Chapter 10: Antimicrobial Medications: Part 1 Flashcards
Primary sites of action of Antimicrobial Drugs on Bacterial Cells
Protein synthesis Cell wall synthesis Nucleic acid synthesis Cell membrane synthesis Folic acid synthesis in the cytoplasm
What are sulfonamides?
Competitive inhibitor of metabolic processes, look similar to intermediates used during folic acid synthesis
Selective toxicity
A drug is more toxic to the microbe than it is to animals
What does the bacterial cell wall contain that makes it unique in construction?
Peptidoglycan
Do antimicrobials that interfere with the synthesis of a cell wall interfere with a eukaryotic cell?
No!!
Do cell wall inhibitors have a high or low therapeutic index?
High; low toxicity with high effectiveness
Cell wall inhibitors include what drugs?
- Beta lactic drugs
- Vancomycin
- Bacitracin
What is bacitracin usually used for?
Usually only as a topical medication
What are the alternating molecules that make up the cell wall?
Nam and nag molecules
Penicillins and cephalosporins are part of what group of drugs?
Beta lactams
What does penicillin / cephalosporin do?
Competitively inhibits functions of penicillin binding protein (by binding directly to the PBP) which inhibits the peptide bridge formation between glycan molecules
What does the PBP do?
Bacteria use it to build peptidoglycan, enzyme used to make the bonds between the sugars and between the proteins
Are penicillins and cephalosporins more effective against gram, positive or gram negative bacteria?
They vary in spectrum; some are more active against gram positive while others are more active against gram negative
How do some organisms resist the effects of penicillins and cephalosporins?
Through production of the Beta lactamase enzyme, which breaks the beta lactam ring, MRSA does this!
What part of the beta lactam ring actually interacts with and stops the synthesis of the cell wall?
The Beta-lactam “ring”
What creates different types of Beta-lactam drugs?
R groups
What can you usually give someone who is allergic to penicillin?
A cephalosporin
Narrow spectrum drugs are effective against….
Only a few microorganisms
Vancomycin
Inhibits formation of glycan chains, PTG, and cell wall construction, binds actually to the cell wall
Does vancomycin cross the lipid membrane of gram negative cells?
No!
Vancomycin is important in treating infections caused by penicillin resistant Gram ________ organisms.
Positive
How must vancomycin be given and why?
Intravenously due to poor absorption from the intestinal tract
What is the danger with vancomycin?
Ototoxicity
Ototoxicity
Causes damage to vestibulocochlear nerve (hearing), can cause deafness
Inhibition of protein synthesis
Structure of prokaryotic ribosome acts as target for many microbial of this class
What is responsible for selective toxicity in drugs that are protein synthesis inhibitors?
Difference in prokaryotic and eukaryotic ribosomes (drugs target 70s ribosome)
Protein synthesis inhibitors include… (7)
Aminoglycosides Tetracyclins Macrolides Cloramphenicol Lincosamides Oxazolidonones Streptogramins
Acronym for protein synthesis
A tall man can look over stairs
Tetracyclins
Reversibly bind 30s ribosomal unit, blocks attachment of tRNA to ribosome
What are Tetetracyclins effective against?
Gram positive and gram negative
Newer tetracycline such as _________ have longer half life
Doxycycline
Half life: time of decay, the amount of time it takes for half of the drug to be eliminated from your body
Resistance to tetracyclins can be caused by what?
Decreased accumulation by bacterial cells (some microorganisms are developing drug transporter systems where they pump the drug back out)
Nucleic acid synthesis inhibitors include..
Fluoroquinolones
Rifamycins
Rifamycins
Block prokaryotic RNA polymerase, block initiation of transcription (transcription will not start at all)
______ most widely used rifamycins
Rifampin
Rifamycins are effective against what cells?
Many gram + and some gram - as well as members of genus Myobacterium
Rifamycins are primarily used to treat…
Tuberculosis (in drug cocktails) as well as prevent meningitis after exposure to N. meningitidis
Resistance to rifamycins are due to..
Mutation coding RNA polymerase
-Develops rapidly
