Anti-Fungal Compounds

1. Anti-Fungal Compounds • Eukaryotic pathogens • Similar cell structure and function • Many fungi are opportunistic • Fungal infections on the rise • Most have detoxification systems

2. Fungal infections (mycoses) may be: • Cutaneous • Dermatophytic • Subcutaneous • Systemic

3. Antifungal Disruption of Cell Membrane • many target membrane sterols (ergosterol) • Polyenes • Produced by Streptomyces • Toxicity is a serious issue • Amphotericin B • Used for systemic mycoses • Nystatin • Effective topical treatment for cutaneous and subcutaneous mycoses

4. Azoles • Synthetic drugs • Fluconazole & Ketoconazole • Used to treat systemic mycoses, dermatophytic infections, cutaneous mycoses

5. Anti-fungal Inhibition of Cell Wall Synthesis • Inhibition of β-glucan results in incomplete cell wall • Echinocandins • Caspofungin • used against many opportunistic mycoses • Candida, Aspergillus and Pneumocystis

6. Anti-fungal Inhibition of Nucleic Acids • Work on specific enzymes not in mammalian cells • Fluorocytocine • Synthetic drug • Cytosine analog interferes with RNA synthesis • Serious toxicity issues • Used to treat systemic yeast infections

7. Other Anti-fungals • Griseofulvin • Given orally; reaches target site through sweat • Inhibits cell division • Tolnaftate • Used for athlete's foot; action unknown

8. Anti-protozoan Inhibition of Nucleic Acids • Nitroimidazoles • Metronidazole • Effective against Trichomonas and Girardia • Effective against anaerobic bacteria • Activated by anaerobic metabolism • Alters DNA • Side effect – black, hairy tongue • Causes birth defects; passed in breast milk

9. Anti-protozoan Inhibition of Necessary Metabolites • Nifurtimox • Effective against Trypanosoma • Interferes with electron transport • Mild gastrointestinal upset

10. Quinine and Quinolines Isolated from a Peruvian tree; replaced with synthetic versions Exact mechanism of action unknown- inhibits protozoan metabolism Chloroquine & mefloquine Malaria treatment Other Anti-protozoan Drugs

11. Niclosamide Prevents ATP generation Tapeworms Praziquantel Causes tetanic contractions Flukes Ivermectin Paralyzes worm Intestinal roundworms and tissue nematodes Anti-helminthic Drugs

12. Anti-viral Drugs • Available antiviral drugs effective specific type of virus • None eliminate latent viruses • Attachment • Un-coating • Nucleic acid synthesis • Protein synthesis • Maturation • Release

13. Anti-viral Inhibition of Nucleic Acids • Nucleoside/nucleotide analogs • Results in an increased mutation rate • Azidothymidine (AZT) • HIV • Ribavirin • Flu, respiratory syncytial virus, hepatitis • Acyclovir • Reduces frequency and severity of herpes outbreaks • Herpes viruses

14. Anti-viral Inhibition of Viral Proteins • Indinavir • Protease inhibitor- inhibit viral assembly/release • HIV • Amantadine • Inhibit viral un-coating • Flu • Zanamivar • Neuraminidase inhibitor- inhibit viral attachment • Flu

15. Mutations lead to resistance Resistance is transferred between cells Resistance genes are often on plasmids or transposons Multi-drug-resistant pathogens Cross resistance Anti-microbial Resistance

16. Mechanisms of antibiotic resistance 1. Drug inactivating enzymes 2. Decreased uptake of the drug 3. Alteration of target molecule • Increased elimination of the drug • Protecting the target

17. Misuse selects for resistant mutants Using outdated, weakened antibiotics Using antibiotics for inappropriate conditions Use of antibiotics in animal feed Failure to complete the prescribed regimen

19. Slowing emergence and spread of resistance • Responsibilities of healthcare workers • Increase efforts to prescribe antibiotics for specific organisms • Educate patients on proper use of antibiotics • Synergism • Responsibilities of patients • Follow instructions carefully • Complete prescribed course of treatment