Microbiology Chapter 12 Test Questions – Flashcards
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| Antibiotic |
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| A chemical substance from one microorganism that can inhibit or kill another microbe even in minute amounts. |
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| Selectively toxic |
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| Drugs should kill or inhibit microbial cells without simultaneously damaging host tissues. |
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| Spectrum |
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| Range of activity of a drug. |
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| Narrow-spectrum |
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| Effective on a small range of microbes. -target a specific cell component that is found only in certain microbes. |
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| Broad-spectrum |
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| Greatest range of activity. -target cell components common to most pathogens. |
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| Medium-spectrum |
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| Effective on both gram + and gram - bacteria but not all. |
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| Antiviral drugs |
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| Any drug that destroys viruses via analogs of purines and pyrimidines. -These insert in viral nucleic acid, preventing replication. |
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| Synergistic effect |
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| Increased intensity (effectiveness) caused by the combination of two substances on an organism, lowering the required dose of each. |
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| Competitive inhibition |
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| Control process that relies on the ability of metabolic analogs to control microbial growth by successfully competing with a necessary enzyme to halt the growth of bacterial cells. |
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| MIC (Minimum Inhibitory Concentration) |
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| The lowest concentration of antibiotic needed to inhibit bacterial growth in a test system. |
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| Parententerally |
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| To be outside of the intestine. |
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| Drug resistance |
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| An adaptive response in which microorganisms begin to tolerate an amount of drug that would ordinarily be inhibitory. |
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| Acquired resistance |
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| Refers to specific immunity developed by lymphocytes responding to antigens. |
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| Kirby-Bauer disk diffusion test (part 1) |
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| This technique is an agar diffusion test that provides useful data on antimicrobial susceptibility. In this test, the surface of a plate of special medium is spread with the test bacterium, and small disks containing a pre-measured amount of antimicrobial are dispensed on to the bacterial lawn. |
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| Kirby-Bauer disk diffusion test (part 2) |
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| After incubation, the zone of inhibition surrounding the discs is measured and compared with a standard for each drug. the profile of antimicrobial sensitivity provides data for drug selection. This procedure is less effective for bacteria that are anaerobic, highly fastidious, or slow-growing (Mycobacterium). |
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| Therapeutic index (TI) |
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| Defined as the ratio of the doe of the drug that is toxic to humans as compared to its minimum effective (therapeutic) dose. The closer these two figures are, the greater is the potential for toxic drug reactions. |
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| Prophylaxis |
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| Use of a drug to prevent potential for infection of a person at risk. |
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| Semi-synthetic drugs |
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| Drugs which are chemically modified in the laboratory after being isolated from natural sources. |
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| Interferons (IFN) |
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| A glycoprotein produced primarily by fibroblasts and leukocytes in responds to various immune stimuli.It has numerous biological activities, including antiviral and anticancer properties. Studies have shown that it is a versatile part of animal host defenses, having a major role in natural immunities. |
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| What is the 1st of the 5 main mechanisms of Drug Action? |
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| 1) Protein Synthesis -Penicillins -Cephalosporins -Vancomycin -Bacitracin -Monobactams/carbapenems -Fosfomycin -Cycloserine -Isoniazd |
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| What is the 2nd of the 5 main mechanisms of Drug Action? |
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| 2) Breakdown of cell membrane structure/function -Polymyxins |
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| What is the 3rd of the 5 main mechanisms of Drug Action? |
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| 3) Inhibition of structures and functions of DNA and RNA -Inhibit gyrase (unwinding enzyme): Quinolones (ciprofloxacin) -inhibit RNA polymerase: Rifampin |
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| What is the 4th of the 5 main mechanisms of Drug Action? |
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| 4) Inhabitation of protein synthesis -Action site of 50s subunit: Chloramphenicol, Erythromycin, Clindamycin, Oxazolidinones -Action site of 30s subunit: Aminoglycosides, Tetracyclines, Streptomycin, Amikacin |
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| What is the 5th of the 5 main mechanisms of Drug Action? |
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| 5) Blocks key metabolic pathways -Sulfonamides (sulfa drugs) -Trimethoprim |
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| What is the primary mode of action of all Beta-lactam drugs? |
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| Interfere with proteins involved in synthesis of the cell wall, leading to lysis and cell death. more than half of all antimicrobic drugs are beta-lactams, with penicillins and cephalosporins being the most prominent representatives. |
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| What are the 2 natural forms of Penicillin that are most important? |
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| Penicillium notatum and Penicillin V |
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| What types of bacteria are the natural forms used against? |
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| Gram - bacteria that are sensitive. Commonly found in the form of wound pathogens. |
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| What types of bacteria are the semisynthetic forms used against? |
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| Gram - bacilli |
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| Why is semisynthetic Penicillin often better? |
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| -Resistance to stomach acids so that they can be taken orally. -A degree of resistance to penicillinase (a penicillin-destroying enzyme produced by some bacteria). -Extended range of activity against some Gram - bacteria. |
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| What are the primary problems with Penicillins? |
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| Widespread development of resistance among target microorganisms and allergic reaction. |
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| What is the primary mode of action of Cephalosporins? |
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| Inhabitation of cell-wall synthesis. |
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| Why are Cephalosporins sometimes superior to Penicillins? |
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| Relatively broad-spectrum, resistant to most penicillinases, and cause fewer allergic reactions. |
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| What are some cephalosporins of the 3rd and 4th generations? |
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| 3rd Gen: broad-spectrum activity against enteric bacteria with beta-lactamases. -Cephalexin, Ceftriazone 4th Gen: Widest range; both Gram - and Gram + -Cefepime |
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| What type of infection is Vancomycin used for? What are its drawbacks? |
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| Type: Narrow-spectrum, most effective in treatment of Staphylococcal infections in cases of Penicillin and Methicillin resistance or if patient is allergic to Penicillin. Drawbacks: Toxic and hard to administer, restricted use. |
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| What is Bacitracin used for? |
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| Narrow-spectrum range produced by a strain of Bacillus subtilis; used topically in ointment. |
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| What is Aminoglycosides mode of action? What type of infection are they used for? |
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| Mode of action: Broad-spectrum. Inhibits protein synthesis. Infection type: Aerobic Gram - rods and certain Gram + bacteria. |
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| What are some examples? What are some specific diseases treated by using Aminoglycosides? |
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| Examples: -Streptomycin (Bubonic Plague, Tularemia, TB) -Gentamicin (Less toxic, used against Gram - rods) -Tobramycin and Amikacin (Gram - bacteria) Diseases: Bubonic Plague, Tularemia, and Tuberculosis. |
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| That is Tetracycline Antibiotics' mode of action? What types of infection are they used for? |
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| Mode of action: Broad-spectrum. Blocks protein synthesis by biding ribosomes. Infection type: STD's, Rocky Mountain Spotted Fever, Lyme Disease, Typhus, Acne and Protozoa. |
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| What is Tetracycline's advantage? What concern is there? |
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| Advantage: Low cost of oral drugs. Concern: Side effects, such as reaction to sunlight while taking this antibiotic. |
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| That is Chloramphenicol's mode of action? What types of infection is it used for? |
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| Mode of action: Potent broad-spectrum drug with unique nitrobenzene structure. Blocks peptide bond formation (i.e. protein formation) Infection types: typhoid Fever, Brain Abscesses, Rickettsial and Chlamydial infections for which there are no other treatments (intracellular bacteria.) |
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| What concern is there when using Chloramphenicol? |
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| Concern: Toxic to people. Tis leads t restricted use, can cause irreversible damage to bone marrow. |
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| What is Macrolides' mode of action? What types of infection are they used for? |
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| Mode of action: Broad-spectrum, fairly low toxicity. Infection types: Mycoplasma pneumonia, legionellosis, Chlamydia, Pertussis, Diphtheria and as a Prophylactic prior to intestinal surgery. |
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| What is the major infection type of Macrolides used to treat? What do you use when someone is resistant to Erythromycin? |
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| Major infection type: Streptococcus pneumoniae Alternatives: Ketolides- Telitromycin (Ketek), new class of drugs with different ring structure from Erythromycin; used for infection when resistant to Macrolides. |
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| What are Sulfa drugs' mode of action? What are they used to treat? |
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| Mode of action: Narrow-spectrum; block the synthesis of folic acid by bacteria. Infection types: -Sulfisoxazole: Shingellosis, UTI, and protozoan infections. -Silver sulfadizine (silvadine): burns, eye infections. -Trimethoprim: given in combination with sulfamethoxazole to treat UTI, Pneumocystis pneumonia, and ear infections. |
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| What is Macrolide polyenes used to treat? What is it's mode of action? |
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| Macrolide polyenes: Produces holes in fungal membranes. -Amphotericin B: mimics lipids, most versatile and effective, topical and systemic treatments. -Nystatin: topical treatment. |
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| What is Azoles used to treat? What is it's mode of action? |
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| Azoles: Borad-spectrum; inhibits the enzymes necessary to convert Lanosterol to Ergosterol. -Ketoconazole -Clotrimazole |
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| What is Flucytosine used to treat? What is it's mode of action? |
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| Flucytosine: Analog of Cytosine; cutaneous mycoses or in combination with Amphotericin B for systemic mycosis. |
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| What are the 3 modes of action of antiviral compounds? |
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| 1) Block penetration into host cell. 2) Block transcription or translation of viral genetic material. -Nucleotide analogs -Acyclovir: Herpes viruses -Ribavirin: a guanine analog - RSV, hemorrhagic fevers -AZT: Thymine analog - HIV 3) Prevent maturation of viral particles. -Protease inhibitors - HIV |
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| What are the different mechanisms of drug resistance? (1-2) |
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| 1) Drug inactivation by acquired enzymatic activity. -ex: Penicillinases. 2)Decreased permeability to drug or increased elimination of drug from cell. -Via acquisition or mutation. |
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| What are the different mechanisms of drug resistance? (3-5) |
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| 3) Change in drug receptors by mutation or acquisition. 4) Change in metabolic patterns. -Mutation of original enzyme. 5) Possession of "pumps" that are able to move drugs outside of the cell wall. |
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| What are some considerations in selecting an antimicrobial drug? |
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| 1) Identifying the microorganism causing the infection. 2) Test the microorganism's susceptibility (sensitivity) to various drugs "in vitro" when indicated. 3) The overall medical condition of the patient. |
