Association between duration of antipseudomonal beta-lactam therapy and infections in monomicrobial bloodstream infections at an academic medical center.

Objective: To evaluate the effects early de-escalation of antipseudomonal β-lactam (APBL) on 90-day CDI risk in bloodstream infections (BSIs).

Design: Retrospective cohort analysis.

Setting: An academic medical center in South Carolina.

Patients: We included patients aged >18 years with monomicrobial BSIs with who received APBL between July 1, 2015, and June 30, 2020.

Methods: Rates of CDI were compared between patients who received an APBL for >72 hours and <72 hours, followed by comparison between formulary APBLs utilized.

Results: In total, 447 patients were included; 292 and 155 patients received APBL for < 72 hours and > 72 hours, respectively. The incidences of CDI for <72 hours compared to >72 hours were 2.4% and 6.5%, respectively (unadjusted hazard ratio [HR], 2.70; 95% confidence interval [CI], 1.03-7.10; = .04). This difference was not statistically significant in the adjusted model (HR, 2.66; 95% CI, 0.97-7.31; = .06). Meropenem was associated with an increased risk of CDI when compared with all other formulary APBLs: 4 (26.7%) of 15 versus 13 (3.0%) of 432 ( < .001).

Conclusions: Utilization of an APBL for >72 hours was associated with a statistically significant increase in the incidence of CDI in an unadjusted model and with a numerically higher CDI incidence in the adjusted model. Meropenem was the formulary APBL that carried the highest risk of CDI. The results of this study provide further evidence supporting active antimicrobial stewardship to reduce unnecessary broad-spectrum antibiotics in the effort to alleviate the burden that CDI imposes on the healthcare system.