Retrospective study finds diverse cephalosporin-resistant Enterobacterales in ICU pneumonia

A retrospective study of 80 adults with intensive care unit pneumonia and third-generation cephalosporin-resistant Enterobacterales found genetically diverse isolates and no statistically significant differences in clinical characteristics or outcomes between patients receiving carbapenems and those receiving non-carbapenem treatment. The findings come from the study abstract; the article was published as an open-access research paper in BMC Infectious Diseases on 19 September 2026.

Researchers identified eligible patients through electronic records covering January 2015 through July 2022. Inclusion required pneumonia, a positive respiratory culture for third-generation cephalosporin-resistant Enterobacterales, and definitive treatment with piperacillin/tazobactam, cefepime or a carbapenem. Of the 80 patients, 56% received a carbapenem, 31% received piperacillin/tazobactam and 13% received cefepime. Nanopore sequencing was used for multilocus sequence typing and comprehensive antibiotic-resistance gene detection. Minimum inhibitory concentrations for piperacillin/tazobactam and cefepime were determined by broth microdilution. Clinical factors and outcomes were compared between carbapenem and non-carbapenem groups through univariable analyses.

The isolates were highly diverse. Three-quarters carried an extended-spectrum beta-lactamase, or ESBL, gene, with blaCTX-M-15 the most common among the ESBL genes at 50%. AmpC genes were found in 19 isolates. In vitro susceptibility differed between the two non-carbapenem agents: 88% of isolates were susceptible to piperacillin/tazobactam and 58% to cefepime. Among isolates with AmpC genes, 83% were susceptible to piperacillin/tazobactam, compared with 93% of ESBL-harboring isolates.

Thirty-day mortality was 14% among patients treated with piperacillin/tazobactam or cefepime and 33% among carbapenem recipients, but the difference was not statistically significant in the reported univariable analysis (p = 0.09). In the subgroup of patients infected only with ESBL-producing isolates, mortality was 8% in the non-carbapenem group and 26% in the carbapenem group, also without statistical significance (p = 0.1). These observational comparisons neither establish that non-carbapenem treatment caused better outcomes nor show that the groups were equivalent. The small, selected population and univariable analyses limit interpretation, and the investigators said larger prospective studies are needed to assess non-carbapenem beta-lactams in this patient population.

Subject of Research: Molecular epidemiology and treatment outcomes of cephalosporin-resistant Enterobacterales causing ICU pneumonia

Article Title: Molecular epidemiology and associated treatment outcomes of third generation cephalosporin-resistant enterobacterales causing pneumonia in intensive care unit patients

Article References: DeLaurentis, C., Hokunson, T. W., Jr., Nelson, B., Annavajhala, M. K., Uhlemann, A.-C., & Gomez-Simmonds, A. (2026). Molecular epidemiology and associated treatment outcomes of third generation cephalosporin-resistant enterobacterales causing pneumonia in intensive care unit patients. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14446-5

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14446-5

Keywords: Enterobacterales, intensive care units, pneumonia, antibiotic resistance, carbapenems, piperacillin-tazobactam, cefepime, whole-genome sequencing, ESBL, AmpC, Molecular, epidemiology