1What is selective toxicity?
A drug harms microbes without significantly harming the host.
2What does therapeutic index measure?
The safety margin between an effective dose and a toxic dose.
3What is the therapeutic index formula?
$TI=\frac{\text{Toxic dose}}{\text{Therapeutic dose}}$
4What does a high therapeutic index mean?
The drug has a wider safety margin.
5What does a low therapeutic index mean?
The effective dose is closer to the toxic dose.
6What is the therapeutic index if the toxic dose is 200 mg and the therapeutic dose is 20 mg?
10.
7Where was penicillin originally obtained?
The fungus Penicillium.
8Where were cephalosporins originally obtained?
The fungus Cephalosporium.
9What are natural antibiotics?
Antibiotics produced by microorganisms.
10What are semi-synthetic antibiotics?
Natural antibiotics chemically modified in a laboratory.
11What are synthetic antibiotics?
Antibiotics manufactured in a laboratory.
12What is broad-spectrum activity?
Activity against many types of bacteria.
13What is narrow-spectrum activity?
Activity against a limited range of bacteria.
14What does bactericidal mean?
Kills bacteria.
15What does bacteriostatic mean?
Stops bacteria from growing and reproducing.
16What do penicillins inhibit?
Bacterial cell-wall synthesis.
17What structural feature do penicillins contain?
A beta-lactam ring attached to a five-sided ring.
18How do penicillins damage bacteria?
They prevent peptidoglycan cross-linking.
19How do cephalosporins work?
They inhibit bacterial cell-wall synthesis.
20How do cephalosporins differ structurally from penicillins?
They have a six-sided ring attached to the beta-lactam ring.
21What are examples of cephalosporins?
Ceftriaxone and cephalexin.
22How does bacitracin work?
It blocks transport of peptidoglycan building blocks.
23What molecule does bacitracin interfere with?
Bactoprenol.
24Where is bacitracin commonly used?
Topical ointments.
25How does polymyxin B work?
It disrupts Gram-negative bacterial membranes.
26What does polymyxin B bind to?
Lipopolysaccharide (LPS).
27What are major polymyxin B side effects?
Kidney damage, numbness, and respiratory arrest.
28Why is polymyxin B generally used topically?
It can be highly toxic when absorbed systemically.
29How do quinolones and fluoroquinolones work?
They inhibit DNA gyrase and bacterial DNA replication.
30How does rifampin work?
It inhibits bacterial RNA synthesis.
31Which ribosomal subunit do tetracyclines bind?
The 30S subunit.
32How do tetracyclines work?
They inhibit bacterial protein synthesis.
33What is the spectrum of tetracyclines?
Broad-spectrum.
34What is an important tetracycline precaution?
They can affect developing bones and teeth.
35What do aminoglycosides do to bacterial protein synthesis?
They cause errors in protein production.
36What are major aminoglycoside side effects?
Kidney damage and hearing loss.
37Why must aminoglycosides be used cautiously?
They have a low therapeutic index.
38Which ribosomal subunit do macrolides bind?
The 50S subunit.
39How do macrolides inhibit protein synthesis?
They prevent peptide-chain elongation.
40What structural feature do macrolides have?
A large macrocyclic lactone ring.
41What are examples of macrolides?
Erythromycin and azithromycin.
42What is the common name for an azithromycin treatment pack?
Z-Pak.
43How does chloramphenicol work?
It inhibits protein synthesis at the 50S subunit.
44What serious side effect is associated with chloramphenicol?
Aplastic anemia.
45How do sulfonamides work?
They interfere with bacterial folic-acid synthesis.
46Are sulfonamides natural or synthetic?
Synthetic.
47What does isoniazid inhibit?
Mycolic-acid synthesis.
48Which bacteria does isoniazid target?
Mycobacteria.
49What is natural antibiotic resistance?
Resistance due to a bacterium naturally lacking the drug's target.
50What is acquired antibiotic resistance?
Resistance gained through mutation or gene transfer.
51How can mutations cause antibiotic resistance?
Changes in DNA can create resistance traits.
52What is horizontal gene transfer?
Transfer of genetic material between bacteria.
53How does antibiotic use select for resistance?
Susceptible bacteria die while resistant bacteria survive and reproduce.
54What practices increase antibiotic resistance?
Unnecessary use and inappropriate prescribing.
55How can antibiotic resistance be reduced?
Use antibiotics only when appropriate and follow treatment instructions.