Genomic characterization of a carbapenem-resistant Leclercia adecarboxylata isolate co-harboring bla _NDM-7 and

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 bla _KPC-4 and bla _NDM-7 . The bla _KPC-4 was identified on an IncFIA(HI1)/repB(R1701) plasmid and bla _NDM-7 on an IncX3 plasmid. The bla _NDM-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 bla _NDM-7 , linking a less common species of Enterobacterales to the increasing prevalence of bla _NDM-7 in the United States. Previous L. adecarboxylata isolates, from outside the United States, have been described harboring bla _NDM-1 ; however, to our knowledge, this is the first description of L. adecarboxylata in the United States harboring bla _NDM-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 bla _KPC and bla _NDM . 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 bla _KPC and bla _NDM . This study describes the genome of a bla _KPC and bla _NDM -containing Leclercia adecarboxylata isolate, an opportunistic human pathogen, identified colonizing a hospitalized patient. International L. adecarboxylata isolates have been described harboring bla _NDM-1 ; however, to our knowledge, this represents the first description of L. adecarboxylata harboring bla _NDM-7 , which is a bla _NDM 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.