Antibiotic resistance Flashcards
what are the most prescribed class of antibiotics in the world?
β-lactams
When was resistance to penicillin reported?
Resistance to penicillin G was reported three years before the drug was approved for prescription use
Macrolides structure
They consist of a macrocyclic lactone ring (typically >12 carbon atoms), substituted with deoxy sugars
How are macrolides similar to penicillin?
They are derived from natural products. Macrolides are often the ‘first choice’ antibiotic for patients who can’t tolerate penicillin
What type of activity does macrolides have?
Macrolides exhibit broad spectrum activity against many gram-positive bacteria.
Erythromycin
The most well-known macrolide, initially isolated in 1952. However, many semi-synthetic molecules have been developed that differ through their substitution pattern of the lactone ring system.
How do macrolides work?
Macrolides work in a different way to the β-lactams in that they inhibit the synthesis of bacterial proteins. It is thought that macrolides bind to a ribosomal unit involved with adding amino acids to tRNA.
bacteriostatic v bactericidal.
Bacteriostatic = restricts growth of bacteria
Bactericidal = causes bacterial cell death
macrolides are bacteriostatic, whereas β-lactams are bactericidal.
Daptomycin
This is one of the most recent antibiotics to be developed. It is a lipopeptide antibiotic used in the treatment of gram-positive bacteria. Crucially, cases of daptomycin resistance are incredibly rare and it is often used in treating multi-drug resistant infections
Daptomycin MOA
its precise mechanism of action is not known, it is generally thought to disrupt multiple cell membrane functions, leading to cell death.
Dosing regimens
They are often driven by PK parameters only.
how antibiotic resistance plays into Dosing regimens?
PD is extremely important and can be used to design dosing regimens that counteract or prevent resistance.
Pharmacokinetics (PK)
The study of how an organism affects a drug
Pharmacodynamics (PD)
The study of how a drug affects an organism
Minimum inhibitory concentration (MIC)
The lowest concentration of an antibiotic that completely inhibits the growth of a microorganism in vitro. Whilst the MIC is a good indicator of the potency of an antibiotic, it indicates nothing about the time course of antimicrobial activity.
