The Effect of a Single-Dose Aminoglycoside With a Beta-Lactam for the Treatment of Gram-Negative Bacteremia

Introduction: Aminoglycosides possess activity against aerobic gram-negative organisms and are often used in combination with beta-lactam antibiotics. Previous studies evaluating combination therapy in gram-negative bacteremia have not shown clear benefits, however antimicrobial resistance was not prevalent in these studies. Our objective is to elucidate potential benefits of adding a single dose of an aminoglycoside to a beta-lactam in patients with gram-negative bacteremia. Methods: This study was a single-center, retrospective, cohort study including patients 18 years old or older and treated for at least 24 hours for a confirmed gram-negative bacteremia. Patients were divided into two groups: receipt of beta-lactam monotherapy (n = 164) and receipt of a beta-lactam in addition to a single dose of an aminoglycoside (n = 79) within 24 hours of bacteremia onset. The primary endpoint was infection-related 30-day mortality per provider documentation. Key secondary outcomes include incidence of acute kidney injury (AKI) and time to improvement of AKI. Data were analyzed using Chi-square or Fisher's exact tests, student's T test, and descriptive statistics as appropriate. Results: The primary outcome occurred in 13/164 vs 2/79 patients in the monotherapy and combination groups (P = 0.10). Incidence of AKI (14% vs. 12%) and time to recovery from AKI (90 hours; IQR [50 - 133] vs 78 hours; IQR [42 - 128]) were comparable between groups (P = 1.00 and P = 0.73, respectively). Conclusions: The addition of a single-dose aminoglycoside was not significantly associated with reduced mortality or increased time to recovery from AKI in our patient population. Larger studies, particularly in more severely ill patient populations, are needed.