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36 Cards in this Set

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What is meant by selective toxicity?
Chemotherapeutic agents should act against the pathogen and not the host.
Why are chemotherapeutic agents that work on the peptidoglycan cell wall of bacteria a good choice of drug?
Humans and other animal hosts lack peptidoglycan cell walls.
Why is polymyxin only used on the skin?
It can also damage living human cell membranes, but the drug is safely used on the skin, where the outer layers of cells are dead.
Quinolones and fluoroquinolones act against what bacterial target?
DNA gyrase
Why is it difficult to find good chemotherapeutic agents against viruses?
Viruses depend on the host cell's machinery, so it is hard to find a viral target that would leave the host cell unaffected.
f penicillin G is chosen as the best treatment for a given infection, what microorganisms are most likely the cause?
gram-positive bacteria
Why is methicillin-resistant Staphylococcus aureus (MRSA) methicillin resistant?
It produces a modified version of the molecule that is targeted by the drug.
Why is it more difficult to treat viral infections than it is to treat bacterial infections?
Viruses use the host cell's processes to carry out their own reproduction.
Viruses have cell walls.
Certain cancer cells have ABC transport molecules at the cell surface. These transporters use energy from ATP to move chemotherapeutic agents out of the cell. Which of the following do you think these transporters are most closely related to?
membrane pumps
A researcher creates an antibiotic that binds to a protein present only on B. anthracis (the causative agent of anthrax), lysing the cell from the outside. After a couple of years using this antibiotic, some resistant organisms are found. Which of the following best outlines the mechanism for development of this resistance?
mutation in B. anthracis → altered target → resistant bacterium
Which antibiotic is overcome by beta-lactamases?
Penicillin
How might efflux pumps increase antibiotic resistance in bacteria?
Resistant bacteria can have more efflux pumps, and can have less specific efflux pumps.
Bacteria that are resistant to sulfonamide have enzymes that have a greater affinity for what?
PABA
Why would an efflux pump for penicillin located on a bacterial cell membrane not be effective at providing resistance to the drug?
Penicillin disrupts the cell wall, which is located outside of the cell membrane.
Membrane transport proteins are required for which mode(s) of antibiotic resistance?
Efflux pumps, beta-lactamases, and modification of porins all utilize membrane transport proteins.
What is meant when a bacterium is said to become "resistant" to an antibiotic?
The bacterium is neither killed nor inhibited by the antibiotic.
When a patient is treated with antibiotics, __________.
the drug will kill or inhibit the growth of all of the sensitive bacterial cells
The process of acquiring antibiotic resistance by means of bacteriophage activity is called
transduction.
Which of the following mutations would not result in antibiotic resistance?
Silent mutation
R-plasmids can be acquired via
bacterial conjugation and horizontal gene transfer
Consider a Kirby-Bauer disk-diffusion assay. If you put penicillin and streptomycin disks adjacent to one another, the zone of inhibition is greater than that obtained by either disk alone. This is an example of __________.
synergism
Which of the following would be selective against the tubercle bacillus?
ethambutol – inhibits mycolic acid synthesis
In the table, which antibiotic would be most useful for treating a Salmonella infection?
can't tell
In the table, the antibiotic that exhibited bactericidal action was
can't tell
In the table, the most effective antibiotic tested was
10mm
Drug resistance occurs
when antibiotics are used indiscriminately.
Which of the following statements about drug resistance is FALSE?
It is found only in gram-negative bacteria.
Which of the following organisms would MOST likely be sensitive to natural penicillin
Streptococcus pyogenes
The antimicrobial drugs with the broadest spectrum of activity are
tetracyclines
To date, most of our natural antibiotics have been found to be produced by members of what genus?
Streptomyces
More than half of our antibiotics are
produced by bacteria.
Which of the following antibiotics is recommended for use against gram-negative bacteria?
polymyxin
Which of the following antimicrobial agents has the fewest side effects?
penicillin
In what way are semisynthetic penicillins and natural penicillins alike?
Both are based on β-lactam
Penicillin was considered a "miracle drug" for all of the following reasons EXCEPT
it was the first antibiotic.
Which statement regarding tests for microbial susceptibility to chemotherapeutic agents is FALSE?
The Kirby-Bauer test is useful because it can differentiate bacteriostatic effects from bactericidal effects