Clinical-Microbiological Discordance and Delayed Mortality in OXA-48/ESBL-Producing Proteus mirabilis Infections
In brief
OXA-48 Proteus infections had 20-point higher 30-day mortality
In this single-center study, 79 patients with OXA-48 and ESBL-producing Proteus infections had 19.7 percentage points higher 30-day mortality than matched controls, with deaths diverging after day 8. Among infected patients, mortality was 50% with carbapenem-based regimens versus 20% with other active therapies, but observational data cannot rule out confounding; early detection may help guide treatment.
- Journal
- Infectious diseases and therapy (Q1)
- Published
- 6 October 2026
- Study design
- Cohort / observational study
- Evidence level
- Level 3, Low (CEBM 3b)
- Authors
- Isabel Machuca, Juan J Pineda, Juan A Marín-Sanz, Cristina Riazzo, Julia Guzmán-Puche, Ángela Cano, et al.
- PMID
- 42836950
- DOI
- 10.1007/s40121-026-01453-x
Why clinicians should know about it
- Picked for Microbiology (medical) (top studies of the week, 11 October 2026): OXA‑48/ESBL Proteus outcomes linked to carbapenem susceptibility
Abstract
INTRODUCTION: OXA-48/extended-spectrum β-lactamase (ESBL)-producing Proteus mirabilis may appear susceptible to carbapenems in routine testing, potentially resulting in inappropriate therapeutic decisions. We aimed to evaluate clinical outcomes and the association between antimicrobial therapy and mortality. METHODS: We conducted a single-center observational study including 1254 patients with P. mirabilis infections (2017-2024). Seventy-nine OXA-48/ESBL cases (6.3%) were matched 2:1 with non-OXA-48/ESBL controls based on age, comorbidity, infection source, and severity. OXA-48 production was detected using the NG-Test CARBA 5 immunochromatographic assay, while ESBL production was inferred phenotypically using cefotaxime, ceftazidime, and cefepime discs alone and in combination with clavulanic acid. Predictors of 30-day mortality were assessed using time-dependent Cox regression models. RESULTS: OXA-48/ESBL-producing infections were associated with higher 30-day mortality (absolute difference 19.7%; population attributable fraction 18.2%). Differences in mortality emerged after day 8, suggesting delayed clinical deterioration. In time-dependent models, OXA-48/ESBL status was not associated with early mortality (days 0-7) but strongly predicted late mortality [hazard ratio (HR) 14.5; 95% confidence interval (CI) 3.19-65.93; p = 0.001]. Among patients with OXA-48/ESBL infections, carbapenem-based regimens were associated with higher mortality than alternative active therapies (50% vs. 20%; p = 0.04), remaining significant after adjustment (HR 3.37; 95% CI 1.27-8.9), although residual confounding by indication cannot be excluded. CONCLUSION: These observational findings support cautious interpretation of carbapenem susceptibility results and highlight the value of early carbapenemase detection to guide appropriate therapy. Graphical abstract available for this article.
Abstract as published, via PubMed.
For healthcare professionals. The summary is generated by AI from the published abstract, and the evidence level is assigned automatically from the study design on the Oxford CEBM hierarchy. Neither is medical advice. Read the full paper before changing practice.