Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Controlling Microbial Growth in the Body Antimicrobial Drugs Antimicrobial Drugs History of Antimicrobial Agents Chemotherapy Paul Ehrlich 1854-1915- Magic Bullets Alexander Fleming 1881-1955- Antibiotics Antimicrobial Drugs Mechanisms of Antimicrobial Action Selective Toxicity Drugs that Inhibit Cell Wall Synthesis Prevent synthesis of the polysaccharide, Peptidoglycan that makes up the bacterial cell wall e.g. penicilins, cephalosporins, vancomycin All penicillins consist of 3 parts Thiazolidin Beta-lactams Variable side chain- group Antimicrobial Drugs Drugs that Inhibit Protein Synthesis Differences in the ribosomes of prokaryotes and eukaryotes Prokaryotes have 70S ribosomes and Eukaryotes have 80S ribosomes Drugs selectively targets bacterial protein synthesis without significantly affecting eukaryotes Examples of drugs include: tetracyclines and the aminiglycosides such as streptomycin and gentamycin Aminiglycosides are composed of amino sugars that change the shape of 30S subunits of prokaryotic ribosomes Antimicrobial Drugs Disruption of Cytoplasmic Membranes Agent becomes incorporated into prokaryotic membranes and damage integrity E.g. Amphotericin B Antimicrobial Drugs Inhibition of Metabolic Pathways Metabolism is sum total of all chemical reactions within an organism Similarities and differences between prokaryotic and eukaryotic cells Exploit differences e.g., Heavy Metals inactivate enzymes, certain agents paralyze worms, and some prevent attachment of viruses Antimicrobial Drugs Sulfonamides are structural analogs of PABA (Para Amino Benzoic Acid) Paba is crucial in synthesis of nucleotides Analogs of paba such as sulfonamides are used to compete with paba. Antimicrobial Drugs Inhibition of Nucleic Acid Synthesis Nucleotide Analogs e.g., Quinolones act against prokaryotic DNA and Rifampin inhibit RNA Polymerases Antimicrobial Drugs Determining Efficacy of Drugs 1. Diffusion Susceptibility Test Variety of Tests Used Called Kirby-Bauer Test Measure zone of Inhibition 2. Minimum Inhibitory Concentration (MIC) Quantitative Expression of Drug Potency Smallest amount of drug to inhibit growth and reproduction of pathogen Determined by Broth Dilution Test Antimicrobial Drugs Minimum Bacteriocidal Concentration (MBC) Subculture into drug-free media Growth- bacteriostatic No Growth- bacteriocidal Lowest concentration of drug for which no growth occurs is MBC.