Antimicrobials in livestock
Excessive use promotes resistance in human pathogens
Antimicrobials are essential for treating bacterial infections in humans and animals. It is well known that crowding and poor sanitary conditions increase the risk of spread of infectious diseases in all populations. Modern animal production is characterised by such conditions and consequently substantial amounts of antimicrobials are used in agriculture and aquaculture to prevent or treat diseases in food animals.
Any use of antimicrobials, however, can result in bacteria that are resistant to treatment. In the digestive tract, billions of bacteria are exposed to the selective pressure of the drugs. Resistant bacteria have a competetive advantage—that is, they multiply while the sensitive strains are supressed. Resistant bacteria can spread from animals to humans in several ways. The food chain is quantitatively the most important; direct contact and environmental transmission—for example, through swimming in contaminated recreational waters—are also important.
Resistant bacteria in food reach consumers through undercooked food, raw food, or