Probiotics After Antibiotics? The Answer May Be No

A week ago or so, I got an email from a physician who follows my blog.  He reminded me of research I had seen a few years back, but at that time, had not read the paper myself.  On his recommendation I took a fresh look; I was surprised that I hadn’t reported on it actually, as it’s out of the Weizmann Institute of Science in Israel, and I try my best to follow research coming out of there.[i]  Certainly their results are worth reporting to you so I apologize for missing the boat on this one.

These scientists wanted to test the effects of reconstituting the microbiome after a round of antibiotics using probiotics, as so many of us do nowadays.  They tested two methods of reconstitution:  oral probiotics and fecal microbiota transplant (FMT).  21 volunteers were given a course of antibiotics and then randomly assigned to one of 3 groups.  The first group (7 people) was given nothing to reconstitute the biome.  The second group (8) was given a multi-strain oral probiotic and the third group (6) was treated with autologous (self-donated before antibiotics were administered) fecal microbiota transplants. Their results were pretty shocking. The oral probiotics effectively colonized the volunteers’ intestines which had the effect of preventing the gut biome from returning to its normal state:  “…our study highlights an important previously unappreciated tradeoff in which improved probiotic gut mucosal colonization under disruptive antibiotic conditions led to a markedly delayed indigenous gut mucosal reconstitution in terms of composition, function and bacterial load, and prolonged dysbiosis that lasted at least 5 months following the cessation of probiotic exposure.”  The FMT, on the other hand, had the gut return to normal within days.

Said the senior author of the study, “Contrary to the current dogma that probiotics are harmless and benefit everyone, these results reveal a new potential adverse side effect of probiotic use with antibiotics that might even bring long-term consequences…”[ii]

There are of course, many questions remaining.  Firstly, are all probiotic species problematic?  The paper states that there is “…antagonistic activity of some probiotics species…,” which does not mean all species, or all combination of species, would have the same effect.  They tested only 1 kind of broad spectrum probiotic (with 11 strains) in only 8 people. (By the way, if the dose of the probiotic was in the paper, I couldn’t find it.)  Anyway, so while their findings are significant, obviously we need way more research before drawing conclusions.  They clearly state this in their discussion:  “Our study features several important limitations. We tested, in mice and humans, a single combination of broad-spectrum antibiotics and one (albeit diverse) orally administered probiotics mixture. Other combinations of antibiotics, probiotics, and treatment routes and timings merit further studies.”

Still, their point is that the use of probiotics may not be “risk free,” and that other treatments like FMT may do a better job of reconstituting the biome after a round of antibiotics.  (FMT is, of course, invasive so not likely to become the standard any time soon.)  This is a really important area of work considering the potential detrimental health effects of antibiotic use (which I have written about frequently), so let’s hope more research is forthcoming.


[i] Suez J, Zmora N, Zilberman-Schapira G, Mor U, Dori-Bachash M, Bashiardes S, Zur M, Regev-Lehavi D, Ben-Zeev Brik R, Federici S, Horn M, Cohen Y, Moor AE, Zeevi D, Korem T, Kotler E, Harmelin A, Itzkovitz S, Maharshak N, Shibolet O, Pevsner-Fischer M, Shapiro H, Sharon I, Halpern Z, Segal E, Elinav E. Post-Antibiotic Gut Mucosal Microbiome Reconstitution Is Impaired by Probiotics and Improved by Autologous FMT. Cell. 2018 Sep 6;174(6):1406-1423.e16. doi: 10.1016/j.cell.2018.08.047. PMID: 30193113.


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