Investigating the molecular transmission dynamics of <i>bla</i> _NDM in antibiotic-selective environments

Carbapenem resistance mediated by <i>bla</i>_NDM-encoded metallo-beta-lactamases is often linked to IS<i>Aba125</i>, an insertion sequence from the IS<i>30</i> family, which is widely distributed among critical and high-priority bacterial pathogens. The rapid dissemination of IS<i>Aba125</i>-linked <i>bla</i>_NDM in both nosocomial and community-acquired infections presents a serious challenge to healthcare systems and pharmaceutical industries. Despite the urgency of this issue, the factors driving <i>bla</i>_NDM spread and the molecular mechanisms governing IS<i>Aba125</i> mobility remain poorly understood. In this study, we engineered the genomes of <i>Vibrio cholerae</i> and <i>Escherichia coli</i> to investigate the mobility of <i>bla</i>_NDM under controlled conditions both with and without the genetically linked IS<i>Aba125</i>. We also examined the transmission efficiency and the stability of <i>bla</i>_NDM in environments with and without sublethal antibiotic concentrations. Our <i>in vitro</i> findings were validated in a rabbit ileal loop model. The results revealed that antibiotic pressure significantly influences the mobility of <i>bla</i>_NDM, shedding light on the molecular dynamics of its transmission. These insights are crucial for developing strategies to curb the spread of <i>bla</i>_NDM and mitigate the growing threat of carbapenem resistance in bacterial pathogens.IMPORTANCEInsertion sequences are the simplest form of mobile genetic elements that play a critical role in the adaptation of bacteria, allowing them to rapidly acquire new traits like resistance genes that enhance their survival. IS<i>Aba125</i> is one such insertion sequence that facilitates the spread of <i>bla</i>_NDM, contributing to the global challenge of carbapenem resistance. In this study, we developed reporter strains that could be used as a valuable tool for investigating the dynamics of IS<i>Aba125-</i>linked <i>bla</i>_NDM<i>sh-ble</i> and evaluated the transposition frequency of IS<i>Aba125-</i>linked <i>bla</i>_NDM<i>sh-ble</i> in the presence and absence of sublethal concentration of antibiotics. Our results demonstrated that IS<i>Aba125</i> enhances the spread of <i>bla</i>_NDM<i>sh-ble</i> under sublethal concentration of antibiotics that induces SOS response.