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TORTORA • FUNKE
• CASE
Microbiology
AN INTRODUCTION
EIGHTH EDITION
B.E Pruitt & Jane J. Stein
Chapter 20, part B
Antimicrobial Drugs
Antifungal Drugs
Inhibition of Ergosterol Synthesis
• Polyenes
• Amphotericin B
• Azoles
• Miconazole
• Triazoles
• Allylamines
Figure 20.15
Antifungal Drugs
Inhibition of Cell Wall Synthesis
• Echinocandins
• Inhibit synthesis of -glucan
• Cancidas is used against Candida and
Pneumocystis
Antifungal Drugs
Inhibition of Nucleic Acids
• Flucytocine
• Cytosine analog interferes with RNA synthesis
• Pentamidine isethionate
• Anti-Pneumocystis; may bind DNA
Antifungal Drugs
Inhibition of Microtubules (Mitosis)
• Griseofulvin
• Used for superficial mycoses
• Tolnaftate
• Used for athlete's foot; action unknown
Antiviral Drugs
Nucleoside and Nucleotide Analogs
Figure 20.16a
Acyclovir
Antiviral Drugs
Nucleoside and Nucleotide Analogs
Figure 20.16b, c
Antiviral Drugs
Enzyme Inhibitors
• Protease inhibitors
• Indinavir
• HIV
• Inhibit attachment
• Zanamivir
• Relenza
• Inhibit uncoating
• Amantadine
• Oseltamivir
• Tamiflu
• Interferons prevent
spread of viruses to
new cells
• Viral hepatitis
Antiprotozoan Drugs
• Chloroquine
• Inhibits DNA synthesis
• Malaria - may require Malarone
• Diiodohydroxyquin
• Unknown
• Amoeba
• Metronidazole
• Damages DNA
• Entamoeba, Trichomonas
Antihelminthic 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
Evaluation of Antimicrobials-Disk-Diffusion Test
Figure 20.17
MIC and MBC
Action on growth after transfer to new media
• MIC
Minimal inhibitory concentration
• MBC
Minimal bactericidal concentration
Broth Dilution Test
Figure 20.19
Figure 20.20
Antibiotic Resistance
• 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• Using outdated, weakened antibiotics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
• Bacterial resistance Paenibacillus
Effects of Combinations of Drugs
• 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
The Future of Chemotherapeutic Agents
• 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
Zmapp
ZMapp is an experimental drug that combines three
“humanized” monoclonal antibodies
The new study explains why ZMapp could have been effective. Using an imaging
technique called electron microscopy, researchers found that two of the ZMapp antibodies
bind near the base of virus, appearing to prevent the virus from entering cells. A third
antibody binds near the top of the virus, possibly acting as a beacon to call the body’s
immune system to the site of infection.
Phage Therapy
Phage Therapy
Phage Therapy