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Questions and Answers
What type of antibiotics are Isoniazid, Penicillin V, and Clindamycin classified as?
What type of antibiotics are Isoniazid, Penicillin V, and Clindamycin classified as?
Which of the following antibiotic classifications inhibits the growth and replication of bacteria?
Which of the following antibiotic classifications inhibits the growth and replication of bacteria?
Which of the following antibiotics is NOT classified as broad spectrum?
Which of the following antibiotics is NOT classified as broad spectrum?
In the classification of antibiotics, what action do glycocalyx-targeting drugs like Glycopeptides and Beta Lactams perform?
In the classification of antibiotics, what action do glycocalyx-targeting drugs like Glycopeptides and Beta Lactams perform?
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Which of the following antibiotics is categorized as bactericidal?
Which of the following antibiotics is categorized as bactericidal?
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What gene transfer mechanism involves bacteriophages to transfer resistance genes among bacteria?
What gene transfer mechanism involves bacteriophages to transfer resistance genes among bacteria?
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Which of the following bacteria is known for its resistance due to a modified penicillin-binding protein?
Which of the following bacteria is known for its resistance due to a modified penicillin-binding protein?
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What mechanism allows bacteria to pump antibiotics out of the cell, preventing the drugs from reaching their target?
What mechanism allows bacteria to pump antibiotics out of the cell, preventing the drugs from reaching their target?
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Which of the following is NOT a method through which bacteria can acquire antibiotic resistance?
Which of the following is NOT a method through which bacteria can acquire antibiotic resistance?
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What type of enzymes do some bacteria produce to inactivate beta-lactam antibiotics?
What type of enzymes do some bacteria produce to inactivate beta-lactam antibiotics?
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How does Salmonella typhi develop resistance to quinolones?
How does Salmonella typhi develop resistance to quinolones?
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Which mechanism of antibiotic resistance does not involve changes to target sites or plasmids?
Which mechanism of antibiotic resistance does not involve changes to target sites or plasmids?
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What is the primary action of quinolones in bacterial treatment?
What is the primary action of quinolones in bacterial treatment?
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Which antibiotic class specifically inhibits the 50S ribosomal subunit?
Which antibiotic class specifically inhibits the 50S ribosomal subunit?
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Which of the following can lead to failure of antibiotic therapy?
Which of the following can lead to failure of antibiotic therapy?
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What type of drug resistance occurs when bacteria develop resistance after exposure to an antibiotic?
What type of drug resistance occurs when bacteria develop resistance after exposure to an antibiotic?
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Vancomycin is primarily effective against which type of bacteria?
Vancomycin is primarily effective against which type of bacteria?
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What is the mechanism by which beta-lactam antibiotics exert their effect?
What is the mechanism by which beta-lactam antibiotics exert their effect?
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Which of the following antibiotics inhibit RNA polymerase?
Which of the following antibiotics inhibit RNA polymerase?
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Which antibiotic class is generally ineffective against bacteria that lack a cell wall?
Which antibiotic class is generally ineffective against bacteria that lack a cell wall?
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Study Notes
Introduction to Antibiotics and Antibiotic Resistance
- Antimicrobial agents are chemical substances that kill or inhibit the growth of microorganisms
- These include antibiotics, antivirals, antifungals, and antiparasitic drugs.
- Antimicrobials are toxic to microbes, not human cells.
Classifications of Antibiotics
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Spectrum of activity:
- Broad spectrum: effective against a wide variety of bacterial species.
- Narrow spectrum: effective only against a single or a limited group of bacteria. Isoniazid, for example, is active only against mycobacteria.
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Mode of action:
- Bacteriostatic: inhibits bacterial growth and replication.
- Bactericidal: kills the bacteria.
- Examples of bacteriostatic: chloramphenicol, erythromycin, clindamycin, sulfonamides, trimethoprim, tetracyclines
- Examples of bactericidal: aminoglycosides, beta-lactams, vancomycin, quinolones, rifampin, metronidazole
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Site of action:
- Inhibition of cell wall synthesis (e.g., glycopeptides, beta-lactams): -Beta-lactams bind to penicillin-binding proteins (transpeptidases), inhibiting peptidoglycan cross-linking. -Beta-lactams include penicillins (e.g., penicillin G, ampicillin), cephalosporins (1st, 2nd, 3rd, 4th, 5th generations), carbapenems (imipenem, meropenem), and monobactam. -Glycopeptides, such as vancomycin, also act on cell walls.
- Disturbance of cell membrane (e.g., polymyxins, daptomycin)
- Inhibition of protein synthesis (e.g., aminoglycosides, macrolides, tetracyclines)
- Inhibition of nucleic acid (e.g., quinolones, rifampin)
Drug Resistance Mechanisms
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Natural (Intrinsic) Resistance: Bacteria naturally resist the antibiotic without previous exposure because they lack the target site of the antibiotic agent.
- Examples: Mycoplasma and Chlamydia (due to lack of cell wall peptidoglycan). Gram-negative bacteria are naturally resistant to vancomycin
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Acquired Resistance: Resistance mechanisms developed after exposure to antibiotics (originally sensitive).
- This is caused by the mutation of existing genes or the acquisition of new resistance genes.
- Resistance genes can be transferred among bacteria via mechanisms like conjugation (sex pili), transduction (bacteriophages), and transformation.
- Modification of Target Sites: Bacteria modify the target sites of antibiotics to prevent binding, such as modifying DNA gyrase (Salmonella typhi resistance to quinolones) or penicillin-binding proteins (MRSA resistance to beta-lactams).
- Increased Drug Efflux: Bacteria pump the antibiotics outside the cell, preventing the drug from reaching its target.
- Drug Inactivation: Bacteria produce enzymes (e.g., β-lactamases, adenyl transferases) that inactivate the antibiotics.
Cross-Resistance
- Bacteria resistant to one antibiotic can also be resistant to others with the same mechanism of action or chemical structure.
- Examples: macrolides (azithromycin) and lincosamides (clindamycin).
How to Decrease Antibiotic Resistance
- Avoid unnecessary antibiotic prescriptions, particularly for viral infections.
- Proper antibiotic selection based on culture and sensitivity results.
- Administer antibiotics in the correct route, dose, and duration.
- Implement antibiotic stewardship programs to ensure responsible antibiotic use.
Antibiotic Combination
- Indication: Mixed infections, severe life-threatening infections (e.g., meningitis), and resistant bacteria.
- Aim: Synergism, where the combination of two antibiotics produces a greater effect than the sum of their individual ones.
- Disadvantage: High cost and increased risk of adverse effects. Antagonism can also occur, reducing the overall effect.
Practice Questions
- Q1: Aminoglycosides inhibit protein synthesis
- Q2: Macrolides are typically the drug of choice for Mycoplasma pneumoniae infections.
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Description
Dive into the fascinating world of antibiotics and their classifications. This quiz covers various antimicrobial agents, their modes of action, and the significance of antibiotic resistance. Learn about broad and narrow-spectrum antibiotics and their impact on microbial infections.
