A 72-year-old woman presents to the emergency room with 1-day history of nausea and vomiting. She was recently discharged from hospital 3 weeks ago after a bronchial asthma exacerbation and has completed a glucocorticoid taper 1 week ago. Over the last year, she has had several hospital admissions due to bronchial asthma exacerbations. On examination, HR 120/min, BP 80/60 mmHg, RR 12/min, and O2 Saturation 94%. Her abdomen is diffusely tender but no peritoneal signs. Her investigations show glucose 70 mg/dL, sodium 125 mEq/L, potassium 3.9 mEq/L, and urine analysis shows 75 leukocytes/HPF. She is treated with 1L of normal saline and empiric broad- spectrum antibiotics. Which of the following is the most appropriate next step in treatment?