My Dermatologist Gave Me Clindamycin Phosphate Topical For A Bacterial

my dermatologist gave me clindamycin phosphate topical for a bacterial infection in my groin area. he did not tell me what the culture was or if it was gr neg or what
I can say that clindamycin does work some but I need to know what type of bacteria it is... he did say that it floreced red under uv
any guesses?