[W5-6] Antibiotics and AMR

Question 1

What are antibiotics?

Answer 1

Low molecular weight compounds, often produced by microbes (e.g., Streptomyces), that kill or inhibit bacteria.

Question 2

What’s the difference between antibiotics and antimicrobials?

Answer 2

Antibiotics = antibacterial; antimicrobials = act against bacteria, viruses, fungi, or protozoa.

Question 3

What’s the difference between bacteriostatic and bactericidal?

Answer 3

Bacteriostatic: Inhibit growth.
Bactericidal: Kill bacteria.

Question 4

What is a broad-spectrum antibiotic?

Answer 4

Active against many bacterial types; used before pathogen identification.

Question 5

What is a narrow-spectrum antibiotic?

Answer 5

Targets specific bacteria; minimizes microbiome disruption.

Question 6

What are common delivery routes for antibiotics?

Answer 6

Oral, intravenous, intranasal, topical.

Question 7

List pharmacological and antimicrobial properties of a good antibiotic.

Answer 7

Antimicrobial:
* Selective toxicity
* Potent cidal activity
* Low resistance development
Pharmacological:
* Good tissue penetration
* Low toxicity
* Stable
* Various forms
* Low protein binding

Question 8

What is intrinsic resistance?

Answer 8

Natural resistance due to structural features (e.g. Gram-negatives and β-lactams).

Question 9

What is acquired resistance?

Answer 9

Resistance via mutation or horizontal gene transfer (HGT).

Question 10

What are MIC and MBC?

Answer 10

MIC: Minimum inhibitory concentration.
MBC: Minimum bactericidal concentration.

Question 11

Name 3 AMR testing methods.

Answer 11

Serial dilution (MIC/MBC), Etest, Disc diffusion assay.

Question 12

What is the target of β-lactams?

Answer 12

Penicillin-binding proteins (PBPs) involved in peptidoglycan crosslinking.

Question 13

What are two key resistance mechanisms to β-lactams?

Answer 13

β-lactamases (enzyme degradation), Altered PBPs (e.g. PBP2a in MRSA).

Question 14

What are extended spectrum β-lactamases (ESBLs)?

Answer 14

Enzymes that hydrolyze a broad range of β-lactams, including cephalosporins.

Question 15

How does clavulanic acid help β-lactam activity?

Answer 15

Inhibits β-lactamases; used in combo with amoxicillin (e.g. Co-amoxiclav).

Question 16

What makes MRSA resistant to methicillin?

Answer 16

PBP2a has low affinity for β-lactams.

Question 17

What infections is MRSA associated with?

Answer 17

Nosocomial infections, surgical wound infections, bloodstream infections.

Question 18

How does vancomycin work?

Answer 18

Binds D-Ala-D-Ala on peptidoglycan precursors to inhibit crosslinking.

Question 19

Why is vancomycin effective against MRSA?

Answer 19

Targets different site than β-lactams (not affected by β-lactamases or PBP2a).

Question 20

Which antibiotics target the 30S subunit?

Answer 20

Tetracyclines: Block tRNA binding.
Aminoglycosides: Cause misreading of mRNA.

Question 21

Which antibiotics target the 50S subunit?

Answer 21

Macrolides (e.g. erythromycin): Block translocation.
Chloramphenicol: Inhibits peptidyl transferase.

Question 22

What are common tetracyclines?

Answer 22

Tetracycline, doxycycline, lymecycline.

Question 23

What are major tetracycline resistance mechanisms?

Answer 23

Efflux pumps (most common), ribosome protection proteins, enzymatic inactivation.

Question 24

What are side effects of aminoglycosides?

Answer 24

Nephrotoxicity and ototoxicity (hearing/balance loss).

Question 25

How do macrolides confer resistance?

Answer 25

Efflux pumps, Methylation of 23S rRNA by ermB.

Question 26

What are the main uses and risks of chloramphenicol?

Answer 26

Used topically (e.g. eye drops). IV use risks aplastic anaemia.

Question 27

What enzyme inactivates chloramphenicol?

Answer 27

Chloramphenicol acetyltransferase (CAT).

Question 28

What is the target of fluoroquinolones like ciprofloxacin?

Answer 28

DNA gyrase (GyrA & GyrB), especially GyrA's ligase activity.

Question 29

How does fluoroquinolone resistance arise?

Answer 29

Single point mutations in the QRDR region of gyrA.

Question 30

What does TMP-SMX target?

Answer 30

TMP: Dihydrofolate reductase SMX: Dihydropteroate synthase.

Question 31

What’s a common resistance mechanism to TMP?

Answer 31

Acquisition of TMP-resistant DHFR genes via MGEs.

Question 32

What infections is nitrofurantoin used for?

Answer 32

First-line for lower UTIs and cystitis.

Question 33

Why is resistance to nitrofurantoin uncommon?

Answer 33

Requires multiple gene mutations; targets multiple processes.

Question 34

What is de novo mutation?

Answer 34

A spontaneous mutation conferring resistance, followed by selection and clonal expansion.

Question 35

What role does HGT play in AMR?

Answer 35

Enables rapid spread of resistance genes between strains, species, and environments.

Question 36

What is antimicrobial stewardship?

Answer 36

Coordinated efforts to ensure effective and judicious use of antibiotics.

Question 37

What is the “One Health” approach?

Answer 37

A strategy integrating human, animal, and environmental health to combat AMR.

Question 38

What is the UK-AWaRe antibiotic classification?

Answer 38

Access: Narrow-spectrum, low resistance risk Watch: Higher resistance risk Reserve: Last resort drugs.

Question 39

Give an example of an antibiotic in each UK-AWaRe category.

Answer 39

Access: Nitrofurantoin Watch: Erythromycin Reserve: Meropenem.

Question 40

What is the WHO Priority Pathogen List for?

Answer 40

Guides global R&D and policy focus toward the most dangerous resistant pathogens.