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52 Cards in this Set
- Front
- Back
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What are 5 mechanisms by which an Antibiotic can kill a bacteria?
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1. Inhibit cell wall synthesis
2. Disruption of Cell Membrane 3. Inhibition of protein synthesis 4. Inhibition of nucleic acid function/production 5. Disruption of metabolic pathways |
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3 Major Mechanisms that confer selectivity to antibiotics?
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1. Absence of Target from host. ex: human cells lack cell wall, thus antibiotics targeting cell walls don't hurt our cells.
2. Permeability Differences. Some antibiotic taken up by bacteria, but not our cells. Ex: Gentamycin 3. Structural Differences. Ex: Humans have different ribosomes than bacteria. Thus, antibiotics that target protein production don't hurt us. |
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Bacteriostatic vs. Bactericidal Antibiotics
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- Bacteriostatic: reversibly inhibit bacterial growth; often resemble metabolite analogs and act as a competitive inhibitor
ex: Choloramphenical - Bactericidal: Lethal; may cause cell lysis. Generally only effective against growing cells |
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What is Minimum Inhibitory Concentration (MIC)?
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The lowest concentration of an antibiotic that effectively inhibits growth of a microorganism.
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What are 2 ways to test Minimum Inhibitory Concentration (MIC)?
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1. Tube Dilution Assay
2. Disc Diffusion Method |
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4 Situations in which Combined Antibiotic Therapy is used?
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1. Chronic Infection
2. Emergencies 3. Mixed Infection 4. Drug Synergies |
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4 Types of Drug Interactions
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1. Indifference - two drugs have no effect on each other
2. Additive - response is same as the sum of the 2 drugs 3. Synergistic - response is greater than the sum of 2 drugs. Ex: Bactrim, Augmentin 4. Antagonistic - response is less than sum of the 2 drugs (very rare) |
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4 Reasons why Antibiotic Treatment may not work
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1. Location - If drugs can't access infection (ex: cross blood-brain barrier)
2. Abscess formation and necrosis - decrease circulation doesn't deliver drug. Ex: Necrotizing pneumonia 3. Presence of foreign bodies - bacteria can adhere to substances such as catheters and create biofilm 4. Drug Resistance |
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5 Mechanisms of Drug Resistance
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1. Enzymatic Inactivation of Drug. Ex: beta lactimases destroy Beta Lactam drugs
2. Inadequate/Decreased Uptake. Ex: Change in porin structure 3. Increased Efflux of Drug 4. Alteration of Target. Ex: Change in Penicillin Binding Proteins (PBP's) 5. Alteration (bypass) of metabolic block |
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What are 4 antibiotics that disrupt the cell wall?
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Beta Latams
- Penicillins - Cephalosporins - Carbapenems / Monobactams Glycopeptides - Vancomycin |
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How do Beta-Lactam antibiotics work / Structure?
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- Competitvely inhibt function of penicillin binding proteins in Peptidoglycan cell wall
- Bactericidal - Effective mainly against Gram Positive Bacteria - All contain Beta-Lactam ring |
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What are the 3 classes of Penicillins?
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1. Natural Penicillins. Ex: Penicillin G and V
2. Penicillinase Resistant Penicillins (Good against Staph, ex: Methicillin) 3. Extended Spectrum Penicillins -improved activity against gram negative |
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What are Natural Penicillins used for?
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1. Strep (pyogenes(A), agalactiae(B), pneumonia)
2. Haemophilus influenzae 3. Neisseria meningitidis 4. Syphiliis |
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What are Penicillinase-Resistant Penicillins used for?
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- Similar to natural Penicillins but with activity against Staph
- Ex: Methicillin, Oxacillin |
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What are Extended Spectrum Penicillins used for?
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Gram Negative Bacteria
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When is a beta-lactimase inhibitor added?
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To improve activity, of Penicillin, against Staph and gram negatives
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What are 2 main side effects of Penicillin?
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1. Hypersensitivity - hives / skin rash
2. Anaphylaxis - rare but lethal |
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What does a Beta Latamase do?
How are they overcome? |
- Cleaves Beta-Lactam ring in Becta-Lactam antibiotics
- Overcome by addition of Beta-Lactamase Inhibitor. Ex: Amoxicillin-clavulanate (Augmentin) |
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How do Cephalosporins differ from Penicillins?
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- Wider antibacterial spectrum
- Resistance to many beta-lactimases - Improved pharmocokinetics |
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What are characteristics of 1st Generation Cephalosporin?
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Beta Lactam
- Start with "ceph/cef" - Very active against gram positive including staph (but not MRSA) - Used for community acquired UTI's and respiratory infections |
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What is 2nd Generation Cephalosporin Used for?
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- Otitis Media in children
- Haemophilis influenzae (note: not directly stated on any of drug sheets 4 bugs) |
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What is 3rd Generation Cephalosporin Used for?
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1. Strep. pneumoniae (pneumococcus)
2. Neisseria meningitidis 3. Hemophilus influenzae |
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What is 4th Generation Cephalosporin Used for?
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Used when hay resistance to 3rd gen
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What are 2 main side effects of Cephalosporins?
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1. Hypersensitivity
2. GI issues (due to increased Gram Negative coverage) |
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How do Carbapenems differ from Penicillins?
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- VERY POWERFUL drugs
- Wider antibacterial spectrum - Resistance to beta-lactimases - Usually given IV - Highly active against Gram Positive, Negative, aerobic, and anaerobic bacteria |
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How do Monobactams differ from Penicillins?
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- ONLY active against Gram Negative aerobic bacteria
- No cross reaction with Penicillin Allergic Pt's |
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What is the mechanism of action of Glycopeptides/Polypeptides?
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Attack/Disrupt Bacterial CELL MEMBRANE
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What are 2 main Glycopeptide Antibiotics?
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1. Vancomycin
2. Bacitracin |
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What/how does Vancomycin attack?
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- Excellent Gram Positive Coverage. Used for Staph and Strep.
- Interferes with peptidoglycan, but in DIFFERENT way than Beta-Lactams. Therefore no cross resistance. - Given IV |
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What is most important side effect of Vancomycin?
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(Glycopeptide)
Red Man Syndrome |
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How is Bacitracin Used, method of Action?
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- Used ONLY topically
- Prevents transport across cell membrane |
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What are 6 drugs that attack bacterial ribosomes?
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1. Macrolides*
2. Aminoglycosides* 3. Tetracyclins 4. Chloramphenicol 5. Oxazolidones 6. Lincosamides *Most Important |
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What is most common Macrolide?
Bacteriostatic or Bactericidal? |
Azithromycin (Z Pak)
Bacteriostatic, reversibly binds to 50S ribosome |
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What is mechanism of action of Aminogylcosides?
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- Irreversible binding to 50s Ribosome
- Bactericidal |
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What are Aminoglycosides most commonly used for?
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- Good coverage against aerobic, GRAM NEGATIVE infection
- Usually reserved for serious infections |
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What are 2 most important side effects of Aminoglycosides?
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1. Nephrotoxicity (kidneys)
2. Ototoxicity (ears) |
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What is mechanism of action of Tetracylcins?
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- Reversibly bind to 30s ribosome
- Bacteriostatic - Broad Spectrum |
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What are Tetracyclins most commonly used for?
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- Acne
- Chronic Bronchitis - Rocky Mountain Spotted Fever - Plague |
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What is the most important side effect of Tetracylin?
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- Discoloring of Teeth in children. Therefore do not give to children or pregnant women.
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When is Chloramphenicol used?
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Used as drug of last resort for life threatening infections due to rare but deadly side effects
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When are Oxazolidones used?
Side Effect? |
- Used for hospital acquired pneumonia and Staph infections, including MRSA
- Very high cost |
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What are 3 antibiotic types that inhibit nucleic acid synthesis?
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1. Quinolones (Ciproflaxacin)
2. Rifampin 3. Metronidazole |
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What is mechanism of action of Quinolones?
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Inhibit Nucleic Acid Syntheis via Attack on DNA Gyrase
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What is Metronidazole used for?
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- Antiprotozoal Drug (ex: Giardia)
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What are Rifampins used for?
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Mainly TB
- cause hepititis - organce/brown urine |
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What is the major class of antibiotics that targets bacterial metabolites?
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Sulfonamides
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When are Oxazolidones used?
Side Effect? |
- Used for hospital acquired pneumonia and Staph infections, including MRSA
- Very high cost |
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What are 3 antibiotic types that inhibit nucleic acid synthesis?
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1. Quinolones (Ciproflaxacin)
2. Rifampin 3. Metronidazole |
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What is mechanism of action of Quinolones?
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Inhibit Nucleic acid synthesis via attacking DNA Gyrase
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What is Metronidazole used for?
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- Antiprotozoal Drug (ex: Giardia)
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What are Rifampins used for?
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Mainly TB
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What is major class of antibiotics that targets bacterial metabolites?
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Sulfonamides
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