Antimicrobial Agents and Therapy Chemotherapeutic Drug The largest category of drugs that is a chemical used to treat wide range of diseases Ex cancer pain etc Antimicrobial Drug A chemical used to treat a disease due to microbes Infectious disease Antibiotics A type of natural antimicrobial drug that is made from microbes such as fungi and kills other microorganisms What Organisms Produce Antibiotics Phylum Actinobacteria Gram Found in soil and water The Actinomycetes Produce the best antibiotics Grows and looks life fungi Mostly aerobic chemohetertrophs Produce spores Most free living and are completely harmless that are found in the soil One species produces one specific type of antibiotic Streptomyces are the main producer of many good antibiotics Narrow spectrum Works on one group of bacteria Broad spectrum Works on multiple groups of bacteria Antibiotics First antibiotics made from fungi and bacteria Primarily used to treat bacterial infections Does NOT work against Viral Infections Many are made in labs derived from the natural antibiotic Penicillin The first antibiotic made from the fungi Penicillium Ampicillin Amoxicillin Antimicrobial Agents and Therapy Selective toxicity effects the microorganism but does not effect the human cells Must be able to reach infected site and remain active Ex An infection in the brain needs to have antibiotics reach that part of the brain and remain active to treat it Antimicrobial Drug Target Sites Figure 12 2 Static Drugs Inhibits growth and replication of microbe then immune system kills the remaining microbes Cidal Drugs Kills the microorganism and is dose dependent Target Sites and Specific Modes of Action Cell wall disruption Disrupts main chemical peptidoglycan Works best on young cells because young cells make up the cell wall Examples o Penicillin prevents protein crosslinks o Bacitracin prevents subunits from being transported out of the cell works on young cells making the cell wall Cell membrane disruption Due to antibacterial drugs Examples o Polymixins Disrupts membrane surface by interacting with phospholipids of Gram bacteria o Polyenes Antifungal drug Disrupts and interacts with sterol lipids cell loses permeability most toxic effects used for most severe fungal infections o Imidazoles Antifungal drugs More widely used less side effects Usually in the form of topical sprays or ointments to get rid of fungus keeps sterol lipids from forming Inhibiting nucleic acids inhibits the unwinding of DNA molecule o Drugs get through the cell wall and membrane o Effects genetic material in cell o Interacts with enzyme directly DNA Girase o Girase Enzyme associated with unwinding DNA o Quinolones Girase inhibitors treat bacteria infections gets into the cell and keeps girase from working Protein Synthesis Disruption Interacts with ribosomes o Fastest way to kill a cell is to stop protein synthesis Drugs binding to 30s Subunit Aminoglycosides Finds ribosome and sticks on 30s piece Most effective and potent Works quickly Treats serious infections Broad Spectrum Tetracyclines Block attachment of tRNA Sticks to slightly different place on 30s subunit Keeps transfer RNA from coming in No protein is made Broad spectrum Drugs binding to 50s Subunit Chloramphenicol Prevents peptide bond formation No protein is formed Erythromycin macrolide Prevents movement of ribosome along mRNA Happens in protein synthesis so no protein is formed Disruption of metabolic pathway Inhibits the formation of nitrogenous bases o Inhibits microbes from making folic acids which are used to make nitrogenous bases o Folic acid inhibitors sulfonamides trimethoprim Antiviral Drugs Selectively toxic Hard to obtain Will damage host cell and get rid of virus Works against a small group of viruses No definitive treatment Antiviral drugs just slow down the replication Antiviral Drug Mechanisms Inhibit viral entry Slows nucleic acid production Slows assembly and release of virus Selecting and Antimicrobial Agent General considerations o Do they have any other diseases that may cause side effects o Type of microbe o Life threatening Or mild o Cost o Sensitivity tests make sure the drug will actually kill the microbe Antimicrobial Drug Resistance Self Study section 12 6 Considerations in selecting antimicrobial drug MIC test and Kirby Tests How do microbes acquire drug resistance Mutation Intermolecular gene transfer conjugation transformation and transduction Mechanisms of Drug Resistance Figure 12 14 Alter binding site on ribosome so drug cannot bind anymore Drug is then no longer effective Decrease in cell permeability microbe keeps drug from getting inside by altering porin proteins in outer membrane of Gram Bacteria is inside but immediately pumps out with the help of efflux pumps Some bacterial species are resistance to all available drugs Super Bugs Multiple Drug Resistance and Prevention Microbes can resist more than one antibiotic Once develops resistance its irreversible Use antimicrobial drugs only for bacterial infection not viral Use proper dosage for given time Limit use of antibiotics as a growth hormone in food cattle chicken There is no way to fully prevent resistance we can just slow it down Do not use potent drugs for a minor infection
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