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119 Cards in this Set
- Front
- Back
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Why are antibiotics important?
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They have drastically reduced the number of deaths due to infection
They have changed the face of health care. |
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Who discovered the first antibiotic? How was it discovered?
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Alexander Fleming
accidentally contaminated a plate with fungus and observed a clearly defined region of no bacterial growth where the bacteria contaminated the plate. |
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How many prescriptions are written in America each year?
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80 million
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How many antibiotics are produced annually?
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12,500 tons
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Why would 25-50% of the antibiotics produced be fed to livestock?
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to increase their rate of weight gain
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True or False: Many new discoveries of natural antibiotics are being found annually.
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FALSE; there has been no major discoveries for several years
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What are the efforts of research now directed towards?
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modifying existing antibiotics
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True or False: Antibiotics are part of bacterial self protection.
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TRUE; many microorganisms produce antibiotics as part of their survival mechanism.
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Why would microorganisms use antibiotics they produce as part of their survival mechanism?
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- they keep other organisms away
- they protect the supply of nutrients and oxygen |
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True or False: Naturally produced antibiotics are products of primary metabolic pathways.
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FALSE; naturally produced antibiotics are products of SECONDARY metabolic pathways.
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What are secondary metabolic pathways?
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SECONDARY METABOLIC PATHWAYS
- are not turned on all the time - (continuous production could adversely affect the organism) |
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In what ways can organisms protect themselves?
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-Some restrict antibiotic production to the stationary phase
-Others keep the intracellular concentrations at low leves (regulate rates of production and export) |
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True or False: Antibiotic molecules are exported in an inactive form.
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TRUE
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How do antibiotic molecules become activated?
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by EXTRACELLULAR ENZYMES
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True or False: The original natural molecules used by humans as antibiotics have a broad spectrum.
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FALSE; they had a very NARROW spectrum
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True or False: Penicillin activity is restricted to Gram-postive bacteria.
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TRUE
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Why is the structure of penicillin useful?
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It is useful as a template for the development of an entire group of antibiotics (more than 50 so far)
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What kind of structure is penicillin composed of in it's native form?
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The beta-lactam ring (4-sided)
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True or False: Only some forms of penicillin contain the beta-lactam ring.
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FALSE: all forms of penicillin contain a beta-lactam ring
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What are examples of how some derivatives of penicillin contain additional specific structures?
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- Side chains attached to the ring
- Chemically changing the side chain |
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How can chemically changing the side chain affect penicillin?
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Affects:
- Antimicrobial activity - Resistance to stomach acid - Overall half-life in body |
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How are semi-synthetic forms of penicillin created?
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They are created through modifications that can be done in the laboratory
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Is penicillin broad spectrum or narrow spectrum?
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VERY narrow spectrum
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What can ampicillin be modified to?
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Mezlocollin or azlocilllin
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Why would semi-synthetic penicillins be further modified?
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To increase the efficiency of inhibiting bacterial growth
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What could modifications do in cephalosporins?
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- change side chain, leaving core intact
- change reactivity patterns and spectrum |
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What is one of the most important bacterial defense mechanisms?
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The production of enzyme beta-lactamase
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What is beta-lactamase and what does it do?
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Enzyme that...
-cleaves open the beta-lactam ring -inactivates the molecule |
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True or False: Organisms that produce B-lactamase are resistant to penicillin
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TRUE
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What is one way to overcome penicillin resistance? Explain how this works.
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Combine penicillin drug with the molecule that protects the penicillin.
- this diminishes/impedes beta-lactamase activity |
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What is an example of a molecule that protects penicillin?
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potassium clavulanate
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What are some combinations that have been developed to fight penicillin-resistant bacteria? (There are 3 examples)
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- Amoxicillin + potassium clavulanate = Augmentin or Timentin
- Imipenum + cilastatin = Primaxin - Ampicillin + sulbactam = Unasyn |
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Why is it so important for antibiotics in medical use to have selective toxicity?
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-The antibiotic should be destructive to the disease-causing organism, but not effect the human host at all.
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Chemicals are useful in restricting bacterial growth. Why can't they be used in a medical setting?
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They are toxic to the human host, so they can't be used therapeutically.
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True or false: Antibiotic molecules tend to be more toxic at lower concentrations.
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FALSE; they are more toxic if administered at HIGHER concentrations
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How long does it take to test the toxicity of a chemical?
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It can take years due to the extensive testing that needs to be done on the chemicals.
(can also cost MILLIONS of dollars) |
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What are the five groups antibiotic targets can be subdivided into?
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- The bacterial cell wall
- The bacterial plasma membrane - Synthesis of bacterial proteins - Bacterial nucleic acids - Bacterial metabolism |
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What is the most appealing target for antibiotics and why?
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The bacterial cell wall
- found in bacteria, but not humans - Meet the criterion of selective toxicity |
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TRUE OR FALSE: The bacteria cell wall is only found in Gram-positive bacteria.
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False; it is found in both Gram +and Gram - bacteria
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What are the peptidoglycan molecules that make up the cell wall?
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NAG and NAM
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How are NAG and NAM related?
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They are cross-linked through activity of transglycosylase and transpeptidase enzymes
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What is the result of an antibiotic that inhibits the activity of NAM and NAG?
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- Results in improper cross-linking; meaning the organism is not able to withstand environmental pressures
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What are PBPs and where are they found?
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They are Penicillin-Binding Proteins that are involved in the construction of the cell wall
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What part of penicillin binds to PBPs?
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The B-lactam ring
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True or False: a new cell wall is continuously built during growth
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TRUE
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What effect does penicillin have on the cell wall?
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prevents formation of the intact cell wall; this is when it's most effective
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True or False: Gram-positive bacteria have less peptidoglycan.
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FALSE: Gram-POSITIVE bacteria have less peptidoglycan.
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True or false: Gram-negative bacteria are normally less sensitive to penicillin.
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TRUE
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How do cephalosportins affect the cell wall?
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They prevent construction of the STABLE CELL WALL
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Which has a greater affect on Gram-negative bacteria: Cephalosportins or Penicillins? Why?
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Cephalosporins
- They are broader spectrum - not susceptible to B-lactamase enzymes |
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How many versions of cephalosporins are in use?
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70
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How is the MOA of cephalosporin different than penicillin?
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it penetrates through porin channels
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When are cephalosportins used?
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preoperatively AND postoperatively
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How are carbapenems similar to penicillins?
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They contain a B-lactam rin
They inhibit the synthesis of bacteria walls |
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What is the purpose of the double bond in B-lactam rings in carbapenems?
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It prevents B-lactamase cleaving the ring
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True or false: Carbapenems are very narrow spectrum.
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FALSE - they are very BROAD SPECTRUM (of antibacterial activity)
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How many carbapenems are approved for clinical use in humans?
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Two
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Of the two carbapenems approved for clinical use, what species do they belong to?
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Pseudomonas
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Describe the ring structure of monobactams.
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-They cannot be recognized by B-lactamase
-They are effective in overcoming abcterial resistance |
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What kind of organisms are Glycopeptide antibiotics derived from?
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Streptomyces organisms
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What antibiotics are derived from Streptomyces
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Glycopeptide antibiotics
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What is an example of a glycopeptide antibiotic?
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Vancomycin
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True or false: Glycopeptide antibiotics have serious side effects.
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TRUE
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How do glycopeptide antibiotics inhibit cell wall synthesis?
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By forming a complex with the substrates that make up peptidoglycan
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Can glycopeptide antibiotics penetrate the porins of Gram-negative cells? Why or why not?
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NO - they are NARROW-SPECTRUM antibiotics that are restricted to Gram-positive bacteria
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What are S. aureus strains that are RESISTANT to vancomycin (a glycopeptide antibiotic) called? Are they dangerous?
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VRSA; yes, they are VERY dangerous
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What 2 antibiotics are used against bacteria with modified cell walls?
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Isoniazid and Ethambutol
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What organism has a modified cell wall? Explain.
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Mycobacterium species (which cause TB and leprosy) have cell walls that are modified by incorporation of mycolic acids
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Why is Isoniazid so effective against Mycobacterium organisms?
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Because Isoniazid inhibits the synthesis of mycolic acid
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What is the treatment of choice for tuberculosis?
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Isoniazid, ethambutol, and rifampin
**combinations lower the potential for development of resistance |
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What are polypeptide antibiotics used for and how are they used?
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-Used TOPICALLY for superficial infections by Gram-positive organisms (like Staphylococcus and Streptococcus)
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What is the significance of Polypeptide antibiotics inhibiting binding between NAG and NAM?
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Prevents formation of linear strands of peptidoglycan
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True or False: any disruption of the bacterial plasma membrane destroys the bacteria
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TRUE
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True or False: The structure of the bacterial plasma membrane is similar to the prokaryotic cell wall.
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FALSE: It is similar to the eukaryotic plasma membrane
(which doesn't allow for selective toxicity) |
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True or False: Ribosomes of prokaryotes are not the same as those in the cytoplasm of eukaryotes.
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TRUE: (this allows for selective toxicity)
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Antibiotics act at diffent sites on bacterial ribosomes. Which target the 30S subunit?
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Spectinomycin, kanamycin, streptomycin, and tetracycline
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Antibiotics act at diffent sites on bacterial ribosomes. Which target the 50S subunit?
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Clindamycin, chloramphenicol erythromycin, clarithromycin, and azithromycin
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In what 2 ways can antibiotics inhibit a bacterial cell.
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- some interfere in PEPTIDE ELONGATION and some with DECODING the message.
-some (like streptomycin) upset accuracy of TRANSLATION |
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How does Chloramphenicol inhibit a bacterial cell?
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blocks binding of tRNA
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How does Erythromycin inhibit a bacterial cell?
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blocks the approach to the peptide exit tunnel
& blocks assembly of the 50S subunit |
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Pristinamycin and streptogramin: What species make these?
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Streptomyces
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Pristinamycin and streptogramin: What do they inhibit?
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translation at the 50S subunit of a ribosome
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Pristinamycin and streptogramin: What antibiotic do they make up? What is this antibiotic used for?
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Synercid
- used for the treatment of vancomycin-resistant enterococci |
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Tetracyclines: How long have they been used?
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Since the 1940s
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Tetracyclines: what is a defining characteristic?
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they are BACTERIOSTATIC
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Tetracyclines: What is their function?
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They block the arrival of tRNA at the A site
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Aminoglycosides: what do they target?
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the 16S RNA portion of the 30S ribosomal subunit
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True or false: Gentamicin is potent against Gram-negative organisms.
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TRUE; also not very effective against Gram-positive bacteria
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What antibiotic is totally synthetic?
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Linezolid
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What does Linezolid do?
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blocks protein synthesis by occuping the P site
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What is Linezolid very active against?
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Gram-positive bacteria and vancomycin-resistant enterococci
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What are the two families of synthetic compounds that can target bacterial nucleic acids?
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RIFAMYCINS and QUINOLONES
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What do quinolones target?
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bacterial topoisomerases;
**BLOCKS THE REPLICATION FORK |
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What are quinolones used in the treatment of?
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UTIs, Osteomyelitis, Community-acquired pneumonia and gastroenteritis, and Anthrax
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What do RIFAMYCINS do?
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bind to RNA polymerase and prevent it from functioning
**occurs away from the active site ** = no protein synthesis --> lethal |
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True or false: rifampin is the only rifamycin in use.
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TRUE; and only used in combination therapy
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What are the two targets for inhibiting bacterial growth?
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- Production of nucleic acid precursors
- Metabolic pathways that occur at the plasma membrane |
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What is one of the intermediates in the folic acid pathway?
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PABA (para-aminobenzoic acid)
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What kind of drugs compete to inhibit the folic acid pathway?
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Sulfa drugs
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How do humans obtain folic acid?
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Through diet
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What drugs are combined to treat UTIs?
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Sulfamethoxazole and trimethoprim
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Why do viruses pose a different set of problems for antibiotic therapy?
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- They are obligate intracellular parasites
- Drugs that are capable of eliminating the virus are dangerous to non-infected cells |
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Why is it difficult to test potential antiviral drugs?
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Because many virus are difficult to grow
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True or False: acute viral infections have a long duration period.
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FALSE - they have a SHORT duration period
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Why is it important that antiviral drugs must eliminate all virions?
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The escape of even one virion could restart the entire infectious cycle
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The first antibiotic to be used against viruses was the sulfa drug derivative _________________.
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Thiosemicarbazone
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Why was amantadine developed?
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To use against influenza in the 1960s
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What is this antiviral drug?
-specific and nontoxic - highly effective against both genital and oral herpes simplex infections - has been used with some succes in treatment of shingles and chickenpox - can be taken intravenously or orally OR used topically. |
ACYCLOVIR
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What antiviral drug is this?
- derivative of acyclovir - less toxic oral derivative - used effectively for cytomegalovirus in immunocompromised patients |
Ganciclovir
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What antiviral drug is this?
- acts against DNA replication by inhibiting the binding site of HBV DNA polymerase and HIV reverse transcriptase - used to treat herpes infections |
FOSCARNET
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What antiviral drug is this?
- a nucleoside analog - highly toxic - unclear MOA - used for Lassa fever and Hantavirus infections |
RIBAVIRIN
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What antiviral drug is this?
-has been around for some time -first highly specific potent antiviral used against influenza A - Targets a viral protein and inhibits uncoating -Influenza A virus frequently mutates the protein target of this drug - Influenza B does not contain the target protein and is unaffected by this drug |
AMANTADINE
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What is this antifungal drug?
- produced by the soil bacterium Streptomyces - interact with sterols and increase the permeability of the plasma membrane - must be used with caution because of side effects |
POLYENES
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What is this antifungal drug?
-inhibit the production of sterols |
AZOLES
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What is this antiviral drug?
- produced by a species of the fungus Penicillium - administered orally - effective for superficial fungal infections - seems to react with keratin, blocking the formation of microtubules and inhibiting mitosis in fungi |
GRISEOFULVIN
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What are two widely used parasitic drugs?
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Quinine and Metronidazole
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What is the choice of treatment for Tapeworm and Flukes?
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Niclosamide
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What is used against Pinworm and Ascariasis?
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Mebendazole
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What is the most widely used test for evaluating new compounds/antibiotics?
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Kirby-Baur test
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