism of action (MOA): Bind to 30s ribosomal subunit, bacteriocidal. Only useful for aerobic infections
    • Concentration dependent: Effective with high concentrations
    • Therapeutic drug monitoring: Accumulate in renal tubular cells, renal failure
    • Clinical indications: gram negative infections, including those caused by Enterobacteriaceae.
    • Important consideration: Oxygen dependent, effectiveness depends on achieving and maintaining therapeutic levels.

    Tetracyclines

    • Mechanism of action (MOA): Bind to 30s ribosomal subunit, bacteriostatic.
    • Spectrum of activity: Broad, G+, G-, Mycoplasma
    • Clinical indications: Tick borne diseases, bacterial respiratory infections in dogs, cats.

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    Description

    This quiz covers the various classes of antimicrobials, their mechanisms of action, and the difference between bactericidal and bacteriostatic agents. It specifically explores concentration-dependent and time-dependent antimicrobials, with a focus on beta-lactams and their role in antibiotic resistance.

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