I can only get to the full article of the first one cited; the second is beyond a wall. Still that first article is very interesting. Thank you for the link.
Before discussing it, if you care to, I do want to emphasize my already stated … skepticism … of the $58 billion probiotic supplement industry. I do not think that fermented foods as a regular part of a dietary pattern is quite the same thing, any more than supplemental vitamins are the same thing as vitamins obtained in complete foods as part of a nutrition pattern. That said …
The article has some fascinating specific results, looking specifically on the expansion of resistance genes in the gut (the resistome) after antibiotic use, measuring not in stool but by direct gut sampling, comparing non treatment, fecal transplant, and with a commercial probiotic supplement.
Relevant to this discussion is that the probiotic after antibiotics arm had an expansion of the resistome, while both the fecal transplant and no treatment arms recovered to baseline, AND that the source of the antibiotic resistance genes (ARGs) was NOT from the probiotic but by fostering the expansion of ARGs of the endogenous microbiome!
This at first read possibly surprising finding is completely consistent with the findings in the article I linked to in the OP: in both cases, fermented foods with active species, and probiotics post-antibiotics, an expansion of diversity of species not of the food/probiotic was obtained. In the fermented foods given to healthy individuals this expansion of diversity was putatively of benefit, associated with other positive markers. In the context of immediately after several broad spectrum antibiotics the expansion allowed ARGs to bloom, increasing the resistome.
So indeed the popular thought to take probiotics during and after being on antibiotics may be having a negative impact rather than a positive one, actually fostering the expansion of antibiotic resistance rather than the reseeding with healthy bacteria that people hope for. Harms more than goods.
But increasing diversity while in good baseline health, ideally antibiotic naive, still seems beneficial. And I am still very curious about the mechanism by which fermented foods and probiotics, in this circumstance anyway, increases microbiome diversity not of the organisms they contain.
Fascinating.