IncX3 plasmid-mediated spread of blaNDM gene in Enterobacteriaceae among children in China

blaNDM gene was prevalent among children, and became the predominant cause of severe infection in infants and children. This study aimed to investigate the epidemiology and molecular characteristics of blaNDM in Enterobacteriaceae among children in China. Carbapenem-resistant Enterobacteriaceae (CRE) were collected in the Children's Hospital of Fudan University from January 2016 to December 2022. Five carbapenemase genes (blaKPC, blaNDM, blaVIM, blaIMP, blaOXA-48) were screened by PCR method. Multilocus sequence typing (MLST) was conducted for phylogenetic analyses. blaNDM-carrying plasmids were typed by PCR-based Incompatibility (Inc) typing method. Moreover, plasmid comparison was performed with 213 publicly available IncX3 plasmids. A total of 330 CRE strains were enrolled, 96.4% of which carried carbapenemase genes. blaNDM gene accounted for 64.8% (214 strains) and included four variants, including blaNDM-1 (59.8%), blaNDM-5 (39.3%), blaNDM-7 (0.5%) and blaNDM-9 (0.5%). There were no predominant MLST lineages of blaNDM carrying strains. IncX3 was the major plasmid carrying blaNDM-1 (68.0%) and blaNDM-5 (72.6%), and was dominant in blaNDM-K. penumoniae (79.8%), blaNDM-E. coli (58.2%) and blaNDM-E. cloacae (61.0%), respectively. Majority (79.0%) of clinical IncX3 plasmids in the world carried blaNDM, and the prevalence of blaNDM in IncX3 plasmids was more common in China (95.8%) than other countries (58.1%, p<0.01). blaNDM is highly prevalent in CREs among children in China. The spread of blaNDM was mainly mediated by IncX3 plasmids. Surveillance and infection control on the spread of blaNDM among children are important.