Which one of the following gram-positive organism is the most common cause of UTI among sexually active women-
Staph saprophyticus 

Staph saprophyticus may be present on normal human skin and the periurethral area and can cause urinary tract infection, particularly in sexually active young women.
Staph saprophyticus strains causing UTI are usually sensitive to most antibiotics, except nalidixic acid.
Staph saprophyticus is novobiocin resistant.
Staphylococcus epidermidis
Staphylococcus aureus
Staphylococcus saprophyticus
Enterococcus