I've had good results with probio as well.
If one gets gas, you should wonder where it comes from. Microbes digest and "outgas", but often times other microbes use this gas... similar to how we breath in oxygen (and other things) and breath out carbon dioxide, while plants take in carbon dioxide but produce oxygen. A good food source for probiotics (and less likely for the harmful type, if at all) are
soluble fiber sources, such as FOS, insulin, lactoferrin, pectin, and others. No surprise that beans give us gas, but I've come to realize even that can be adjusted to, because the balance of microflora are also adjusting and with the high fiber content in beans, it is not surprising this is what is occurring. So I'll take some discomfort in the short term for better long term results. Recently I have upped my fiber intake and just dealing with the gas, as of about
3 or 4 days ago, and it seems to be lightening up and I am feeling better so far. I was also taking large and frequent amounts of probiotics ahead of time, which may have helped. So gradually increasing the probiotics and then gradually increasing the
soluble fiber (or fiber in general) is probably best.
There should be no great risk in taking probiotics, but it is still possible that a negative reaction would occur, more because the immune system confuses the good bacteria for a bad bacteria because it looks so similar to the former (e.g. there is both a pathogenic [bad] form of E. coli and there are also good strains, but I don't think it is commercially available). I think AIDS patients are at a higher risk with negative reactions. With IBD patients, the studies indicate that it is rare to have a negative reaction and it may just be that in those cases the dose was too high or particular allergies to the other substances in the capsule.
That's my two or three cents on the matter.
**Edit note: It dawned on me several hours later that I wrote insoluble instead of soluble fiber. Sorry.