Antimicrobial Resistance

Antimicrobial Resistance
Introduction

Before antibiotics were used, microorganisms possessed antimicrobial resistance (AMR) mechanisms to combat natural antimicrobials. Antibiotic pressure can select for AMR in bacterial populations e.g. target site (pathogenic), commensal, or environmental.
• Antibiotic pressure inhibits/kills susceptible cells
• AMR cells survive and proliferate and transfer AMR to daughter cells
• New AMR populations may colonise and transfer their resistant genes to other bacteria (same or different genera or species)
• AMR genes or bacteria shed into the environment and/or food chain, or transfer to in-contact individuals.
• If AMR genes exert a fitness cost to the host the bacteria may be out-competed by susceptible isolates in the absence of a selection pressure.
• Genetic adaption by natural selection over time can overcome fitness costs so the AMR strains may thrive and different AMR traits can accumulate over time resulting in multidrug resistance (MDR; resistance ≥ 3 antimicrobial classes). […]