Synergistic Effects of Capric Acid and Colistin against Colistin-Susceptible and Colistin-Resistant Enterobacterales

Abstract

Colistin is a last-line antibiotic against Gram-negative pathogens. However, the emergence of colistin resistance has substantially reduced the clinical effectiveness of colistin. In this study, synergy between colistin and capric acid was examined against twenty-one Gram-negative bacterial isolates (four colistin-susceptible and seventeen colistin-resistant). Checkerboard assays showed a synergistic effect against all colistin-resistant strains [(FICI, fractional inhibitory concentration index) = 0.02–0.38] and two colistin-susceptible strains. Time–kill assays confirmed the combination was synergistic. We suggest that the combination of colistin and capric acid is a promising therapeutic strategy against Gram-negative colistin-resistant strains.

Antibiotic-Resistant ESKAPE Pathogens and COVID-19: The Pandemic beyond the Pandemic

“…Some noncarbapenem agents, including colistin (or polymyxin E) [ 117 ] and tigecycline [ 118 ], and some Gram-negative bacteria acquired resistance to these drugs [ 119 , 120 ]. Nowadays there are new therapies adopted against CR and colistin-resistant Gram-negative bacteria, including synergistic antimicrobials [ 121 ], such as clofoctol [ 122 ], capric acid [ 123 ], flufenamic acid [ 124 ] and polymyxyn [ 38 ].…”