Blastocystis has been classified as a yeast, related to Schizosaccharomyces, and as a
sporozoan. A fragment of the rRNA has been sequenced, yet it was not clear to me whether this
was sufficient to relate Blastocystis to other organisms. I could find little that clearly
indicated this organism was pathogenic, although there are several such reports. These
reports usually indicate diarrhea as the primary symptom. I could not find any indications of
Even though your wife has blastocystis infection, her symptoms may be caused by some other
infectious agent or by some other problem. If her physicians were convinced that there were
no other problem and that side effects would not be a problem, they might try treatment with
antifungals like ketoconazole, or antiprotozoals like metronidazole, or even
trimethoprim-sulfamethoxazole. These would all be shots in the dark. There is a culture
system for blastocystis, so a very interested laboratory might be able to at least test
the in vitro susceptibility of blastocystis to these treatments before treating your wife.
Note that most of these drugs can cause serious side effects in certain clinical situations,
so be certain that the physician carefully considers the potential value of such therapies.