Final answer:
A patient with a vaginal yeast infection is most commonly suffering from an overgrowth of the yeast Candida albicans, which can lead to inflammation, itching, and discharge, and is treated with antifungal medications.
Step-by-step explanation:
The microorganism that causes a vaginal yeast infection is the yeast Candida albicans. This fungus is a common member of the normal microbiota of the skin, mouth, intestine, and vagina but can cause an infection when there is a disruption in the body's environment that allows it to overgrow. Such disruptions can include antibiotic use, changes in hormonal levels, immune suppression, or diabetes, among others. The medical assistant should inform the patient that vaginitis is most commonly caused by this yeast (Candida albicans) overgrowth, resulting in symptoms such as inflammation, itching, white or yellow discharge, and sometimes odor. Diagnosis of this condition can be made through microscopic evaluation of vaginal secretions, and it is treatable with topical or oral antifungal medications.