Antibiotics Flashcards
What are chemotherapeutic agents used for?
Used to treat disease
Antibacterials, antifungals, antivirals
What are 2 ways we can determine the effectiveness of antimicrobials?
Dilution susceptibility tests for MIC
Disk diffusion tests
What is a dilution susceptibility test?
Involves inoculating media containing different concentrations of a drug
The agar with the lowest concentration showing no growth is the MIC
What is the disk diffusion test?
Inoculate plate with a culture of bacteria and place disks containing antibiotics on it
The zone of inhibition will show you how effective an antibiotic is against the bacteria
What do antibiotics target?
Inhibitors of cell wall synthesis
Protein synthesis inhibitors
Metabolic antagonists
Nucleic acid synthesis inhibition
How do penicillins work?
Blocks the enzyme that catalyzes transpeptidation
Prevents the synthesis of complete cell walls leading to lysis of the cell
Acts only on growing bacteria that are synthesizing new peptidoglycan
How do vancomycin and teicoplanin work?
Inhibit cell wall synthesis
What is vancomycin important for?
Important for the treatment of antibiotic-resistant MRSA or enterococcal infections
What are aminoglycosides effective against?
Gram-negative aerobic and facultatively anaerobic bacteria
How do aminoglycosides work?
Bind to the 30S ribosomal unit, interfere with protein synthesis by directly inhibiting the process and by causing misreading of the messenger RNA
What type of antibiotic are tetracyclines?
Broad-spectrum and bacteriostatic
How do tetracyclines work?
Combine with the 30S ribosomal subunit and inhibits binding of aminoacyl-tRNA molecules to the A site of the ribosome
What type of antibiotic are macrolides?
Broad-spectrum and bacteriostatic
How do macrolides work?
binds to 23S rRNA of 50S ribosomal subunit and inhibits peptide chain elongation
How do sulfa drugs work?
Selective toxic due to competitive inhibition of folic acid synthesis enzymes
What type of antibiotics are sulfa drugs?
Bacteriostatic
How do quinolones work?
Act by inhibiting bacterial DNA-gyrase and topoisomerase 2
What type of antibiotics are quinolones?
Broad-spectrum and bactericidal
How do lipopeptides work?
Inserts into membrane near phosphatidylglycerol, then aggregate changing membrane curvature and allowing little holes to form
What do antifungals do?
Disrupt membrane permeability
Inhibit sterol synthesis
Disrupt spindle formation
Inhibit nucleic acid and protein synthesis
What is amphotericin B?
An antifungal is one of the few that can be used systematically
Bind the fungal steroid ergosterol to cause membrane leakage
What is clotrimazole?
Inhibits sterol synthesis and damages fungal cell wall
Bind the fungal steroid ergosterol to cause membrane leakage
What are antiparasitic drugs?
Used to treat malaria and helminths
Peroxide-containing
Poor bioavailability
Potential for resistance
What are some ways that bacteria develop resistance?
Efflux pumps
Inactivating enzymes
Decreased uptake
Alterations of the targets
What is the basis of antimicrobial resistance?
Microbial warfare
Horizontal gene transfer
Evolutionary pressure from widespread antibiotic use
