 Deeper infections may be discoloured, ulcerative and purulent.A "Candida" yeast infection can also be identified by a KOH test by taking scrapings from the mouth (oral thrush), vagina (vaginitis) and skin (candidiasis).There are over 40 different fungus species known to cause disease in humans, of which "Candida albicans" is the most common and most frequently tested for.