What possible infections might Caitlyn have?

It was so exciting! Caitlyn was the only freshman girl selected for Varsity Singers, her high school’s touring show choir. Their summer “retreat” was a six-day mega-rehearsal to learn all of the choreography for their upcoming show season. Monday through Saturday the week before school resumed, the 28 performers danced from 8 A M to 8 P M in their un-air-conditioned gymnasium. Caitlyn didn’t particularly mind the hot, humid rehearsal conditions, but sweating profusely in dance leotards every day was really starting to aggravate the acne on her shoulders and back. After a special preliminary performance for their families on Saturday night, Caitlyn showered and dressed to go home. It was then she discovered a very large, angry “pimple” that rubbed uncomfortably on the back waistband of her jeans. By morning, it was raised and the size of a dime. Caitlyn’s mother washed the
affected area, cleansed it with hydrogen peroxide, and applied an antibiotic ointment, telling her they would call the doctor tomorrow if it didn’t improve.

What possible infections might Caitlyn have?
What microbes would normally cause these infections? Are these microorganisms normal skin flora, pathogens, or both? Explain.

Monday morning, the first day of school, Caitlyn’s back was sore. “A great way to start high school,” she thought. Caitlyn’s mother took her to the pediatrician’s office right after school. The PA examined her back and was alarmed to see a lesion almost two inches in diameter. It was tender to the touch with poorly demarcated margins. The region was raised, warm, and Erythematous (reddened) with several smaller red lines radiating outward.

What is your diagnosis? Describe the nature of this condition.