# Comparative effectiveness of ertapenem versus other empirical antibiotics in elderly patients with complicated intra-abdominal infection: a real-world inverse probability of treatment weighting study

## TL;DR

This study compares ertapenem with other antibiotics in elderly patients with abdominal infections, finding similar effectiveness and suggesting it could be a good option for some patients.

## Contribution

The study provides real-world evidence on the effectiveness of ertapenem compared to other antibiotics in elderly patients with complicated intra-abdominal infections.

## Key findings

- Ertapenem showed comparable clinical cure or improvement rates to other antibiotics in elderly patients with complicated intra-abdominal infections.
- Mortality outcomes were similar across all treatment groups.
- Ertapenem was associated with higher cure rates in younger elderly patients and those with non-gastrointestinal infections, though results were exploratory.

## Abstract

Elderly adults with complicated intra-abdominal infection (cIAI) represent a functionally immunocompromised population due to immunosenescence, multimorbidity, and frailty. Optimizing empirical antibiotic therapy in this group is essential to improve outcomes while minimizing unnecessary broad-spectrum antimicrobial exposure and antimicrobial resistance (AMR) selection pressure. Ertapenem is a once-daily carbapenem with favorable pharmacological properties, yet contemporary real-world comparative data in older adults are limited.

We conducted a retrospective, real-world comparative-effectiveness study of hospitalized adults aged ≥65 years with cIAI at a tertiary academic medical center from 2019 to 2025. Eligible patients received empirical monotherapy with ertapenem, meropenem, cefoperazone–sulbactam, or moxifloxacin for ≥72 hours. A multinomial propensity score-based inverse probability of treatment weighting (IPTW) approach was used to balance baseline covariates across the four regimens. The primary outcome was clinical cure or improvement. Secondary outcomes included all-cause in-hospital mortality, infection-related mortality, intra-abdominal infection–related mortality, duration of antibiotic treatment, and length of hospitalization. Prespecified subgroup analyses were conducted by age group (65–70, 71–80, ≥81 years) and infection source (gastrointestinal vs non-gastrointestinal).

A total of 609 patients met eligibility criteria: 129 received ertapenem, 135 meropenem, 125 cefoperazone–sulbactam, and 220 moxifloxacin. IPTW achieved excellent covariate balance, with all standardized mean differences <0.10. In IPTW-adjusted analyses, clinical cure or improvement did not differ significantly between ertapenem and comparator regimens, with adjusted risk differences ranging from 1.80% to 6.44% (all 95% confidence intervals including zero). Mortality outcomes were likewise comparable across groups. Subgroup analyses suggested that ertapenem was associated with higher cure rates and lower mortality in patients aged 65–70 years and those with non-gastrointestinal infection sources, although confidence intervals were wide, and these findings should be interpreted as exploratory. Differences in secondary outcomes varied across regimens.

In this IPTW-adjusted real-world analysis of elderly adults with cIAI, ertapenem demonstrated clinical effectiveness comparable to meropenem, cefoperazone–sulbactam, and moxifloxacin. Given its once-daily dosing convenience and narrower ecological impact, ertapenem may represent a reasonable and stewardship-aligned empirical option for selected older patients. Prospective and multicenter studies incorporating microbiological and illness severity data are needed to validate these findings.