Antimicrobial Pharmacology I Study Quiz

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Questions and Answers

Which of the following agents is classified as bacteriostatic?

Clindamycin (correct)

Aminoglycosides

Daptomycin

Beta-lactam antibiotics

What is a common mechanism through which antimicrobial resistance occurs?

Reduced concentration of the antibiotic at its target site (correct)

Increased potency of the antibiotic

Slowed metabolism of the antibiotic by the host

Enhanced drug affinity for bacterial ribosomes

What type of antibiotic is Linezolid categorized as?

Both bacteriostatic and bactericidal (correct)

Bacteriostatic

Narrow-spectrum bactericidal

Bactericidal

Which of the following combinations includes both bacteriostatic and bactericidal actions?

Trimethoprim-Sulfamethoxazole Signup and view all the answers

What is the role of efflux pumps in antimicrobial resistance?

They expel antibiotics from the bacterial cell. Signup and view all the answers

What distinguishes bacteriostatic agents from bactericidal agents?

Bacteriostatic agents prevent bacterial growth, whereas bactericidal agents kill bacteria. Signup and view all the answers

Which of the following statements is true regarding time-dependent bactericidal agents?

Their effectiveness is sustained as long as drug serum concentrations remain above the minimum bactericidal concentration (MBC). Signup and view all the answers

In which scenario are bacteriostatic and bactericidal agents considered equivalent for treatment?

In immunocompetent hosts. Signup and view all the answers

Which type of bactericidal agent is characterized by concentration-dependent killing?

Aminoglycosides. Signup and view all the answers

What is a defining characteristic of bacteriolytic agents?

They initiate cell lysis to kill bacteria. Signup and view all the answers

Which cephalosporins should patients with a history of anaphylaxis to penicillins avoid?

First- and second-generation cephalosporins Signup and view all the answers

What is the primary mechanism of allergic cross-reactivity in beta-lactam antibiotics?

R1 side chain similarity Signup and view all the answers

What type of bacteria does Aztreonam act against?

Aerobic gram-negative bacteria Signup and view all the answers

Which of the following is true regarding carbapenems?

They require renal clearance. Signup and view all the answers

Why is cilastatin administered with imipenem?

To inhibit renal dehydropeptidase from hydrolyzing imipenem Signup and view all the answers

What is a key feature of β-lactamase inhibitors?

They bind to β-lactamases to prevent hydrolysis of β-lactam agents. Signup and view all the answers

Which β-lactam antibiotics lack allergic cross-reactivity, except for the possible exceptions of certain cephalosporins?

Monobactams Signup and view all the answers

What percentage of administered imipenem is typically recovered in urine when given with cilastatin?

70% Signup and view all the answers

What is the primary mechanism of resistance employed by bacteria against β-lactam antibiotics?

Enzymatic degradation by β-lactamase Signup and view all the answers

Which of the following penicillins is classified as a β-lactamase resistant penicillin?

Oxacillin Signup and view all the answers

Which penicillin is primarily used intravenously due to its poor oral absorption?

Piperacillin Signup and view all the answers

What is a common adverse effect associated with penicillins?

Cross-sensitivity allergies Signup and view all the answers

Which cephalosporin generation is primarily effective against gram-positive bacteria?

First generation Signup and view all the answers

What effect does β-lactamase have on the β-lactam antibiotics like penicillin?

Inactivates them by hydrolyzing the β-lactam ring Signup and view all the answers

Which of the following is NOT a natural penicillin?

Nafcillin Signup and view all the answers

What is the main pharmacological action of cephalosporins?

Disrupt bacterial cell wall synthesis Signup and view all the answers

Which of the following adverse reactions is the least common with penicillin use?

Gastrointestinal discomfort Signup and view all the answers

Which generation of cephalosporins is primarily effective against gram-negative bacteria?

Third generation Signup and view all the answers

What type of bacteria is vancomycin primarily effective against?

Gram positive bacteria Signup and view all the answers

How does vancomycin inhibit bacterial cell wall synthesis?

By binding to the D-ala-D-ala terminus Signup and view all the answers

Which characteristic of vancomycin limits its absorption in the gastrointestinal tract?

Poorly absorbed Signup and view all the answers

What is the molecular weight of vancomycin?

1,449.3 Signup and view all the answers

What is the role of transglycosylase in bacterial cell wall synthesis?

To catalyze the polymerization of NAG and NAM Signup and view all the answers

What is the primary consequence of the alteration of the D-alanine terminus in bacteria?

Formation of a weak cell wall Signup and view all the answers

Why is vancomycin given intravenously?

It is poorly absorbed from the gastrointestinal tract Signup and view all the answers

What happens to the D-alanine when vancomycin is present?

It cannot crosslink to glycine Signup and view all the answers

What causes resistance to vancomycin in bacterial cell walls?

D-alanine to D-lactate modification Signup and view all the answers

What is the primary source of vancomycin?

Bacteria Signup and view all the answers

Which of the following is a key pharmacokinetic characteristic of vancomycin?

Widely distributed in adipose tissue Signup and view all the answers

Why is dose adjustment necessary for vancomycin in patients with renal impairment?

Reduced excretion leading to accumulation Signup and view all the answers

Which adverse effect is associated with high trough levels of vancomycin?

Nephrotoxicity Signup and view all the answers

What is the impact of administering vancomycin with another ototoxic drug?

Increased risk of toxicities Signup and view all the answers

How is vancomycin primarily excreted from the body?

Glomerular filtration Signup and view all the answers

What effect does the accumulation of vancomycin have in cases of renal impairment?

Higher risk of adverse effects Signup and view all the answers

Study Notes

Antimicrobial Pharmacology I - Study Notes

Course taught by Altaf Darvesh, M. Pharm., Ph.D. on 11-12-2024
Recommended Reading:
- Katzung's Basic and Clinical Pharmacology (16th edition) by Vanderah, McGraw Hill
- Goodman and Gilman's The Pharmacological Basis of Therapeutics (14th edition) by Brunton, Knollman, McGraw Hill (Available online on Access Medicine & Access Pharmacy)
Objectives:
- Identify targets of antimicrobial pharmacotherapy
- Distinguish between bacteriostatic and bactericidal agents
- Describe general mechanisms of antimicrobial resistance
- Describe the structure of the bacterial cell wall
- Distinguish between Gram-positive and Gram-negative bacteria
- Classify beta-lactam antibiotics
- Describe the mechanism of action of beta-lactams
- Describe the mechanism of resistance of beta-lactams
- Describe the adverse effects of beta-lactams
- Discuss beta-lactamase inhibitors

Targets of Antimicrobial Pharmacotherapy

Antibiotics target microbial proteins essential for biochemical reactions.
Antibiotics disrupt biochemical pathways and inhibit microbial replication or directly kill microorganisms.
Common inhibited processes include cell wall synthesis, cell membrane synthesis/function, ribosomal translation, and nucleic acid metabolism.

Bacteriostatic and Bactericidal Agents

Bacteriostatic agents reversibly inhibit bacterial growth.
Minimum Inhibitory Concentration (MIC) is the lowest drug concentration that inhibits bacterial growth.
Bactericidal agents irreversibly kill bacteria.
Minimum Bactericidal Concentration (MBC) is the lowest drug concentration that kills bacteria

Bacteriostatic and Bactericidal Classification

Primarily bacteriostatic agents have lower concentrations than bactericidal agents.
Cell wall-active agents are generally bactericidal; drugs inhibiting protein synthesis are bacteriostatic.
Bacteriostatic antibiotics prevent bacterial growth through interference with protein production, DNA replication, or other metabolic processes.
Bactericidal antibiotics disrupt bacterial cell parts like walls or DNA.

Bactericidal Agents

Agents exhibiting concentration-dependent killing (e.g., aminoglycosides, quinolones) are more effective with increased concentration.
Agents exhibiting time-dependent killing (e.g., beta-lactams) maintain bactericidal activity as long as serum concentrations exceed the Minimum Bactericidal Concentration (MBC).

Structure of Bacterial Cell Wall

The cell wall is a rigid structure surrounding the cytoplasmic membrane.
The cell wall maintains integrity and prevents osmotic pressure damage
The cell wall is composed of peptidoglycan, a complex polymer of polysaccharides and peptides.
Alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) compose the polysaccharide.
A five-amino-acid peptide is attached to NAM terminating in D-alanyl-D-alanine
Transpeptidase (PBP) enzyme forms cross-links in the peptidoglycan to maintain cell wall rigidity.

Gram Positive and Negative Bacteria

Gram-positive bacteria have a thick peptidoglycan layer, retaining crystal violet.
Gram-negative bacteria have a thin peptidoglycan layer, retaining safranin/carbol fuchsin.

Beta-lactam Antibiotics

Penicillins, cephalosporins, carbapenems, and monobactams are beta-lactams
Share a common 4-membered beta-lactam ring.
They have a common mechanism of action, inhibiting bacterial cell wall synthesis by binding to and inactivating PBP.

Mechanism of Action of Beta-Lactams

Beta-lactam antibiotics block the transpeptidase reaction.
This prevents cross-linking of peptides in the peptidoglycan, resulting in a weakened cell wall and eventual bacterial death.

Beta-lactamase Inhibitors

Beta-lactamase inhibitors bind to beta-lactamases, preventing these enzymes from hydrolyzing beta-lactam antibiotics.

Mechanisms of Resistance

Reduced antibiotic concentration at the target site (efflux pumps)
Inactivation/alteration of antibiotic targets through enzyme production
Alteration of the bacterial target site

Vancomycin

A Glycopeptide antibiotic.
Large molecular weight (1,449.3).
Targets Gram-positive bacteria.
Poorly absorbed orally; usually administered intravenously.
Inhibits bacterial cell wall synthesis by binding to the D-alanyl-D-alanine terminus.
Vancomycin mechanisms of resistance involve altering the D-alanyl-D-alanine target.

Lipoglycopeptides

Telavancin, Dalbavancin, and Oritavancin are lipoglycopeptides.
Mechanism of action and resistance are similar to vancomycin.
Indicated for complicated skin and skin structure infections (CSSI)

Cephalosporins

Newer generations have greater activity against Gram-negative bacteria than previous ones.
Simpler mechanisms of action that mimic beta-lactams.

Cephamycins

A subclass of cephalosporins.
Possess a methoxy group and activity against anaerobic bacteria.

Ceftaroline fosamil

Fifth-generation cephalosporin.
Active against methicillin-resistant Staphylococcus aureus (MRSA).

Cefiderocol

Unique cephalosporin that uses a siderophore moiety.
Resistant to many beta-lactamases.
Shows activity against multi-drug-resistant Gram-negative bacteria via iron-binding capability.

Pharmacodynamics of Penicillins

Diverse pharmacokinetic properties (Oral absorption)
Penicillins exhibit differences in oral absorbability and resistance to beta-lactamases.

Adverse Effects of Penicillins/Cephalosporins

Hypersensitivity reactions (allergies) are common.
Nephrotoxicity and ototoxicity are potential adverse effects.
Infusion reactions, including flushing, itching, or hypotension.

Oral/Intravenous Administration; Indications

Specific indications for oral vs. intravenous administration exist based on drug and infection characteristics.
Usage varies with drug type, infection severity or drug sensitivity from patient/bacteria.

Practice Questions

Provided in pages 44 and 45. Refer to those sections for detailed questions and answer choices.

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Description

Test your knowledge on Antimicrobial Pharmacology I, focusing on the targets of antimicrobial pharmacotherapy, mechanisms of action, and resistance. This quiz covers key concepts from recommended readings, including Katzung's Basic and Clinical Pharmacology and Goodman and Gilman's The Pharmacological Basis of Therapeutics.