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54 Cards in this Set
- Front
- Back
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What are two goals of antimicrobial drugs?
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1. Disrupt the cell processes or structures of bacteria, fungi, and protozoa
2. Inhibit the virus multiplication cycle |
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Describe chemotherapy drugs
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1. Interfere with the function of enzymes required to synthesize/assemble macromolecules
2. Destroy structures already formed in the cell 3. Selective Toxicity |
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What is SELECTIVE TOXICITY?
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drugs should kill/inhibit growth of microbes w/out simultaneously damaging host tissue
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GIVE AN EXAMPLE OF DRUGS WITH SELECTIVE TOXICITY
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Penicillins - block synthesis of cell wall in bacteria.
Best drugs target structure/function not found in human cells |
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What is a structure that many TOXIC DRUGS act upon?
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Cell membrane - common to both infective agent and host
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Give an example of a TOXIC DRUG that acts on the cell membrane
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Amphotericin B - treats fungal infections
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What is goal of chemotherapy?
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Target an infectious agent with a chemical that irreversibly damages/inhibits it
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what are the five major drug targets
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1. cell wall 2.cell membrane
3. genetic material 4. protein synthesis 5. metabolic pathways |
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what microbes have specialized targets
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viruses have specialized targets for drugs
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what is a drug's SPECTRUM
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range of activity based on a specific structure or function of a microbe
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what limits the range of NARROW-SPECTRUM drugs
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they usually target a specific component that is only found in certain bacteria
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give examples of narrow spectrum drugs
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1. BACITRACIN - blocks elongation of peptidoglycan in GRAM POSITIVE bacteria
2. POLYMIXIN - breaks down outer membrane of GRAM NEGATIVE |
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give an example of a MEDIUM SPECTRUM DRUG
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AMPICILLIN - effective on both gram negative/positive bacteria, but not all types
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give an example of a BROAD SPECTRUM drug
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TETRACYCLINE - effective on gram negative/positive Bacteria, Rickettsias, Mycoplasmas, Spirochetes
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what components do broad spectrum drugs affect
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common components like ribosomes and mitochondria
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what does peptidoglycan protect the cell against
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cell rupture from hypotonic environments
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describe the action of drugs that affect the cell wall
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react w/ enzymes required to complete peptidoglycan synthesis
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what does drug action on cell wall cause
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cell develops weak points at growth sites & becomes osmotically fragile
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name 2 drugs that affect the cell wall
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penicillins and cephalosporins
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why are penicillins & cephalosporins considered sporocidal
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the weakened cell is subject to lysis
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why are penicillins & cephalosporins only active in young, growing cells
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older cells do not synthesize peptidoglycan
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what are "-penems"
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new class of antibiotics that work on cells not synthesizing peptidoglycan
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describe the specific actions of penicillins and cephalosporins
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bind and block peptidases that cross-link glycan molecules
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what are penicillins LESS effective against and why
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gram-negative - they cannot penetrate outer memrane
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what are penicillins & cephalosporins MORE effective against and why
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gram-positive - they can pass into the cell wall
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give examples of drugs that are effective on gram-positive bacteria
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1. Carbenicillin (penicillin)
2. Ceftriaxone (cephalosporin) |
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describe CYCLOSERINE
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acts on cell wall - inhibits formation of peptidoglycan subunits
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describe VANCOMYCIN
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acts on cell wall - inhibits elongation of the peptidoglycan
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name a difference in drugs that act on cell wall and those that act on cell membrane
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cell wall - mostly young, active cells
cell membrane - does not have to be actively dividing |
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describe the specificity of drugs that act on cell membrane
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they are based on different lipids found in cell membranes
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what do POLYMIXINS act on
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membrane phospholipids
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what do polymixins cause
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leakage of proteins and nitrogen bases, esp. in gram negative
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what do POLYENE ANTIFUNGAL ANTIBIOTICS targe
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STEROLS - they form complexes w/ sterols on fungal membranes
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what do complexes w/ sterols cause
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abnormal openings & seepage of small ions
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give two examples of polyene antifungal antibiotics
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amphotericin B and Nystatin
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how do antimicrobial drugs interfere w/ nucleic acid synthesis
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1. block synthesis of nucleotides
2. inhibit replication 3. stop transcription |
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what antimicrobial drugs inhibit DNA synthesis
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1. chloroquine (antimalarial)
2. quinolones (broad spectrum) |
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what is the action of chloroquine
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binds & cross-links DNA double helix
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what is the action of quinolones
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inhibits DNA unwinding enzymes or helicases
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which antiviral drugs affect nucleic acid synthesis
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analogs of purines and pyrimidines
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what is an analog
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a compound that closely resembles another in structure (can compete for its receptor site)
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how do the analogs of purines and pyrimidines work
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insert into viral nucleic acid like a normal base & block replication
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what do most drugs that block protein synthesis react with
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the ribosome-mRNA complex
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why do drugs that block protein synthesis have selective action
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ribosomes of eukaryotes & prokaryotes differ in size and structure
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why would a drug attack a eukaryotic mitochondria
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because it has prokaryotic ribosomes within it
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what are 2 targets of ribosomal inhibition
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30S subunit and 50S subunit
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what drugs interact with 30S subunit
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aminoglycosides - streptomycin, gentamycin, tetracycline (30S = as God Talked)
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what is the action of aminoglycosides
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insert on sites on 30S & cause misreading of mRNA = abnormal proteins
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what is the action of tetracycline
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block attachment of tRNA on the A acceptor site = stop synthesis of protein
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which antibiotics interact w/ the 50S subunit
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chloramphenicol and erythromycin (50 CEnt)
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what is the action of chloramphenicol
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prevents formation of peptide bonds
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what is the action of erythromycin
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inhibits translocation of subunit during translation
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which drugs interact with both 30S and 50S
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oxazolidinones
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what is action of oxazolidinones
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affect assembly of the completed ribosome by blocking the attachment site for the 30S and 50S subunit
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