# Within patient horizontal gene transfer dynamics of a blaNDM−7 plasmid among four different bacterial species

## TL;DR

A patient carried a carbapenem-resistant plasmid across four bacterial species, showing how antibiotic resistance spreads within a single person.

## Contribution

This case report demonstrates horizontal gene transfer of a blaNDM−7 plasmid among multiple bacterial species within one patient.

## Key findings

- A patient carried a blaNDM−7 plasmid in Citrobacter freundii, Klebsiella oxytoca, Raoultella planticola, and Serratia marscescens.
- The plasmid was horizontally transferred within the patient, not through identical bacterial strain spread.
- Mobile genetic elements like the incX3 plasmid play a key role in spreading antimicrobial resistance.

## Abstract

We describe the case of a 73-year old male who was found to be a carrier of an blaNDM -producing Citrobacter freundii shortly after admission. During his admission, he developed abdominal abscesses and received multiple courses of piperacillin-tazobactam. In the following months, he was found to carry three other carbapenemase-positive species: Klebsiella oxytoca, Raoultella planticola and Serratia marscescens.

Two of these strains had clustering carbapenem-sensitive isolates cultured before. The species all carried an blaNDM−7 encoding incX3 plasmid, which demonstrated horizontal gene transfer within this patient.

This case report underlines the importance of mobile genetic elements in infection control, as they serve as transmission vehicles for antimicrobial resistance beyond the spread of identical bacterial strains.

The online version contains supplementary material available at 10.1007/s10096-025-05327-x.