AUTHOR=Wu Shi , Yin Dandan , Zhi Peiyuan , Guo Yan , Yang Yang , Zhu Demei , Hu Fupin 

TITLE=In Vitro Activity of MRX-8 and Comparators Against Clinical Isolated Gram-Negative Bacilli in China

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=12

YEAR=2022

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2022.829592

DOI=10.3389/fcimb.2022.829592

ISSN=2235-2988

ABSTRACT=<p>To evaluate <italic>in vitro</italic> antibacterial activity of MRX-8 against gram-negative bacteria recently isolated from China, 765 clinical isolates were collected randomly from 2017 to 2020, including <italic>Enterobacterales</italic> and <italic>P. aeruginosa</italic> and <italic>A. baumannii</italic>, <italic>S. maltophilia, B. cepacia, Alcaligenes app.</italic> and <italic>Haemophilus</italic> 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 <italic>E.coli</italic> isolates, the MIC<sub>50/90</sub> of MRX-8 was 0.125/0.25 mg/L and 0.06/0.125 mg/L, respectively. For carbapenem-susceptible and carbapenem-resistant <italic>K. pneumoniae</italic> isolates, the MIC<sub>50/90</sub> 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 <italic>E. coli</italic> and <italic>K. pneumoniae</italic>, MIC<sub>50</sub> of MRX-8 was 4-16 mg/L and MIC<sub>90</sub> was &gt;32 mg/L. The MIC<sub>50</sub> and MIC<sub>90</sub> of MRX-8 for other <italic>Klebsiella</italic> spp. except <italic>K. pneumoniae</italic>, <italic>Citrobacter</italic> spp., <italic>S. enterica</italic> and <italic>Shigella</italic> spp. isolates ranged 0.06-0.125 mg/L and 0.06-0.25mg/L, respectively. For <italic>Morganella</italic> spp.<italic>, Proteus</italic> spp.<italic>, Providencia</italic> spp.<italic>, Serratia</italic> spp., <italic>S. maltophilia</italic> and <italic>B. cepacia</italic>, all MIC<sub>50</sub> of MRX-8 was &gt;32mg/L. For carbapenem susceptible and resistant <italic>P. aeruginosa</italic>, the MIC<sub>50</sub> and MIC<sub>90</sub> of MRX-8 was both 1mg/L, and that for <italic>A. baumannii</italic> was 0.5mg/L and 0.5-1mg/L. For <italic>Alcaligenes</italic> spp. and <italic>Haemophilus</italic> spp., MIC<sub>50/90</sub> 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 <italic>E. coli</italic>, <italic>K. pneumoniae</italic>, <italic>P. aeruginosa</italic> and <italic>A. baumannii</italic>, highlighting its potential as valuable therapeutics.</p>