Session 4 Lecture Notes Flashcards
What is the antibacterial class referring to?
The chemical structure of the antibiotic
What is a bactericidal antibiotic?
An antibiotic that kills the organism
Note: a bacteriostatic antibiotic inhibits the activity of an organism but with a high enough concentration will become bactericidal
What 4 ways can an antibiotic act on a bacteria?
- On cell wall
- On cell membrane (rarely used)
- On protein synthesis
- On nucleic acid synthesis
What is the cell wall of a bacteria comprised of?
Peptidoglycine chains
In which ways do penicillin and vancomycin act on the bacterial cell wall?
Penicillin = acts on the penicillin binding protein (preventing cross linking of chains) Vancomycin = sticks onto the side chains so that the cross linking enzyme can't do its job (no cross linking)
What do fluroquinolones do?
Inhibit DNA gyrase and topoisomerase (this drug acts on nucleic acid of bacteria)
What are the 3 types of bacterial resistance?
- Intrinsic
- Acquired - acquires new genetic material or mutates
- Adaptive - responds to a stress (usually reversible)
Explain the concept of chromosomal gene mutation
There is a mutation in the gene of one of the bacteria that makes it resistant
The antibiotics kills all susceptible bacteria but the resistant one survives
This then multiplies and the whole strain is now resistant
Explain the concept of horizontal gene transfer
Genes can reside in 3 places: - chromosome - plasmids - transposon (free floating fragments) Genes from any of these locations can move to another bacteria (to the same species or a different one)
In horizontal gene transfer (DNA moving from one bacteria to another) it can happen in 1 of 3 ways. What are they?
- Conjugation
- Phages (injected in a bacteria by viruses)
- Free DNA (transposon can get through porins in cell wall)
Explain disc testing as a method of measuring antibiotic activity
Antibiotic on a disc in the centre of a plate
The organism is added and you can see where it grows
If it grows away from the disc and not in areas the antibiotic has spread you can see the level of activity
Name some classes of beta-lactam antibiotics
What is the problem with these?
Penicillin
Cephalosporin
Carbapenems
Many organisms have developed a resistance to beta lactams by synthesising beta lactamase enzyme making attaching the molecular structure of the beta lactam antibiotic
What drug is important in the emergency treatment of meningitis and why? What class and category of drug does it fall under?
Cetriaxone
It is a cephalosporin class of the beta lactam antibiotics
It is good because it works in the CSF
Name a type of glycopeptide antibiotics and state what type of bacteria it works against
Vancomycin
It works against most gram positive bacteria
When might you give tetracyclines and when would you give them?
Would:
Pneumonia
Chlamydia
Useful if the patient has a penicillin allergy
Usually work against gram positive bacteria
wouldn’t:
To young patients - as it stains you teeth
if the patient was very unwell (can only be taken orally)
