Ch 12 Chemotherapy Flashcards
Antibiotic
An antimicrobial that is produced by the natural metabolic processes of some microorganisms, that can inhibit or destroy others. “Biological warfare “
Define antimicrobial
All inclusive term for any antimicrobial drug regardless of origin
Selectively toxic
Kill or inhibit microbes but not harm host
Broad spectrum
Effective against a wide variety of microbial types. ex: gram-positive and gram-negative
Narrow spectrum
Effective against a limited array of microbial types. Ex: only gram-positive
Examples of antibiotics that affect bacteria Cell walls
“Cillins” and cephalosporins, Augmentin, vancomycin bacitracin, Neosporin
Explain the mechanism of action of cephalosporins and “cillins”
cephalosporins and “cillins”have a beta lactam ring that lures transpeptidase away from bacteria preventing transpeptidase and so it cannot divide
What do some bacteria have that specifically causes resistance to antibiotics
Beta lactamase
What can be added to “cillins” that stops the bacteria’s resistance to antibiotics
Clavulanic acid
How does Clavulanic acid work
Mimic’s the beta-lactam ring causing beta-lactamase to bind to it allowing transpeptidation to continue
Most antibiotics are the product of which two genera of molds
Penicillium and Cephalosporium
Antibiotics are the product of which 2 genera of bacteria
Bacillus and streptomyces
Explain the mechanism of drug action when it affects nucleic acid synthesis
Inhibits replication or transcription
Two examples of antibiotics that affect nucleic acid synthesis
Ciprofloxacin and rifamycin
Explain how aminoglycosides (Streptomycin) affect protein synthesis
Bonds to the smaller subunits of a ribosome so that mRNA is translated incorrectly; ** protein is still built but will be incorrect**
Antibiotics typically affect what size ribosomes
70S
Explain how chloramphenicol affects protein synthesis
Stops the peptide bond from forming between the amino acids. Protein is NOT assembled
Explain how oxazolidinones affect protein synthesis
Blocks initiation (prevents large subunit from attaching two small subunit). Protein is not assembled
Explain how tetracyclines affect protein synthesis
Blocks tRNA from entering the ribosome. Protein is not assembled
Explain how erythromycin affects protein synthesis
Blocks the exit, stops translation. “Translocation of mRNA blocked” protein is not assembled
Of all the examples of drugs that affect protein synthesis only one still builds a protein. Which one is it
Aminoglycosides (streptomycin)
Explain the drugs that affect cell membrane function
Not normally first choice, disrupt bacteria membranes by interacting with the phospholipids causing leakage of proteins (similar to how surfactants or detergents work)
Polymyxins
What are examples of drugs that affect folic acid synthesis in bacteria and why are they effective
Sulfonamides (sulfa drugs) because bacteria cannot make their own folic acid
How do antibiotics that affect folic acid synthesis work
Act as competitive inhibitors by occupying the active site so the normal substrates can’t enter; sulfonamides (sulfa drugs)
Examples of what antifungals treat and what they target
Target fungi ; ex: yeast infection, jock itch, athletes foot
What do antiparasitic’s target
Target parasites (protozoans) ex: chlamydia, amoeba
Antivirals
Target viruses. Ex: Tamiflu and Valtrex
Two ways in which microbes can acquire drug resistance
Spontaneous mutations in chromosome or acquisition of new genes via horizontal gene transfer
Name the six mechanisms of drug resistance
Drug inactivating mechanisms, decreased drug permeability or increased drug elimination, change of drug receptors, change in metabolic patterns, natural selection, change the site that the drug affects
Probiotics or prebiotic’s are referred to as
“Good germs “
Three possible undesirable drug interactions
Toxicity to organs, allergic reactions, suppression of normal flora
What does the Kirby Bauer method test for
A microbes Sensitivity to different antibiotics
Three possible results of the Kirby Bauer test
Resistance, intermediate, sensitive
What is the zone of inhibition
The zone around the disk of antibiotics where no growth occurs
What is meant by the minimal inhibitory concentration of an anabiotic
Lowest dosage of a drug that will prevent growth; Growth remains constant
What is meant by the minimal lethal concentration of a drug
The lowest dosage of a drug that will kill bacteria, no living cells are present
How is the therapeutic index of a drug calculated
It is a ratio of the dosage that is toxic to humans divided by the minimal inhibitory concentration
Explain how to pick a drug based on the therapeutic index
The higher the ratio the safer the drug
