Volume 196 - Issue 5
Does antibiotic use in farmed animals pose a risk to human health? – Yes
Author: Peter J Collignon
Med J Aust 2012; 196 (5): 302. || doi: 10.5694/mja12.10329
Published online: 19 March 2012
Published online: 19 March 2012
Infectious diseases expert Peter Collignon supports tight control over food-production practices. Worldwide, increases in deaths and morbidity in humans are associated with rapid increases in rates of antibiotic resistance in bacteria. This problem is escalating more quickly in gram-negative bacteria such as ...
Infectious diseases expert Peter Collignon supports tight control over food-production practices
Worldwide, increases in deaths and morbidity in humans are associated with rapid increases in rates of antibiotic resistance in bacteria. This problem is escalating more quickly in gram-negative bacteria such as Escherichia coli. On occasion, no antibiotics work. As no new antibiotic classes are in the development pipeline for gram-negative bacteria, we need to preserve the antibiotics we have for as long as possible.1
Most of our resistance problems result from overuse of antibiotics in people, where resistant bacteria spread from person to person via suboptimal infection-control practices. In developing countries, poor water supplies facilitate spread of resistant bacteria from person to person and between sectors (eg, from animals to people and vice versa).
But the agricultural industry is also a major contributor to antibiotic resistance problems in humans. In developed countries, Campylobacter and Salmonella (including antibiotic-resistant strains) are almost exclusively transmitted to people from food animals and cause deaths. This was established decades ago for Salmonella.2 In the case of bacteria that cause more common infections, such as E. coli, Staphylococcus aureus, Enterococcus species and Clostridium difficile, a proportion is also transmitted to people from food animals.
Antibiotic resistance levels are related to the volumes of antibiotics used. Greater volumes are used in food animals than in people — such animals often ingest antibiotics continuously for the majority of their lives, mostly for growth promotion and infection prophylaxis. The benefits of this, if any, are marginal. Industry argues that without this large-scale use, disease epidemics will frequently wipe out whole herds, food production will decline precipitately and foods will become prohibitively expensive. There have never been well controlled studies to back up these beliefs and the available evidence suggests otherwise. Denmark, the world’s largest pork exporter, has tighter controls on antibiotic use and lower usage than other countries. Australia is a big beef exporter, but antibiotics are not used routinely in our cattle, in contrast to countries where feedlot cattle are given continuous in-feed antibiotics.
E. coli is the commonest bacterial pathogen that infects humans; it causes common infections such as those in the urinary tract, but also bloodstream infections in thousands of people in Australia every year and millions worldwide. It is not readily transmissible from person to person, but is acquired by all of us every day from foods.3 In the United States, most antibiotic-resistant E. coli carried by people are derived from food animals.3 In the Netherlands, a large proportion of the antibiotic resistance in E. coli that cause serious bloodstream infections is derived from food animals.4
In Australia, fluoroquinolone use is banned in food animals. Despite over 30 years of fluoroquinolone use in humans and high overall antibiotic use per capita in Australia, only low levels of fluoroquinolone-resistant E. coli cause community-acquired infections (about 5%); in nearly all other countries, much higher fluoroquinolone resistance rates, often exceeding 50%, have been reported. Unlike other countries, almost no fluoroquinolone-resistant foodborne Salmonella and Campylobacter infections have been acquired in Australia.
Self-regulation in the Australian poultry industry has not allowed third-generation cephalosporin use, unlike in most other countries where meat chickens are injected with third-generation cephalosporins (and are given fluoroquinolones via water). Isolates that are resistant to third-generation cephalosporins are not found in foods derived from poultry here. Third-generation cephalosporin resistance in community-acquired isolates of E. coli in Australia is less than 3%, which is in stark contrast to most other countries.
There is ample evidence showing that resistance in bacteria to antibiotics of critical importance to people, such as third-generation cephalosporins and fluoroquinolones, is related to the use of these drugs in food animals.5
The factors that drive methicillin-resistant S. aureus (MRSA), multiresistant E. coli and C. difficile infections in people (increased use of any antibiotics and poor infection control) are the same as those that drive these bacteria to develop and spread in food animals.
Thus the evidence is overwhelming that antibiotic use in food animals (particularly critically important antibiotics) results in resistance in bacteria such as E. coli in food animals and leads to serious and life-threatening disease in humans.
It is very important that we stop the development of multiresistant bacteria in food animals and the spread of resistant bacteria and their resistance genes. We need better control over antibiotic use in agriculture, and we need to cease using critically important antibiotics in food animals.
Competing interests
No relevant disclosures.
References
- Carlet J, Collignon P, Goldmann D, et al. Society’s failure to protect a precious resource: antibiotics. Lancet 2011; 378: 369-371. 0_CHDFFHDF
- Anderson ES. Drug resistance in Salmonella typhimurium and its implications. Br Med J 1968; 3: 333-339. 0_CACFHEIB
- Collignon P. Resistant Escherichia coli — we are what we eat. Clin Infect Dis 2009; 49: 202-204. 0_i1115607
- Overdevest I, Willemsen I, Rijnsburger M, et al. Extended-spectrum β-lactamase genes of Escherichia coli in chicken meat and humans, the Netherlands. Emerg Infect Dis 2011; 17: 1216-1222. 0_i1115609
- Collignon P, Powers JH, Chiller TM, et al. World Health Organization ranking of antimicrobials according to their importance in human medicine: a critical step for developing risk management strategies for the use of antimicrobials in food production animals. Clin Infect Dis 2009; 49: 132-141. 0_i1115613
Provenance: Commissioned; not externally peer reviewed.