Novel Molecular Mechanisms Providing Fitness in Carbapenem Resistance

DOTTA GINA; CAROLINA LÓPEZ; A. J. VILA; GONZÁLEZ LISANDRO J; BAHR GUILLERMO; GIANNINI ESTEFANÍA; PALACIOS ANTONELA R.; TOMATIS PABLO E.; JULIANA DELMONTI

Simposio; Middleton Symposium, Cleveland, 2018.; 2018

Metallo-beta-lactamases (MBLs) are the latestresistance mechanism of pathogenic and opportunistic bacteria againstcarbapenems, considered as last resort drugs. The worldwide spread of genescoding for these enzymes, together with the lack of a clinically usefulinhibitor, have raised a sign of alarm. Inhibitor design has been mostlyimpeded by the structural diversity of these enzymes.  Zn(II) binding is critical in the bacterialperiplasm, not only to activate these enzymes and provide resistance, but alsoto stabilize the protein scaffold. This phenomenon is not paralleled by in vitro studies. We have developed astrategy aimed to correlate the biochemical and biophysical features inpurified enzymes with those in the bacterial periplasm, ultimately leading tothe selected phenotype, i.e., resistance to antibiotics. We show that optimizationof the Zn(II) binding affinity is key in MBL evolution, and this feature istuned by the response of the immune system that elicits metal starvation duringinfection. Finally, we have found that in NDM, the NewDelhi Metallo-beta-lactamase, one of the most potent and widespread lactamases,membrane anchoring provides a stabilizing effect upon zinc starvationconditions, as those present during bacterial infection. Moreover, this cellularlocalization allows selective export of this enzyme into outer membranevesicles that provide a novel mechanism to spread resistance.  References 1.      L.J. González et al. Nature Chemical Biology 2016 12, 516.2.      Bahret al., Antimicrob Agents Chemother. 2017;62(1). pii: e01849-173.      Lisa,Palacios et al. Nature Commun. 2017,8, 5384.      M.R. Meini et al. Mol.Biol.Evol. 2015, 32, 1774.