Chemotherapy - Antibacterials

Question 1

What are the 3 types of antibacterials?

Answer 1

1. Products of micro-organisms (antibiotics)
2. Human designed drugs (chemotherapeutic / synthetic)
3. Hybrid of the two (semi-synthetic agents)

Question 2

Differences between bacteria & human cells

Answer 2

Bacteria
- no nuclear membrane - naked DNA
- 70s ribosomes (in prokaryotes) - large 50s & small 30s subunits
- peptidoglycan cell wall
- no mitochondria

Human
- nuclear membrane
- 80s ribosomes (in eukaryotes) - large 60s & small 40s
- no cell wall

Question 3

Antibacterial drugs that target protein synthesis (30s inhibitors) (2)

Answer 3

Streptomycin
Kanamycin

Question 4

Antibacterial drugs that target bacterial cell wall synthesis (2)

Answer 4

Penicillins
Vancomycin

Question 5

Antibacterial drugs that target folic acid metabolism in bacteria

Answer 5

Trimethroprim
Sulfonamides

Question 6

What enzyme do Sulfonamides target (in folate pathway in bacteria) ?

Answer 6

Dihydropteroate synthetase

Question 7

What enzyme does trimethoprim target (in folate pathway in bacteria)

Answer 7

Dihydrofolate reductase
(Which converts dihydrofolate —> tetrahydrofolate)

Question 8

Why is the folate pathway an effective pathway for antibacterial drugs?

Answer 8

Mammalian cells can only take up folate from surrounding environment - DONT SYNTHESISE IT

Bacteria synthesise from GTP and take up from surrounding environment

Question 9

Vancomycin

Answer 9

Works against gram positive bacteria only

Inhibits transglycosylation of peptidoglycan molecules

‘Drug of last resort’ - resistant S.aureus (MRSA)

Question 10

Antibacterial drugs inhibiting protein synthesis

Answer 10

Chloramphenicol - binds 50s, inhibits transpeptidation
Tetracycline - binds 30s, interferes with mRNA-tRNA interactions
Erythromycin - binds 50s, prevents translocation
Streptomycin - binds 30s, causes misreading of mRNA

Question 11

Symptoms of mycobacterium tuberculosis

Answer 11

Development of cough with mucosal secretions
Acute & chronic inflammation
Lung scarring

Question 12

3 treatments for TB

Answer 12

1. Pyrazianamide - mechanism not fully known, believed to interact with coA
2. Isoniazid - inhibits mycolid acid synthesis (important constituent in mycobacterium cell wall)
3. Rifampicin - DNA dependent RNA polymerase inhibitor