I can't say that I've seen examples or testimonies, but I did find a scientific paper on it. Here's the abstract:
There are two aspects about the presence of Candida in the human orointestinal tract: (i) it is a part of normal human flora and (ii) it is a risk factor for immunocompromised patients. The orointestinal tract can be considered a reservoir for Candida species, several of which are from the oral cavity, stomach, duodenal juice and faeces. Their germ counts in normal small and large bowel do not exceed 10(4) cfu/ml resp.g. The input of Candida to a well-developed faecal flora system under continuous flow culture conditions did not lead to a multiplication of the yeast. The take in of faecal flora into a Candida continuous flow culture diminish Candida germ counts. If, however, the faecal flora was destroyed, e.g. by Antibiotics , we found the yeasts multiplying, with the formation of germ tubes and mycelial structures. Colonization by Candida has to be seen as a starting-point of the development of subsequent candidosis in immunosuppressed or intensive care patients. The best protection against Candida colonization in the gut is the existence of a normal bacterial flora. Lactulose, which promotes the Gram-positive potential of faecal flora, may protect indirectly by supporting the indigenous flora.
It's been cited many times, as well. I also read that lactulose is a great food grade prebiotic, so maybe we'll be seeing more of it in the future. Great find!