Antimicrobial drugs Flashcards
(20 cards)
What are the characteristics of an ideal antibiotic?
Non-toxic, broad-spectrum, bactericidal, orally active, long half-life, good tissue penetration, stable, inexpensive, few side effects, and compatible with other drugs.
What is selective toxicity?
The ability of a drug to harm the target pathogen without harming the host.
What does the therapeutic index of an antibiotic measure?
The ratio of the toxic dose (TD50) to the effective dose (ED50). A higher index indicates greater safety.
Which antibiotics have a narrow therapeutic index?
Aminoglycosides and vancomycin.
What is the difference between broad-spectrum and narrow-spectrum antibiotics?
Broad-spectrum antibiotics act against a wide range of bacteria (e.g., tetracyclines), while narrow-spectrum antibiotics target specific bacteria (e.g., glycopeptides for Gram-positive only).
How does antibiotic concentration affect bacteriostatic and bactericidal actions?
Some antibiotics can be bacteriostatic at low concentrations and bactericidal at higher ones.
What factors determine the route of antibiotic administration?
Nature of infection, patient condition, drug absorption, and required speed of action.
What is the half-life of an antibiotic?
The time it takes for half the drug to be eliminated from the body.
What factors affect antibiotic penetration into tissues and fluids?
Drug properties, protein binding, and tissue accessibility.
What are examples of serious side effects of antibiotics?
Anaphylactic shock (penicillin), nephrotoxicity (aminoglycosides), and superinfections (C. difficile).
How do antibiotics affect the normal microbiota?
They can disrupt normal flora, allowing overgrowth of resistant or pathogenic microbes, causing superinfections.
What is antibiotic resistance?
The ability of microbes to survive exposure to an antibiotic concentration that would normally inhibit or kill them.
What are the classifications of microbial susceptibility?
S: Susceptible; I: Increased exposure required; R: Resistant.
What are the main mechanisms of antibiotic resistance?
Enzymatic inactivation, reduced permeability, efflux pumps, target modification.
What is transformation in antibiotic resistance?
Uptake of free DNA by competent bacteria from the environment.
What is transduction in antibiotic resistance?
Transfer of DNA between bacteria via bacteriophages.
What is conjugation in antibiotic resistance?
Transfer of plasmids through direct contact using a pilus.
How do β-lactamases confer resistance?
They break down β-lactam antibiotics, rendering them ineffective.
What are efflux pumps?
Protein channels that expel antibiotics from bacterial cells, reducing their effectiveness.
What is target modification in resistance?
Changes to the antibiotic’s binding site, preventing its action (e.g., altered ribosomes or enzymes).
