Pharm: Antibacterial introduction

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Questions and Answers

What is the minimum inhibitory concentration?

It is the lowest concentration for inhibition of growth

What is the MBC?

The lowest concentration for killing bacteria

The MIC and the zone diameter of inhibition are _________ correlated

Inversely

What is the effect of a bactericidal?

<p>it kills the bacteria and reduces the total number of viable organisms</p> Signup and view all the answers

What does a large MBC/MIC ratio indicate for a bacteriostatic drug?

<p>The minimum bactericidal concentration (MBC) is significantly higher than the minimum inhibitory concentration (MIC) (B)</p> Signup and view all the answers

When are bactericidal antibiotics indicated over bacteriostatic antibiotics?

<p>When treating YOPI (young, old, pregnant, or immunocompromised) patients (D)</p> Signup and view all the answers

What does a low MBC/MIC ratio indicate for bactericidal drugs?

<p>The MBC and MIC values are close together, meaning the drug effectively kills bacteria at concentrations near the inhibitory dose (A)</p> Signup and view all the answers

Why do bacteriostatic antibiotics with a large MBC/MIC ratio require a functional immune system?

<p>They only slow bacterial growth, requiring the immune system to clear the infection (C)</p> Signup and view all the answers

Why should bactericidal and bacteriostatic drugs generally NOT be given together?

<p>Bacteriostatic drugs stop bacterial replication, which some bactericidal drugs rely on to be effective (B)</p> Signup and view all the answers

What happens to bacterial killing rates when bactericidal and bacteriostatic drugs are combined?

<p>They decrease compared to using a bactericidal drug alone (C)</p> Signup and view all the answers

How do time-dependent antibiotics achieve their effect?

<p>Their efficacy depends on the time the drug concentration remains above the MIC (A)</p> Signup and view all the answers

What percentage of the dosing interval should a time-dependent drug remain above the MIC for optimal efficacy?

<p>60-80% (C)</p> Signup and view all the answers

Why does increasing the concentration of a time-dependent drug beyond the MIC NOT significantly improve efficacy?

<p>Only the duration above MIC matters, not the peak concentration (B)</p> Signup and view all the answers

Which of the following is true about time-dependent antibiotics?

<p>They have minimal post-antibiotic effects (PAE) (A)</p> Signup and view all the answers

What is the primary factor that determines the efficacy of concentration-dependent antibiotics?

<p>Achieving a high peak concentration (Cmax) relative to the MIC (B)</p> Signup and view all the answers

Why is it NOT beneficial to maintain a high concentration of a concentration-dependent drug for prolonged periods?

<p>It may increase the risk of bacterial resistance (A)</p> Signup and view all the answers

How does the mechanism of concentration-dependent drugs differ from time-dependent drugs?

<p>Concentration-dependent drugs rely on peak concentration rather than the duration above the MIC (A)</p> Signup and view all the answers

What is a common feature of concentration-dependent antibiotics?

<p>They often have prolonged post-antibiotic effects (PAE) (A)</p> Signup and view all the answers

What is the post-antibiotic effect (PAE)?

<p>The ability of an antibiotic to delay bacterial regrowth after exposure (A)</p> Signup and view all the answers

Why do drugs with long post-antibiotic effects (PAE) need to be dosed less frequently?

<p>They continue suppressing bacterial growth even after drug levels drop below MIC (B)</p> Signup and view all the answers

Which of the following is true about antibiotics with short PAE?

<p>They require more frequent dosing to maintain efficacy (A)</p> Signup and view all the answers

What are the common routes of administration?

<p>Systemic, local and topical</p> Signup and view all the answers

What is the most common side effect of antibiotics in general?

<p>Disturbance of the gut microflora: diarrhea</p> Signup and view all the answers

List the bactericidals that are concentration dependent

<p>Aminoglycosides, fluoroquinalone, nitroimidazoles and polymixin</p> Signup and view all the answers

List the antibiotics that have a long post antibiotic effect

<p>Rifampin, tetracyclin, chloramphenicol, macrolides, fluoroquinolones, aminoglycosides and metronidazole</p> Signup and view all the answers

List the antibiotics with an intermediate postantibiotic effect

<p>Penicillins, cephalosporins and aminoglycosides</p> Signup and view all the answers

Which of the following antibiotic(s) have a long postantibiotic effect and an intermediate effect?

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

Which of the following antibiotic(s) has an intermediate postantibiotic effect and a short post antibiotic effect?

<p>Penicillins (A), Cephalosporins (D)</p> Signup and view all the answers

Which of the following bactericidals are time dependent?

<p>Beta lactam (B), Ansamycin (C)</p> Signup and view all the answers

Glycopeptides are a bactericidal that are time dependent

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

What antibiotics with a bacteriostatic effect are time dependent?

<p>Tetracyclines, sulfonamide, trimethoprim, amphenicol, macrolides and lincosamides</p> Signup and view all the answers

Match the antibiotic to its effect

<p>Tetracycline = Bacteriostatic Polymyxin = Bactericidal Beta-lactam = Bactericidal Sulfanomides = Bacteriostatic</p> Signup and view all the answers

Aminoglycosides have a _______________ (bactericidal/bacteriostatic) effect

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

Diaminopyrimidines have a ___________________ (bactericidal/bacteriostatic) effect

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

In general, folic acid synthesis inhibitors have a bactericidal effect

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

The antibiotic rifampin , can have both bactericidal and bacteriostatic effects

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

Metronidazole has a __________________ (bactericidal/bacteriostatic) effect

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

Tetracyclines inhibit protein synthesis

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

Aminoglycosides impair proofreading, resulting in production of faulty proteins

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

Flashcards

What is MIC?

Lowest concentration of an antimicrobial that inhibits bacterial growth.

What is MBC?

Lowest concentration of an antimicrobial that kills bacteria.

MIC and zone diameter correlation.

They are inversely related: higher MIC means smaller inhibition zone

What is a bactericidal?

An agent that kills bacteria, reducing the total viable count.

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Large MBC/MIC ratio meaning

Indicates that higher concentrations are needed to kill bacteria compared to inhibiting their growth.

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Bactericidal use cases

When treating young, old, pregnant, or immunocompromised patients.

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Low MBC/MIC ratio meaning

The drug effectively kills bacteria at concentrations near the inhibitory dose.

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Bacteriostatic Immune Requirement

These antibiotics only slow bacterial growth allowing the immune system to clear the infection.

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Why not combine?

Bacteriostatic drugs stop bacterial replication, which some bactericidal drugs rely on to be effective, decreasing bacterial killing rates

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Time-dependent antibiotics

Antibiotic efficacy depends on the duration drug concentrations remain above the MIC.

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Optimal time above MIC

60-80% of the dosing interval.

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Concentration-dependent antibiotics

Efficacy depends on peak concentration (Cmax) relative to the MIC.

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High concentration risk

It can increase the risk of bacterial resistance.

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Concentration vs Time

Concentration-dependent drugs rely on peak concentration rather than the duration above the MIC

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Concentration Dependent PAE

They often have prolonged post-antibiotic effects (PAE).

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What is PAE?

Ability of an antibiotic to delay bacterial regrowth after exposure.

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Long PAE frequency

They continue suppressing bacterial growth even after drug levels drop below MIC.

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Short PAE dosing

They require more frequent dosing to maintain efficacy.

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Common routes of administration

Systemic, local, and topical

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Most common side effect

Disturbance of the gut microflora: diarrhea

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Concentration Dependent Bactericidals

Aminoglycosides, fluoroquinolones, nitroimidazoles, and polymyxins

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Antibiotics with long PAE

Rifampin, tetracycline, chloramphenicol, macrolides, fluoroquinolones, aminoglycosides, and metronidazole

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Antibiotics with intermediate PAE

Penicillins, cephalosporins and aminoglycosides

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Beta lactam

Beta lactams.

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Bacteriostatic Time Dependent

Tetracyclines, sulfonamide, trimethoprim, amphenicol, macrolides and lincosamides

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Aminoglycosides effect

Bactericidal.

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Diaminopyrimidines effect

Bacteriostatic.

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Aminoglycosides impairment

True. Impair proofreading, resulting in production of faulty proteins

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