Genomic Insights into the First Emergence of -Carrying Carbapenem-Resistant Serovar London Strain in China.

Carbapenem-resistant pose a significant threat to public health, causing gastroenteritis and invasive infections. We report the first emergence of a carbapenem-resistant serovar London strain, A132, carrying the gene in China. Whole-genome sequencing and bioinformatics analysis assigned A132 to be ST155, a multidrug-resistant clone frequently reported in China. The strain A132 exhibited resistance to multiple antibiotics, with 20 acquired antibiotic resistance genes (ARGs) identified, predominantly located on the IncFIB plasmid (pA132-1-NDM). Notably, the gene was located within an IS flanked-class 1 integron-IS complex, comprising two genetic cassettes. One cassette is the class 1 integron, which may facilitate the transmission of the entire complex, while the other is the -containing ISISflanked cassette, carrying multiple other ARGs. Genbank database search based on the -carrying cassette identified a similar genetic context found in transmissible IncFIA plasmids from (p91) and (p388) with a shared host range, suggesting the potential for cross-species transmission of . To our knowledge, this is the first reported case of serovar London ST155 harboring gene. Phylogenetic analysis indicated a close relationship between A132 and eight . London ST155 strains isolated from the same province. However, A132 differed by carrying the gene and four unique ARGs. Given the high transmissibility of the F-type plasmid harboring and 18 other ARGs, it is imperative to implement vigilant surveillance and adopt appropriate infection control measures to mitigate the threat to public health.