Drugs, Microbes, Host – Flashcards
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| The central problem of drug design is balancing what things? |
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| Destruction of the infective agent and doing as little harm as possible to the patient. |
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| Doctrine of Signatures |
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| A historical pharmaceutical system in which it was believed that plants would indicate which body part they were curative agents of, as a "sign". Example: Liverwort has liver-shaped leaves, so was assumed to help liver illnesses. |
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| Penicillium spp. |
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| A species of fungi, discovered by Fleming to have antibacterial effects. Forey was the first to suggest using the fungus to combat human illness. |
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| From what organisms are most modern drugs derived? |
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| Bacteria Fungi |
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| How can drugs harvested from organisms be improved upon? |
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| Selective breeding Modification of the drug post-collection Seeking alternative drugs from other organisms |
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| Antibiotic |
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| A metabolic compound produced by a microorganism with the intent of destroying or inhibiting other organisms. |
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| Natural antibiotic |
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| An antibiotic that has been taken straight from a microbial producer, with no modification. |
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| Semisynthetic antibiotic |
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| An antibiotic that has been modified after harvest from an organism. |
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| Synthetic antibiotic |
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| An antibiotic made in the lab, whose composition is based on designs found in microbial production. |
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| Broad spectrum antibiotic |
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| An antibiotic that is effective against a diverse range of microbes |
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| Narrow spectrum antibiotic |
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| An antibiotic that is effective against only a few types of microbe |
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| Why do microbes produce antibiotics? |
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| The microbes are fighting for real estate and resources. If neighboring species aren't around to take up any room, all the better for their survival. |
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| How do cephalosporin and penicillin inhibit cell wall synthesis? |
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| They inhibit transpeptidase from accomplishing crosslinking. |
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| How does cycloserine inhibit cell wall synthesis? |
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| It inhibits peptidoglycan subunit construction. |
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| How does vancomycin inhibit cell wall synthesis? |
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| It inhibits elongation of peptidoglycan chains. |
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| How does chloroquine interfere with nucleic acids? |
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| It cross-links the double-helix. |
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| How do nucleotide analogues (like AZT or acyclovir) interfere with nucleic acids? |
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| They mimic nucleotides, are picked up during elongation, and render the resulting nucleic acid dysfunctional. |
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| Which nucleic acid-associated enzymes do quinolones inhibit? |
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| They inhibit gyrases. |
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| Which nucleic acid-associated enzymes do rifamycins inhibit? |
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| They inhibit polymerases. |
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| How does streptomycin interfere with ribosome function? |
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| It binds to the 30s subunit and causes mRNA to be misread. |
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| How does chloramphenicol interfere with ribosome function? |
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| It binds to the 50s subunit and stops the formation of peptide bonds between amino acids. |
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| How does erithromycin interfere with ribosome function? |
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| It binds to the 50s subunit and prevents detachment of the protein or mRNA translocation. |
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| How does tetracycline interfere with ribosome function? |
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| It inhibits tRNA docking. |
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| How do protease inhibitors mess with proteins? |
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| Some proteins need to be cleaved into units before they can be packaged and used. Protease inhibitors prevent this from happening. |
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| How does polymyxous disrupt the integrity of the cell membrane? |
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| It disrupts phospholipid integrity. |
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| How do amphitemicin B and mystatin disrupt integrity of the cell membrane? |
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| They disrupt embedded molecules, like proteins, sugars, or fats (Mystatin binds to sterols and pushes against them. When enough mystatins have pushed in, they form a pore, which allows outflow of the cell contents. |
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| How do Sulfas and trimethoprim interfere with folic acid synthesis? |
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| They get into the pteridine synthetase active site and prevent PABA binding. |
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| Pteridine synthetase |
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| An enzyme that converts PABA to dihydropteroic acid (which is a precursor of folic acid) |
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| Why does the creation of antiviral drugs pose such a big problem? |
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| Viruses don't have metabolic pathways of their own - they simply hijack ours. So, if we shut down our own pathways, the viruses die, but so do we. |
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| What are the three main modes of activity in antiviral drugs? |
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| Blocking adsorption (engagement with the cell membrane) Blocking transcription/translation/replication (example: AZT) Preventing virion maturation (example: protease inhibitors) |
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| Interferons |
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| Produced by leukocytes and fibroblasts, they have antiviral and anticancer properties. There are three types: alpha, beta, and gamma. |
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| What are some of the effects of interferons? |
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| They reduce healing time and side effects from viral infections, prevent or reduce symptoms of chronic viral infection, and slow cancer progress. However, they can also cause dementia. |
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| Beta-lactam compounds |
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| All have a beta-lactam ring. Includes penicillin and cephalosporin. |
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| Aminoglycosides |
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| Are composed of amino sugars and a 6-carbon ring, and are derived from soil bacteria. Includes gentamycin and streptomycin. |
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| Tetracyclines |
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| Composed of four circles, derived from Streptomyces spp. Includes aureomycin, tetracycline, and doxcycline, and both natural and synthetic drugs. |
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| Clindamycin, erythromycin, rifamycin, and vancomycin |
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| products of Streptomyces spp. |
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| Products of Bacillus |
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| Bacitracin and polymyxin |
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| Sulfonamides (Sulfas) Sulfones Trimethoprim Oxazolidones |
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| Synthetics and derivative drugs |
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| What is the concern in the making of antifungal drugs? |
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| Fungi and humans are both eukaryotic, so they share many of the same pathways. |
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| Macrolide polyenes (Amphotericin B, Nystatin) Griseofulvin Azoles Flucytosine |
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| Antifungal drugs |
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| Griseofulvin |
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| Disrupts spindle fibers during mitosis, meaning that the daughter cells will end up with uneven distribution of chromosomes. Has difficulty differentiating between fungal and liver cells. |
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| Mebendazole and thiabendazole Piperazine and pyrantel Niclosamide Ivermectin Praziquantel |
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| Antieukaryotic drugs |
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| Quinine |
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| The active component of the bark of the cinchona tree, which is used to treat malaria. Today, most quinine is synthetic, because cinchona trees take so much labor, and because we can make better-acting quinine in lab. |
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| Intrinsic drug resistance |
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| Microbes that produce antimicrobial substances must be resistant to their own products. This isn't a major concern in pharmacy. |
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| Acquired drug resistance |
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| Drug resistance that comes about through mutations or recombination. It's a major concern in pharmacy. |
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| R factors |
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| The general name for any plasmid that confers drug resistance. They are mostly transferred through conjugation, but can also be transduced or transformed. |
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| Transposons |
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| Hypermobile genetic elements that do not have a set position in the genome. They are usually identifiable by their sequence. They can move from chromosome to plasmid or vide versa, or within a type, and in moving, can dirsupt or enhance genes or take pieces of genes with them. |
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| How do humans hasten drug resistance? |
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| 200 million antimicrobial prescriptions per year Doctors prescribe broad-spectrum drugs more often than narrow (because of time constraints on diagnosis) Drugs sold OTC with minimal regulation Hospitals, since they provide so many selective pressures (like drugs and steriliztion) are a breeding ground for especially resistant strains Drugs in livestock feed cause drug resistance in the anima and in the environment |
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| Mechanisms of drug resistance |
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| Inactivate the drug Decrease drug permeability Increase drug elimination Change drug receptor Change the metabolic pattern |
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| How do pathogens inactivate a drug? |
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| An enzyme acts on the drug, rendering it dysfunctional. As an example, beta-lactamases cut off penicillin's beta-lactam ring, inactivating it. |
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| How do pathogens decrease drug permeability? |
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| They change the transport mechanism (i.e. external receptor). |
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| How do pathogens increase drug elimination? |
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| They use efflux pumps to spit drugs back out once they're in. |
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| How do pathogens change the drug receptor? |
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| They modify or shield the drug's target. Examples include changing ribosome structure, changing protein structure, and changing expression of proteins. |
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| How do pathogens change their metabolic pattern? |
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| They utilize alternative metabolic pathways or simply stop the metabolic activity altogether until the drug is gone. This means that drugs may be able to survive a two-week treatment regimen. |
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| How can physicians combat drug resistance? |
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| Make accurate, specific diagnoses Prescribe the right drug for the job Don't prescribe drugs when they're not needed Administer multiple drugs simultaneously (because it's less likely pathogens will be able to resist multiple drugs at once) |
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| How can patients combat drug resistance? |
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| Take correct dosages and don't skip doses Take medication as directed and at the specified time Don't whine for drugs inappropriately |
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| How can industry combat drug resistance? |
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| Change chemical structures of drugs to make them less accessible to pathogens Make drugs that operate in ways microbes have a hard time circumventing Focus on short-term, high-dose regimens |
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| Why isn't industry combating drug resistance? |
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| The economy doesn't favor development of new antibiotics - it's more fiscally sound to make a blood pressure medication that a patient will take for the rest of their life than an antibiotic they'll take for two weeks. |
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| How can the global community combat drug resistance? |
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| Use drug alternatives - go without if you can, and use vaccines Better physician and patient education Reduce antibiotic use in animal feed Restrict antibiotic use Increase specificity |
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| What are some novel approaches in drug mechanisms? |
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| Targeting siderophores Targeting riboswitches Pre- and pro-biotics Lantibiotics |
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| Siderophores |
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| Mobile iron-hunting unites that pathogens use to collect iron they need. |
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| Riboswitches |
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| Regulatory proteins within untranslated mRNA, found in all bacteria, that regulate whether the mRNA to which they are attached is translated. |
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| Prebiotics |
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| Beneficial bacteria cocktails that supplement an already-existing colonies, to help crowd out bad bacteria. |
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| Probiotics |
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| Microbe cultures that completely flush out and replace the gut flora, to reestablish a beneficial environment. |
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| Lantibiotics |
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| Short polypeptides that are produced by bacteria as a control measure against other bacteria - they do so by inhibiting enzymes or puncturing cell membranes. |
