(596) Time to Treatment Initiation of Piperacillin-Tazobactam Compared to Ampicillin-Gentamicin for the Treatment of Intraamniotic Infection

Objective: Both the traditional regimen of ampicillin-gentamicin and the new regimen of piperacillin-tazobactam, have been proven to successfully treat intraamniotic infection (IAI). We sought to evaluate the time from diagnosis to initiation of antibiotics in the setting of IAI when comparing the recommended traditional regimen of ampicillin (2g IV q6h) and gentamicin (5mg/kg IV q24h), to the alternative regimen of piperacillin-tazobactam (4.5 g IV q8h).

Study Design: Retrospective cohort study of women with suspected IAI as defined by the ACOG at ³ 34 weeks of gestation, with singleton gestation, who received either regimen at a university hospital from November 2022 to May 2024. The primary outcome was time to treatment initiation (TTI). This was defined by an analysis of both provider and nursing input into an electronic medical record system, from time of medication order placement to administration initiation.  Mann-Whitney analysis was used to study the difference in time to treatment.

Results: We included 394 patients of which 199 received piperacillin-tazobactam, and 195 received ampicillin-gentamicin. Most patients (57.8%) were diagnosed with suspected IAI based on maternal fever and fetal tachycardia. Median TTI was 21 minutes (interquartile-range 28 minutes) for the piperacillin-tazobactam group, and 68 minutes (interquartile-range 51.2) for the ampicillin-gentamicin group (p-value < 0.01). There was no significant difference in the rate of postpartum fever, ICU admission, or postpartum readmissions (Table 1). Regarding neonatal outcomes, there were no clinically significant differences in early onset sepsis (EOS) score, rate of NICU admission or cord gas pH (Table 2).

Conclusion: Interestingly, the TTI of the complete antibiotic regimen from time of diagnosis is over twice as long with ampicillin-gentamicin than piperacillin-tazobactam, likely due to the weight-based dosing rather than fixed dosing regimen and ease of medication availability for administration to nursing staff.