Probiotic Supplements After Antibiotics May Do More Harm Than Good


Findings from a pair of studies from investigators in Israel suggest that probiotic supplements may not be as beneficial as previously thought.

The popularity of probiotic foods and products—touted for their gut health benefits—has grown in recent years, but a new pair of studies suggest that taking probiotics may not have the desired effects, including when they’re taken along with antibiotics.

Consumption of probiotic-infused foods and dietary supplements has grown as a strategy to use “good” bacteria to fight “bad” pathogenic bacteria. A 2017 National Health Interview Survey conducted by the National Institutes of Health (NIH) found that 3.9 million adults in the United States consume probiotic and prebiotic supplements, although there is lacking literature on the safety of probiotic supplementation. Recent studies have found that probiotic isolates such as Lactobacillus reuteri may offer a powerful weapon against dangerous antibiotic-resistant bacteria such as Clostridium difficile, Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumonia. A 2017 study detailed the benefits of Lactobacillus supplementation in infants in India, where treatment with the probiotic was found to significantly reduce sepsis deaths in low birth weight infants.

Now, investigators from the Weizmann Institute of Science in Israel studying the human gut have authored 2 new papers regarding probiotics that were published on September 6, 2018 in the journal Cell. In the first study of 25 human participants, investigators found that not everyone who takes probiotics experiences intestinal colonization of the beneficial bugs. After participants received upper endoscopies and colonoscopies to sample their baseline gastrointestinal (GI) microbiome, the investigators then gave 15 participants either an 11-strain probiotic preparation or a placebo. Rather than using stool samples to analyze participants’ GI microbiomes—which the authors say may not accurately reflect the microbial gut mucosal composition and function—the investigators administered a second round of upper endoscopies and colonoscopies.

The investigators found that while the probiotics colonized the guts of some participants, dubbed “persisters,” the other participants were “resisters” and expelled the probiotics. "Surprisingly, we saw that many healthy volunteers were actually resistant in that the probiotics couldn't colonize their GI tracts,” senior author Eran Elinav, MD, PhD, in a recent statement. “This suggests that probiotics should not be universally given as a 'one-size-fits-all' supplement. Instead, they could be tailored to the needs of each individual."

The second study examined the use of probiotic supplementation after antibiotic use to repopulate gastrointestinal flora. For the study, investigators recruited 21 participants and assigned them to 1 of 3 groups: a “watch-and-wait” group whose microbiomes would recover on their own, a group that received the same probiotic preparation as the first group, and a group receiving autologous fecal microbiome transplants (aFMT) made up of their own bacteria that had been collected before antibiotic use. The research team was surprised to observe that in the probiotic group, normal microbiome and gut gene expression profile was prevented from returning to a normal state for months afterward, while the aFMT group saw their native gut microbiome and gene program return to normal within days.

“Here too, we demonstrate that replenishment with your individually-tailored microbiome (collected before antibiotic exposure) induces a rapid and complete reconstitution of the indigenous microbiome and host gene expression profile,” said Dr. Elinav in an interview with Contagion®. “In contrast, empiric probiotics induce a marked and persistent inhibition in the indigenous microbiome and host gene expression reconstitution toward their naive pre-antibiotic configuration, even when compared to a ‘watchful waiting’ approach.”

The take home message, according to Dr. Elinav, is that providers should practice caution in universally applying probiotics after antibiotics, as the prolonged dysbiosis his team noticed may be associated with long-term consequences that merit future studies.

“We need to wait for the generation of patient-tailored methods of post-antibiotic probiotic approaches (currently underway in follow up studies),” concluded Dr. Elinav.

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