Spread of Resistant Bacteria and Resistance Genes from Animals to Humans –
The Public Health Consequences
The paper reviews the lines of evidence which link the use of antimicrobial drugs for food animals with the emergence of antimicrobial drug resistance in bacteria pathogenic to humans, with a particular focus on the public health aspects. Deductions from the epidemiology of food-borne infections, ecological studies, outbreak investigations, typing studies and direct epidemiological observations show that resistant bacteria are transferred from food animals to man. In addition to transfer in the food chain, exchange of mobile genetic elements among commensal and pathogenic bacteria contributes to the emergence of drug resistance. There is growing evidence that this has measurable consequences for human public health.
One consequence is increased transmission supported by unrelated use of anti-microbials in humans. Other consequences are related to reduced efficacy of early empirical treatment, limitations in the choices for treatment after confirmed microbiological diagnosis, and finally a possible co selection of virulence traits. Recent epidemiological studies have measured these consequences in terms of excess mortality associated with resistance, increased duration of illness, and increased risk of invasive illness or hospitalization following infections with resistant Salmonella.
The public health significance of antimicrobial resistance transferred from food producing animals in the food chain has been debated for many years. The issue was raised in 1968 in a description of a rise in Salmonella Typhimurium DT29 infection in calves in Britain during the period 1964–1966 (Anderson, 1968). The increase was observed following the adoption of intensive farming methods and attempts to treat and control the disease with a range of antibiotics proved to be ineffective, but resulted in the acquisition of transferable multiple drug...