Conessine as a novel inhibitor of multidrug efflux pump systems in Pseudomonas aeruginosa

Abstract

Background Holarrhena antidysenterica has been employed as an ethnobotanical plant for the treatment of dysentery, diarrhoea, fever, and bacterial infections. Biological activities of the principle compound, conessine including anti-diarrhoea and anti-plasmodial effects were documented. Our previous study reported potency of Holarrhena antidysenterica extract and conessine as resistance modifying agents against extensively drug-resistant Acinetobacter baumannii. This study aimed to investigate (i) whether conessine, a steroidal alkaloid compound, could act as a resistance modifying agent against multidrug-resistant Pseudomonas aeruginosa, and (ii) whether MexAB-OprM efflux pump involved in the mechanism.MethodsConessine combined with various antibiotics were determined for synergistic activity against P. aeruginosa PAO1 strain K767 (wild-type), K1455 (MexAB-OprM overexpressed), and K1523 (MexB deletion). H33342 accumulation assay was used to evaluate efflux pump inhibition while NPN uptake assay was assessed membrane permeabilization.ResultsConessine significantly reduced MICs of all antibiotics by at least 8-fold in MexAB-OprM overexpressed strain. The levels were comparable to those obtained in wild-type strain for cefotaxime, levofloxacin, and tetracycline. With erythromycin, novobiocin, and rifampicin, MICs were 4- to 8-fold less than MICs of the wild-type strain. Loss of MexAB-OprM due to deletion of mexB affected susceptibility to almost all antibiotics, except novobiocin. Synergistic activities between other antibiotics (except novobiocin) and conessine observed in MexB deletion strain suggested that conessine might inhibit other efflux systems present in P. aeruginosa. Inhibition of H33342 efflux in the tested strains clearly demonstrated that conessine inhibited MexAB-OprM pump. In contrast, the mode of action as a membrane permeabilizer was not observed after treatment with conessine as evidenced by no accumulation of 1-N-phenylnaphthylamine.ConclusionsThe results suggested that conessine could be applied as a novel efflux pump inhibitor to restore antibiotic activity by inhibiting efflux pump systems in P. aeruginosa. The findings speculated that conessine may also have a potential to be active against homologous resistance–nodulation–division (RND) family in other Gram-negative pathogens.

Detection of adeABC efllux pump encoding genes and antimicrobial effect of Mentha longifolia and Menthol on MICs of imipenem and ciprofloxacin in clinical isolates of Acinetobacter baumannii

“…Many compounds extracted from the plant were introduced as EPI which inhibited bacterial pathogens. These compounds affected different efflux pumps including: MexAB-OprM in Pseudomonas aeruginosa; Nor A in Staphylococcus aureus, Bacillus cereus, Staphylococcus epidermidis, and Salmonella enteritidis; ND in Escherichia coli and Food-borne pathogens; and Msr A and Tet K in S. epidermidis [34][35][36][37][38][39][40][41][42].…”

Indigenous Medicinal Plants as Biofilm Inhibitors for the Mitigation of Antimicrobial Resistance

“…Conessine (HF1C) is a well-established constituent of H. floribunda [ 19 ]. Although the antibiofilm inhibitory property of H. floribunda and its constituents was not previously investigated, a recent study demonstrated the resistance-modifying ability of conessine through the inhibition of multidrug efflux pumps [ 35 – 38 ]. Another study has shown that compounds with efflux pump inhibition may also cause biofilm disruption [ 39 ].…”

Steroidal alkaloids and conessine from the medicinal plant Holarrhena antidysenterica restore antibiotic efficacy in a Galleria mellonella model of multidrug-resistant Pseudomonas aeruginosa infection

“…Available evidence suggests that H. antidysenterica steroidal crude extract, and conessine may be acting as EPIs [ 19 , 20 ]. The steroidal extract and the alkaloid conessine have recently been reported to enhance antibiotic activity due to interference with the AdeIJK efflux pump in A. baumannii [ 19 ] which is functionally equivalent to the MexAB-OprM pump of P. aeruginosa [ 30 ].…”

“…The steroidal extract and the alkaloid conessine have recently been reported to enhance antibiotic activity due to interference with the AdeIJK efflux pump in A. baumannii [ 19 ] which is functionally equivalent to the MexAB-OprM pump of P. aeruginosa [ 30 ]. Furthermore, conessine restored antibiotic susceptibility to an otherwise resistant P. aeruginosa strain that overexpressed the MexAB-OprM efflux pump [ 20 ]. The data reported in the present study does not demonstrate that either the steroidal extracts or conessine are EPIs but is consistent with this hypothesis.…”

“…Exposure to either H. antidysenterica extract, or conessine alone, at concentrations that did not result in increased membrane disruption, resulted in accumulation of the fluorescent dye Pyronin Y suggesting that both treatments may have EPI-like properties [ 19 ]. Moreover, exposure to conessine restored the MICs of antibiotics against a P. aeruginosa strain over-expressing MexAB-OprM to values comparable with the wild-type parent and conessine induced the accumulation of Hoechst 33342 in cells over-expressing the same efflux pump [ 20 ].…”