Microbiology Chapter 20 Test Questions – Flashcards
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| antibiotic |
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| substance produced by a microbe, then in small amounts, inhibits another microbe |
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| selective toxicity |
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| a drug that kills harmful microbes without damaging the host. more difficult in eukaryotic pathogens because they are more like the host |
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| paul ehrlich |
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| developed the concept of chemotherapy |
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| chermotherapeutic agents |
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| kill pathogens without harming the host |
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| gerhard domagk |
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| developed sulfa drugs, which came into prominence in the 1930s during WW2 |
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| alexander fleming |
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| discovered first antibiotic, penicillin in 1929 |
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| narrow-spectrum drugs |
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| affect only a small group of microbes |
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| broad-spectrum antibiotics |
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| affect a more diverse range of microbes. disadvantage to them is that they can harm normal flora |
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| super infections |
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| when you kill all of the normal flora, so it is easy or another microbes to take their place |
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| bactericidal |
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| directly killing microorganisms |
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| bacteriostatic |
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| inhibiting thier growth |
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| actions of antimicrobial drugs |
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| inhibition of cell wall synthesis, of protein synthesis (inhibits 70s ribosomes), nucleic acid replication (RNA polymerase has diff structure in eukaryotes), injury to plasma membrane, and inhibition of essential metabolites (folic acid) |
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| ?-lactam ring |
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| all penicillins contain this |
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| natural penicillins |
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| produced by penicillum and effective against gram positive cocci and spirochetes |
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| penicillin G |
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| requires injections because it is destroyed in stomach acid |
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| penicillin V |
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| can be taken orally |
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| penicillinases (?-lactamases) |
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| bacterial enzymes that destroy natural penicillins by cleaving the ?-lactam ring |
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| semi-synthetic penicillins |
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| mad ein the lab by adding different side chains on the the ?-lactam ring |
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| oxacillin |
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| narrow spectrum (only gram pos but resistant to penicillinase) |
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| ampicillin |
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| extended spectrum so many gram negatives |
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| methacillin |
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| penicllinase-resistant penicillins |
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| cephalosporins |
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| inhibit cell wall synthesis and are used against penicillin resistant strains. 1-4 generations and each has a progressively wider spectrum. 4th is oral while others are injected. |
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| bacteracin |
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| inhibit cell wall synthesis primarily in gram positive bacteria |
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| vancomyacin |
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| inhibits cell wall synthesis. It is a last line against S. aureus and are penicillinase resisant |
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| isoniazid and ethambutol |
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| inhibit cell wall synthesis in mycobacteria by effecting the mycolic acid in their cell membranes |
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| chloramphenicol |
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| broad spectrum, potentially toxic. binds to the 50s and inhibits peptide bond formation |
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| aminoglycosides |
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| streptomyacin, neomyacin (in neosporin) and gentramyacin. broad spectrum, can cause hearing loss, changes shape of 30s subunit |
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| tetracyclines |
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| broad spectrum, interferes with tRNA attachment |
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| macrolides (erythromyacin) |
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| against gram positives, used as an alternative to penicillin, binds to 50s and prevents translocation |
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| streptogramins |
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| against gram pos, binds to 50s subunit and inhibits translation |
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| synercid |
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| combo of two streptogramins that act as different steps in protein synthesis (to reduce possibility of resistance and to be more effective) |
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| oxazolidinones |
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| linezolid= totally synthetic, against gram pos, binds to 50s subunit and prevents formation of 70s ribosome |
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| polymyxin B |
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| damages cell membranes |
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| bacitracin |
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| inhibits cell wall synthesis |
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| neomycin |
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| inhibits cell wall synthesis |
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| rifamycin |
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| inhibts RNA synthesis; it is used to treat TB |
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| quinolones and fluoroquinolones |
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| inhibit DNA gyrase for treating UT infections |
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| ciprofloxacin |
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| used against anthrax infections |
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| sulfonamides |
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| competitively inhibit folic acid synthesis by competing with the intermediate PABA to bind to the enzyme |
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| sulfamethoxazole |
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| (SMZ)- inhibts PABA |
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| trimethoprim |
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| TMP inhibitsdihydrolic acid to going to tetrahydrofolic acid |
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| ergosterols |
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| in plasma membrane |
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| miconazole |
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| targets sterols in plasma membrane, for treatment of athlete's foot and vaginal infections |
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| ?-glucans |
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| in cell wall |
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| fluctosine |
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| antimetabolite of cytosine/cytosine analog that interferes with RNA synthesis. Enzyme converts flucytosine to 5-fluorouracil that's incorporated into mRNA |
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| griseofluvin |
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| interferes with eukaryotic cell division and is ed orimary to treat skin infections caused by fungi. binds selectively to keratin (in skin) then inhibits microtubule production in the fungi on the skin |
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| acyclovir |
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| nucloside that looks like guanine and used to treate herpes virus infections (chicken pox, shingles, genital); phosphate binds to the fals nucleoside thus inhibiting DNA synthesis |
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| zidovudine |
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| inhibit DNA or RNA synthesis |
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| fusion inhibitors |
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| fusion is required to enter the cell |
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| reverse transcriptase inhibitors |
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| inhibit replication of nucleic acids |
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| protease inhibitors |
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| inhibit the viral DNA from being cutting up, so remains long |
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| Disk diffusion test |
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| filter paper disks with chemotherapeutic agenst are overlaid on the culture and the diameter of the zone if inhibition is used to determine whether the organism is sensitive, intermediate or resistant to a drug |
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| MIC |
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| minimal inhibitory concentration, the lowest concentration of drug capable of preventing microbial growth |
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| E test |
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| plastic strip with varying concentrations to help determine MIC |
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| Broth Dilution tests |
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| microorganism is grown in liquid media with different concentrations to determine the MIC |
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| MBC |
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| minimal bactericidal concentration, lowest concentrations of a chemotherapeutic agent the kills bacteria |
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| Drug resistance factors |
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| carried by plasmids and transposons, resistant mutants develop and replace the sensitive strains |
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| enzymatic destruction |
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| have enzymes that inhibit the antibiotic |
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| prevention of penetration |
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| drug can't penetrate the outer membrane |
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| cellular or metabolic changes at target sites |
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| bacteria changes the shape of the ribosomal proteins so now the antibiotic can't bind to the ribosome to inhibit it |
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| Rapid efflux of the antibiotic |
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| ex: tetracycline is pumped out of the cell |
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| misuse of antibiotics |
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| using them for the common cold, in animal feed, failure to complete prescription, using outdated antibiotics, using someone else's leftover medication |
