Questions and Answers
The following are true of Penicillin with the exception of:
A drug that inhibits mitosis, such as griseofulvin, would be more effective against:
Most of the available antimicrobial agents are effective against:
In what way are semisynthetic penicillins and natural penicillins alike?
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Which of the following antibiotics is NOT bactericidal?
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Which one of the following does NOT belong with the others?
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Which of the following antimicrobial agents has the fewest side effects?
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Which of the following antimicrobial agents is recommended for use against fungal infections?
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Who is the individual that first identified penicillin coming from the mold penicillium?
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Actinobacteria or actinomycetes is a phylum of Gram-positive bacteria with high _____ and _____ content in their DNA.
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The classic example of a broad-spectrum antibiotic is:
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The following are modes of action of antimicrobial drugs with the exception of:
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_________ are applied to nonliving surfaces or substances with the intent of purifying an area of all or most microorganisms that could cause harm.
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Which of the following antibiotics does NOT interfere with cell wall synthesis?
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Drug resistance occurs:
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The following results were obtained from a disk-diffusion test for microbial susceptibility to antibiotics. In Table 20.2, the most effective antibiotic tested was:
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Which of the following would be selective against the tubercle bacillus?
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In the presence of penicillin, a cell dies because:
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Mebendazole is used to treat cestode infections. It interferes with microtubule formation; therefore, it would NOT affect:
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An example of a competitive inhibitor of the synthesis of essential metabolites includes:
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Beta-lactam antibiotics include which of the following:
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This is an important 'last line' medication against antibiotic-resistant S. Aureus:
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The following drug can cause irreversible aplastic anemia:
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Fungi and animal cell membranes have different sterols. Which sterol is found on fungal membranes?
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Treatment for helminthic infection includes:
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Penicillin was considered a 'miracle drug' for all of the following reasons EXCEPT:
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Which of the following statements about drug resistance is false?
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Drug resistance occurs:
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In Table 20.2, the most effective antibiotic tested was:
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In Table 20.2, the antibiotic that exhibited bactericidal action was:
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In Table 20.2, which antibiotic would be most useful for treating a Salmonella infection?
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Which of the following would be selective against the tubercle bacillus?
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In the presence of penicillin, a cell dies because:
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Lamisil is an allylamine used to treat dermatomycoses. Lamisil's method of action is similar to that of:
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Niclosamide prevents ATP generation in mitochondria. You would expect this drug to be effective against:
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The data in Table 20.3 show that these bacteria:
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Which of the following statements about drugs that competitively inhibit DNA polymerase or RNA polymerase is false?
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The substrate for transpeptidase used to synthesize peptidoglycan is shown in Figure 20.5. Which of the drugs shown would inhibit peptidoglycan synthesis?
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The structures of the influenza drug Tamiflu and sialic acid, the substrate for the influenza virus's neuramidase, are shown in Figure 20.6. What is the method of action of Tamiflu?
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Which of the following does NOT affect eukaryotic cells?
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Mebendazole is used to treat cestode infections. It interferes with microtubule formation; therefore, it would NOT affect:
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Which of the following antibiotics causes misreading of mRNA?
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The antibiotic actinomycin D binds between adjacent G-C pairs, thus interfering with:
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Study Notes
Antibiotics and Antimicrobial Agents
- Penicillin: Inhibits gram-positive cell wall synthesis and has selective toxicity but does not inhibit protein synthesis.
- Griseofulvin: Effective against fungi by inhibiting mitosis.
- Antimicrobial Agents: Most are effective against bacteria rather than viruses, fungi, or protozoa.
- Semisynthetic Penicillins: Both semisynthetic and natural penicillins are based on β-lactam structure.
Antibiotic Classification
- Bactericidal vs. Bacteriostatic: Not all antibiotics are bactericidal; for example, polyene antibiotics are not bactericidal.
- Mode of Action: Includes inhibition of cell wall synthesis, protein synthesis, and disruption of plasma membranes.
- Broad-Spectrum Antibiotic: Amoxicillin is a classic example known for its effectiveness against a variety of bacteria.
Specific Antibiotics and Their Uses
- Amphotericin B: Recommended for fungal infections.
- Streptomycin: Causes misreading of mRNA and inhibits protein synthesis.
- Ethambutol: Selective against the tubercle bacillus by inhibiting mycolic acid synthesis.
- Chloramphenicol: Binds to the 50S subunit of ribosomes, preventing peptide bond formation.
Mechanisms of Drug Resistance
- Drug Resistance: Occurs due to indiscriminate use of antibiotics and the transfer of resistant genes between bacteria. It is not limited to gram-negative bacteria.
- Competitive Inhibition: Several drugs act as competitive inhibitors on biochemical pathways, including sulfonamides.
Impacts of Antibiotic Use
- Use in Animal Feed: Leads to antibiotic-resistant bacteria due to selective pressure where resistant strains survive and reproduce.
- Selective Toxicity: Indicates that antibiotics are generally less harmful to eukaryotic cells compared to prokaryotic cells.
Unique Properties and Actions
- Actinobacteria: A phylum of gram-positive bacteria known for high guanine and cytosine content in DNA.
- Fungal Membranes: Contain ergosterol, which is different from cholesterol found in animal cell membranes.
Clinical Considerations
- Minimal Inhibitory Concentration (MIC): The lowest concentration of an antibiotic that inhibits growth of a microorganism.
- Minimal Bactericidal Concentration (MBC): The lowest concentration that kills the microorganism.
- Adjunct Therapy: Using two antibiotics together can prevent drug resistance and reduce toxicity, but it does not guarantee increased effectiveness.
Notable Figures in Antibiotic Discovery
- Alexander Fleming: First identified penicillin from the mold Penicillium.
Fungal and Helminthic Treatment
- Mebendazole: Used for helminthic infections by interfering with microtubule formation, ineffective against bacteria.
- Flucytosine: An antifungal agent effective against candidiasis.
Mechanisms of Inhibition
- Translation Inhibition: Different antibiotics affect peptide bond formation and ribosome function at various subunits (30S or 50S).
- DNA/RNA Interference: Certain antibiotics inhibit nucleic acid synthesis and transcription processes.
Side Effects and Risks
- Chloramphenicol: Risk of causing aplastic anemia as a serious side effect.
- Antimicrobial Peptides: Disrupt the plasma membrane as part of their antimicrobial action.
Summary
- Antibiotics vary widely in structure, function, and spectrum of activity, and understanding their mechanisms is crucial for effective treatment and combating antibiotic resistance.
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Description
Test your knowledge on key concepts from Microbiology Chapter 20 with these flashcard-style questions. This quiz covers important details about antibiotics such as Penicillin and the effects of various drugs on microorganisms. Challenge yourself and reinforce your understanding of microbiological treatments.