<i>Enterobacterales</i> use capsules, transporters, mobile genetic elements, and other evolutionary adaptations to survive antibiotics exposure in the absence of resistance genes

In the absence of canonical carbapenemase and <i>mcr</i> genes, <i>K. pneumoniae</i> and <i>Enterobacter</i> species can deploy a spectrum of adaptive mechanisms, including efflux pumps, mobile elements, and altered outer membrane/capsule structures, to overcome colistin and carbapenem treatments. These findings support the need for ongoing surveillance of novel or underrecognized resistance mechanisms to preserve the efficacy of last-line antibiotics.