Antibiotics

Question 1

What antibiotics are cell wall synthesis inhibitors?

Answer 1

Penicillin
Cephalosporins
Vancomycin

Question 2

What antibiotics are protein synthesis inhibitors?

Answer 2

Tetracycline
Chloramphenicol
Erythromycin
Streptomycin

Question 3

Which antibiotics are nucleic acid synthesis inhibitors?

Answer 3

Ciprofloxin
Naladixic Acid

(These are quinolones)

Question 4

Which of the antibiotics are metabolic antagonists?

Answer 4

Sulfamethoxazole
Trimethoprim
Isoniazid

Question 5

Mechanism of Penicillin

Answer 5

[Cell wall synthesis inhibition]

Blocks the enzyme that catalyzes the transpeptidation reaction, so there will be no formation of cross-links in peptidoglycan

Prevents synthesis of complete cell wall, leading to cell lysis

Acts only on growing bacteria that are synthesizing peptidoglycan, so most effective on gram positive cells

CIDAL

Question 6

Mechanism of Cephalosporins

Answer 6

[Cell wall synthesis inhibition]

SAME AS PENICILLIN
Blocks the enzyme that catalyzes the transpeptidation reaction, so there will be no formation of cross-links in peptidoglycan

Prevents synthesis of complete cell wall, leading to cell lysis

Acts only on growing bacteria that are synthesizing peptidoglycan, so most effective on gram positive cells

CIDAL

Question 7

Mechanism of Vancomycin

Answer 7

[Cell wall synthesis inhibition]

Prevents transpeptidation of peptidoglycan subunits by binding to D-Ala-D-Ala amino acid at the end of the peptide side chains

Since this has a different binding site than Penicillin, it can be used when someone has a Penicillin allergy (“last resort”)

CIDAL

Question 8

Mechanism of Tetracycline

Answer 8

[Protein synthesis inhibition]

Binds to small ribosomal subunit (30S) and interferes with protein synthesis by directly inhibiting synthesis and causing misreading of the mRNA

Works on gram-negative cells

CIDAL

Question 9

Mechanism of Chloramphenicol

Answer 9

[Protein synthesis inhibition]

Binds to the 23S rRNA of the large ribosomal subunit (50S) to inhibit peptide chain elongation during protein synthesis

Works on gram negative and gram positive

STATIC

Question 10

Mechanism of Erythromycin

Answer 10

[Protein synthesis inhibition]

Binds to the 23S rRNA of 50S subunit of ribosome and inhibits peptide chain elongation

Question 11

Mechanism of Streptomycin

Answer 11

[Protein synthesis inhibition]

works on gram negative bacteria

Question 12

Mechanism of Ciprofloxin

Answer 12

[Nucleic acid synthesis inhibition]

Inhibits bacterial DNA gyrase and topoisomerase II, interfering with DNA replication

Question 13

Mechanism of Naladixic Acid

Answer 13

[Nucleic acid synthesis inhibition]

SAME AS CIPRO
Inhibits bacterial DNA gyrase and topoisomerase II, interfering with DNA replication

Question 14

Mechanism of Sulfamethoxazole

Answer 14

[Metabolic antagonist]

Inhibits folic acid synthesis

Analog of PABA

Often combined with Trimethoprim in order to block 2 steps of Folic acid synthesis

Question 15

Mechanism of Trimethoprim

Answer 15

[Metabolic antagonist]

Structural analog of a portion of dihydrofolic acid, competitively inhibits the synthesis of tetrahydrofolic acid

Often combined with Sulfamethoxazole in order to block 2 steps in Folic acid synthesis

Question 16

Mechanism of Isonaziod

Answer 16

[Metabolic antagonist]

Mechanism is unclear, it is thought to inhibit lipid synthesis

Can act as CIDAL or STATIC