B is the correct answer

Mastitis often occurs in lactating women secondary to nipple trauma and poor milk drainage. Symptoms are typically unilateral, and they generally present with an erythematous breast mass that is painful and swollen along with associated fever. Most cases of lactational mastitis are caused by Staphylococcus aureus. Treatment includesdicloxacillin and continued breastfeeding. Other antibiotics that can be used include cephalexin, erythromycin, and clindamycin.

Breast ultrasound (A) would be appropriate if you suspected a breast abscess, patients who have continued fever, swelling, and a palpable breast mass should have an ultrasound to rule out abscess. Discontinue breastfeeding (C) is incorrect, as patients with lactational mastitis should continue breastfeeding or pumping. Vancomycin (D) would be an appropriate treatment for inpatients in the setting of severe infection.