Anti-VIM monoclonal antibody, clone Wjn 4C5

In the search for new inhibitors of bacterial metallo beta-lactamases (MBLs), a series of commonly used small molecule carboxylic acid derivatives were evaluated for their ability to inhibit New Delhi metallo-beta-lactamase (NDM)-, Verona integronencoded metallo-beta-lactamase (VIM)-, and imipenemase (IMP)-type enzymes. Nitrilotriacetic acid (3) and N-(phosphonomethyl)iminodiacetic acid ( 5) showed promising activity especially against NDM-1 and VIM-2 with IC50 values in the low-to-sub mu M range. Binding assays using isothermal titration calorimetry reveal that 3 and 5 bind zinc with high affinity with dissociation constant (K-d) values of 121 and 56 nM, respectively. The in vitro biological activity of 3 and 5 against E. coli expressing NDM-1 was evaluated in checkerboard format, demonstrating a strong synergistic relationship for both compounds when combined with Meropenem. Compounds 3 and 5 were then tested against 35 pathogenic strains expressing MBLs of the NDM, VIM, or IMP classes. Notably, when combined with Meropenem, compounds 3 and 5 were found to lower the minimum inhibitory concentration (MIC) of Meropenem up to 128-fold against strains producing NDM- and VIM-type enzymes.

Carbapenemase-producing Enterobacterales expressing OXA-48, KPC, NDM, VIM or IMP enzymes are increasingly reported worldwide. We have characterized LMB-1, a novel metallo-beta-lactamase (MBL) of Ambler class B3 from Citrobacter freundii 164 (Cf164) clinical isolate from Buenos Aires, Argentina. Cf164 displayed reduced susceptibility to carbapenems but gave inconsistent results with carbapenemase confirmatory tests, indicating the presence of a weak carbapenemase. Analysis of whole-genome sequencing (WGS) of Cf164 using Resfinder revealed four beta-lactamase genes coding for CTX-M-8, PER-2, TEM-1 and CMY-150, a novel chromosomally-encoded CMY variant. Kinetic parameters of purified CMY-150 did not reveal any carbapenemase activity. However, CMY-150 conferred higher minimum inhibitory concentrations (MICs) to E. coli for ceftazidime and aztreonam compared with CMY-2. The in-house-developed beta-lactamase search software (ResMiner) in WGS data revealed a novel subclass B3 MBL named LMB-1. LMB-1 conferred resistance to penicillins and expanded-spectrum cephalosporins and reduced susceptibility to carbapenems in E. coli. The bla(LMB-1) gene was located on a 176-kb IncA/C2 plasmid. LMB-1 shared 99% amino acid sequence identity with the MBL encoded in the chromosome of Rheinheimera pacifica, it's likely progenitor. Despite repeated attempts, LMB-1 could not be purified, thus only specific activities could indicate hydrolysis of carbapenems. Here we report on CMY-150, a novel CMY-2 variant that confers increased ceftazidime and aztreonam MICs to E. coli and the first description of LMB-1 in Argentina. This work underlines the need for several carbapenemase-producing Enterobacteriaceae (CPE) confirmatory tests, as this novel enzyme might have been missed using only one. (C) 2019 Elsevier B.V. and International Society of Chemotherapy. All rights reserved.