Flashcards in Antibiotics Deck (20):
Where are antibiotics derived from?
Describe the animal cell.
~ 100u, no cell wall, 80S ribosome
Describe bacterial cell.
~ 1-10u, cell wall, 70S ribosome
What does Gram + and Gram - mean?
Gram + = will take up stain
Gram - = will not take up stain. complex envelope
If a bacteria is aerobic or anaerobic, where would they be located?
Aerobic: Surface areas (skin, resp tract)
Anaerobic: Bowel or deep puncture wounds
What shape is a cocci, bacilli and spirochaete?
Cocci - spherical
Bacilli - rod shaped
Spirochaete - spiral shaped
What are the 2 main types of antibiotics?
Bacteriostatic and Bactericidal.
What do bacteriostatic drugs do?
Prevent/inhibit bacterial replication, but don't kill.
Slows growth so immune system can kill bacteria.
What do bactericidal drugs do?
Actually kill bacteria.
e.g. Penicillins, quinolones...
What are the 3 main mechanisms of how antibiotics work?
1. inhibition of bacterial wall synthesis
2. inhibition of bacterial protein synthesis
3. inhibition of DNA replication
What inhibits the transpeptidase enzyme involved in cross-linking during synthesis of the cell wall?
B-lactams (4 member ring structure)
e.g. penicillin, cephalosporins
In the inhibition of protein synthesis, what do drugs act on?
The bacterial ribosome (70S). Has little effect on human ribosomes as they differ.
---> Selective toxicity.
How do sulfonamides inhibit DNA synthesis?
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.
What happens when you combine sulfonamides with trimethoprim?
You get Cotrimoxazole and it inhibits DHFR, the next enzyme in the folate synthetic pathway.
What do quinolones do?
Inhibit DNA gyrase (topoisomerase II) which changes the 3D structure of DNA needed for replication.
What are the 3 main mechanisms of antibiotic resistance?
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
Resistant bacteria usually have what? What does it do?
B-lactamase. It breaks down B-lactam ring in drug. Resistance can be over come by adding B-lactamase inhibitor.
What is MRSA?
Methicillin Resistant Staphylococcus aureus. A resistant bacteria that's a big issue. It multiplies rapidly and causes different infections.
What is Vancomycin?
A 'last resort' against superbugs such as MRSA.