Module 6: Antimicrobial Agents Flashcards
Antimicrobial Agent
A type of chemotherapeutic agent used specifically for the treatment of infectious diseases. Most antimicrobial agents are antibiotics but not all of them are
Antimicrobial Agents Spectrum(s)
Broad spectrum–> Affects a wide variety of microorganisms. Gram+ and Gram- bacteria Narrow spectrum–> Affects a small group of microorganisms Gram+ OR Gram-
Antimicrobial Agents, Bactericidal or Bacteriostatic
Bactericidal–> Agent actually kills the bacteria Bacteriostatic–> Agent only prevents the bacteria from multiplying
Antimicrobial Agents Mode of Action
- inhibitors of cell wall synthesis 2. inhibitors of protein synthesis 3. inhibitors of DNA and RNA synthesis 4. inhibitors of cell membrane functions 5. inhibitors of other metabolic processes
Criteria for an antibiotic in order for it to be used clinically
-should have selective toxicity, allowing it to selectively kill microorganisms and not host cells -shouldn’t cause allergic reactions in the patient -should be soluble in body fluids and be capable of penetrating infected tissue -microorganisms shouldn’t readily develop resistance to the antibiotic
Natural Penicillins
Original compounds extracted from the mold, Penicillium
Penicillins bacterial resistance
Inactivated or sensitive against beta-lactamase, an enzyme that opens the beta-lactam ring and makes the antibiotic useless.
Penicillins clinical use
Penicillin G= not taken orally Penicillin V= can be given orally Natural penicillins are sometimes given with other drugs to improve absorption and retention properties of the penicillin
Penicillin mode of action
Bactericidal- kills bacteria Inhibits cell wall synthesis
Examples of Penicillins
Penicillin G and Penicillin V
Beta-Lactamase Resistant Penicillins
Oxacillin Methicillin Cloxacillin
Beta-Lactamase Resistant Penicillins
A “bulky” side chain was added to the penicillin core that protects the beta-lactam ring from enzymatic destruction
Beta-Lactamase Resistant Penicillins mode of action
Beta-lactam cell wall inhibitor
Beta-Lactamase Resistant Penicillins spectrum
Very narrow Gram + spectrum Mainly used for treatment of Staphylococcal Infections
Beta-Lactamase Resistant Penicillins bacterial resistance
Not inactivated by beta-lactamase Resistance from penicillin binding proteins
Beta-Lactamase Resistance Penicillins clinical use
Orally or injected, Cloxacillin is most common
Extended Spectrum Penicillins
In the group of penicillins the Extended Spectrum Penicillins like Aminopenicillins are now a broad spectrum that includes gram- organisms
Beta-Lactamase Resistant Penicillins class concept
Applies
What is the spectrum of Extended Spectrum Penicillins?
Broad spectrum
Extended Spectrum Penicillins mode of action
Inhibiting synthesis of the bacterial cell wall
Extended Spectrum Penicillins spectrum
Broad spectrum Treatment of infections from both Gram+ and Gram- bacteria
Extended Spectrum Penicillins bacterial resistance
Susceptible to beta-lactamase and inactivated by these enzymes
Two Groups of Anti-Pseudomonal Penicillins
- Carboxy Pencillins (carbenicillin, ticarcillin) 2. Ureidopenicillins (azlocillin, mexlocillin, pipercillin)
Anti-Pseudomonal Penicillins Spectrum
Broad, less active against Gram+ than natural penicillins
Anti-Pseudomonal Penicillins Bacterial Resistance
Inactivated by staphylococcal beta-lactamase but more stable against Pseudomonas and Enterobacteriacea beta-lactamase
Anti-Pseudomonal Penicillins Clinical Use
Very expensive, used when bacteria are resistant to other antibiotics Often given with aminogylcosides, the combination is used for pseudomonal infections
Cephalosporins
-second group of the Beta-Lactam antibiotics -nucleus contains a beta-lactam ring fused to a different structure than the one in penicillins -over 20 of them developed for clinical use -Cephalosporins are placed in four groups based on their spectrum
Cephalosporins First Gen. Spectrum
Broad
First Gen. Clinical Use
More expensive than penicillins Cephalothin and Cefazolin are injected but Cephalexin can be taken orally
Cephalosporin Second Gen. Examples
Cefaclor Cefamandole Cefonicid Ceforanide Cefotiam Cefuroxime Cefotetan Cefoxitin
Cephalosporin Second Gen. Spectrum
Broad Individual antibiotics in this group are effective against specific organisms but not effective against Pseudomonas
