The polyamino-isoprenyl potentiator NV716 revives disused antibiotics against Gram-negative bacteria in broth, infected monocytes, or biofilms, by disturbing the barrier effect of their outer membrane

International audiencePotentiators can improve antibiotic activity against difficult-to-treat Gram-negative bacteria like Escherichia coli, Klebsiella pneumoniae or Acinetobacter baumannii. They represent an appealing strategy in view of the paucity of therapeutic alternatives in case of multidrug resistance. Here, we examine the ability of the polyamino-isoprenyl compound NV716 to restore the activity of a series of disused antibiotics (rifampicin, azithromycin, linezolid, fusidic acid, novobiocin, chloramphenicol, and doxycycline, plus ciprofloxacin as an active drug) against these three species in planktonic cultures, but also in infected human monocytes and biofilms and we study its underlying mechanism of action. NV716 considerably reduced the MICs of these antibiotics (2–11 doubling dilutions), the highest synergy being observed with the more lipophilic drugs. This potentiation was related to a strong interaction of NV716 with LPS, ensuing permeabilization of the outer membrane, and leading to an increased accumulation of the antibiotics inside bacteria. Moreover, NV716 increased the relative potency of all drugs against intracellular infection by the same bacteria as well as their maximal efficacy, probably related to an improvement of antibiotic activity against persisters. Lastly, NV716 also enhanced rifampicin activity against biofilms from these three species. All these effects were observed at sub-MIC concentrations of NV716 (and thus unrelated to a bactericidal effect), and in conditions for which no toxicity was evidenced towards eukaryotic cells. Altogether, these data highlight for the first time the potential interest of NV716 as an adjuvant against these Gram-negative pathogens placed in the priority list of WHO for search of new therapies