People could be exposed to antibiotic-resistant bacteria from breathing the air from concentrated swine feeding facilities, according to researchers at the Johns Hopkins Bloomberg School of Public Health.They detected bacteria resistant to at least two antibiotics in air samples collected from inside a large-scale pork operation in the Mid-Atlantic region of the United States. The key is that they only sampled one swine unit.

Researchers contend the study shows the various pathways in which humans can be exposed to antibiotic-resistant bacteria, such as consumption of retail pork products and contact with or ingestion of soil, surface water and groundwater near production operations. The article is published in the online edition of Environmental Health Perspectives.

“Eating retail pork products is not the only pathway of exposure for the transfer of antibiotic-resistant bacteria from swine to humans. Environmental pathways may be equally important,” says Amy Chapin, the study’s lead author and a doctoral candidate at the Bloomberg School of Public Health’s Department of Environmental Health Sciences.

Chapin explains that the use of antibiotics in large-scale animal production has a significant impact on the emergence of antibiotic-resistant bacteria that could impact human health. Using antibiotics in animals can decrease the effectiveness of the same antibiotics used to combat human infections, she contends.

The airborne bacteria samples that were found to be multidrug-resistant were: Enterococcus, coagulase negative staphylococci and viridans group streptococci. These bacteria are associated with a variety of human infections. The study found that 98 percent of the isolated samples were resistant to at least two of the following antibiotics: erythromycin, clindamycin, virginiamycin and tetracycline.

All of these drugs (or their human drug counterparts) are important antibiotics in the treatment of human infections. In contrast, none of the bacterial samples were resistant to vancomycin – an antibiotic that has never been approved for use in pork production in the United States.

The researchers believe employees at concentrated animal feeding operations are at greatest risk for airborne exposure to antibiotic-resistant bacteria. However, the same employees also may become reservoirs of drug-resistant bacteria that can be spread to family and the broader community.

The study also raises questions about the spread of drug-resistant bacteria to areas beyond the immediate site through ventilation fans and by the application of manure from feeding operations to off-site fields.

For more information about the study, contact the Center for a Livable Future: Donna Mennitto at 410-502-7578 or dmennitt@jhsph.edu.

Public Affairs media contacts for the Johns Hopkins Bloomberg School of Public Health: Tim Parsons or Kenna Lowe at 410-955-6878 or paffairs@jhsph.edu

Johns Hopkins Bloomberg School of Public Health