Clinical evolution of New Delhi Metallo-beta-lactamase (NDM) optimizes resistance under Zn(II) deprivation

BAHR, GUILLERMO; VITOR-HOREN, LUISINA; BETHEL, CHRISTOPHER R.; BONOMO, ROBERT A.; VILA, ALEJANDRO J.; GONZÁLEZ, LISANDRO J.

ANTIMICROBIAL AGENTS AND CHEMOTHERAPY

AMER SOC MICROBIOLOGY

Año: 2017

0066-4804

Carbapenem-resistant Enterobacteriaceae (CRE) are rapidly spreading and taking a staggering toll on all healthcare systems, largely due to the dissemination of genes coding for potent carbapenemases. An important family of carbapenemases are the Zn(II)-dependent β-lactamases, known as Metallo-β-lactamases (MBLs). Among them, the New-Delhi Metallo-β-lactamase (NDM) has experienced the fastest and widest geographical spread. While other clinically important MBLs are soluble periplasmic enzymes, NDM β-lactamases are lipoproteins anchored to the outer membrane in Gram-negative bacteria. This unique cellular localization endows NDM with an enhanced stability upon the Zn(II) starvation elicited by the immune system response in the sites of infection. Since the first report of NDM-1 β-lactamase, new allelic variants (16 in total) have been identified in clinical isolates, differing by a limited number of substitutions. Here we show that these variants have evolved by accumulating mutations that enhance their stability or the Zn(II) binding affinity in vivo, overriding the most common evolutionary pressure acting on catalytic efficiency. We identified the ubiquitous mutation M154L as responsible of improving the Zn(II) binding capabilities of the NDM variants. These results also reveal that Zn(II) deprivation imposes a strict constraint in the evolution of this MBL, overriding the most common pressures acting on catalytic performance, and shed light on possible inhibitory strategies.