Genomic characterization of a carbapenem-resistant Leclercia adecarboxylata isolate co-harboring blaNDM-7 and blaKPC-4 in a hospitalized patient.

UNLABELLED: Carbapenems are a last-resort treatment for severe infections caused by multidrug-resistant organisms. Acquired carbapenemases located on plasmids can be harbored by frequent pathogens as well as opportunistic pathogens such as Leclercia adecarboxylata, which can colonize and cause infections in immunocompromised patients. In this study, we describe a carbapenem-resistant L. adecarboxylata rectal surveillance isolate La1358 from a hospitalized patient in Maryland in 2025. This isolate was obtained during routine rectal swab surveillance to detect drug-resistant organisms colonizing patients in intensive care units (ICUs). This is the first known description of an L. adecarboxylata isolate harboring both blaKPC-4 and blaNDM-7. The blaKPC-4 was identified on an IncFIA(HI1)/repB(R1701) plasmid and blaNDM-7 on an IncX3 plasmid. The blaNDM-7-containing IncX3 plasmid was nearly identical to a plasmid from an Enterobacter hormaechei isolate obtained in 2023 from another patient at the same hospital, demonstrating L. adecarboxylata is contributing to persistence of this plasmid among this patient population. These findings demonstrate that L. adecarboxylata colonizing patients can provide a reservoir of carbapenemases, including blaNDM-7, linking a less common species of Enterobacterales to the increasing prevalence of blaNDM-7 in the United States. Previous L. adecarboxylata isolates, from outside the United States, have been described harboring blaNDM-1; however, to our knowledge, this is the first description of L. adecarboxylata in the United States harboring blaNDM-7, acquired via a conserved IncX3 plasmid. Also, these findings highlight the importance of genomic surveillance to track plasmid-mediated dissemination of acquired carbapenemases among organisms colonizing hospitalized patients, in addition to isolates from clinical specimens associated with infection.

IMPORTANCE: Carbapenem-resistant infections are a serious concern for hospitalized patients and have been increasing in the United States. This has been driven by acquired carbapenemases, in particular blaKPC and blaNDM. A majority of acquired carbapenemases among hospitalized patients are harbored by frequent human pathogens; however, less common Enterobacterales can also acquire and disseminate plasmids harboring blaKPC and blaNDM. This study describes the genome of a blaKPC and blaNDM-containing Leclercia adecarboxylata isolate, an opportunistic human pathogen, identified colonizing a hospitalized patient. International L. adecarboxylata isolates have been described harboring blaNDM-1; however, to our knowledge, this represents the first description of L. adecarboxylata harboring blaNDM-7, which is a blaNDM variant becoming more prevalent in the United States. These findings highlight the importance of genomic surveillance of drug-resistant organisms colonizing hospitalized patients to identify and disrupt reservoirs and transmission pathways linked to the spread and persistence of carbapenem resistance in hospitals.