The Polyaminoisoprenyl Potentiator NV716 Revives Old Disused Antibiotics against Intracellular Forms of Infection by Pseudomonas aeruginosa

Active efflux confers intrinsic resistance to multiple antibiotics in Pseudomonas aeruginosa, including old disused molecules. Beside resistance, intracellular survival is another reason for failure to eradicate bacteria with antibiotics. We evaluated the capacity of polyaminoisoprenyl potentiators (designed as efflux pump inhibitors [EPIs]) NV716 and NV731 compared to PA/3N to restore the activity of disused antibiotics (doxycycline, chloramphenicol [substrates for efflux), and rifampin [nonsubstrate]) in comparison with ciprofloxacin against intracellular P. aeruginosa (strains with variable efflux levels) in THP-1 monocytes exposed over 24 h to antibiotics alone (0.003 to 100x MIC) or combined with EPIs. Pharmacodynamic parameters (apparent static concentrations [C-s] and maximal relative efficacy (E-max]) were calculated using the Hill equation of concentration-response curves. PA beta N and NV731 moderately reduced (0 to 4 doubling dilutions) antibiotic MICs but did not affect their intracellular activity. NV716 markedly reduced (1 to 16 doubling dilutions) the MIC of all antibiotics (substrates or not for efflux; strains expressing efflux or not); it also improved their relative potency and maximal efficacy (i.e., lower C-s; more negative E-max) intracellularly. In parallel, NV716 reduced the persister fraction in stationary cultures when combined with ciprofloxacin. In contrast to PA beta N and NV731, which act only as EPIs against extracellular bacteria, NV716 can resensitize P. aeruginosa to antibiotics whether they are substrates or not for efflux, both extracellularly and intracellularly. This suggests a complex mode of action that goes beyond a simple inhibition of efflux to reduce bacterial persistence. NV716 appears to be a useful adjuvant, including to disused antibiotics with low antipseudomonal activity, to improve their activity, including against intracellular P. aeruginosa.

Automated summary

The study found that the polyaminoisoprenyl potentiator NV716 significantly reduced the minimum inhibitory concentration of multiple antibiotics against Pseudomonas aeruginosa and improved their intracellular activity. Compared to other two potentiators, NV716 can resensitize P. aeruginosa to antibiotics both extracellularly and intracellularly, indicating a complex mode of action.