2.2 Spread of antimicrobial resistance in bacteria
Some species of bacteria have
Activity 6 Plasmids
From your study of the Introducing antimicrobial resistance module what can you remember about the role plasmids play in the spread of antimicrobial resistance? Make notes in the text box provided.
Discussion
- Plasmids are mobile genetic elements easily transmitted between bacteria, including between different strains and species.
- Plasmids can readily acquire multiple resistance genes which can quickly lead to MDR transmissible strains, making them important in the spread of resistance.
- Plasmid acquisition, unlike the accrual of multiple mutations, confers immediate high-level resistance to one or often, multiple, antimicrobials and threatens the ability to treat severe infections.
- Antimicrobial use provides selection pressure on bacteria to retain their plasmids.
Resistance can be shuffled between chromosomal and plasmid DNA on small mobile genetic elements, facilitating recombination and promoting the rapid evolution of new resistant forms. Resistance genes can remain on the plasmid or be integrated into the chromosome; chromosomal mutations can also find their way onto plasmids. This, coupled with
The current greatest AMR threat to modern medicine is from plasmids with a carbapenemase gene plus resistance to multiple antimicrobials. In any of the three organisms in the WHO ‘critical’ R&D category, carbapenem-resistance leads to infections that can only be treated with combinations of drugs or toxic ‘third line’ antimicrobials, for example, colistin. These plasmids can lead to untreatable infections, hence the high priority placed on these pathogen-AMR combinations.
2 Antimicrobial resistance