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27 Cards in this Set
- Front
- Back
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Why were antibiotics called a miracle cure?
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they were selective in that they could kill microbes without killing the pt
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Compare the terms antibiotic and antimicrobic.
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abt means "antilife". antimicrobial is more descriptive because it denotes specificity of agent for microbes.
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Differentiate between narrow-spectrum and broad-spectrum antibacterials.
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narrow target specific type of bacteria, broad inhibit the growth of nearly all bacteria
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What is the common problem of using a broad spectrum antibiotic?
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Broad spectrum do not diff btwn undesirable microbes and the normal flora. By eliminating the normal flora, superinfection can result
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Why do some bacteria and fungi produce antibiotics?
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Bact and fungi produce abts to inhibit other microbes and retain more nutrients
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What is the importance of selective toxicity?
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the higher the selective toxicity, the less likely the pt will experience side effects
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Which antibiotic is the most common to induce allergic reactions? Which ones are not allergenic?
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PCN induces the most allergic reactions. All antibacterials are allergenic.
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What is the side effect of chloramphenicol treatment?
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A side effect of chloramphenicol tx is depression of the immune system.
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Based on its mode of action, why is pcn cidal?
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cells walls can not develop in its presence. They become thinner and thinner until they cytoplasmic membrane bulges out and the cell lyses.
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Do drugs like pcn and cephalosporin, which act on the cell wall, at equally well on growing and nongrowing bacteria? Why or why not?
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Drugs like PCN and cephalosporin do not work well on stationery-phase bact because the cells are only weakened when cells try to make new PG that needs to be cross-linked into existing cell wall.
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Why do we call sulfa highly selective?
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Sulfa drugs inhibit the synthesis of folic acid, a vitamin that bact and several other microbes must synthesize on their own. Humans cannot synthesize folic acid, therefore, there is no inhibition to human cells.
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Name four other target sites for abt action besides the cell wall.
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1. functs of 70S ribosomes in translational activity, the inhibition of bacterial RNA synthesis, bact DNA synthesis, and disruption of the cell membrane.
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How does a B lactamase protect a bacterium from PCN or the third generation pcn, cephalosporin?
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A B lactamase is an enzyme that degrades PCNs. ∆'s in the ß lactam (the four membered ring) make it resistant to the original penicillinase, but penicillinase has mutated again, so it can degrade cephalosporins, too.
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What is the noted mechanism of tetracycline resistance?
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In tetracycline resistance, bact obtain a gene that literally pumps the tetracycline from the inside to the outside of the cell.
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Are tetracyclines (one from of the bacteriostatic drugs) narrow spectrum? Why or why not?
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Tetracyclines are broad spectrums abts because all bacteria have ribosomes.
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How can fungi become resistant to drugs that bind to ergosterol?
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Resistant fungi make less ergosterol, so there are fewer targets for anti-ergosterol drugs to bind to.
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Drugs do not cause mutation, they select for resistant cells. Explain.
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If there are bact in the population that are not killed or inhibited by the drug, they are selected as the only ones that replicated and multiply.
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How can we minimize the spread of drug resistance?
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To minimize the spread of drug resistance, we can do the following: reduce the amounts of antibiotics used in animal feeds; discourage the indiscriminate use of abts in humans; give more than one abt to simultaneously to completely eliminate infections, as needed.
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Why do tetracyclines have limited use?
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In tetracycline resistance, bact obtain a gene that literally pumps the tetracycline from the inside to the outside of the cell.
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What practices have led to widespread drug-resistance organisms?
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unnec use of abts
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Why is it important to identify the pathogen before deciding on which therapy to use?
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It is important to identify the pathogen first so that the antibiotic susceptibility of the organism can be determined and the correct abt used
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What is the drug susceptibility testing and why is it done?
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Drug susceptibility testing determines which drug will most effective kill the isolated microbe.
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What does the larger zone of inhibition by infectious strain A relative to that of strain B indicate?
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measures abt potenc and would indicate which microbe is more susceptible to the drug
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What is the Kirby Bauer test?
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In the Kirby-Bauer test, bacteria are spread on a petri plate, and abt disks are added on top. The antibact chems diffuse into the agar medium and kill/ inhibit growth of susceptible organisms.
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What does MIC refer to?
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minimum inhibitory concentration, It is used when microbes are grown in liquid broth in tubes that contain a range of antimicrobial concentrations. The lowest antimicrobial conc that inhibits microbial gowth is the MIC.
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How do the dilution tube and Kirby-Bauer tests work?
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In tube dilution testing, the antibiotic is serially diluted to determine at what conc the drug will be effective; the Kirby Bauer test determines the potency of an antibiotic by establishing the zone of inhibition when the abt diffuses into agar plate.
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If a given drug has a therapeutic index of one hundred thousand, would that be considered good or bad?
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A TI of 100, 000 would be excellent. Drug could be used clinically throughout a one hundred thousandfold range.
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