Antibacterial Drug Resistance Flashcards
What are the two types of antibacterial resistance?
Intrinsic: results from inherent features of a particular bacterial population.
Acquired: results from a spontaneous mutation or horizontal acquisition of resistance in a previously antibiotic susceptible bacterial population.
What drives antibiotic resistance?
Antibiotic use, through evolution, selection pressure and survival of the fittest.
What are the mechanisms of resistance?
Altered target site (mutation, modification or target over expression ), decreased uptake (efflux or reduced permeability), inactivation or modification, target bypass.
Give an example of resistance caused by mutation of the target site?
Point mutation in RNA polymerase which mediates Rifampicin resistance.
Give an example of resistance caused by modification of the target site?
Methylation of ribosomal RNA by Cfr methylase on A2503 of 23s rRNA, causes horizontal resistance to Linezolid and chloramphenicol in S.aureus.
Give an example of resistance caused by over expression of the target site?
Vancomycin resistance in S.aureus, many genetic changes, common significant thickening of the cell wall and affinity trapping.
Give an example of resistance caused by decreased uptake due to efflux?
AcrAB/TolC in E.coli for beta-lactams, tetracyclines and fluoroquinones etc.
Give an example of resistance caused by inactivation?
Beta-lactamase inactivate beta-lactams by hydrolysing the cyclic amide bond.
Give an example of resistance caused by modification?
Amino glycosides: can be adenylated, acetylated, or phosphorylated.
Give an example of resistance caused by target bypass?
Acquisition of an alternatives target, methicillin resistance in S.aureus.
What is antibacterial resistance?
The ability of bacteria to survive and grow in the presence of antibiotic concentrations that can be safely achieved in patients at the site of infection.
