Activity of MRX-8 and Comparators Against Clinical Isolated Gram-Negative Bacilli in China.

To evaluate antibacterial activity of MRX-8 against gram-negative bacteria recently isolated from China, 765 clinical isolates were collected randomly from 2017 to 2020, including and and , and spp. isolates. All strains were performed with antimicrobial susceptibility testing by broth microdilution method according to the CLSI 2021. Antimicrobial agents included MRX-8, polymyxin B, colistin, amikacin, ceftriaxone, ceftazidime, cefepime, ceftazidime-avibactam, cefoperazone-sulbactam, meropenem, ciprofloxacin, ampicillin, ampicillin-sulbactam and levofloxacin. For carbapenem-susceptible and carbapenem-resistant isolates, the MIC of MRX-8 was 0.125/0.25 mg/L and 0.06/0.125 mg/L, respectively. For carbapenem-susceptible and carbapenem-resistant isolates, the MIC of MRX-8 was 0.25/0.5 mg/L and 0.125/0.5 mg/L, respectively. For polymyxins (polymyxin B and colistin)-resistant and , MIC of MRX-8 was 4-16 mg/L and MIC was >32 mg/L. The MIC and MIC of MRX-8 for other spp. except , spp., and spp. isolates ranged 0.06-0.125 mg/L and 0.06-0.25mg/L, respectively. For spp. spp. spp. spp., and , all MIC of MRX-8 was >32mg/L. For carbapenem susceptible and resistant , the MIC and MIC of MRX-8 was both 1mg/L, and that for was 0.5mg/L and 0.5-1mg/L. For spp. and spp., MIC was 1/4 mg/L and 0.25/0.5 mg/L. MRX-8 was more effective against most clinically isolated gram-negative isolates, including carbapenem-resistant , , and , highlighting its potential as valuable therapeutics.