Gram Research analysis found that pasture-raised chicken farms in the Southeastern United States harbor multidrug-resistant E. coli bacteria that can spread their antibiotic resistance to other germs. Researchers tested 560 bacteria from 11 farms and identified 27 strains resistant to multiple antibiotics. Laboratory tests confirmed these resistance genes can transfer to Salmonella and other bacteria, raising concerns about environmental contamination and potential human health risks through the food supply.
Researchers tested bacteria from pasture-raised chicken farms in the Southeast and found dangerous germs that resist multiple antibiotics. These bacteria, called E. coli, were found in chicken droppings, soil, and on chicken carcasses. What’s concerning is that the bacteria carry genes that allow them to spread antibiotic resistance to other germs, including Salmonella. The study shows that pasture environments may be spreading these resistant bacteria, which could eventually affect human health if people eat contaminated poultry or come into contact with resistant germs.
Key Statistics
A 2026 study of 560 E. coli bacteria from 11 pasture-raised chicken farms in the Southeastern United States identified 27 multidrug-resistant strains, each carrying 2 to 7 different antibiotic resistance genes.
Researchers found that the blaTEM antibiotic resistance gene appeared in 16 of 27 multidrug-resistant E. coli isolated from pasture chicken farms, and laboratory conjugation assays confirmed it could transfer to Salmonella bacteria.
Genetic analysis of resistant bacteria from pasture-raised poultry revealed 19 different sequence types, indicating that antibiotic resistance is emerging independently across multiple bacterial populations rather than spreading from a single source.
Whole-genome sequencing of multidrug-resistant E. coli from pasture chicken farms showed that resistance genes were located on plasmids in some isolates, enabling horizontal gene transfer to other bacterial species including Salmonella enterica.
The Quick Take
- What they studied: Whether pasture-raised chicken farms in the Southeastern United States have antibiotic-resistant bacteria and whether these bacteria can spread their resistance to other germs.
- Who participated: Researchers collected samples from 11 pasture-raised chicken farms with 41 different flocks. They tested 560 E. coli bacteria found in chicken droppings, soil, chicken intestines, and rinses from chicken carcasses.
- Key finding: Scientists found 27 strains of E. coli that resisted multiple antibiotics. These bacteria carried genes that made them resistant to five different classes of antibiotics. Most importantly, lab tests showed these resistance genes could jump from one bacterium to another, including to Salmonella.
- What it means for you: If you eat pasture-raised chicken, there’s a potential risk of exposure to antibiotic-resistant bacteria, though proper cooking kills these germs. This research suggests we need better practices on pasture farms to prevent the spread of resistant bacteria in the environment.
The Research Details
Researchers visited 11 pasture-raised chicken farms and collected samples from four different sources: chicken droppings, soil from the pasture, the inside of chicken intestines, and rinses from chicken carcasses after processing. From these samples, they isolated 560 E. coli bacteria and tested each one to see which antibiotics could kill it.
For the 27 bacteria that resisted multiple antibiotics, the researchers used a technique called whole-genome sequencing, which is like reading the complete instruction manual of the bacteria’s DNA. This allowed them to identify exactly which resistance genes each bacterium carried and where those genes were located in the bacterial DNA.
To confirm that resistance genes could actually spread between bacteria, scientists performed conjugation assays, which are laboratory tests where they put resistant bacteria next to non-resistant bacteria and watched to see if the resistance genes transferred. They tested this with both E. coli and Salmonella bacteria.
This research approach is important because it shows not just that resistant bacteria exist on farms, but that they can actively spread their resistance to other bacteria. Simply finding resistant bacteria isn’t as concerning as finding bacteria that can transfer their resistance genes to other species. This study bridges that gap by proving the genes are actually mobile and transferable.
The study used rigorous scientific methods including whole-genome sequencing and confirmed lab tests. However, the research only looked at 11 farms in one region of the United States, so the findings may not apply to all pasture farms everywhere. The study was published in a peer-reviewed journal, meaning other scientists reviewed it before publication. The sample size of 560 bacteria is substantial for this type of research.
What the Results Show
The researchers identified 27 multidrug-resistant E. coli strains, meaning each one could survive treatment with multiple different antibiotics. These 27 strains came from samples collected across the 11 farms, appearing in chicken droppings, soil, chicken intestines, and processed carcasses.
Each resistant bacterium carried between 2 and 7 different antibiotic resistance genes. These genes protected the bacteria against five major classes of antibiotics: beta-lactams (like penicillin), tetracyclines, folate pathway antagonists, amphenicols, and aminoglycosides. The most common resistance gene found was blaTEM, which was detected in 16 of the 27 resistant bacteria.
The genetic analysis revealed 19 different sequence types, meaning the resistant bacteria were genetically diverse rather than all being identical clones. This diversity suggests that resistance is emerging independently in different bacterial populations on these farms.
Most importantly, conjugation assays confirmed that resistance genes could transfer between bacteria. Specifically, the blaTEM gene located on certain plasmids (small circular pieces of DNA) successfully transferred from resistant E. coli to non-resistant E. coli and to Salmonella bacteria in laboratory conditions.
The study found that antibiotic resistance genes were not randomly scattered throughout the bacterial DNA. Instead, many were located on plasmids, which are small circular DNA molecules that bacteria can easily share with each other. The plasmids identified included types called IncI2 alpha, IncFII, and IncFIB. The presence of resistance genes on plasmids is particularly concerning because plasmids transfer between bacteria much more readily than genes embedded in the main chromosome.
The detection of the same resistance genes in both pre-harvest samples (from live chickens) and post-harvest samples (from processed carcasses) suggests that contamination persists through the processing stage, potentially reaching consumers.
Previous research has documented antibiotic-resistant bacteria in conventional poultry operations, but data specifically on pasture-raised systems has been limited. This study fills that gap by showing that resistance is also a concern in pasture environments. The finding that resistance genes can transfer between different bacterial species aligns with what scientists have observed in other agricultural settings. However, the specific plasmid types and resistance gene combinations found in this study appear to be characteristic of the Southeastern poultry environment.
The study only examined 11 farms in the Southeastern United States, so results may not represent all pasture-raised chicken operations nationwide or in other regions. The research focused specifically on E. coli bacteria, so it doesn’t tell us about resistance in other bacteria that might be present on these farms. While the lab tests proved that resistance genes could transfer in controlled conditions, this doesn’t necessarily mean transfer happens at the same rate in real farm environments. The study was cross-sectional, meaning it captured a snapshot in time rather than following farms over months or years to see how resistance patterns change.
The Bottom Line
Based on this research, pasture-raised chicken farms should implement enhanced biosecurity measures to reduce bacterial contamination of soil and pasture areas. Farmers should consider rotating pasture locations more frequently and avoiding the use of antibiotics in healthy animals. Consumers should continue practicing proper food safety: cook chicken thoroughly to an internal temperature of 165 degrees Fahrenheit, avoid cross-contamination with other foods, and wash hands after handling raw poultry. These recommendations have high confidence because they address the documented risk of resistant bacteria in the environment.
Pasture-raised chicken farmers should care about these findings because they show a real problem on their farms that needs addressing. People who raise backyard chickens should also be aware. Consumers who eat pasture-raised chicken should understand the potential risks, though proper cooking eliminates the danger. Public health officials and policymakers should use this research to develop better guidelines for pasture poultry operations. People with weakened immune systems should be particularly cautious about undercooked poultry.
If farms implement better practices today, it would take several months to see meaningful reductions in environmental contamination. The spread of resistant bacteria in soil can persist for extended periods, so improvements won’t be immediate. However, preventing new antibiotic use on healthy animals could show results within one to two production cycles (roughly 8 to 12 weeks for broiler chickens).
Frequently Asked Questions
Can you get sick from eating pasture-raised chicken with antibiotic-resistant bacteria?
Cooking chicken to 165 degrees Fahrenheit kills these bacteria, making it safe to eat. The risk comes from undercooked poultry or cross-contamination of other foods. Proper food handling eliminates the danger from resistant bacteria on pasture-raised chicken.
Why is antibiotic resistance in chicken farms a problem for humans?
Resistant bacteria can spread from farms to soil and water, potentially reaching human populations. If you get infected with antibiotic-resistant bacteria, antibiotics won’t work to treat the infection. This makes common infections harder or impossible to cure.
Do pasture-raised chickens have more antibiotic-resistant bacteria than conventional chickens?
This study only examined pasture-raised farms, so direct comparison isn’t possible from this research. However, previous studies suggest resistance exists in both systems. The key finding here is that pasture environments can harbor and spread resistant bacteria.
What can farmers do to reduce antibiotic-resistant bacteria on their farms?
Farmers should avoid using antibiotics in healthy animals, rotate pasture locations frequently, and improve biosecurity practices. These measures reduce bacterial contamination in soil and the pasture environment, limiting the spread of resistance genes.
How do bacteria transfer antibiotic resistance genes to each other?
Bacteria can transfer resistance genes through plasmids, small circular DNA pieces that move between bacteria like tiny packages. This horizontal gene transfer allows resistance to spread rapidly between different bacterial species, even between E. coli and Salmonella.
Want to Apply This Research?
- Track weekly poultry purchases and cooking methods used, noting the source (pasture-raised vs. conventional) and internal temperature reached during cooking. This helps users monitor their exposure risk and reinforce safe food handling habits.
- Set a reminder to check chicken’s internal temperature with a meat thermometer before serving. Users can log each meal where they verified proper cooking temperature, building a habit that eliminates the bacterial risk regardless of the chicken’s origin.
- Over three months, track any gastrointestinal symptoms after eating poultry and correlate with cooking method and source. While most people won’t get sick, this creates awareness of the connection between food safety practices and health outcomes. Users can also track their farm-to-table sourcing choices if they purchase from local farms.
This research describes the presence of antibiotic-resistant bacteria on pasture-raised chicken farms. While the findings are concerning from a public health perspective, proper cooking of poultry to 165 degrees Fahrenheit eliminates these bacteria. This article is for informational purposes and should not replace advice from healthcare providers or food safety officials. If you have concerns about foodborne illness or antibiotic resistance, consult with a healthcare professional. Always follow USDA food safety guidelines for handling and cooking poultry.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.