Co-integrate Col3m -harboring plasmids in clinical isolates from Argentina.

The first cases of in Argentina were detected in three (Pre) recovered from two hospitals in Buenos Aires city in 2013. The isolates were genetically related, but the plasmid profile was different. Here, we characterized the -harboring plasmids of the first three cases detected in Argentina. Hybrid assembly obtained from short- and long-read sequencing rendered in Col3M plasmids of . 320 kb (p15268A_320) in isolate PreM15268, 210 kb (p15758B_210) in PreM15758, and 225 kb (p15973A_225) in PreM15973. In addition, PreM15758 harbored a 98-kb circular plasmid (p15758C_98) flanked by a putative recombination site (-Tn), with 100% nucleotide ID and coverage with p15628A_320. Analysis of PFGE/S1-nuclease gel, Southern hybridization with probe, hybrid assembly of short and long reads suggests that pM15758C_98 can integrate by homologous recombination. The three -plasmids were non-conjugative . Moreover, genes were incomplete, and oriT was not found in the three -plasmids. In two isolates, bla was embedded in a partially conserved structure flanked by two IS. In addition, all plasmids harbored , , and D1 genes and , , B3, and as part of a class 1 integron. Also, p15268A_320 and p15973A_225 harbored . To the best of our knowledge, this is the first report of clinical harboring bla in an atypical genetic environment and located in unusual chimeric Col3M plasmids. The study and continuous surveillance of these pathogens are crucial to tracking the evolution of these resistant plasmids and finding solutions to tackle their dissemination. IMPORTANCE Infections caused by carbapenem hydrolyzing enzymes like NDM (New Delhi metallo-beta-lactamase) represent a serious problem worldwide because they restrict available treatment options and increase morbidity and mortality, and treatment failure prolongs hospital stays. The first three cases of NDM in Argentina were caused by genetically related recovered in two hospitals. In this work, we studied the genetic structure of the plasmids encoding in those index cases and revealed the enormous plasticity of these genetic elements. In particular, we found a small plasmid that was also found inserted in the larger plasmids by homologous recombination as a co-integrate element. We also found that the plasmids were not able to transfer or move to other hosts, suggesting their role as reservoir elements for the acquisition of resistance genes. It is necessary to unravel the dissemination strategies and the evolution of these resistant plasmids to find solutions to tackle their spread.