ASM Microbe

ASM Microbe

June 08, 2017
2 min read

Antibiotic-resistant bacteria abundant in produce

You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

We were unable to process your request. Please try again later. If you continue to have this issue please contact

NEW ORLEANS — According to the CDC, at least two million people are infected with antibiotic-resistant bacteria each year in the United States, and 23,000 patients die as a result of these infections. Research presented during ASM Microbe demonstrated the extent to which humans may be exposed to these antibiotic-resistant bacteria through ready-to-eat foods like produce and dairy.

Researchers at California State University, Northridge, quantified the antibiotic-resistant bacteria found in foods that are bought and mostly consumed without cooking. Uncooked foods may retain antibiotic-resistant bacteria, which can be directly consumed or contaminate surfaces in the kitchen or other food, the researchers said.

Bryan Sanchez
Bryan Sanchez

“These levels of antibiotic resistance may have come from the overuse of antibiotics in the food industry,” undergraduate researcher Bryan Sanchez told Infectious Disease News.

Sanchez and colleagues, including Kerry Cooper, PhD, assistant professor of biology, purchased organic and conventional produce — fruits and vegetables — and dairy products at local grocery stores in the San Fernando Valley outside Los Angeles and counted the bacteria resistant to eight antibiotics: ampicillin, cefotaxime, chloramphenicol, ciprofloxacin, colistin, erythromycin, gentamicin and tetracycline.

On average, produce had 10,000 times more antibiotic-resistant bacteria than dairy, with conventionally grown fruits and vegetables containing more than those grown organically, according to the researchers. Produce tested highest for bacteria resistant to cefotaxime, and numerous samples showed bacteria resistant to colistin, they said.

Around 80% of antibiotics in the U.S. are used by the agricultural industry, according to the researchers. Antibiotics are not used in the produce industry, so fruits and vegetables are likely being contaminated through the soil, they said.

In this preliminary study, the majority of the identified bacteria are common produce inhabitants that are nonpathogenic and naturally resistant to many antibiotics, according to Cooper.

Dairy products also tested highest for bacteria resistant to cefotaxime. Among them, yogurt had the most antibiotic-resistant bacteria, including a single sample that showed resistance to colistin. The researchers also tested cheese and milk.

Sanchez said they expected the levels to be lower in dairy products compared with produce because cheeses are generally dry and processed, leading to fewer bacteria.

“The levels were brought down a lot by the cheeses. The milks and yogurts had higher levels,” Sanchez said. – by Gerard Gallagher


Sanchez B, et al. Levels of antibiotic resistant bacteria in ready-to-eat foods. Presented at: ASM Microbe; June 1-5, 2017; New Orleans.

Disclosure: The researchers report no relevant financial disclosures.