Hua Wang of The Ohio State University in Columbus has been working with fermented food manufacturers, such as cheesemongers, for over 20 years to verify that they are free of antibiotic-resistant microorganisms.
Wang and her colleagues looked for such microbes in 10 types of kimchi - a traditional Korean dish made with salted and fermented vegetables - and four artisan cheeses purchased from local or national retail stores, as well as Japanese or Korean restaurants in the Columbus, Ohio area.
The researchers discovered antibiotic-resistant bacteria in nine of the kimchi products and all of the cheeses, some of which could induce gut-related symptoms or more serious health problems if they enter the bloodstream.
These also contained a variety of lactic acid bacteria, which are responsible for fermentation, and were similarly resistant to several antibiotics.
Fermentation bacteria can acquire or evolve antibiotic resistance. However, this would only be an issue if they created an infection or passed the antibiotic-resistance gene to another bacterium,
which "is possible but hasn't yet been shown" according to Mark Turner of the University of Queensland in Australia, who was not involved in the study.
However, one of the retail-bought kimchi varieties tested by the researchers contained a strain of Weissella, a type of fermentation bacteria that was proven to be extremely antibiotic resistant.
"If these strains get into the bloodstream through gastrointestinal tract issues, they can cause bacteraemia [a bloodstream infection] or sepsis, untreatable by antibiotics," Wang said. "This is regardless of the transfer of antibiotic resistance genes in the gut."