Membrane anchoring of Metallo-β-lactamase NDM-1 enhances bacterial resistance under zinc deprivation

LISANDRO JAVIER GONZALEZ; GUILLERMO BAHR; TOSHIKI G. NAKASHIGE; ELIZABETH M. NOLAN; ROBERT A. BONOMO; ALEJANDRO JOSÉ VILA

Mount Snow, Vermont

Conferencia; Gordon Research Conference - Cell Biology of Metals; 2015

Gordon Research Conferences

Carbapenems, considered as last resort antibiotics, are inactivated by metallo-β-lactamases. Within this family, worldwide dissemination of New Delhi Metallo-β-lactamase (NDM-1) among Enterobacteriaceae is threatening their therapeutic utility. NDM-1, unlike other known metallo-β-lactamases, is a lipoprotein anchored to the inner leaflet of the outer membrane in Gram-negative bacteria. We show that membrane localization improves the enzyme stability under conditions of Zn(II) starvation, such as those elicited by calprotectin, a chelating protein produced by the host immune system. Membrane-anchoring also facilitates selective secretion of NDM-1 in outer membrane vesicles (OMVs). These OMVs possess carbapenemase activity and are able to protect nearby populations of bacteria from otherwise lethal antibiotic levels, increasing the chances for horizontal gene transfer. Furthermore, we detected the presence of the gene coding for NDM-1 in the lumen of OMVs produced by both lab and clinical strains. Thus, membrane anchoring promotes long-term survival of NDM-1 in OMVs, providing a vehicle for concurrent transfer of NDM-1 and its corresponding DNA sequence. We propose that protein export via OMVs has favored the worldwide spread of NDM-1.