Antibiotics 2 Flashcards
(24 cards)
What are the main bacterial targets for antibiotics?
Ribosomes (protein synthesis), DNA synthesis, RNA synthesis, cell wall, cell membrane, and biochemical pathways.
What is the role of polymyxins in targeting bacteria?
Polymyxins interact with lipopolysaccharides (LPS) in the outer membrane of Gram-negative bacteria, disrupting the phospholipid bilayer and causing cell death. They are drugs of last resort due to significant renal toxicity.
What are examples of polymyxins?
Polymyxin E (colistin) and polymyxin B.
What is the mechanism of action for aminoglycosides?
Aminoglycosides bind to the 30S ribosomal subunit, causing misreading of genetic code, interfering with codon:anticodon pairing, and inhibiting protein synthesis, resulting in bactericidal effects.
What are some examples of aminoglycosides?
Gentamicin, amikacin, tobramycin, neomycin, and streptomycin.
What are the adverse effects of aminoglycosides?
They have a narrow therapeutic index and can cause neurotoxicity and ototoxicity, particularly in cases of prolonged use or high doses.
How do tetracyclines work?
Tetracyclines bind to the 30S ribosomal subunit, blocking the attachment of aminoacyl-tRNA to the ribosome and inhibiting protein synthesis, which is bacteriostatic.
What are the adverse effects of tetracyclines?
They can chelate metal ions, form non-absorbable salts, and deposit in bones and teeth. They should be avoided in children under 8 years, pregnant women, and with dairy products due to calcium binding.
What is the mechanism of action for macrolides?
Macrolides bind to the 50S ribosomal subunit, inhibiting ribosomal translocation and blocking protein synthesis by halting the elongation of the polypeptide chain.
What are some examples of macrolides?
Erythromycin, clarithromycin, and azithromycin.
How do oxazolidinones work?
Oxazolidinones bind to the 50S ribosomal subunit and inhibit the formation of the initiation complex, preventing protein synthesis.
What is an example of an oxazolidinone?
Linezolid.
What is the novel mechanism of pleuromutilins?
Pleuromutilins bind to the A and P sites on the 50S ribosomal subunit, preventing tRNA binding, which blocks protein synthesis.
What is an example of a pleuromutilin?
Lefamulin.
What is the mechanism of action for fluoroquinolones?
Fluoroquinolones inhibit DNA gyrase and topoisomerase IV, enzymes essential for bacterial DNA replication and transcription. This mechanism is specific to bacteria, resulting in bactericidal effects.
What are examples of fluoroquinolones?
Ciprofloxacin, levofloxacin, and moxifloxacin.
What is the mechanism of action for rifamycins?
Rifamycins inhibit bacterial RNA polymerase, halting transcription and leading to bactericidal effects.
What is an example of a rifamycin?
Rifampicin.
What is the role of sulfonamides in antibiotic therapy?
Sulfonamides inhibit dihydropteroate synthase, an enzyme involved in folic acid synthesis, which is essential for bacterial growth.
How does trimethoprim enhance the effect of sulfonamides?
Trimethoprim inhibits dihydrofolate reductase, and when combined with sulfonamides (e.g., co-trimoxazole), it creates a synergistic effect.
What are the general mechanisms of antimicrobial resistance?
Altered permeability, inactivation of the antibiotic, altered binding sites, efflux pumps, and bypass of metabolic pathways. Examples include efflux pumps for tetracyclines and enzymatic inactivation for β-lactams.
What are intrinsic and acquired resistance mechanisms?
Intrinsic resistance involves natural barriers like the Gram-negative outer membrane, while acquired resistance involves genetic mutations or horizontal gene transfer.
What are the types of horizontal gene transfer?
Transformation (uptake of naked DNA), transduction (DNA transfer by phages), and conjugation (DNA transfer through cell-to-cell contact).
What are MDR pathogens?
Multi-drug resistant bacteria are resistant to at least one agent in three or more antimicrobial classes, such as ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species).
