Tight linkage between the SOS response and horizontal transfer of blaNDM-carrying IncX3 plasmid in Carbapenem-resistant Enterobacteriaceae

The rapid dissemination of the blaNDM gene among Enterobacteriaceae in children has become a prominent public health concern in the pediatric population. blaNDM is mainly located on IncX3 and can be horizontally transferred across different bacterial species via conjugation. The SOS response can promote plasmid conjugation, thereby facilitating the plasmid-mediated transfer of antimicrobial resistance genes. However, it remains unclear whether, and if so, how the SOS response participates in the spread of blaNDM mediated by IncX3 plasmids (blaNDM-IncX3).Herein, we collected a total of 250 clinical CRE strains from Children’s Hospital of Fudan University, and retrieved 4210 carbapenemase gene-carrying plasmids and 1780 publicly available IncX3 plasmids from public databases. After confirmation the close linkage between blaNDM and IncX3 plasmids, we found blaNDM-IncX3 plasmids specifically express the SOS-promoting factors including stpA, rfaH, pir, bin3, virD4, and virB1-11, while lacked the anti-SOS genes such as psiB, ssb, and spo0C. These findings reveal a compelling genetic basis: blaNDM-IncX3 plasmids are enriched in SOS-promoting factors but deficient in SOS inhibitors, indicating that an enhanced SOS response may contribute to their successful dissemination.