M: Antibiotic Action - week 9 Flashcards
What may antirmicrobials be directed against? (5)
bacteria, viruses, fungi, protozoa and helminths (so basically everything)
Name 4 subsets of antimicrobials
- antibiotics (antibacterial, so don’t work on viruses)
- antivirals
- antifungals
- antiparasitic drugs
What status of organism (i.e. quiescent or replicating) are antimicrobials directed against
Replicating organisms
What 4 ways can we classify antibiotics?
- Source
- Chemical structure (where name often comes from)
- Spectrum (whether broad or narrow)
- Broad mechanism of action (what they target and whether they are bacteriocidal or bacteriostatic)
What types of antibiotics are there and how are they derived? (3)
Natural: naturally, from moulds and bacteria
Semi-synthetic: natural, chemically modified
Chemotherapeutic agents: chemicals, synthetic
What is the reasoning behind adding a side chain to the base penicillin to create a penicillin variant?
For increasing resistance by stopping the activity of B-lactomase, which cleaves the molecule.
Why would you prefer a narrow spectrum of antimicrobial action over a broad spectrum? (2)
- the more organisms you attack the more likely one will develop resistance
- a broad spectrum can harm normal microbiota and cause problems that way
Provide 2 examples of bacteriostatic antibiotics
- chloramphenicol
- erythromycin
Provide 2 examples of bactericidal antibiotics
- aminoglycosides
- beta-lactams
Why might you decide to give bacteriostatic antibiotics rather than bactericidal? When might you not want to use bacteriostatics?
To give your immune system time to fight the bacteria. So don’t want to use in immunosuppressed people
How do bacteriostatics effect bacterial growth over time? How do bactericidals differ?
Growth is stopped however the bacteria are still viable and the viable bacteria count has not stopped.
Bactericidals actually remove/kill the viable bacteria
Name the 3 key considerations for antimicrobial action i.e. the 3 factors that determine whether an organism will be ‘sensitive’ or ‘resistant’ to the antimicrobial in question
- Selecive toxicity: want to target the organism, not the humans
- Access to site of infection: achieve adequate levels to where the organism is
- Provision of appropriate levels for an appropriate time: maintain adequate levels to allow inhibition or killing
How is selective toxicity achieved?
by exploiting the differences in the structure and metabolism of the bacterium and host cells
Name 6 classes of antimicrobials (S4) used by registered optometrists in ocular infections
- Beta Lactams
- Aminioglycosides
- Quinolones
- Macrolides
- Tetracyclins
- Cyclic Peptides
Note there are a few others i didn’t mention here, which can count as an answer for this question: chloramphenicol, rifamycins, glycopeptides, nitroimidazoles, nucleoside analogues
Name 4 antibacterial agents that act on peptide synthesis of the bacteria
- Macrolides
- Chloramphenicol
- Tetracyclines
- Aminoglycosides
Remember by: MCAT
Name 2 antibacterial agents that act on peptidoglycan synthesis of the bacteria
- beta lactams (e.g. penicillins, cephalosporins)
- glycopeptides (e.g. vancomysin)
Remember by: the BGs
Name 1 antibacterial agent that acts on cell membrane synthesis of the bacteria
Polymyxins
Name 2 antibacterial agents that act on folic acid of the bacteria
- Trimethoprim
- Sulphonamides
Name 1 antibacterial agent that acts on nucleic acid replication of the bacteria
- Quinolones