Protecting the Health of American Pigs Using a One Health Approach

Posted by Tracy Nicholson, Research Microbiologist, Agricultural Research Service, National Animal Disease Center in Animal Health and Safety Research and Science

Jul 29, 2021

The ARS remains committed to conducting research for our comprehensive understanding of antimicrobial resistance in pork pathogens.

This week is Global Antibiotic Awareness Week and the USDA Agricultural Research Service (ARS) remains committed to using a ‘One Health‘ approach to conduct research that will identify solutions to help extend the usefulness of ‘a very precious resource: antibiotics. For example, research on ARS includes understanding the impact of current production practices on antimicrobial resistance and understanding whether certain animal pathogens may constitute a public health problem. Methicillin-resistant Staphylococcus aureus (MRSA) is a type of bacteria that poses a public health concern due to its resistance to certain antibiotics, which can make it difficult to treat. MRSA has been found in cattle – mainly in pigs. A particular strain of MRSA, called ST5, has raised additional public health concerns as it is a major cause of human infections worldwide.

To address these public health concerns, the ARS conducted research to determine whether production practices such as the use of zinc in the diet as an antidiarrhoeal agent contribute to the emergence and spread of MRSA in patients. American pig populations, and whether ST5 bacterial isolates from pigs and humans are genetically related.

Data from the ARS demonstrated that the application of zinc in feed does not play a role in the prevalence of ST5 MRSA associated with cattle in the American pig population. More importantly, the ARS has found that ST5 isolates from agricultural sources are genetically distinct and separate from clinical isolates of ST5 MRSA obtained from human clinical settings. Specifically, isolates from agricultural sources were found to be extremely similar to each other on farms and lacked genes typically carried by human isolates. Collectively, the data from the ARS indicate that isolates of MRSA associated with livestock and clinical isolates of MRSA ST5 are genetically distinct and that there is currently no transmission and / or genetic exchange between them over the basis of the results of this study.

ARS researchers continue to use these results to better determine the distribution and impact of MRSA ST5 associated with livestock outside of the livestock environment. As we celebrate Global Antibiotic Awareness Week, we remain committed to a “One Health” approach to prevent, and not just respond to, complex public and animal health issues. The information obtained from these studies is important to our overall understanding of animal pathogens and any potential risk to public health.

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