Ch. 20 Antimicrobial Drugs Flashcards
1
Q
What are antibiotics?
A
A substance produced by a microbe that, in small amounts, inhibits another microbe
2
Q
Difference between narrow and broad spectrum antibiotics?
A
- Depends on what you are targeting- bacterial cells vs. eukaryotic cells vs. viruses
- Narrow Spectrum- small range of different microbial types they affect EX. gram + or gram -
- Broad spectrum- affect a wide range of gram-positive and gram-negative bacteria
3
Q
What is the drawback of using broad-spectrum antibiotics?
A
It often kills norma flora too
4
Q
What are the 5 modes of action for antimicrobial drugs?
A
- Inhibiting cell wall synthesis – target peptidoglycan
- Inhibiting protein synthesis - can interfere with eukaryotic cells
- Inhibiting nucleic acid synthesis – can interfere with eukaryotic cells
- Injuring the plasma membrane – target specific components to alter permeability
- Inhibiting the synthesis of essential metabolites
5
Q
What are the modes of actions for anti fungal drugs?
A
- Target fungal sterols (plasma membrane)
- Target fungal cell walls
- Inhibit nucleic acids
- Inhibit mitotic microtubules (Note: used for fungal infections of the skin)
6
Q
Modes of action for antiviral drugs?
A
Inhibit:
- entry and fusion
- uncoating
- genome integration and nucleic acid synthesis
- assembly and exit
- & Interferons
7
Q
Modes of action for antiprotozoan drugs?
A
- Inhibit DNA synthesis
- Interfere with anaerobic metabolism
8
Q
Modes of action for antihelminthic (worm) drugs?
A
- Prevent ATP generation in mitochondria (tapeworms)
- Alter permeability of plasma membranes
- Neuromuscular block (roundworms)
- Inhibit absorption of nutrients (intestinal roundworms)
- Paralyze worm (primarily intestinal roundworms; occasionally for scabies, mites and lice)
9
Q
What is Disk-diffusion method (Kirby-Bauer test)?
A
- Lawned microbes
- Filter disks is saturated with antiseptic agent
- Creates an area around filter disk called Zone of Inhibition
- An organism can be reported as sensitive*, *intermediate* or *resistant
10
Q
What is E- Test?
A
- its a more advanced diffusion method
- estimates minimum inhibitory concentration (MIC) – the lowest antibiotic concentration that prevents visible bacterial growth
11
Q
What is Broth dilution tests?
A
- determines minimum bactericidal concentration (MBC)
- MIC is determined through decreasing dilutions of the agent that is inoculated with the test bacteria
- organism are placed in wells of a tray containing dilutions of a drug and growth is determined
- Wells that do not show growth can be cultured without the drug to see if growth occurs
- If growth – bacteriostatic
- If no growth – bactericidal
12
Q
Define Therapeutic index?
A
- assessing risks and benefits of drug administration
- Interactions with other drugs can be negative – toxic effects or neutralization of one
- Allergic reactions
13
Q
Characteristics of Penicillin G?
A
- Narrow Spectrum
- against most staphylococci, streptococci, and spirochetes
- Injected intramuscularly and excreted within 3 to 6 hours
14
Q
Characteristics of Penicillin V?
A
- Stable in stomach acids
- Taken Orally
- Natural penicillins have narrow spectrum of activity and susceptibility to penicillinase
- Penicillinases are enzymes produced by many bacteria (Staphylococcus), that cleave the -lactam ring
15
Q
1st generation of Cephalosporin
A
- Used for skin and soft tissue infections
- Primarily active against gram-positive bacteria
