There is a lot of confusion about this topic. Jini Patel has raised concerns about soil-based organisms (SBOs) in
this article, based on claims made by Natasha Trevnev, the founder of Natren (a company that sells lactic acid-based probiotics). Most of the objections raised in the article are either technically inaccurate or outdated by current research. It has become clear through DNA sequencing of the gut microbiota that the human gut has a makeup of bacteria similar to or already of SBO origin. From an evolutionary perspective, it's likely that we were exposed to SBOs to a much larger degree than we are now, due to the industrialization of agriculture and food distribution, and changes in soil quality and diversity.
The term "spore former" refers to microflora that can form spores that are biologically active, i.e. reproduce in the spore form, and are highly resistant to the environment and cause disease. Endospore formers, on the other hand, are biologically inactive and remain that way until environmental conditions allow resuming normal forms. Prescript Assist does have endospore formers, but they simply pass out of the system if they ever form in the gut of any mammal.
The Relman-Stanford group studies have shown that SBOs are more numerous in the gut than lactic acid microflora, and that the microflora resident in the healthy mucosa of the gut differ considerably from what is present in fecal material (which tends to have higher numbers of lactobacilli and bifidobacteria).
Finally, Prescript-Assist microflora are recognized Class 1 Etiological Agents, non-toxic, non-pathogenic, from independently maintained lines -- this is well documented in both of the Clinical Therapeutics Articles.
More than a decade of use as a supplement has revealed no adverse effects and/or side-effects [including reportedly patients with impaired immune systems], as well as the initial demonstrations with repeated consumptions of doses amounting to 500X that recommended for ordinarily daily use with no ill effect.