Microbiology B.E Pruitt & Jane J. Stein AN INTRODUCTION EIGHTH EDITION TORTORA FUNKE CASE Chapter 20, part B Antimicrobial Drugs

Polyenes Amphotericin B Azoles Miconazole Triazoles Allylamines Antifungal Drugs Inhibition of Ergosterol Synthesis Figure 20.15

Echinocandins Inhibit synthesis of  -glucan Cancidas is used against Candida and Pneumocystis Antifungal Drugs Inhibition of Cell Wall Synthesis

Flucytocine Cytosine analog interferes with RNA synthesis Pentamidine isethionate Anti-Pneumocystis; may bind DNA Antifungal Drugs Inhibition of Nucleic Acids

Griseofulvin Used for superficial mycoses Tolnaftate Used for athlete's foot; action unknown Antifungal Drugs Inhibition of Microtubules (Mitosis)

Antiviral Drugs Nucleoside and Nucleotide Analogs Figure 20.16a

Acyclovir

Antiviral Drugs Nucleoside and Nucleotide Analogs Figure 20.16b, c

Protease inhibitors Indinavir HIV Inhibit attachment Zanamivir Relenza Inhibit uncoating Amantadine Oseltamivir Tamiflu Interferons prevent spread of viruses to new cells Viral hepatitis Antiviral Drugs Enzyme Inhibitors

Chloroquine Inhibits DNA synthesis Malaria - may require Malarone Diiodohydroxyquin Unknown Amoeba Metronidazole Damages DNA Entamoeba, Trichomonas Antiprotozoan Drugs

Niclosamide Prevents ATP generation Tapeworms Praziquantel Alters membrane permeability Flatworms Pyantel pamoate Neuromuscular block Intestinal roundworms Antihelminthic Drugs

Mebendazole Inhibits nutrient absorption Intestinal roundworms Ivermectin Paralyzes worm Intestinal roundworms Antihelminthic Drugs

Evaluation of Antimicrobials-Disk-Diffusion Test Figure 20.17

Action on growth after transfer to new media MIC Minimal inhibitory concentration MBC Minimal bactericidal concentration MIC and MBC

Broth Dilution Test Figure 20.19

Figure 20.20

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. Antibiotic Resistance

Misuse of antibiotics selects for resistance mutants. Misuse includes: Using outdated, weakened antibiotics Using antibiotics for the common cold and other inappropriate conditions Use of antibiotics in animal feed Failure to complete the prescribed regimen Using someone else's leftover prescription Antibiotic Resistance

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. Effects of Combinations of Drugs

Figure 20.22

Antimicrobial peptides Broad spectrum antibiotics from plants and animals Squalamine (sharks) Protegrin (pigs) Magainin (frogs) Antisense agents Complementary DNA or peptide nucleic acids that binds to a pathogen's virulence gene(s) and prevents transcription The Future of Chemotherapeutic Agents