A 31-year-old woman has had vulvar pruritus along with a thick, whitish, odorless, globular vaginal discharge for the past week. On pelvic examination, the cervix appears erythematous, but there are no erosions or masses. A Pap smear shows budding cells and pseudo hyphae. No dysplastic cells are present. Which of the following infectious agents is most likely to produce these findings?