Characterization of Enterobacter cloacae complex clinical isolates: comparative genomics and the role of the efflux pump AcrAB-TolC over-expression and NDM-1 production

Once the carbapenem MIC surpassed 8 mg/L, the tandem action of the chromosomally over-expressed AcrAB-TolC efflux pump and plasmid-borne <i>bla</i> _NDM-1 carbapenemase rendered ECC virtually untreatable. Mutations in <i>ramR</i> and <i>soxR</i> regulators, as well as promoter insertions or deletions that amplify either system should also be tracked in real-time via sustained surveillance.Effective containment would require combination strategies that simultaneously inhibit efflux, neutralize β-lactamase activity, and destabilized or eliminated the IncF/IncN/IncX3 plasmids carrying <i>bla</i> _NDM-1.