The global impact of antibiotic-resistant bacteria

The emergence of antibiotic-resistant bacteria after the introduction of antibiotics 50 years ago has prompted the proliferation of new antimicrobials to challenge the resistant bacterial strains. Today, the battle between antimicrobials and bacteria has not yet been won. Globally, antibiotic-resistant bacteria continue to have a detrimental effect in the causation of serious bacterial infections. Although the carriage of antibiotic-resistance determinants among clinical isolates has been studied extensively and it has been established that the widespread use of antimicrobials in clinical practice encourages the selection of resistant strains, the source of these resistance genes has been overlooked. The use of antibiotics has not been restricted to the clinical environment, neither has the impact of antibiotics been confined to clinical isolates, and there are other areas where resistance genes may be selected and linger before entering clinically-important bacteria. Antibiotics have been employed widely in farming practice where such a reservoir of antibiotic-resistance genes has become established. Similarly, and perhaps more importantly, we now know that the commensal human bacteria can act as reservoirs of many resistance determinants. However, up until now, there has been very little recognition and discussion of these considerable reservoirs of resistance genes.