If gram-negative infection is suspected (eg, in patients with immunosuppression or serious comorbid disorders, injection drug use, a recent infection with antibiotic use, or an indwelling vascular catheter), empiric treatment includes a parenteral 3rd-generation cephalosporin with antipseudomonal activity (eg, ceftazidime 2 g IV every 8 hours) and, if infection is severe, an aminoglycoside.