ANTIMICROBIAL CHEMOTHERAPY (Incomplete)

Question 1

Mention 5 desired properties of antimicrobial drugs.

Answer 1

1. Selective
2. Broad spectrum
3. Non toxic to host
4. Long plasma half life
5. Good tissue distribution
6. Low plasma-protein binding
7. No drug inference

Question 2

What are the bases for the classification of antibacterials?

Answer 2

1. Chemical structure e.g. 4 rings - tetracyclines
2. Target site e.g.
   - cell wall inhibitors [penicillins, cephalosporins, vancomycins],
   - nucleus inhibitors [Quinolones]
   - protein synthesis inhibitors [Aminoglycosides, Macrolides]
3. Bacteriostatic/bactericidal
4. Chemotherapeutic spectra e.g. narrow spectrum, extended spectrum, broad spectrum

Question 3

What are the factors to be considered in the selection of antimicrobial agents?

Answer 3

1. Identity of the microorganism and its sensitivity to a particular agent
2. Site of infection: effective levels of the drug must reach the infection site. Poor perfusion of an anatomic area, like the lower limbs of the diabetic, make infections in that region harder to treat. The BBB blocks many antibiotics. Treatment of CNS infections depends on the drug’s ability to penetrate into the CSF.
3. Safety of the agents
4. Cost of therapy
5. Patient factors e.g. renal and hepatic dysfunction, allergy, pregnancy, age, poor perfusion

Question 4

Erythromycin and Tetracycline are contraindicated in patients with liver disease.

True or False?

Answer 4

True.

Question 5

All antibiotic cross the placenta.

True or False?

Answer 5

True.

Question 6

________ causes dysplasia and inhibition of bone growth in fetuses.

Answer 6

Tetracycline

Question 7

Classify antibiotic drugs based on chemotherapeutic spectrum. Give examples.

Answer 7

1. Narrow spectrum: acts only on a single or limited group of microorganisms e.g. Isoniazid is active against mycobacteria only
2. Extended spectrum: effective against gram +ve and gram -ve bacteria e.g. Ampicillin
3. Broad spectrum: affects a wide variety of microbial species. e.g. Tetracycline and Chloramphenicol.

Question 8

Treating with the single agent that is specific to the infective microbe is advisable, as it reduces the possibility of a superinfection and the occurrence of resistant organisms.

True or False?

Answer 8

True.

Question 9

________ is an example of a situation in which the combination of different antimicrobial drugs is advised.

Answer 9

Treatment of tuberculosis.

Question 10

Mention 2 problems that may arise from treatment with multi-drug combinations.

Answer 10

i. Superinfection
ii. Increased incidence of toxicity

Question 11

What is antibiotic resistance?

Answer 11

Bacteria are said to be resistant if their growth is not halted by the maximum level of antibiotic that is tolerated by the host.