Effect of oral beta-lactam dosing on outcomes of bacteremic Gram-negative urinary tract infections: a real-world analysis

Among 452 adult patients with Gram-negative bacteremia from a urinary tract infection source who received oral step-down therapy with highly bioavailable oral beta-lactam, we observed no difference in 60-day recurrence in patients treated with higher consensus-recommended dosing compared to lower, standard dosing (odds ratio = 0.76 [95% confidence interval = 0.43-1.32]), although the directionality of the effect was favorable. The study was limited by inadequate sample size and confounding. Randomized or large observational comparative effectiveness studies are needed.IMPORTANCEDefinitive treatment of Gram-negative bacteremia with oral antibiotic agents is not one size fits all. Use of oral fluoroquinolones and sulfamethoxazole/trimethoprim is evidence-based but carries risk for adverse events. Data supporting the use of oral beta-lactams are mixed, likely in part due to variable agent selection and dosing. This analysis shows that higher, consensus-recommended dosing of highly bioavailable beta-lactam antibiotics was not significantly different from patients treated with lower dosing on 60-day recurrence. Our study was limited by the number of patients with discrete MICs and overinfluence of complicated urinary tract infection on outcomes.