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22 Cards in this Set
- Front
- Back
Antimicrobial Drugs
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-Chemotherapy: the use of drugs to treat a disease
-Antimicrobial drugs: interfere with the growth of microbes within a host -Antibiotic: a substance produced by a microbe that, in small amounts, inhibits another microbe -Selective toxicity: a drug that kills harmful microbes without damaging the host |
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History of Chemotherapy
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1928: Fleming discovered penicillin, produced by Penicillium
1940: Howard Florey and Ernst Chain performed first clinical trials of penicillin |
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The Spectrum of Antimicrobial Activity
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-Broad spectrum: treats a lot
-Narrow spectrum: treats little -Superinfections may result when normal flora are disrupted |
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The Action of Antimicrobial Drugs
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Bactericidal
-kills microbes directly Bacteriostatic -prevent microbes from growing |
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The Inhibition of Protein Synthesis by Antibiotics
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Chloramphenicol
-binds to 50S portion and inhibits formation of peptide bond Tetracyclines -interfere with attachment of tRNA to mRNA-ribsome complex Streptomycin -changes shape of 30S portion, causing code on mRNA to be read incorrectly |
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B-Lactam Antibiotics
^(beta) |
Penicillin
-penicillinase-resistant penicillins -penicillins + B-lactamase inhibitors Carbapenems -substitute a C for a S, add a double bond Monobactam -single ring |
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Competitive Inhibitors
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Sulfonamides (sulfa drugs)
-inhibit folic acid synthesis -broad spectrum -when use in combination with trimethoprim synergism results |
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Effects of Combinations of Drugs
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-Synergism occurs when the effect of two drugs together is greater than the effect of either alone
-Antagonism occurs when the effect of two drugs together is less than the effect of either alone |
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Antiviral Drugs
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-Nucleoside and nucleotide analogs
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Antiviral Drugs: Modes of Action
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Inhibit attachment
-block CCR5: HIV Inhibit uncoating -Amantadine: Influenza Inhibit nuclei acid synthesis -Nucleotide analogs -->Acyclovir, nucleotide analog, herpesviruses -->AZT, thymine analog, HIV -->Reverse transcriptase inhibitors, HIV Prevent maturation and release -protease inhibitors, HIV |
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HIV: Human Immunodeficiency Virus
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Acquired immunodeficiency syndrome
Retrovirus, genus Lentivirus -use reverse transcriptase to make double stranded DNA from the single-stranded RNA genome -Viral genes permanently integrated into host DNA HIV can only infect host cells taht have the required CD4 marker plus a coreceptor |
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HIV Epidemiology
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-First nationally notifiable in 1984
-6th most common cause of death among people aged 25-44 years in the US -In 2007, the number of infected individuals worldwide is estimated to be 33 million with ~1.2 million in the US |
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HIV Transmission
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Transmission
-sexual intercourse -transfer of blood or blood products -babies can be infected before or during birth, and from breast feeding -->20% of infants born to infected mothers are HIV+ HIV does not surive long outside the body Some individuals are resistant to HIV infection due to mutations in CCR5 |
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Pathogenesis of HIV
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1. HIV enters through mucous membrane or skin and travels to dendritic phagocytes beneath the epithelium, multiplies and is shed
2. Virus is taken up and amplified by macrophages in the skin, lymp organs, bone marrow, and blood 3. HIV attaches to CD4 and coreceptor; HIV fuses with cell membrane 4. Reverse transcriptase makes a DNA copy of RNA 5. Viral DNA is integrated into host chromosome (provirus) 6. Can produce a lytic infection or remain latent |
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Signs and Symptoms in the Stages of HIV Infections and AIDS
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1. Initial infection: mononucleosis-like symptoms that soon disappear
2. Antibodies are detectable 8-16 weeks after infection 3. Asymptomatic phase 2-15 years (avg. 10) 4. AIDS Symptoms: -T4 cell levels fall below 200/uL -fever, swollen lymph nodes, diarrhea, weight loss, neurological symptoms, opportunistic infections and cancers |
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Preventing and Treating HIV
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Prevention
-monogamous sexual relationships -condoms -universal precautions Therapies -inhibit viral enzymes: reverse transcriptase, protease, and integrase -inhibit fusion -inhibit viral translation -highly active anti-retroviral therapy |
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Antibiotic Resistance
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-A variety of mutations can lead to antibiotic resistance
-Mechanisms of antibiotic resistance 1. Enzymatic destruction of drug 2. Prevention of penetration of drug 3. Alteration of drug's target site 4. Rapid ejection of the drug -Resistance genes are often on plasmids or transposons that can be transferred between bacteria |
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Antibiotic Resistance
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Misuse of antibiotics selects for resistance mutants. Misuse includes:
-using outdated or weak antibiotics -using antibiotics for the common cold and other inappropriate conditions -using antibiotics in animal feed -failing complete the prescribed regimen -using someone else's leftover prescription |
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5 Actions of Antimicrobial Drugs
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1. Inhibition of cell wall synthesis: penicillins, cephalosporins, bacitracin, vanocomycin
2. Inhibition of protein synthesis: chloramphenicol, erythromycin, tetracyclines, streptomycin 3. Inhibition of nucleic acid replication and transcription: quinolones, rifampin 4. Injury to plasma membrane: polymyxin B 5. Inhibition of synthesis of esssential metabolites: sulfanilamide, trimethoprim |
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Methods of Drug Action that Inhibit Protein Synthesis
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Choloramphenicol
-binds to 50S portion and inhibits formation of peptide bond Tetracyclines -interfere with attachment of tRNA to mRNA- ribsome complex Streptomycin -changes shape of 30S portion, causing code on mRNA to be read incorrectly |
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**REVIEW QUESTION**
List top 4 "hardest to kill" microbes |
1. prions
2. endospores 3. mycobacteria 4. protozoan cysts |
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**REVIEW QUESTION**
Explain Quorum Sensing |
??
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