Severe diffuse cutaneous or systemic infection is best treated with one of the following: Penicillin G (2 to 3 million units IV every 4 hours) Ceftriaxone (2 g IV once a day) A fluoroquinolone (eg, ciprofloxacin 400 mg IV every 12 hours, levofloxacin 500 mg IV once a day) Endocarditis is treated with penicillin G for 4 to 6 weeks.