Meropenem-Vaborbactam Tested against Contemporary Gram-Negative Isolates Collected Worldwide during 2014, Including Carbapenem-Resistant, KPC-Producing, Multidrug-Resistant, and Extensively Drug-Resistant Enterobacteriaceae

We evaluated the activity of meropenem-vaborbactam against contemporary nonfastidious Gram-negative clinical isolates, includingEnterobacteriaceae isolates with resistance phenotypes and carbapenemase genotypes. Meropenem-vaborbactam (inhibitor at 8 μg/ml) and comparators were susceptibility tested by reference broth microdilution methods against 14,304 Gram-negative clinical isolates collected worldwide during 2014. Carbapenemase-encoding genes were screened by PCR and sequencing. Meropenem-vaborbactam (MIC50/90 , ≤0.015/0.06 μg/ml) inhibited 99.1 and 99.3% of the 10,426Enterobacteriaceae isolates tested at ≤1 and ≤2 μg/ml, respectively. Meropenem inhibited 97.3 and 97.7% of these isolates at the same concentrations. AgainstEnterobacteriaceae isolates displaying carbapenem-resistantEnterobacteriaceae (CRE) (n = 265), multidrug-resistant (MDR) (n = 1,210), and extensively drug-resistant (XDR) (n = 161) phenotypes, meropenem-vaborbactam displayed MIC50/90 values of 0.5/32, 0.03/1, and 0.5/32 μg/ml, respectively, whereas meropenem activities were 16/>32, 0.06/32, and 0.5/32 μg/ml, respectively. Among all geographic regions, the highest meropenem-vaborbactam activities were observed for CRE and MDR isolates from the United States (MIC50/90 , 0.03/1 and 0.03/0.12 μg/ml, respectively). Meropenem-vaborbactam was very active against 135 KPC producers, and all isolates were inhibited by concentrations of ≤8 μg/ml (133 isolates by concentrations of ≤2 μg/ml). This combination had limited activity against isolates producing metallo-β-lactamases (including 25 NDM-1 and 16 VIM producers) and/or oxacillinases (27 OXA-48/OXA-163 producers) that were detected mainly in Asia-Pacific and some European countries. The activity of meropenem-vaborbactam was similar to that of meropenem alone againstPseudomonas aeruginosa ,Acinetobacter spp., andStenotrophomonas maltophilia . Meropenem-vaborbactam was active against contemporaryEnterobacteriaceae isolates collected worldwide, and this combination demonstrated enhanced activity compared to those of meropenem and most comparator agents against CRE isolates and KPC producers, the latter of which are often MDR.