Review Question - QID 213776

A 37-year-old woman presents to her gynecologist with a 2-week history of pain during sex. She says that she noticed discomfort and itchiness in her vulvar region that progressed to pain and bleeding during sex. She denies pain at rest and says that she has not noticed any other symptoms. She is active with multiple partners and does not use protection. Physical exam reveals the lesion shown in Figure A on the inferior aspect of the left labia majora. Palpation reveals that the lesion is soft and bleeds when irritated. Infection with which of the following organisms is most likely responsible for this patient's presentation?