# Dissemination of a blaNDM − 1-harboring IncH plasmid associated with concurrent ST30 Klebsiella pneumoniae and ST2 Klebsiella oxytoca outbreaks in a Chinese neonatal unit

## TL;DR

This study reports a neonatal outbreak in China involving drug-resistant Klebsiella strains sharing a plasmid that spreads antibiotic resistance.

## Contribution

First global neonatal outbreak by CRKP ST30 and first CRKO ST2 report in China, revealing novel plasmid-mediated transmission patterns.

## Key findings

- CRKP ST30 and CRKO ST2 strains were clonally disseminated in a NICU, carrying the blaNDM-1 gene.
- IncH-type plasmids with high homology to pNDM-MAR were identified, containing multiple resistance genes and mobile elements.
- Conjugation experiments confirmed plasmid transfer to E. coli, highlighting the risk of resistance spread.

## Abstract

Carbapenem-resistant Klebsiella pneumoniae (CRKP) and Klebsiella oxytoca (CRKO) strains threaten neonatal health. This study investigates concurrent outbreaks in a Chinese neonatal intensive care unit (NICU).

We characterized 13 clinical isolates (10 CRKP [TJ01–TJ10] and 3 CRKO [TJ11–TJ13]) recovered from preterm infants between September 2013 and January 2014. The whole genome sequencing of strains (CRKP TJ03 and CRKO TJ11) was performed using MiSeq and MinION platforms, while the plasmids pNDM-TJ03 and pNDM-TJ11 were derived from the above-mentioned strains. Antimicrobial susceptibility testing, plasmid conjugal transfer, and other experiments were conducted.

PFGE revealed clonal dissemination of CRKP ST30 and CRKO ST2 strains. This represents both the first documented neonatal outbreak caused by CRKP ST30 globally and the first report of CRKO ST2 in China, demonstrating novel transmission patterns of these high-risk clones in neonatal settings. All isolates carried blaNDM − 1, blaOXA − 1, blaDHA − 1, qnrB4, and aac(6′)-Ib-cr genes. Plasmid analysis identified both as IncH-type, showing high homology with pNDM-MAR. Their structure included contained a conserved IncH backbone region and separate accessory modules that contained five insertion sequences, transposon Tn6344, and a multidrug-resistant (MDR) region. The MDR region contained four mobile elements (ΔTn125, ΔInRBDHA, ΔTn1548, and ΔTn5393c) carrying a complement of 10 resistance genes. Conjugation experiments confirmed successful transfer of both plasmids to Escherichia coli J53AziR.

This study demonstrates that there may have been intra-strain and inter-species spread of a blaNDM − 1-harboring IncH plasmid in the NICU. Our findings provide new insights into horizontal transfer of resistance genes mediated by IncH-type plasmids.