Pentamidine Sensitizes FDA-approved Non-antibiotics For The Inhibition Of Multidrug-resistant Gram-negative Bacteria

Gram-negative pathogens have rendered many antibiotics ineffective and their increasing resistance is seriously endangering human health.Pentamidine has been serving as a good example for the combination-based approach of drug repurpo sing.Originally used as an anti-malarial and anti-fungal drug,pentamidine was later found to sensitize FDA-approved antibiotics,such as rifampin,novobiocin and erythromycin,granting them the ability to combat against multiple gram-negative pathogens,such as Escherichia coli,Acinetobacter baumannii and Klebsiella pneumoniae.The mechanism of such sensitization was reported to be lipopolysaccharide（LPS）binding,followed by permeabilization of the outer membrane of gram-negative bacteria to increase t he intracellular concentration of antibiotics.In this research,we show that pentamidine,which itself is a repurposed antimicrobial drug,can also sensitize compounds that were not commonly used as antibiotics,repurposing them into new antimicrobial age nts.We screened 1374 FDA-approved non-antibiotics for their ability to be sensitized by pentamidine against E.coli,and identified mitomycin C and mefloquine as potent hits effective against multiple drug-resistant,gram-negative bacteria.Killing kineti cs revealed that the combination of pentamidine with mitomycin C or mefloquine produced synergy against colistin-resistant Enterobacter cloacae,reducing the bacterial load by 5.1 and7.9 log₁₀ CFU/m L,respectively,within 24 h.The study using an infectio n model of Caenorhabditis elegans also showed synergistic effect of pentamidine/mitomycin C in bacterial inhibition and killing,which is comparable to the antibiotic ciprofloxacin.In general,the combination of pantamidine showed excellent and broad-spectrum synergistic inhibition against clinically resistant gram-negative bacteria.