Session 2 - Infection Model Flashcards
Give 2 examples of Viruses, Bacteria, Fungi (yeast and mould) and Parasites (protozoa and helmniths)
Viruses – HIV, HPV, influenza,
Bacteria – E. coli, staph aureus
Fungi:
a) Yeast – Candida albicans (vaginal flora), cryptococcus neoformans
b) Mould – Aspergillus, dermatophytes (e.g. athletes foot)
Parasite:
a) Protozoa – Trypanosoma cruzi, Cryptosporidium parvum
b) Helminth (worm) – Tape worm, roundworms, flukes
How can you assess the minimum inhibitory concentration required to kill bacteria?
Minimum inhibitory concentrations can be assessed by placing a varying concentration of the antibiotic in a number of vials containing the bacteria and seeing what the smallest amount of concentration is needed to kill the bacteria. Usually assessed by having the vial change colour in the presence of bacteria.
What 3 ways can render an antibiotic no longer effective against an MO?
a) Drug inactivating enzymes produced, e.g. beta lactamases
b) Altered target – target enzyme develops lower affinity for antibiotic
c) Altered uptake – either an increase in the efflux of the drug or a decrease in the permeability of the membrane to the antibiotic
What are the 2 ways a bacteria can gain resistance?
1) Chromosomal gene mutation – A mutation In the genetic material encoding the target enzyme results in an altered enzyme which the drug is less able to impact
2) Horizontal gene transfer – Transposons (parts that be transferred between plasmids or between plasmids and chromosomes) can move from one organism to another by 3 processes:
a. Conjugation – Resistance passing from one organism to another by direct transfer
b. Transduction – A vector, usually a phage, picks up the transposon from one bacteria and gives it to another.
c. Transformation – free sections of DNA can transfer from one bacteria to another by crossing the PM
What are the 4 areas that an antibiotic can act on?
Cell wall synthesis, protein synthesis, cell membrane function, nucleic acid synthesis
What are the 2 types of AnB attack cell wall synthesis?
BCG
Beta lactams
Cell wall synthesis
Glycopeptides
Beta lactams and glycopeptides
What 3 types of AnB attack protein synthesis?
TAMPon
Tetracyclines
Aminoglycosides
Macrolides
Protein Synthesis
on
Tetracyclins, aminoglycosides, and macrolides
What type of AnB attacks cell membrane function?
Child Pornography
Cell membrane
Polymixins
Polymixins
What type of AnB attacks nucleic acid synthesis?
NewQuay
Nucleic acid synthesis
Quinolones
Quinolones
Tampons, BCG and Child pornography in NewQuay
What is the mechanism of action of penicillin?
- Cross linkage between cell walls achieved by penicillin binding protein
- Penicillin gets into penicillin binding protein and blocks enzyme from forming cross links
What is the mechanism of action of vancomycin?
• Sits on the peptide chains that cross link and stops the penicillin binding proteins from binding and forming cross links.
What is the mechanism of action of fluoroquinolones?
• Bind to two nuclear enzymes and inhibit DNA ligase and therefore replication
Name the 4 categories of beta lactams
1) penicillins
2) cephalosporins
3) carbapenems
4) monobactams
What are cephalosporins used for? give example
Broad spectrum and c difficile. e.g. ceftriaxone
What are carbapenems used for? give example
Broad spectrum gram -ve, safe for penicillin allergy e.g. meropenem
