The Journal of antimicrobial chemotherapy · 2026
Genomic evidence of clonal and IncX3 plasmid-mediated dissemination of blaNDM-7 in the Klebsiella pneumoniae complex.
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Zhang Yujing, Ren Guqi, Wu Jing, Xu Jun, Ji Yan, Li Guiling, Wang Zhenyu, Wang Jing, Jiao Xinan, Sun Lin
Аннотация
BACKGROUND: Carbapenem-resistant Enterobacterales (CRE), particularly those carrying New Delhi metallo-β-lactamase (NDM) variants, pose a major global health threat. Among these, NDM-7 has attracted increasing attention due to its enhanced carbapenemase activity and clinical relevance. This study investigated the prevalence, genomic characteristics and dissemination of blaNDM-7-positive Klebsiella pneumoniae complex isolates from clinical and environmental sources in Yangzhou, China.
METHODS: A total of 401 clinical isolates, 282 hospital surface swabs and 366 wastewater samples collected between 2018 and 2024 were screened for blaNDM. Antimicrobial susceptibility testing and whole-genome sequencing were performed to characterize resistance profiles, genomic features and phylogenetic relationships. Conjugation and serial-passage assays were used to assess plasmid transferability and stability, respectively.
RESULTS: Seven blaNDM-7-positive isolates were identified, including one clinical isolate, one hospital environmental isolate and five wastewater isolates. All exhibited multidrug resistance. The blaNDM-7 gene was located on highly conserved ∼46 kb IncX3 plasmids that exhibited high conjugation frequencies (10-5-10-4) and stability (96.0%-98.7% mean retention after approximately 600 generations). Phylogenetic analysis revealed close genomic relatedness among the six ST196 K. quasipneumoniae isolates recovered from different sources, with only 0-7 core-genome SNP differences. All six isolates were recovered within approximately 6 months, consistent with recent common ancestry and possible clonal dissemination across settings.
CONCLUSIONS: The close genomic relatedness of ST196 isolates from different sources supports possible clonal dissemination, while the high conservation, transferability and stability of IncX3 plasmids highlight their important role in the dissemination of blaNDM-7. These findings underscore the importance of continued genomic surveillance of blaNDM-7 and its associated mobile genetic elements across clinical and environmental settings.
METHODS: A total of 401 clinical isolates, 282 hospital surface swabs and 366 wastewater samples collected between 2018 and 2024 were screened for blaNDM. Antimicrobial susceptibility testing and whole-genome sequencing were performed to characterize resistance profiles, genomic features and phylogenetic relationships. Conjugation and serial-passage assays were used to assess plasmid transferability and stability, respectively.
RESULTS: Seven blaNDM-7-positive isolates were identified, including one clinical isolate, one hospital environmental isolate and five wastewater isolates. All exhibited multidrug resistance. The blaNDM-7 gene was located on highly conserved ∼46 kb IncX3 plasmids that exhibited high conjugation frequencies (10-5-10-4) and stability (96.0%-98.7% mean retention after approximately 600 generations). Phylogenetic analysis revealed close genomic relatedness among the six ST196 K. quasipneumoniae isolates recovered from different sources, with only 0-7 core-genome SNP differences. All six isolates were recovered within approximately 6 months, consistent with recent common ancestry and possible clonal dissemination across settings.
CONCLUSIONS: The close genomic relatedness of ST196 isolates from different sources supports possible clonal dissemination, while the high conservation, transferability and stability of IncX3 plasmids highlight their important role in the dissemination of blaNDM-7. These findings underscore the importance of continued genomic surveillance of blaNDM-7 and its associated mobile genetic elements across clinical and environmental settings.