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50 Cards in this Set
- Front
- Back
Antimicrobial Drugs |
- drugs that may be synthetic or nonsynthetic and inhibit the growth of microbes within a host |
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Chemotherapy |
- using drugs to treat disease caused by microbes |
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Antibiotic |
a substance produced by microrganisms that in small amounts inhibits the growth of another microorganism |
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Selective Toxicity |
- a drug that kills harmful microbes without damaging the host - this is done by affecting some aspect of the pathogen that is not part of the host's physiology |
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Spectrum of a Drug |
- range of organisms affected by a drug |
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Broad Spectrum Drug |
- affects both Gram - and Gram + organisms
- more likely to affect an unidentified pathogen, but may damage beneficial flora and thus have a greater chance of superinfection (infection by another pathogen) |
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Narrow Spectrum Drug |
- affects one or the other
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Superinfection |
- infection by another pathogen when beneficial flora are killed - occurs when a pathogen develops resistance to the drug being used or when normally resistant microbiota multiply excessivey |
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Synergism |
- combined effect of two drugs used at the same time is greater than the sum of their individual effects ie. Damage to bacterial cell walls by penicillin makes it easier for streptomycin to enter |
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Antagonism |
- combined effect of two drugs used at same time is less than the sum of their individual effects ie. Tetracycline is bacteriostatic and interferes with the action penicillin. Tetracyclin halts growth so penicillin can't do anything since the bacteria is not synthesizing peptidoglycan. |
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Superbugs |
- bacteria that resistant to large numbers of antibiotics 1. MRSA 2. KPC 3. VRE 4. ESBLs 5. MRPA |
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MRSA |
Methicillin Resistant Staphylococcus Aureus |
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KPC |
Klebsiella Pneumonia Carabapenemase producing |
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VRE |
Vancomycin Resistant Enterococcus
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ESBLs |
Extended Spectrum Beta Lactamase producing bacteria |
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MRPA |
Multidrug-Resistant Pseudomonas Aeruginosa |
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Name the microbes that produce the most antibiotics |
Streptomyces spp. |
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Describe the problems of chemotherapy for viral, fungal, protozoan, and helminthic infections. |
- fungal, protozoan, and helminthic infections are more difficult to treat because these organisms have eukaryotic cells. - viral infections are difficult because the pathogen is within the human host's cell and the virus is directing the human cell to make viruses. |
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Identify five modes of action of antimicrobial drugs. (Study Foundationg Figure 20.2) |
1. Inhibition of Cell Wall Synthesis (penicillins) 2. Inhibition of Protein Synthesis (streptomycin) 3. Inhibition of Nucleic Acid Replication and Transcription (quinolones, rifampin) 4. Injury to Plasma Membrane (polymyxin B) 5. Inhibition of Essential Metabolite Synthesis (sulfanimide) |
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Explain why drugs can be specific for bacteria (and not human cells or virions) |
This is because these drugs affect a physiologcial aspect of bacteria that hosts don't have. 1. Bacteria have 70s ribosomes, we have 80s ribosomes 2. they have Peptidoglycan in their cell walls, humans don't have cell walls |
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Explain how a drug can be more toxic to a pathogen than to the host. |
This is because these drugs affect a physiological aspect of bacteria that hosts don't have. |
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Describe how Sulfa drugs inhibit microbial growth |
Sulfa drugs block the ability of folic acid to be synthesized. They do this by blocking PABA binding on the active site of enzymes. Folic acid is a precursor for bacteria to produce DNA/RNA . |
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Action of Antimicrobial Drugs: Inhibiting Cell Wall Synthesis |
Penicillin - prevents the synthesis of intact peptidoglycan. Only actively growing cells are affected by these antiobiotics. |
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Action of Antimicrobial Drugs: Inhibiting Protein Synthesis |
- Eukaryotes 80s ribosomes - Prokaryotes 70s ribosomes allows for selective toxicity. - Mitochondria contain 70s ribosomes also which may have adverse efects on the cells of the host. - Streptomycin |
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Action of Antimicrobial Drugs: Inhibiting Nucleic Acid Synthesis
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- some drugs have an extremely limited usefulness because they interfere with mammalian DNA and RNA also - quinolones, rifampin |
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Action of Antimicrobial Drugs: Inhibiting the Plasma Membrane
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- brings about changes in permeability of plasma membrane resulting in loss of important metabolites from the microbial cell - combine with sterols in functional plasma membrane to disrupt the membrane - act on fungal diseases - polymyxin B |
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Action of Antimicrobial Drugs: Inhibiting the Synthesis of Essential Metabolites
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- enzymatic acitvity can be compettitively inhibited by a substance (antimetabolite) that closely resembles the normal substrate for the enzyme ie. suldanamine blocks PABA from binding and synthesizing folic acid (a coneznyme for the synthesis of amino acids) |
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Penicillin (and how they work against bacteria) |
refers to a group of over 50 chemically related antibiotics containing a B-lactam ring called the nucleus. They prevent the cross-linking of peptidoglycans which interferes with the construction of cell walls, mostly Gram +. |
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Natural Penicillins |
Penicillins extracted from cultures of the mold Penicillium. It is useful against most staphylococci, streptococci, and several spirochetes. Muscular Injection: rapid excretion Oral: stomach dimishes its concentrations Have long retention times in the body, but the concentration is so low that organisms must be very sensitive to it. They are susceptible to Penicillinases which cleave the B-lactam ring. |
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Semysynthetic Penicillins |
Developed: 2. Removal of side chains from completed natural molecules and then chemically add other chains that make them more resistant to penicillinase. |
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The Diffusion Methods |
1. Disk Diffusion Method 2. E Test sensitive, intermediate, or resistant |
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Disk Diffusion Method |
1. Inoculate agar plate with pathogen 2. Place paper disks dipped in different disinfectants on surface of agar 3. Incubate 4. Compare Zones of Inhibition Larger the zone = more senstivity to drug |
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Disadvantages of the Diffusion Methods
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1. less soluable drugs may have a smaller zone of inhibtion 2. does not determine if drug is -cidal or -static |
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E test |
enables a lab technician to estimate the minimal inhibitory concentration (MIC), the lowest antibiotic concentration that prevents visible bacterial growth - a plastic-coated strip contains a gradient of antibiotic concentrations, and the MIC can be read from a scale printed on the strip |
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Broth Dilution Test |
determines MIC (minimal inhibitory concentration) and MBC (minimal bactericidal concentration) - sequence of decreasing concentrations of the drug in a broth, which is then inoculated with test bacteria |
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Importance of the Broth Dilution Test |
- it avoids the excessive use of expensive antibiotics and minimizes the chance of toxic reactions that larger-than-necessary doses might cause |
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Drug Resistance Develops in the Pathogens |
Some microbes develop drug resistance through mutation. Once they acquire this drug resistance, they can transfer these drug resistance genes to other bacteria through conjugation. |
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Study Foundation Figure: 20.20 Bacterial Resistance to Antibiotics |
1. Blocking entry 2. Inactivation by enzymes 3. Alteration of target molecule 4. Efflux of antibiotic |
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Acinetobacter baumanii |
- has developed resistance by means of all five of the major target sites illustrated in Foundation Figure 20.20 |
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Inactivation of the Drug |
d |
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penicilllinase (beta-lactamase) |
Bacterial enzymes that destroy natural penicillins. Semisynthetic penicillins are made to resist penicillinases/have a broader spectrum of activity. |
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Drug Resistance Factors |
- carried by plasmids, or small segments of DNA called transposons, which can jump from one piece of DNA to another. |
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Drug Susceptibility |
- the ability of a drug to affect a pathogen, the lack of resistance to a drug |
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Drug Resistance |
- pathogen is not affected by a drug (opposite of drug susceptibility) |
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Drug Susceptiblity Testing |
- determines which drugs might control an infection - includes: 1. Kirby-Bauer Disk Diffusion Method 2. E test 3. Broth Dillution Test |
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Synthetic Drugs |
- drug produced in lab/factory through chemical reactions
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Biosynthesis |
- production of a chemical by a living organism |
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Explain antibiotic misuse as stated on page 572. |
1. Outdated/impure antibiotics 2. counterfeit antibiotics 3. Dose regimens are shorter than needed to eradicate infection, encouraging the survival of resistant strains of bacteria 4. unneccessary or inappropriate prescriptions
5. antibiotics used in animal feeds to promote growth increases drug resistance pathogens |
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How can drug resistance be delayed? |
1. finishing full regimen of antibiotic prescriptions 2. never use left over antibiotics 3. healthcare workers should avoid unneccessary prescriptions and ensure that choice and dosage are appropriate for the situation 4. prescribe most specific antibiotic possible, instead of broad-spectrum antimicrobials 5. inserting needle into cotton to prevent aerosols from being inhaled |
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Identify 3 Areas of Research on New Chemotherapeutic Agents |
1. peptides 2. bacteriocins 3. bacteriophages |