Emerging -positive in Chinese pediatric infections.

Non-typhoidal (NTS) is a common zoonotic foodborne pathogen, whose rising antimicrobial resistance has been an urgent threat to global public health. Here, we reported two carbapenem-resistant (CRSE) strains (NBFE-049 and NBFE-164) carrying the genes, which were recovered from two Chinese children, belonged to serovar Typhimurium (. Typhimurium) monophasic variant (. 1,4,[5],12:i:-) ST34 (a sequence type) and . Typhimurium ST19, respectively. Genes and were detected in NBFE-049 and NBFE-164, respectively. The in NBFE-049 was located in an IncHI2-type plasmid, named pNBFE-049. In NBFE-164, the was located in an IncI1-type plasmid, named pNBFE-164. The plasmid pNBFE-164 successfully transferred its resistance phenotype into the recipient strain J53 with a high efficiency of 1.1 × 10, while no transconjugants were obtained in pNBFE-049 conjugation assays. We further elucidated the genetic relationships of globally occurring New Delhi Metallo-β-lactamase (NDM)-positive strains and locally distributed clinical strains within the same serovar. The closest relative of NBFE-049 was clinical strain 1722, which was recovered in 2020 and differed by only three Single Nucleotide Polymorphisms (SNPs). No NDM-positive ST19 could be found in the National Center for Biotechnology Information (NCBI) database, and NBFE-164 showed a close genetic relationship with the other ST19 in this area. To sum up, we suggested the potential contributions of clonal spread and plasmid-mediated transfer in CRSE dissemination. This study reported the complete genome of two -carrying . Typhimurium isolates, shedding new insights into the antimicrobial resistance mechanisms and dissemination patterns of the emerging CRSE.IMPORTANCENTS is one of the most common zoonotic pathogens that causes foodborne illnesses, while . Typhimurium is one of the most common serovars. With the rising prevalence of multi-resistant worldwide, carbapenems have emerged as the last-line antibiotics for treating severe bacterial infections. In this study, we reported the genomic characteristics of two carbapenem-resistant . Typhimurium strains, which were recovered from two pediatric patients, carrying and , providing new insights into the antimicrobial resistance deteriminants and transmission risk of -positive NTS in China. We suggested the potential contributions of clonal spread and plasmid-mediated transfer in CRSE dissemination. Future enhanced surveillance policy should mitigate CRSE spreading, and more importantly, clinical antimicrobial therapeutic regimens should be adjusted accordingly.