Antimicrobial resistance describes the ability of a micro-organism to resist the action of antimicrobial drugs. This is important as it can make the treatment of infections more difficult and increase hospital costs. Undertaking laboratory testing of organisms causing infections can play a role in deciding the most effective treatment options.
In a few instances some micro-organism are naturally resistant to particular antimicrobial agents, but a more common problem is when micro-organisms that are normally susceptible to the action of particular antimicrobial agents become resistant. The resistance often arises as a result of changes in the micro-organism's genes. In some cases, the genes causing resistance can be transferred between different strains of micro-organism, and when this happens the recipient organisms will also become resistant. Irrespective of how they arise, resistant micro-organisms may spread and it seems likely that the extensive use of antimicrobial agents helps this process along by eliminating competing susceptible micro-organisms.