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

O van Katwijk1, M Mulder2, L van Alphen2

  • 1Department of Medical Microbiology, Infectious Diseases and Infection Prevention, Maastricht University Medical Centre, Maastricht, the Netherlands. Oscar.katwijk@mumc.nl.

European Journal of Clinical Microbiology & Infectious Diseases : Official Publication of the European Society of Clinical Microbiology
|October 31, 2025
PubMed
Abstract

Insights

A patient became a carrier of NDM-producing Citrobacter freundii, later developing abscesses and acquiring three more carbapenem-resistant species. Mobile genetic elements facilitated resistance gene transfer within the patient.

Area of Science:

  • Medical Microbiology
  • Infectious Diseases
  • Antimicrobial Resistance

Background:

  • Carbapenemase-producing Enterobacteriaceae (CPE) pose a significant global health threat.
  • The blaNDM gene is a common carbapenemase, often located on mobile genetic elements.
  • Horizontal gene transfer (HGT) plays a crucial role in the dissemination of antimicrobial resistance.

Purpose of the Study:

  • To report a case of a patient colonized with blaNDM-producing Citrobacter freundii.
  • To investigate the emergence of additional carbapenemase-producing species in the same patient.
  • To explore the role of mobile genetic elements in the spread of antimicrobial resistance within a single host.

Main Methods:

  • Case report detailing clinical course and microbiological findings.
  • Identification of bacterial species and antimicrobial susceptibility testing.
  • Molecular analysis to characterize the carbapenemase genes and plasmids, including incX3 plasmid analysis.
  • Assessment of horizontal gene transfer events.

Main Results:

  • A 73-year-old male was identified as a carrier of blaNDM-producing Citrobacter freundii post-admission.
  • The patient developed abdominal abscesses and received piperacillin-tazobactam treatment.
  • Over subsequent months, three additional carbapenemase-positive species (Klebsiella oxytoca, Raoultella planticola, Serratia marscescens) were detected.
  • All identified species harbored the blaNDM-7 gene on an incX3 plasmid, indicating HGT within the patient.

Conclusions:

  • This case highlights the dynamic nature of antimicrobial resistance acquisition within a single patient.
  • Mobile genetic elements, specifically the incX3 plasmid carrying blaNDM-7, facilitated the spread of resistance among different bacterial species.
  • Effective infection control strategies must consider the role of mobile genetic elements in transmitting antimicrobial resistance.
Keywords:
Antimicrobial resistanceCarbapenemase-producingHorizontal gene transferIncX3Infection controlblaNDM7

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