L27_Mechanisms of Actions of Antibiotics Flashcards
What is the difference between bactericidal and bacteriostatic?
Bactericidal kills, bacteriostatic inhibits further growth.
What is a MIC, What is a MBC?
MIC- Minimal Inhibitory Concentration
MBC- Minimal Bactericidal Concentration
If you know an MIC, what concentration of antibiotic do you optimally prescribe?
4xMIC
Are most antibiotics prescribed bactericidal or bacteriostatic?
Even though some may be bactericidal, most antibiotics are effectively bacteriostatic at the concentrations given.
What is the most common class of clinical antibiotics?
Beta-Lactams (i.e. penicillin)
What is the mechanism of action of most anti-fungals?
Attack cell membrane
What is a downside of broad-spectrum antibiotics?
Shotgun approach. A lot of collateral damage, especially to normal flora
What is the only antibiotic that can treat MRSA?
Vancomycin
Describe the difference between pharmacokinetics and pharmacodynamics?
Pharmacokinetics encompasses all the ways that the body manipulates a drug, including absorption, distribution, metabolism, and excretion. Pharmacodynamics describes the biochemical and physiological effects of the drug and its mechanism of action on the bacteria.
What are the four main classes of cell wall inhibiting antibiotics.
Beta-Lactams, Glycopeptides, Fosfomycin, Daptomycin
What is the mechanism of action of Beta-Lactams? Are they bactericidal or bacteriostatic?
They inhibit cell wall synthesis. They bind irreversibly to transpeptidase enzyme (PBPs) and inhibits cross linking of peptidoglycan sheets. They are bactericidal.
What are the four main classes of Beta Lactams? Which are the strongest?
Penicillin, Cephalosporins, Monobactams, Carbapenems (Strongest)
How does vancomycin work? What type of bacteria is it ineffective against? What class of antibiotic is it?
It binds up D-alanyl-D-Alanine residues to prevent cross linking. Effective only against Gram Pos. It is a glycopeptide.
What are the only type of beta lactams that you can use against bacteria that produce extended spectrum beta lactamases (ESBLs)
Carbapenems
What are tetracyclines particularly effective against? Are they bacteriostatic or cidal. When are they containdicative?
Chlamydiae, Rickettsiae, and Mycoplasma
(Bacteriostatic and broad spectrum) can cross cell membrane. Dont give to pregnant women or children
What is a concern with aminoglycosides?
Toxicity, must monitor peak and trough levels. Can mess up kidneys and hearing
What class of bacteria are macrolides, lincosamides, streptogramins, and ketolides effective against?
Gram Positive cocci
What is clydamycin’s mechanism of action? What is a concern when using it?
Protein synthesis inhibition, it is a lincosamide. Inducible resistance is a concern.
What are Phenicols (Chloramphenicol) used against? What are dangers of it?
Used against many gram pos and neg bacteria in serious infections. Last resort as it is very toxic, especially to bone marrow.
What is linezolid mechanism of action and what can it be used against that many other antibiotics cant.
Protein synthesis inhibitor, can be used against MRSA and other multi-drug resistant infections but only as a last resort.
What are Ansamycins and Rifamycins commonly used to treat?
Tb
Name some drug classes that interfere with cytoplasmic membrane function
Polymyxins, Bacitracin, Anti-fungals
Name the two main drug classes used synergistically to kill bacteria by inhibiting metabolic activity/pathways
Sulfonamindes and Trimethoprim, both inhibit differents steps of folic acid synthesis (humans do not produce folic acid so this does not screw us up)
What are some problems with Sulfonamides?
Allergies, kernicterus, and hemolytic anemia
What are the three main classes of drugs that inhibit nucleic acid synthesis?
quinolones/fluoroquinolones, furanes, metronidazole.
How do quinolones and fluoroquinolones inhibit Nucleic Acid Syntheiss,
Target Topoisomerases
What cephalosporins generations are considered the Extended Spectrums? What gram stain bacteria are they active mainly against?
3rd gen - Gram negative
4th Gen- both (cefepime)
What are the first gen cephalosporins active against?
Gram pos
What are monobactams active against?
aerobic gram neg bacilli
What type of bacteria does daptomycin work against?
Gram Pos
What are carbepenemes active against?
Basically all pathogens and desistant to destruction by extended spectrum beta lactamases (ESBLs)
how do fosfomycins work?
halts muramic acid synthesis
Can you use carbepenemes against MRSA?
No
Name the classes of antibiotics that inhibit protein synthesis. Which is the only one that is bactericidal?
Aminoglycosides, Oxazolidinones (linezolid), Macrolides, Lincosamides (clindamycin), Phenicols (chloramphenicol), Ansamycins (rifampin)
