ANTIBIOTIC DRUG CLASSES AND MECHANISM Flashcards
What are the possible reasons for adverse reactions to antibiotics?
Membrane interacting antibiotics may interact with patient membranes at high concentrations
Breakdown and release of bacterial components can cause a reaction
What is a narrow spectrum antibiotic?
Target narrow group of bacteria (e.g., gram +ve or Gram -ve)
What is a broad spectrum antibiotic?
Targets Gram +ve ANd gram -ve
What is a bacteriocidal antibiotic?
Kills organism
e.g., penicillin’s, cephalosporin’s
What is a bacteriostatic antibiotic?
Drugs that temporarily inhibit the growth of an organism (i.e. reversible if removed).
Examples Tetracycline’s, Chloramphenicol
What is the MIC of an antibiotic?
(minimum inhibitory concentration): The concentration required at the site of infection to achieve bacterial inhibition.
What is the MBC of an antibiotic?
(minimum bactericidal concentration): The concentration required at the site of infection to kill the bacteria
What are the different targets of antibiotics on bacteria
Inhibition of protein synthesis
Inhibition of cell membrane function
Inhibition of cell wall synthesis
Interference with other pathways
Inhibition of DNA dependent RNA polymerase
Disruption of DNA structure
Give examples of antibiotics which inhibit protein synthesis
Chloramphenicol
Lincosamides
Macrolides
Amino glycosides
Pleuromutilin
Tetracyclines
Nitrofurans
Give examples of antibiotics which inhibit cell membrane function
Polypeptides Antimicrobial peptides
Give examples of antibiotics that inhibit cell wall synthesis
B-lactam antibiotics
Vancomycin
Bacitracin
Give examples of antibiotics that inhibit DNA dependent RNA polymerase
Rifampicins
Give examples of antibiotics that disrupt DNA structure
Nitroimidazoles
Metronidazole
How do antibiotics inhibit cell wall synthesis
Targets peptidoglycan (unique to bacteria)
Lysozyme produced by host breaks bonds in polysaccharide
Beta-lactam inhibits penicillin binding protein (transpeptidase) weakening cell wall => increased osmotic pressure => burst
Glycopeptides cap peptide chains to weaken cell wall => bursts
Describe how Beta-lactam antibiotics work
Penicillins (narrow and broad) and cephalosporins )1st - 5th gen)
Beta-lactam inhibits penicillin binding protein (transpeptidase) weakening cell wall => increased osmotic pressure => burst
How do antibiotics inhibit protein synthesis
inhibit translation of RNA to proteins by binding to ribosomal complex
How do aminoglycosides work?
Bacteriocidal
Inhibit protein synthesis by binding to 30S and effects a number of steps of protein synthesis leading to non-functional proteins
GRAM -VE
How do tetracyclines work?
Bacteriostatic
Inhibit protein synthesis
Actively enter cell and bind to 30S subunit preventing tRNA attachment
GRAM -VE and +VE
How does chloramphenicol work?
Bacteriostatic
Inhibits protein synthesis by binding to 50S subunit and preventing linkage of amino acids to growing peptides
Broad spectrum
How do sulphonamides/trimethoprim (TMPS) work?
Affect DNA
Competitive inhibitors of dihydropteroate synthetase to inhibit dihydrofolate synthesis which is required for DNA synthesis
How do Quinolones and Novobiocin work?
Affect DNA
Bind to and stops DNA Gyrase preventing packing of DNA, inhibits supercoiling of chromosome => disrupts associated processes
How do Nitroimidazoles work?
Affect DNA
Reduction products are reactive with DNA causing DNA strands to break
How does Rifampicin work?
~Inhibits DNA dependent RNA polymerase => blocks initiation of protein synthesis
Describe the use of antimicrobial peptide
Topical application
Interact and disrupt membranes
Licensed for dermatology (ears)
Work via difference in charge
How can the site of infection alter antimicrobial activity?
Aerobic vs anaerobic
Time
Concentration
