Antimicrobial Drugs

Question 1

Penicillins

Answer 1

• type of beta-lactam
• disrupts cell wall synthesis
• competitively inhibit enzymes that catalyze the formation of peptide bridges between NAG and NAM
• Binds to transpeptidase enzymes

Question 2

Cephalosporins

Answer 2

• type of beta-lactam
• disrupts cell wall synthesis
• competitively inhibit enzymes that catalyze the formation of peptide bridges between NAG and NAM
• Binds to transpeptidase enzymes

Question 3

Carbapenems

Answer 3

• type of beta-lactam
• disrupts cell wall synthesis
• competitively inhibit enzymes that catalyze the formation of peptide bridges between NAG and NAM
• Binds to transpeptidase enzymes
• resist beta-lactamases
• active against both gram positive and negative and anaerobes

Question 4

Monobactums

Answer 4

• Type of beta-lactam?
• disrupt cell wall synthesis
• resist beta-lactamases
• work only against aerobic gram-negative bacteria

Question 5

Vancomycin

Answer 5

• Blocks peptidoglycan synthesis by binding to peptide side chain of NAM molecules and blocking tetrapeptide bridge formation
• ONLY effective for gram positive bacteria

Question 6

Aminoglycosides

Answer 6

• inhibitor of protein synthesis
• bind 30s ribosomal proteins
• work synergistically with beta-lactams
• do not work against anaerobes or intracellular bacteria

Question 7

Tetracyclines

Answer 7

• inhibitor of protein synthesis
• block transfer of tRNA of the 30s subunit
• broad spectrum

Question 8

Chloramphenicol

Answer 8

• inhibitor of protein synthesis
• binds 50s subunit
• bacteriostatic
• toxic

Question 9

Macrolide and lincosamide

Answer 9

• inhibitor of protein synthesis

- binds 50s subunit and prevents translation

Question 10

Oxazolidinones

Answer 10

• blocks formation of the tRNA:mRNA:50s complex

- first new class of antibiotics in 30 years

Question 11

Trimethoprim

Answer 11

• inhibit synthesis of folic acid

- blocks dihydrofolate reductase

Question 12

Sulfamethoxyzole

Answer 12

• inhibits synthesis of folic acid

- blocks pteridine synthetase

Question 13

Quinolones and Fluouroquinolones

Answer 13

• inhibit nucleic acid synthesis
• main target is DNA gyrase
• active against gram negative aerobes and faculative anaerobes

Question 14

Rifamycins

Answer 14

• inhibition of bacterial DNA-dependent RNA synthesis with high affinity for the prokaryotic RNA polymerase
• effective against mycobacteria (TB)

Question 15

Isoniazid

Answer 15

• inhibits mycolic acid synthesis

- targets cell wall of mycobacteria

Question 16

Ethambutol

Answer 16

• targets cell wall of mycobacteria

- inhibits enzymes required for synthesis of other cell wall components

Question 17

Antimicrobial susceptibility testing - Kirby-Bauer Test

Answer 17

• qualitative assay
• put discs with abx on them on a plate of bacteria and see if it kills them
• can classify as sensitive, intermediate or resistant

Question 18

Antimicrobial susceptibility testing - E-Test

Answer 18

• quantitative assay
• uses strip of plastic marked with a gradient unique to each abx
• read zone of occlusion after incubation
• produces a ug/ml value

Question 19

Chemoprophylaxis

Answer 19

• drug given to a patient not currently infected but that may be at risk of acquiring an infection
• justified: tx of neonates with erythromycin, prophylaxis against malaria, animal bites, surgeries that cross mucosal barrier
• unjustified: patient demands, clean surgeries that do not cross mucosal barrier