Hey, Seb:
I don't know what a "short" fast is, exactly, but will assume it is under four days.
The overall issue in AS is the health of the gut, and candidiasis (which compromises the gut wall) is a lifestyle (nearly 100% diet-related) issue, so even if You had a magic bullet that could knock the fungus down to zero, unless You made some permanent changes to Your diet, the fungus among us would return.
Do not be discouraged from fasting, but upon resumption of consumption it would be better to make the choices away from fungal-encouraging foods.
FASTING can considerably alter the course of this disease, if kept up, so there is very good reason, even beyond the potential to reduce
C. albicans, to do this for even short periods and
often is better than seldom.
I believe it was fasting which perhaps reduced the fungus enough that I never seemed to have any problems with it when I was taking antibiotics and even steroids (after operations), but it was something I was always looking out for.
The anti-fungals are a reasonable approach, but again, as AS is a lifestyle issue, it will require a restructuring of Your palette, overall, to successfully overcome the chronic part of this disease including the contribution due to both fungus and NSAIDs.
HEALTH,
John