Introduction to Antibiotics Flashcards
Difference between narrow and wide spectrum antibiotics?
Narrow spectrum only affects a small number of microorganisms, while wide spectrum affects a large number.
Definition of sensitivity?
Concentration of a drug at site of infection must inhibit microorganism and remain below level toxic to human cells and be a level that can be clinically achieved at site of action. Or the mother of Mark. She is a sensitive woman.
Bactericidal vs Bacteriostatic
Bactericidal antibiotics kill organisms and must be used for life-threatening infections, whereas bacteriostatic antibiotics prevent microorganisms from growing/replicating, but require a functional immune system to remove the infecting microorganism
Reasons for prophylactic therapy?
1) To protect healthy patients (rifampin for meningococcal meningitis exposure) 2) To protect immune suppressed or at-risk patients (in chemotherapy) 3) To prevent post-operative wound infections (Clean surgeries)
Superinfection
Evidence of a new infection occurring during drug treatment of an existing infection
Mechanisms of action of antibiotics
1) Cell Wall Synthesis Inhibitors
2) Cell Membrane Inhibitors
3) Nucleic Acid Inhibitors
4) Microbial Protein Synthesis Inhibitors
5) Microbial Metabolism Inhibitors or Modifiers
Cell Wall Synthesis Inhibitor Antibiotics and their Actions
Penicillins, ampicillins, cephalosporins, Vancomycin: Inhibit cell wall synthesis or damage peptidoglycan
Bacitracin: Regeneration of specific membrane lipid carriers All bactericidal
Cell Membrane Inhibitor Antibiotics and Actions
Polymyxins: inhibit synthesis of or damage microbial cytoplasmic membrane, affecting permeability and resulting in intracellular content leakage
Nucleic Acid Inhibitor Antibiotics and Actions
Quinolones: Modify DNA synthesis, bactericidal
Rifampin: Modify RNA synthesis, can be bactericidal or bacteriostatic
Microbial Protein Synthesis Inhibitor Antibiotics and Actions
Inhibit or modify by affecting ribosomal subunits
Tetracycline, spectinomycin, streptomycin, aminoglycosides: 30S
Macrolides, chloamphenicol, clindamycin (bacteriostatic): 50S
Daptomycin (bactericidal): Non-specific
Linzeolid (binds to 50S but affects 30S): Other
Microbial Metabolism Inhibitor Antibiotics and Actions
Sulfonamides, trimethoprim: folic acid synthesis
Apart from the mechanism of action, how else is the effectiveness of an antibiotic determined?
Must reach the target tissue and bind to the target (pharmacodynamics and sensitivity)
Categories of bacterial resistance
1) Prevention of access to target
2) Altered target
3) Inactivation of drug/Drug cannot be converted to active form
Ways that prevention of access to target occurs?
1) Altered uptake: cell wall prevents drug entry into cell
2) Altered efflux mechanisms: improved transport out of the cell faster than the rate of pumping in
Ways that antibiotic cannot bind based on altered target?
Modification of drug binding sites.
Example: Vancomycin-resistant enterococci and staph aureus strains have an altered D-ala-D-ala binding site and high affinity binding of drugs is lost
