LINDELL BEACH, B.C. — A new study has found that poultry farms that switch from conventional to organic practices and stop using antibiotics have significantly lower levels of the drug-resistant enterococci bacteria.
The study, recently published in Environmental Health Perspectives,is the first to suggest that removing antibiotic use from large-scale poultry farms in the United States can result in immediate and significant reduction in antibiotic resistance for some bacteria.
“We initially thought we would see some differences in on-farm levels of antibiotic-resistant enterococci (micro-organisms) when poultry farms transition to organic practices,” said Amy Sapkota, an assistant professor at the University of Maryland’s School of Public Health.
Read Also
Growth plates are instrumental in shaping a horse’s life
Young horse training plans and workloads must match their skeletal development. Failing to plan around growth plates can create lifelong physical problems.
“But we were surprised to see that the differences were so significant across several different classes of antibiotics, even in the very first flock of birds that was produced after the transition to organic standards. It is very encouraging.”
Sapkota and her team, which included scientists from Pennsylvania State University and Johns Hopkins Bloomberg School of Health, investigated the impact of removing antibiotics by studying 10 conventional and 10 newly organic large-scale poultry houses on farms in the mid-Atlantic region.
They tested for the presence of the bacteria in poultry litter, feed and water and tested its resistance to 17 common antimicrobials.
While all the farms tested positive for enterococci, as expected, the researchers were surprised at the drop in antibiotic resistance.
For instance, 67 percent of the bacteria recovered from conventional farms were resistant to the antibiotic erythromycin, compared to only 18 percent of the bacteria from the newly organic poultry farms.
Researchers also saw dramatic changes in the levels of multi-drug resistant bacteria, which are organisms resistant to three or more antimicrobial classes.
Forty-two percent of E. faecalis from conventional farms was multi-drug resistant compared to only 10 percent from new organic farms.
For E. faecium bacteria, 84 percent were multi-drug resistant on conventional farms compared to 17 per-c e nt of those from new organic farms.
“I think the farmers were encouraged as well, particularly the organic folks we were working with,” said Sapkota.
“It costs a lot to produce organic broilers compared to conventional poultry, so it’s nice to see that the expense that goes into the production is making a difference when we look at resistance.”
Sapkota said she studied the enterococci bacteria because they are found in all poultry, both conventional and organic, and cause infections in hospital patients.
Enterococci is a good model for studying the impact of changes in antibiotic use because it has a reputation for being able to exchange resistance genes with other bacteria.
She said the genes that encode for the effective resistance can be transferred several different ways between bacterial species and also between bacterial genes. Enterococci can do this easily.
Sapkota’s study is the first of several and follows European studies of the past decade that found that removing the non-therapeutic use of antibiotics from poultry farms can result in statistically significant reductions in antibiotic-resistant bacteria in animals and food products.
“We plan to continue the study to look and see what happens over time,” she said.
“This is the first year and the first flock tested. We would like to see if the farms that did transition to organic remain organic. We were just looking at enterococci in this study, but we would like to look at other organisms such as salmonella, which is a pathogen that can make even healthy people ill.”
Sapkota doesn’t know if the same results would occur for beef cattle and pigs, but she hypothesized that there might be advantages. However, she stressed that those industries would have to be the subject of their own specific studies.
Doctors and scientists have sounded the alarm in recent years about the use of antibiotics in livestock feed in the belief that they pose a health hazard to humans.
The prevailing argument in the medical community is that antibiotic use in conventional animal food production builds resistance to antibiotics necessary to fight bacterial infections in humans.
Antibiotics are administered to poultry for therapeutic, prophylactic and non-therapeutic uses. Some researchers have estimated that antibiotic use on conventional poultry farms increased 307 percent from 1985 to the late 1990s with the use of non-therapeutic growth promoters accounting for a significant portion of that increase.
It is estimated that resistance to antibiotics at least doubles the cost of treating a bacterial infection and adds $40 and $52 million per year to direct and indirect health care costs in Canada.
U.S. health care costs associated with antibiotic-resistant bacteria exceed $4 billion a year in direct costs, not including lost workdays and lost productivity.
Antibiotics belong to a category of drugs called antimicrobials and include penicillin, tetracycline, amoxicillin and others with the ability to kill bacteria causing infection.
Penicillin and tetracycline are used to treat cattle diseases and are of high importance as human medicine.
