In Vitro Susceptibility of Nonfermenting Gram-negative Rods to Meropenem-Vaborbactam and Delafloxacin.

Aim: Meropenem-vaborbactam and delafloxacin activities were not assessed against Achromobacter spp. (Achr), Burkholderia cepacia complex (Bcc) and Stenotrophomonas maltophilia (Smal). Methodology: A total of 106 Achr, 57 Bcc and 100 Smal were tested with gradient diffusion test of meropenem-vaborbactam, delafloxacin and comparators. Results: Meropenem-vaborbactam MIC50 were 4 mu g/ml for Achr, 1 mu g/ml for B. cepacia, 2 mu g/ml for B. cenocepacia and B. multivorans, and 32 mu g/ml for Smal. Delafloxacin MIC50 were 4 mu g/ml for Achr, 0.25 mu g/ml for B. cepacia and B. multivorans, 2 mu g/ml for B. cenocepacia, and 0.5 mu g/m for Smal. meropenem-vaborbactam MICs were fourfold lower than meropenem for 28.3% Achr, 77.2% B. cepacia, 53.8% B. cenocepacia and 77.2% B. multivorans. Conclusion: Meropenem-vaborbactam and delafloxacin are in vitro active against Bcc and Achr. Plain language summary: We assess the efficacy of two new antibiotics, meropenem-vaborbactam and delafloxacin, to kill rarely encountered bacteria. These bacteria, Achromobacter, Burkholderia and Stenotrophomonas maltophilia, mainly cause respiratory tract infections. Both antibiotics are found active against Achromobacter and Burkholderia, but not S. maltophilia. Meropenem-vaborbactam (Vaborem((R))) and delafloxacin (Quofenix((R))) are active against most strains of Achromobacter and Burkholderia cepacia complex, but against not S. maltophilia