A study conducted by scientists from the University of Maryland, USA has revealed that organic poultry farms have significantly lower levels of drug-resistant bacteria than conventional units.

The study, published in Environmental Health Perspectives, which was led by Dr. Amy R. Sapkota of the University of Maryland School of Public Health, is the first to demonstrate that lower levels of drug-resistant bacteria exist on newly organic farms in the United States. Dr Sapkota’s findings suggest that removing antibiotics from large-scale U.S. poultry farms can result in immediate and significant reductions in antibiotic resistance for some bacteria.

Antibiotic use in conventional animal food production in the United States has spawned public health concerns after it has been shown to contribute to the development of antibiotic-resistant bacteria that can potentially spread to humans.

However, the newly published data shows that poultry farms which have transitioned from conventional to organic practices and ceased using antibiotics have significantly lower levels of drug-resistant enterococci bacteria.

Dr Sapkota commented on her findings, "We initially hypothesized that we would see some differences in on-farm levels of antibiotic-resistant enterococci when poultry farms transitioned to organic practices. But we were surprised to see that the differences were so significant across several different classes of antibiotics even in the very first flock that was produced after the transition to organic standards. It is very encouraging."

The team studied ten conventional and ten newly organic large-scale poultry farms in the mid-Atlantic region. They tested for the presence of enterococci bacteria in poultry litter, feed, and water, and tested its resistance to 17 common antimicrobials. The newly organic farms were found to have a significantly lower prevalence of resistant bacteria.

67 per cent of Enterococcus faecalis recovered from conventional poultry farms were resistant to erythromycin, while 18 per cent of Enterococcus faecalis from newly organic poultry farms were resistant to this antibiotic. Furthermore, the test found encouraging effects of reducing the prevalence of multi-drug resistant bacteria, which are of particular concern due to the difficulty of treating them if when contacted by an animal or human. 42 per cent of Enterococcus faecalis from conventional farms were multi-drug resistant, compared to only 10% from newly organic farms, and 84 per cent of Enterococcus faecium from conventional farms were multi-drug resistant compared to 17 per cent of those from newly organic farms.

Dr Sapkota said she expects that reductions in drug-resistant bacteria on US farms that "go organic" are likely to be more dramatic over time as reservoirs of resistant bacteria in the farm environment diminish. She is now pushing to carry out longer-term studies.