BIOL 442- Antimicrobial Drugs

Chemotherapy

chemicals are used to treat microbial infections

Antimicrobial drugs

antibacterials, antifungals, antiheltminths, antivirals

Spectrum of microbial activity of a drug- Narrow

where one specific type of microbe is targeted and killed by an antimicrobial drug; magic bullet

Spectrum of microbial activity of a drug- Broad

where most microbes are targeted and killed by an antimicrobial drug

Mechanism of antibacterials- Cell wall synthesis

inhibition of cell wall synthesis

Inhibition of Cell wall synthesis- examples

Beta-lactam drugs; Natural penicillins (narrow spectrum and bactericidal), Penicillin G and V; Semisynthetic penicillins (mostly broad spectrum and bactericidal), amoxicillin

Inhibition of Cell wall synthesis- Beta-lactam drugs binding

they bind to penicillin binding proteins which are enzymes used by bacteria to synthesize their cell wall; this action stops enzymes from making cell wall

Mechanism of antibacterials- Protein synthesis

inhibition of protein synthesis

Inhibition of Protein Synthesis- examples

streptomycin (bactericidal and broad spectrum), last chance drug; tetracycline (bacteriostatic and broad spectrum)

Inhibition of Protein Synthesis- Binding site

streptomycin and tetracycline bind to 70s ribosomes

Mechanism of antibacterials- Plasma membrane

injury to the plasma membrane

Injury to Plasma Membrane- example

Polymyxin B (bacteriocidal and narrow spectrum), topicals

Injury to Plasma Membrane- Interference

drug interferes with fatty acid synthesis used to help synthesize the plasma membrane

Mechanism of antibacterials- Nucleic acid synthesis

inhibition of nucleic acid synthesis

Inhibition of nucleic acid synthesis- Rifampin

Rifampin (bacteriocidal and narrow spectrum) which inhibits the synthesis of mRNA by interfering with RNA polymerase; tuberculosis

inhibition of nucleic acid synthesis- Ciprofloxacin

Ciprofloxacin (bacteriocidal and broad spectrum), inhibits supercoiling of bacterial DNA by interfering DNA gyrase; UTI

Mechanism of antibacterials- Metabolism

inhibition of metabolism

Inhibition of metabolism- Sulfa Drug

Sulfa drugs (bacteriostatic and broad spectrum) combined with trimethoprim

Ways of Antibiotic resistance

inactivation of the drug, alter the drugs target site, stop the uptake of the drug, ejection of drug (efflux pumps or multidrug resistant pumps)

Kirby-Bauer disk diffusion test

test the effectiveness of an antibiotic, method for antibiotic disk diffusion test

Kirby-Bauer disk diffusion test- Zone of inhibition

zones of inhibition form around antibiotic disk if drug is effective; diameter of zone is meassured and the smaller the zone the more resistance, the bigger the zone the more sensitive microbe is to the drug

Antifungal Drugs

Miconazole, Amphotericin B; drugs interfere with plasma membrane of fungal cell by targeting ergosterol, don’t target human cells as cholesterol is in plasma membrane

Antiprotozoan drugs

Flagyl; interferes with anaerobic metabolism in protozoan

Antiparasitic drugs

Ivermectin; interferes with glucose metabolism in the parasite