Human World

Robert Lawrence on antibiotic resistance and livestock

Robert Lawrence: By using antibiotics as growth promoters rather than to treat sick animals, the industry is placing at risk the health of the public.

Robert Lawrence is a professor at the Johns Hopkins Bloomberg School of Public Health. Lawrence said that bacterial infections in Americans are becoming harder to treat. That’s because of the widespread and non-therapeutic use of antibiotics in farm animals. The drugs are used to fatten animals, and speed them to market.

Robert Lawrence: And we have now learned that the widespread use of antibiotics as growth promoters in the industrial food animal industry has been responsible for selecting out resistance genes in a wide range of bacteria against antibiotics that are important not only to animal health, but also to human health.

Lawrence helped guide a 2.5 year independent study released in 2008 that looked at factory farming, where animals are raised in close confinement. The study concluded that the use of antibiotics as growth promoters should stop. Other studies at pig and poultry farms revealed resistance to common antibiotics in four kinds of bacteria, including staph and E. coli.

Robert Lawrence: The reason that we’re highly confident that the emergence of these resistant organisms is related to the use of low-dose antibiotics in animal feed or water as growth promoters is that none of the bacteria were resistant to vancomycin, an antibiotic that has never been approved by the FDA for use in animal treatment.

Lawrence also thinks it’s important to investigate the possibility that ‘community-acquired’ cases of the bacterial infection known as ‘MRSA’ – methicillin-resistant Staphylococcus aureus – could be related to the swine industry.

Robert Lawrence: We do know that MRSA – methicillin-resistant Staphylococcus aureus – is now killing between 17 thousand and 18 thousand Americans a year. Much of that has been in hospital-acquired infections, so-called nosocomial spread. But increasingly in recent years newly diagnosed cases of MRSA are so-called community acquired cases. And we just desperately need to know in order to protect the health of the American people whether or not those community-acquired cases are linked in some way to the swine industry.

Contaminated water from farms could also be tainting crops grown for human consumption, warns Lawrence.

Robert Lawrence: We know that we had a terrible problem with e.coli contaminated spinach a year and a half ago. There have been other episodes where irrigation water used on large produce farms in the central valley of California have been contaminated by the outflow of confined animal feeding operations. Regularly, the large amounts of waste from poultry and swine in particular is applied on fields that are growing usually corn and soybeans to produce the animal feed, but sometimes growing vegetables for human consumption, and contamination can occur that way as well.

Our thanks to:
Robert Lawrence served for three years as an epidemic intelligence service officer at the Centers for Disease Control and Prevention, U.S. Public Health Service. Dr. Lawrence is the Center for a Livable Future Professor and Professor of Environmental Health Sciences, Health Policy, and International Health at the Johns Hopkins Bloomberg School of Public Health and Professor of Medicine at the Johns Hopkins School of Medicine.

November 23, 2009
Human World

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