Antibiotics

Question 1

Where are antibiotics derived from?

Answer 1

Microorganisms

Question 2

Describe the animal cell.

Answer 2

~ 100u, no cell wall, 80S ribosome

Question 3

Describe bacterial cell.

Answer 3

~ 1-10u, cell wall, 70S ribosome

Question 4

What does Gram + and Gram - mean?

Answer 4

Gram + = will take up stain

Gram - = will not take up stain. complex envelope

Question 5

If a bacteria is aerobic or anaerobic, where would they be located?

Answer 5

Aerobic: Surface areas (skin, resp tract)
Anaerobic: Bowel or deep puncture wounds

Question 6

What shape is a cocci, bacilli and spirochaete?

Answer 6

Cocci - spherical
Bacilli - rod shaped
Spirochaete - spiral shaped

Question 7

What are the 2 main types of antibiotics?

Answer 7

Bacteriostatic and Bactericidal.

Question 8

What do bacteriostatic drugs do?

Answer 8

Prevent/inhibit bacterial replication, but don’t kill.
Slows growth so immune system can kill bacteria.

e.g. Sulphonamides

Question 9

What do bactericidal drugs do?

Answer 9

Actually kill bacteria.

e.g. Penicillins, quinolones…

Question 10

What are the 3 main mechanisms of how antibiotics work?

Answer 10

1. inhibition of bacterial wall synthesis
2. inhibition of bacterial protein synthesis
3. inhibition of DNA replication

Question 11

What inhibits the transpeptidase enzyme involved in cross-linking during synthesis of the cell wall?

Answer 11

B-lactams (4 member ring structure)

e.g. penicillin, cephalosporins

Question 12

In the inhibition of protein synthesis, what do drugs act on?

Answer 12

The bacterial ribosome (70S). Has little effect on human ribosomes as they differ.

—> Selective toxicity.

Question 13

How do sulfonamides inhibit DNA synthesis?

Answer 13

It is an analog of PABA, which is how bacteria form folic acid for DNA synthesis. It competes with PABA to inhibit folic acid synthesis.

Question 14

What happens when you combine sulfonamides with trimethoprim?

Answer 14

You get Cotrimoxazole and it inhibits DHFR, the next enzyme in the folate synthetic pathway.

Question 15

What do quinolones do?

Answer 15

Inhibit DNA gyrase (topoisomerase II) which changes the 3D structure of DNA needed for replication.

Question 16

What are the 3 main mechanisms of antibiotic resistance?

Answer 16

1. change in site where drug acts
2. reduced bacterial uptake or enhanced efflux of drug
3. bacteria produces an enzyme that inactivates the drug

Question 17

Resistant bacteria usually have what? What does it do?

Answer 17

B-lactamase. It breaks down B-lactam ring in drug. Resistance can be over come by adding B-lactamase inhibitor.

Question 18

What is MRSA?

Answer 18

Methicillin Resistant Staphylococcus aureus. A resistant bacteria that’s a big issue. It multiplies rapidly and causes different infections.

Question 19

What is Vancomycin?

Answer 19

A ‘last resort’ against superbugs such as MRSA.

Question 20

When choosing antibiotics, what should you consider?

Answer 20

1. Bacterial factors
2. Drug factors
3. Patient variables.