Researchers from the Johns Hopkins Bloomberg School of Public Health have for the first time found an association between living in proximity to high-density livestock production and community-acquired infections with methicillin-resistant Staphylococcus aureus, commonly known as MRSA.
Their analysis concluded that about 11 percent of community-acquired MRSA and soft tissue infections in the study population could be attributed to crop fields fertilized with swine manure.
The study is the first to examine the association between high-density livestock operations, manure-applied crop fields and MRSA infections in the community.
The results were published online in JAMA Internal Medicine.
According to the U.S. Food and Drug Administration, nearly 80 percent of antibiotics in the United States are sold for use in livestock feeds. The manure produced by these livestock and applied to crop fields contains antibiotic-resistant bacteria, resistance genes and about 75 percent of the antibiotics consumed by the animals.
For the study, researchers identified patients with MRSA infections, and skin and soft tissue infections reported in electronic medical records provided by Geisinger Health System.
The two case groups were compared with patients who never had a MRSA infection. Patients received an exposure score based on their distance from the production, the number of animals at livestock operations, the amount of manure spread on crop fields, and the size of the field.
The researchers noted that between 2005 and 2010 there were about 3,000 patients with MRSA and 50,000 with skin and soft tissue infections who were diagnosed and treated in the Geisinger Health System.
The cases came from more than 446,000 Pennsylvania residents between 2005 and 2010. The study identified 1,539 cases of community-associated MRSA and 1,335 cases of health-care-associated MRSA.
The researchers found a significant association between community-associated MRSA and application of swine manure to crop fields. A similar but weaker association was found between swine operations and community-associated MRSA.
No association was found between dairy farms and MRSA infections.
Source: American Association for the Advancement of Science.