Antimicrobial Stewardship Quiz
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Questions and Answers

What is the MOST critical distinction between an antimicrobial and an antibiotic?

  • Antibiotics are used prophylactically; antimicrobials are for active infections.
  • Antimicrobials can be synthetic, whereas antibiotics are derived from microorganisms. (correct)
  • Antimicrobials are effective against viruses, while antibiotics target only bacteria.
  • Antibiotics inhibit growth; antimicrobials always destroy microorganisms.

In what scenario would de-escalation of antimicrobial therapy be MOST appropriate?

  • When a patient shows no clinical improvement after 72 hours on the empiric regimen.
  • When the initially prescribed empiric antibiotic covers a broader spectrum than necessary based on culture results. (correct)
  • When the patient develops a secondary fungal infection during antibiotic treatment.
  • When emerging resistance to the current antibiotic is detected during treatment.

Which of the following accurately describes Alexander Fleming's contribution to the field of antimicrobial therapy?

  • He developed the concept of using antibiotic cocktails to combat multi-drug resistant bacteria.
  • He discovered that a mold could inhibit bacterial growth, leading to the isolation of penicillin. (correct)
  • He identified the mechanism of action for a broad class of antibiotics, revolutionizing drug design.
  • He synthesized the first fully synthetic antimicrobial compound effective against Gram-negative bacteria.

What is the PRIMARY rationale for initiating empiric antimicrobial therapy?

<p>To immediately address a suspected infection before definitive culture results are available. (A)</p> Signup and view all the answers

Which factor is MOST crucial when transitioning from empiric to definitive antimicrobial therapy?

<p>Availability of specific identification and susceptibility data of the infecting organism. (A)</p> Signup and view all the answers

Which of the following scenarios would be LEAST appropriate for the use of oral vancomycin?

<p>A patient with a catheter-related bloodstream infection due to methicillin-resistant staphylococci. (C)</p> Signup and view all the answers

A patient receiving vancomycin develops a rapid onset of flushing, erythema, and pruritus during the infusion. Which of the following mechanisms is MOST likely responsible for these symptoms?

<p>Histamine release due to non-immunologic mast cell degranulation. (C)</p> Signup and view all the answers

A retrospective study reveals that patients treated with cefazolin for MSSA bacteremia had a significantly lower mortality rate compared to those treated with vancomycin. Which of the following factors could BEST explain this observed difference?

<p>Vancomycin is associated with a higher risk of nephrotoxicity, potentially contributing to adverse outcomes. (D)</p> Signup and view all the answers

Which of the following mechanisms of action describes how Fosfomycin inhibits bacterial cell wall synthesis?

<p>Blocking the addition of phosphoenolpyruvate to UDP-N-acetylglucosamine. (B)</p> Signup and view all the answers

Which of the following pathogens would be LEAST likely to be effectively treated with fosfomycin?

<p><em>Enterococcus</em> species. (B)</p> Signup and view all the answers

Which of the following statements BEST describes the mechanism of action of polymyxins?

<p>Disruption of the bacterial cell membrane, leading to increased permeability. (A)</p> Signup and view all the answers

A hospital implements a new antimicrobial stewardship program promoting cefazolin over vancomycin for MSSA bacteremia. Which of the following outcomes would be the MOST anticipated benefit of this change?

<p>Improved clinical outcomes related to minimizing nephrotoxicity (C)</p> Signup and view all the answers

A patient with a severe penicillin allergy requires treatment for a confirmed MSSA infection. Considering the data regarding cefazolin and vancomycin, which of the following represents the MOST appropriate course of action?

<p>Initiate vancomycin therapy, ensuring therapeutic drug monitoring to maintain appropriate levels. (B)</p> Signup and view all the answers

Which of the following is an example of a Glycopeptide?

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

Which route of administration is NOT available for Fosfomycin?

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

Which of the following correctly pairs a bacterial genus with an antibiotic primarily effective against it?

<p>P. aeruginosa - Aminoglycoside (D)</p> Signup and view all the answers

A patient with myasthenia gravis requires antibiotic treatment. Which antibiotic class should be administered with extreme caution?

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

A patient develops tinnitus and high-frequency hearing loss during antibiotic therapy. Which class of antibiotics is most likely responsible?

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

Which of the following antibiotics is available in both parenteral and oral formulations?

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

A patient is diagnosed with a Mycoplasma infection. Which antibiotic is the MOST appropriate choice for treatment?

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

Which of the following mechanisms describes how tetracyclines inhibit bacterial growth?

<p>Binding to the 30S ribosomal subunit (D)</p> Signup and view all the answers

A patient undergoing aminoglycoside therapy is closely monitored for adverse effects. Which assessment is MOST critical to detect irreversible ototoxicity?

<p>Regular audiometry to detect high-frequency hearing loss (A)</p> Signup and view all the answers

A patient is prescribed an antibiotic known to cause nephrotoxicity. Which laboratory value should be monitored most closely to detect this adverse effect?

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

In which of the following clinical scenarios would a macrolide be LEAST appropriate, considering potential adverse drug reactions (ADRs) and drug interactions (DIs)?

<p>A patient taking theophylline for chronic obstructive pulmonary disease (COPD) who develops a gram-positive bacterial infection, such as streptococci. (A)</p> Signup and view all the answers

A patient with a severe penicillin allergy and a community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infection requires an oral antibiotic. Considering the information provided, which of the following would be the MOST appropriate choice:

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

A patient is prescribed a macrolide antibiotic. Which pre-existing condition or concurrent medication would MOST significantly raise concern for potentially life-threatening adverse effects?

<p>Prolonged QTc interval. (D)</p> Signup and view all the answers

Which mechanism of action is shared by both macrolides and lincosamides?

<p>Inhibition of protein synthesis by binding to 50S ribosomal subunits. (B)</p> Signup and view all the answers

A patient is diagnosed with a severe anaerobic infection. Considering the spectrum of activity for lincosamides, which of the following anaerobic bacteria would be LEAST likely to respond to treatment with clindamycin?

<p><em>Clostridium difficile</em>. (B)</p> Signup and view all the answers

A researcher is investigating the metabolism of a new drug. They discover that the drug is primarily metabolized by CYP3A4 into inactive metabolites. If this drug were co-administered with a macrolide antibiotic, what effect would be MOST likely?

<p>Inhibition of CYP3A4, leading to increased plasma concentration of the new drug. (B)</p> Signup and view all the answers

A patient is being treated for a Mycobacterium infection with a combination of antibiotics, including a macrolide. What is the PRIMARY reason for using multiple antibiotics in this scenario?

<p>To prevent or delay the development of antibiotic resistance. (B)</p> Signup and view all the answers

A microbiology lab report indicates that a patient is infected with methicillin-sensitive Staphylococcus aureus (MSSA). Which antibiotic would be LEAST appropriate, considering the information provided?

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

Which of the subsequent adverse drug reactions (ADRs) is MOST likely associated with prolonged linezolid use exceeding eight weeks?

<p>Peripheral neuropathy, optic neuritis, and lactic acidosis. (B)</p> Signup and view all the answers

What is the PRIMARY mechanism through which aminoglycosides exert their bactericidal effects?

<p>Binding to the 30S ribosomal subunit, causing misreading of mRNA and premature termination of protein synthesis. (C)</p> Signup and view all the answers

Linezolid's potential for drug interactions is MOST directly related to its action as what?

<p>A weak, nonspecific inhibitor of monoamine oxidase. (A)</p> Signup and view all the answers

Chloramphenicol is known to inhibit hepatic CYPs. What is the MOST likely consequence of this inhibition regarding other co-administered drugs?

<p>Elevated plasma concentrations and potential toxicity of drugs metabolized by the affected CYPs, such as warfarin. (C)</p> Signup and view all the answers

Why is chloramphenicol typically reserved for bacterial meningitis or rickettsial diseases only when other drugs have failed?

<p>Because of its significant risk of causing irreversible aplastic anemia. (A)</p> Signup and view all the answers

Aminoglycosides are often used in combination with cell wall-active agents to treat infections caused by which type of bacteria?

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

What is the MOST critical factor that determines the effectiveness of aminoglycosides?

<p>The peak concentration of the drug achieved relative to the MIC of the organism. (C)</p> Signup and view all the answers

Which characteristic distinguishes aminoglycosides from many other antibiotics concerning their bactericidal activity?

<p>Concentration-dependent killing activity. (B)</p> Signup and view all the answers

Why is neomycin administered via the oral route, unlike other aminoglycosides?

<p>Because it is poorly absorbed systemically and is used for local effect in the GI tract. (D)</p> Signup and view all the answers

What is the MOST significant advantage of using amikacin over other aminoglycosides in treating multidrug-resistant Gram-negative bacterial infections?

<p>Reduced susceptibility to aminoglycoside-modifying enzymes. (A)</p> Signup and view all the answers

For what reason is caution advised when administering linezolid to patients also taking selective serotonin reuptake inhibitors (SSRIs)?

<p>Elevated risk of serotonin syndrome due to MAO inhibition. (A)</p> Signup and view all the answers

What aspect defines linezolid's spectrum of activity?

<p>Primarily targets Gram-positive bacteria, including vancomycin-resistant strains. (C)</p> Signup and view all the answers

Which statement accurately describes the route of administration and primary use of aminoglycosides?

<p>Administered parenterally for severe Gram-negative infections. (C)</p> Signup and view all the answers

Which mechanism describes how chloramphenicol inhibits protein synthesis?

<p>By binding to the 50S ribosomal subunit, which prevents peptide bond formation. (A)</p> Signup and view all the answers

Which factor contributes MOST significantly to the nephrotoxicity associated with aminoglycoside antibiotics?

<p>Accumulation in the proximal tubular cells, causing cellular damage. (C)</p> Signup and view all the answers

What is the primary mechanism of action of linezolid within bacterial cells?

<p>Inhibiting protein synthesis by binding to the P site of the 50S ribosomal subunit. (A)</p> Signup and view all the answers

In which clinical scenario is clindamycin most likely to be considered as a first-line treatment option?

<p>As an alternative for penicillin-allergic patients in treating skin and soft tissue infections. (D)</p> Signup and view all the answers

What is the most significant concern associated with the use of clindamycin that prescribers should consider?

<p>The risk of antibiotic-associated colitis caused by <em>C. difficile</em>. (B)</p> Signup and view all the answers

Which property is characteristic of clindamycin's antimicrobial activity?

<p>Time-dependent killing activity against anaerobic bacteria. (B)</p> Signup and view all the answers

Considering its mechanism of action, against which type of organisms is linezolid primarily effective?

<p>Gram-positive bacteria, including multi-drug resistant strains like MRSA and VRE. (C)</p> Signup and view all the answers

In what clinical scenario would clindamycin be LEAST appropriate?

<p>Infections caused by drug-resistant strains of Streptococcus pneumoniae (C)</p> Signup and view all the answers

What is the primary reason for combining clindamycin with anti-staphylococcal beta-lactams in the treatment of toxic shock syndrome?

<p>To suppress the production of bacterial toxins by inhibiting protein synthesis. (A)</p> Signup and view all the answers

Which of these is NOT an adverse drug reaction (ADR) associated with clindamycin?

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

Flashcards

Antimicrobial

A substance that destroys or inhibits the growth of microorganisms, especially pathogens.

Antibiotic

An antibacterial substance isolated from microorganisms or synthesized to combat bacterial growth.

Antibacterial

Specifically directed or effective against bacteria.

Empiric treatment

Initial treatment before definitive diagnosis; broader spectrum coverage.

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Definitive treatment

Treatment based on specific identification of a pathogen, often narrower than empiric.

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Cefazolin

An antibiotic used for MSSA that reduces mortality in bloodstream infections.

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Vancomycin

An antibiotic used primarily for MRSA and severe infections, associated with flushing syndrome.

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Flushing syndrome

A reaction to vancomycin causing extreme flushing, known as Red man syndrome.

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Nephrotoxicity

Kidney damage or toxicity caused by certain antibiotics, including vancomycin.

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Ototoxicity

Hearing damage related to exposure to certain antibiotics, especially aminoglycosides.

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Fosfomycin

An antibiotic that inhibits bacterial cell wall synthesis through MurA inhibition.

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Polymyxins

A class of antibiotics effective against Gram-negative bacteria, administered parenterally.

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MSSA

Methicillin-Sensitive Staphylococcus Aureus, a type of bacteria sensitive to certain penicillins.

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MRSA

Methicillin-Resistant Staphylococcus Aureus, a multi-drug resistant type of bacteria.

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Drug-resistant S.pneumoniae

A strain of Streptococcus pneumoniae resistant to many antibiotics, complicating treatment.

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Atypical Bacteria

Bacteria causing atypical infections, not typically detected by standard methods.

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NTM

Non-Tuberculous Mycobacteria, often causing lung infections.

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Macrolides

A class of antibiotics effective against various bacterial infections.

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ADRs of Macrolides

Common adverse drug reactions include GI upset and arrhythmias.

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CYP 3A4 Inhibitors

Substances that interfere with the metabolism of drugs processed by CYP 3A4.

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Lincosamides

Antibiotics effective against gram-positive bacteria and some anaerobes.

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Mechanism of Action of Lincosamides

They inhibit protein synthesis by binding to the 50S ribosomal subunit.

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Gram-Positive Spectrum

Lincosamides primarily target gram-positive bacteria like MSSA and CA-MRSA.

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Aminoglycosides

A class of antibiotics that inhibit bacterial protein synthesis.

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Tetracyclines

A class of antibiotics that inhibit protein synthesis by binding to the 30S ribosomal subunit.

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Protein synthesis inhibition

The mechanism by which certain antibiotics stop bacteria from making proteins.

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Gram-positive bacteria

Bacteria that retain the crystal violet stain used in the Gram staining procedure.

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Mycobacterium tuberculosis

A type of bacteria that causes tuberculosis, treated with specific antibiotics.

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Chlamydia spp.

A genus of bacteria that are obligate intracellular pathogens, often treated with tetracyclines.

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Clindamycin

An antibiotic alternative for penicillin-allergic patients, effective against skin infections and anaerobic bacteria.

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Primaquine

An antimalarial medication used in combination with other drugs, often effective in treating certain infections.

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Time-dependent killing activity

A property where antibiotic effectiveness relies on the duration of exposure rather than concentration.

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Clindamycin's ADRs

Adverse effects include rash, gastrointestinal discomfort, and antibiotic-associated colitis caused by C.difficile.

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Pneumocystis jirovecii pneumonia

A type of pneumonia caused by a yeast-like fungus, commonly seen in immunocompromised individuals.

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Oxazolidinones

A class of antibiotics, including Linezolid, that inhibit bacterial protein synthesis.

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Linezolid

An antibiotic used for treating Gram-positive infections, including those resistant to other treatments.

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CA-MRSA infections

Community-associated Methicillin-resistant Staphylococcus aureus infections, known for their resistance to multiple drugs.

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ADRs of Linezolid

Common: rash, GI issues. Serious: myelosuppression, peripheral neuropathy.

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Chloramphenicol

An antibiotic that inhibits protein synthesis in bacteria, with a broad spectrum.

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Aplastic anemia

Severe condition leading to failure of blood cell production, irreversible with chloramphenicol.

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Bactericidal effect

Killing effect on bacteria, as seen with aminoglycosides.

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Concentration-dependent killing

Aminoglycosides' effectiveness increases with higher drug concentration.

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Gram-negative bacteria

Bacteria with a complex cell wall, often resistant to antibiotics.

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MDR-GN

Multidrug-resistant Gram-negative bacteria, challenging to treat.

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Tuberculosis treatment

Amikacin is a second-line agent against tuberculosis.

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Vancomycin-resistant Enterococci (VRE)

A type of bacteria that is resistant to the antibiotic vancomycin.

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Peripheral neuropathy

Damage to nerves causing weakness, numbness, or pain, potential ADR of linezolid.

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Optic neuritis

Inflammation of the optic nerve, a serious ADR of linezolid.

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50S ribosomal subunit

Part of the bacterial ribosome inhibited by certain antibiotics like linezolid.

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Gram-positive anaerobes

Bacteria without oxygen required for growth, often susceptible to specific antibiotics.

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Study Notes

Antimicrobial Agents

  • Antimicrobial agents destroy or inhibit growth of microorganisms, especially pathogenic ones.
  • Antibiotics are antimicrobial substances isolated from microorganisms (fungi) or synthetic/semi-synthetic.
  • Antibacterials are effective against bacteria.
  • Alexander Fleming discovered the first antibiotic.
  • Antimicrobial therapy has stages.

Outline of Topics

  • Introduction
  • General principle of antibiotic treatment
  • Classification of antibiotics
  • Mechanisms of antibiotic resistance
  • How to deal with MDR bacteria
  • Exercise

Suggested Reading Materials

  • Katzung, Basic & Clinical Pharmacology
  • Goodman & Gilman's The Pharmacological Basis of Therapeutics (14th ed)
  • Brunton & Knollmann, pharmacological basis of therapeutics (15th edition)

Time-Dependent Antibiotics

  • T > MIC (time above minimum inhibitory concentration)
  • 40-50% of dosing intervals are required.
  • Examples include beta-lactams.

Concentration-Dependent Antibiotics

  • Cpeak/MIC ≥ 10 – 12 times
  • Examples include Aminoglycosides.

AUC (Total Exposure)-Dependent Antibiotics

  • AUC/MIC ≥ x
  • Examples include Vancomycin and Fluoroquinolones.

Combination Antimicrobial Therapy

  • Indication : Septic shock, polymicrobial infections, drug-resistant organisms
  • Benefits: Synergism (additive, synergistic), e.g. Meropenem + Colistin for P. aeruginosa infection (1+1=2); Penicillins + Aminoglycosides for infective endocarditis (1+1>2).

Parenteral to Oral Switch Therapy

  • Advantages include fewer complications and faster recovery.
  • Includes Ciprofloxacin, Ampicillin, Vancomycin, Amoxicillin, and Clindamycin.
  • Provides information to switch from intravenous to oral medications.

Bacterial Target Sites for Antibiotics

  • Bacterial cell wall synthesis
  • Bacterial protein synthesis

Steps in Bacterial Cell Wall Synthesis

  • Precursor formation (NAG and NAM)
  • Peptide chain assembly
  • Crosslinking (transpeptidation)
  • Enzymes involved: Transpeptidase, Glucosyltransferase

Bacterial Protein Synthesis

  • 30S, 50S subunits.
  • Initiation, elongation and termination is blocked by antibiotics.

Antibiotic Mechanisms & Targets

  • Penicillins, Cephalosporins, Carbapenems, Monobactams (target cell wall)
  • Aminoglycosides (target ribosome, 30s, bactericidal action)
  • Tetracyclines (target ribosome, 30s, bacteriostatic action)
  • Fluoroquinolones (target DNA or TOPO enzymes bactericidal)
  • Macrolides (target ribosome, 50s, bacteriostatic action)
  • Lincosamides (target ribosome, 50s, bacteriostatic action)
  • Sulfonamides, Trimethoprim (target folic acid synthesis bacteriostatic)
  • Glycopeptides (target cell wall, bactericidal)
  • Metronidazole (target DNA, bactericidal)
  • Polymyxins (target cell membrane, bactericidal)
  • Oxazolidinones (target ribosome, 50s, static)

Beta-Lactamase Inhibitors

  • Examples include clavulanate, sulbactam, avibactam, tazobactam.
  • This is a strategy against antibiotic resistance.

Mechanisms of Antimicrobial Resistance

  • Intrinsic: efflux pumps, target modification, reduced permeability, chromosomally encoded enzymes, adaptive/acquired resistance.
  • Acquired: horizontal gene transfer, efflux pumps, modified cell wall, modified antibiotic targets, degrading enzyme production, modification of porins.

Modified Antibiotic Targets

  • Changes in porins, decreased porin level, reduced antibiotic target accessibility
  • Bacterial cell wall alterations
  • Efflux pumps

Emerging Non-Antibiotic Approaches

  • Human monoclonal antibodies
  • Antibody-antibiotic conjugate therapy
  • Antimicrobial peptides
  • Bacteriophages
  • Gene therapy

Alternative Antibiotic Dosing Strategies

  • Combination Therapy
    • at least 2 agents
    • treat CRAB (Carbapenem-resistant A. baumannii)
  • Modifiled drug dosing
    • Increase dose (toxic potential exists)
    • change administration methods e.g. prolonged infusion time (β-lactam antibiotics)

Exercise Bacteria

  • Staphylococcus aureus
  • Enterococcus spp.
  • Streptococcus pneumoniae
  • Enterobacterales (E. coli, K. pneumoniae)
  • Pseudomonas aeruginosa
  • Acinetobacter baumannii
  • Anaerobes.

Classification of Antibiotics

  • β-Lactam
  • Macrolides
  • Lincosamides
  • Aminoglycosides
  • Quinolones
  • Glycopeptides
  • Sulfonamides
  • Polymyxins
  • Nitroimidazoles
  • Oxazolidinones
  • Others (e.g., fosfomycin, phenicols)

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Description

Test your knowledge of antimicrobial stewardship, including distinguishing antimicrobials from antibiotics, de-escalation strategies, and empiric therapy. Questions cover vancomycin usage, and adverse drug reactions. Designed to improve antimicrobial knowledge.

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