Chapter 10: Antimicrobial Therapy

why are antibiotics becoming ineffective?

overprescription, over the counter accessibility, agriculture overuse

selective toxicity

necessary trait for antimicrobial drugs so that they don't cause damage to the human body

bacteria that produce antimicrobials

Streptomyces and Bacillus

molds that produce antimicrobials

Penicillium, Cephalosporium

Kirby-Bauer Technique

putting disks with antimicrobials onto a petri dish covered in bacteria from a liquid culture to measure how effective they are at preventing growth, incubating at 37 degrees C

zone of inhibition

in the kirby technique, area around an antimicrobial disk with no growth. The wider the better.

epsilometer test

test that uses different amounts of an antibiotic on a petri dish to determine the lowest concentration needed to be effective

tube dilution test

test that uses different concentrations of an antibiotic in a liquid culture to determine the minimum needed to prevent growth

therapeutic index

ratio of toxic dose to minimum effective (therapeutic) dose, the larger the safer

protein synthesis inhibitors

antibiotics that act on ribosomes to stop protein synthesis. can target 50s, 30s, and both

folic acid synthesis targeters

antibiotics that interfere with pathways and metabolism of the cell

cell wall inhibitors

antibiotics that block synthesis and repair of the cell wall

cytoplasmic membrane targeters

antibiotics that cause loss of selective permeability

DNA/RNA targeters

antibiotics that inhibit replication, transcription, unwinding, or RNA polymerase

Broad-spectrum drugs

drugs that are effective against more than one group of bacteria

Narrow-spectrum drugs

drugs that target a specific group of bacteria.

Biofilm treatment targets

interrupting quorum sensing, DNAse aids penetration through extracellular debris, adding devices to antibiotics prior to implantation

why are antifungals hard to develop?

Only a few agents are developed

Why are antiprotozoans hard to develop?

Several species have different stages of life, so no single drug is universally effective

why are antihelminths hard to develop?

Similar physiology to humans, blocking reproduction does not affect adults, need to immobilize, disintegrate, or inhibit metabolism of all life cycle stages

why are antivirals hard to develop?

they're simply not giving. they're just a bunch of nucleic acid so there's not much to target

actions of antiviral drugs

inhibits entry, nucleic acid synthesis, and assembly/release

what is zidovudine (AZT) and what does it do?

first anti retroviral drug to be effective against HIV, inhibits nucleic acid synthesis

what is tamiflu and what does it do?

drug that targets the flu, inhibits viral assembly/release

drug resistance

organisms adapting to stronger levels of drugs due to fast reproduction, can be intrinsic as well as acquired

chromosomal resistance

spontaneous mutations in critical chromosomal genes that provide drug resistance

resistance via horizontal gene transfer

acquired drug resistance from the sharing of genes via pilli

mechanisms of drug resistance

induce enzyme production, mutates receptor to stop entry, efflux pump kicks antibiotic out, changes binding site, alters pathways

new approaches to antimicrobial therapies

RNA (translation) interference, mimicking defense peptides, crispr, noncultivable bacteria, bacteriophages

difference between allergy and regular illness?

allergen is targeted by lymphatic system but does not usually cause harm to the body