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58 Cards in this Set
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- 3rd side (hint)
First microbiologist to search for what we now know as antibiotics? What was he searching for? |
Paul Ehrlich Searched for a "magic bullet", or selective toxicity |
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Selective toxicity |
A characteristic that causes the death of microbes while leaving host tissue unharmed |
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What term did Paul Ehrlich coin? |
Chemotherapy |
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Chemotherapy |
Using chemicals to treat a disease |
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Who invented penicillin? |
Alexander Fleming |
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How was Penicillin invented? |
A plate of Staphylococcus aureus was left out and grew mold, specifically the genus Penicillium. It was found that this mold inhibited the growth of the bacteria |
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Antibiotics |
Substances produced by microorganisms that inhibit the growth of other microorganisms |
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Sulfa Drugs |
Developed by three Germans during WWII to combat Streptococcal infections Technically not an antibiotic because it was derived from a chemical, not microbe |
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What is the source of more than half of antibiotics? |
Streptomyces |
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What are some other sources of antibiotics? |
- Bacillus subtilis produces Bacitracin - Molds such as Penicillium and Cephalosporium |
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Spectrum classifications of antimicrobial activity |
1. Narrow spectrum 2. Broad spectrum |
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Narrow spectrum |
Antibiotics only affect a few organisms |
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Broad spectrum |
Large range of organisms is affected Overused Damage normal flora |
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Example of broad spectrum activity |
Some drugs that combat both gram + and gram- bacteria |
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What are some limitations in antimicrobial activity against organisms other than bacteria? What is the significance? |
- protozoans, fungi, and helminths are more closely related to humans - viruses aren't cellular and only reproduce inside cells using our cellular machinery - antibiotics tend to be more effective against bacteria |
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What is the purpose of bacteriostatic agents against infection? |
The inhibited growth allows the immune system to catch up and destroy the organisms |
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How does penicillin act against microbes? |
Inhibits cell wall synthesis by blocking peptidoglycan synthesis This leads to cell lysis |
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Drugs that inhibit cell wall synthesis |
1. Natural penicillins 2. Semisynthetic Penicillins 3. Cephalosporins 4. Polypeptide antibiotics |
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Semisynthetic penicillins |
Amoxicillin Ampicillin Carbapenems Monobactams |
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Cephalosporins |
Resemble Penicillin, but beta-lactam ring is slightly different |
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Polypeptide antibiotics |
Bacitracin Vancomycin |
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Bacitracin |
Topical antibiotic derived from B. subtilis |
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Vancomycin |
Used to combat MRSA |
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How have certain bacteria built a resistance to penicillins and cephalosporins? |
They have developed the ability to cut up beta-lactam rings, making these classes ineffective |
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Ways that drugs target microbes |
1. Inhibition of cell wall synthesis 2. Inhibition of protein synthesis 3. Injury to the plasma membrane 4. Inhibition of nucleic acid synthesis 5. Inhibition of the synthesis of essential metabolites |
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Drugs that act as inhibitors of protein synthesis |
1. Aminoglycosides 2. Tetracyclines 3. Macrolides |
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How do drugs inhibit protein synthesis? |
Bacterial ribosome differs from what is found in eukaryotic ribosomes, so drugs can be made to target them and prevent protein synthesis |
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Macrolides |
Erythromycin Azithromycin |
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Aminoglycosides |
Streptomycin Gentamicin |
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How do antibiotics injure plasma membranes? |
By binding to the cell membrane and changing its permeability, leading to lysis |
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How do some antifungal bind to the cell membrane of fungi? |
They bind to sterols in the phospholipid bilayer |
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What drugs cause injury to the plasma membranes of microbes? |
1. Polymyxin B 2. Lipopeptides |
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What is an example of a Lipopeptide? |
Daptomycin |
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What is a common use for daptomycin |
Used against MRSA |
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How do some antibiotics inhibit nucleic acid synthesis? |
By interfering with DNA replication or transcription by targeting DNA gyrase and RNA polymerase |
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What is the affect of antibiotics targeting DNA gyrase? |
Bacteria can't uncoil DNQ |
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Antibiotics that inhibit Nucleic acid synthesis |
- Rifampin - Quinolones - Fluoroquinolones |
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Fluoroquinolones |
Ciprofloxacin Levofloxacin |
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How do drugs inhibit the synthesis of essential metabolites? |
Some drugs block the synthesis of folic acid, which is synthesized by bacteria but not humans |
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What are common drugs that inhibit the synthesis of essential metabolites and how do they do it? |
Sulfa drugs, by mimicking PABA, which is a precursor to folic acid |
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Types of antiviral drugs |
1. Nucleotide analogs 2. Enzyme inhibitors 3. Interferons |
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Nucleotide analogs |
Drugs that mimic nucleotides, preventing viral replication |
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What is an example of a common Nucleotide analog? |
Acyclovir |
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Enzyme inhibitors |
Block viral enzymes |
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What is an example of a common enzyme inhibitor and how does it work? |
Tamiflu Blocks neuraminidase in influenza |
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Interferons |
Proteins that are produced by cells infected with a virus Cause uninfected cells to produce antiviral proteins |
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How do we test the effectiveness of antibiotics? |
Disk diffusion method |
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Disk diffusion method |
Adding discs laden with antibiotics to a spread plate and looking for zones of inhibition |
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How do we determine the necessary strength of an antibiotic? |
We find the Minimal Inhibitory Concentration (MIC) by using a broth dilution test to find the lowest concentration of an antibiotic that will still prevent bacterial growth |
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Mechanisms of resistance to antimicrobial drugs |
1. Enzymatic destruction or inactivation of the drug 2. Blocking entry/ prevention of penetration to target site 3. Alteration of the target molecule 4. Rapid efflux of the antibiotic |
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Enzymatic destruction or inactivation of the drug |
B-Lactamases target the B-lactam ring shared by penicillins and cephalosporins |
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Blocking the entry/ prevention of penetration to the target site |
Some bacteria alter the structure of porins, which no longer allow entry of the antibiotic |
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Alteration of the target molecule |
Minor changes in the structure of bacterial proteins can prevent the antibiotic from binding to them |
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Rapid efflux of the antibiotic |
The bacteria have molecular pumps that spit the antibiotics out of the cell before they can have an effect |
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Effects of combining drugs |
1. Synergism 2. Antagonism |
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Synergism |
When 2 or more antibiotics are more effective when taken together |
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Antagonism |
Antibiotics taken in tandem are less effective than when taken alone |
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Microdilution plate |
Used in broth dilution test to determine MIC using many different wells with varying concentrations of antibiotics |
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