Which one of the following Gram positive organism is most common cause of UTI among sexually active women :
Staphylococcus epidermidis
Staphylococcus aureus
Staphylococcus saprophyticus
Enterococcus
Remember:

MC cause of UTI - E. coli
MC cause of nosocomial UTI - E. coli
MC nosocomial infection - UTI
S. saprophyticus produce UTI characteristically in sexually active young woman
Enterococci and S.aureus cause infections in patients with renal stones or previous instrumentation or surgery.