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Bacteria in probiotic beverages harbor antibiotic resistance genes
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SAN FRANCISCO — A genetic analysis of Bacillus strains found in probiotic products that researchers purchased at a supermarket showed that some are resistant to antibiotics, according to data presented at ASM Microbe.
“The study started with one of our collaborators. I read an email between him and my [primary investigator] about how he was feeding his chickens some type of probiotic feed and was thinking how probiotics can transfer genetic information to other bacteria and could also transfer antimicrobial resistance,” Emmanuel Flores, a masters student at California State University, Fresno, told Infectious Disease News. “It was a ‘what if’ that started with him feeding his chickens.”
Flores and colleagues searched Whole Foods for items containing commercial Bacillus strains, which they identified through gram and endospore staining before confirming the strain with 16S rRNA gene sequencing. Once confirmed, they performed antibiotic sensitivity assays on each strain using a disk-diffusion method with a panel of 15 antibiotics.
According to Flores, they collected 15 samples, including some from kombucha, coconut kefir, Japanese fermented soybeans, a probiotic version of root beer and chicken feed.
The testing revealed that one version of kombucha contained a strain of Bacillus resistant to five different antibiotics, including ampicillin. Flores said all the strains were resistant to bacitracin, “which is good,” he said, “because they produce that naturally, so it works as a control.”
“We need to understand the risks of probiotics. [This study] is not us saying they’re bad for you, but we need to keep an eye on them,” Flores said. “Currently, there is a global health crisis going on with antimicrobial-resistant infections that could lead to global expenditures of $100 trillion by 2050 and 10 million deaths per year. So, basically, this is a good way to monitor resistance. We drink these live bacteria for beneficial purposes, so we have to make sure there aren’t any adverse effects.”– by Caitlyn Stulpin
Reference:
Flores E, et al. Antimicrobial resistance in Bacillus strains found in probiotics. Presented at: ASM Microbe; June 20-24, 2019; San Francisco.
Disclosures: Flores reports no relevant financial disclosures.
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Jennifer K. Spinler, PhD
Flores and colleagues have identified antimicrobial resistance genes in Bacillus species isolated from functional food products, suggesting the associated probiotics have the potential to transfer antimicrobial resistance after consumption. The spread of antimicrobial resistance through probiotics is a valid global health concern. Antibiotics are prevalent in modern health care, as well as in our food supply, and evasion of antimicrobial pressure has become a necessary mechanism for naturally occurring beneficial microbes to co-evolve with their host. Many organisms that are generally recognized as safe are inherently resistant to antibiotics by nontransferrable means — otherwise known as intrinsic resistance. However, acquired antimicrobial resistance traits that persist on mobile genetic elements should be an important safety consideration in probiotic strain selection aimed at responsible product development, and further evidence by Flores and colleagues is required to confirm if the transferability of these antimicrobial-resistant genes to susceptible organisms is possible.
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