Antibiotics Midterm Flashcards
-illins
Related to PCN
-cyclins
Related to tetracyclins
-mycins
Related to macrolide antibiotics
What does Vancomycin target?
Peptidoglycan in cell walls, gram positive bacteria
What does Chloramphenicol target?
Ribosomal subunits
Bacteriostatic vs. Bactericidal
Bacterial growth vs. Bacterial death
MIC vs. MLD
Minimal inhibitory concentration vs minimal lethal dose. MIC is the lowest concentration needed to inhibit growth in 99% and MLD is minimal amount needed to kill 99.9%
Drugs that target essential metabolic pathways?
Sulfa/Trimethoprim
P-Aminosalicylic acid
Drugs that target nucleic acid synthesis
Rifampin and Rifabutin
Quinolones
Metronidazole (flagyl)
Drugs that disrupt bacterial membranes
Polymyxins/Colistin (Polymixin E)
Specific effect of sulfa drugs
These are broad spectrum antibiotics that inhibit folic acid biosynthesis from the start. Often used with trimethoprim which inhibits another step in the pathway by stopping the cell from using pools of materials it has already made. Both of these guys act as competitive inhibitors.
S + T = Bactrim
What other drug is Sulfa related to?
P-aminosalicylic acid - Effective against TB
Drugs that are bactericidal
Rifampin and Rifabutin
Quinolones
Metronizadole (Flagyl)
Polymixins
How do rifampin and rifabutin work?
narrow spectrum, gram + bacteria. Binds to beta subunit of RNA polymerase, inhibits transcriptional initiation
How do quinolones work?
inhibit DNA replication by inhibiting bacterial DNA gyrases and/or topoisomerase IV
How does flagyl work?
narrow spectrum, administered as a prodrug, disrupts DNA structure, inhibits DNA replication, causes breaks and mutations (enzymes to convert prodrug only in bacterial cells)
How do Polymixins work?
narrow spectrum, inserts hydrophobic tail into membrane, hydrophilic head group disrupts PE and LPS on membrane (host dos not have PE or LPS)
What drugs target the bacterial cell wall?
Vancomycin
PCN
How does Vanco work?
Prevents transglycosylation in the cell wall
How does PCN work?
Inhibits transpeptidation by mimicking the beta-lactam molecule to bind transpeptidases and carboxypeptidases.
All -cillins work in this way
What do we give -cillins to help the mfight bacteria resistances?
Clavulanic acid, which when given with the -cillin, fights the Beta-lactamase that inhibits the antibiotic.
Ex. Augmentin = Amoxicillin + clavulanic acid
What drugs target the cell membrane
Polymixins
Daptomycin
How do polymixins work?
Integrates a lipophilic tail in the outher membrane and destroys it. Effects Gram negative bacteria.
How does Daptomycin work?
Affects gram negative bacteria making it a good alternative to Vancomycin. Integrates lipophilic tail in membrane and destroys it. Calcium dependent though
What is the danger of targeting bacterial ribosomes?
Very similar to our mitochondrial ribosomes. Antibiotics can’t cross this!
Antibiotics that inhibit the production of initiation complexes
Linezolid (member of oxazolidiones) - Inhibits the formation of 70s initiation complex by targeting the 50s subunit. Only works on gram positive bacteria.
Different effects for linezolid?
It is bacteriostatic against staph and enterococci but interacts more strongly with trep, killing it.
Antibiotics that inhibit peptide chain synthesis specifically by inhibiting recognition of protein synthesis structures?
Aminoglycosides
Streptinomycin
Tetracyclines
How do aminoglycosides work?
They target the proteins in the 30s subunit, are broad spectrum and are bactericidal.
Key antibiotic in this category is streptomycin.
What does streptomycin do?
- Causes misreading/insertion in a chain
- Causes structural protein failure in cell membrane
- Cyclic polysomal blockade where 70s forms but falls apart
Problems with using aminoglycosides?
Toxicity, ineffective against most intracellular bacteria and can cause biofilm creation from catheters.
How does streptinomycin work?
Another type of antibiotic that inhibits protein synthesis, but it is an aminocyclitol antibiotic. It’s bcteriostatic and causes unstable formation of 70s. Used to treat gonorrhea.
How do Tetracyclins work?
Broad spectrum antibiotic that treats chlamydia, mycoplasma, and rickettsia. Binds to 30s unit and inhibits binding of aa-tRNA to the activation site
Antibiotics that inhibit protein synthesis specifically by inhibiting peptidyl transfers
Cloramphenicol
Lincomycin and Clindamycin
How dos Chloramphenicol work?
Broad spectrum, bacteriostatic. Binds to 50s and alters tRNA structure to block peptidyl transfer
How do lincomycin and clindamycin work?
Narrow spectrum bacteriostatic, effective against gram positive. Same function as chloramphenicol
What antibiotics inhibit protein synthesis specifically by inhibiting translocation?
Macrolides
Ketolides
Streptogramins
How do macrolides work?
Medium spectrum, bacteriostatic that treats mycoplasma, chlamydia and gram +. We use these for patients allergic to PCN.
Targets 50s and stops transpeptidation
Examples of macrolides
Azithromycin, clarithromycin
How do Ketolides work?
Bind 50s unit and block exit of polypeptides. Ketolides differ from macrolides in that they bind two domains of 23s, whereas macrolides bind one domain.
What type of streptogramins do we have?
Streptogramins are the thid category of antibiotics that inhibit translocation. It comes in three types:
Dalfopristin
Quinupristin
and Synercid, whic his just D and Q together = bactericidal
Dalfopristin and Quinupristin
Binds to 50s and prevents elongation and facilitates binding of quinupristin to 50s, which causes premature release of peptide chains from the ribosome. Both of these are bacteriostatic alone
