Antibiofilm and Antivirulence Efficacies of Flavonoids and Curcumin Against Acinetobacter baumannii

Abstract

Acinetobacter baumannii is well adapted to hospital environments, and the persistence of its chronic infections is mainly due to its ability to form biofilms resistant to conventional antibiotics and host immune systems. Hence, the inhibitions of biofilm formation and virulence characteristics provide other means of addressing infections. In this study, the antibiofilm activities of twelve flavonoids were initially investigated. Three most active flavonoids, namely, fisetin, phloretin, and curcumin, dose-dependently inhibited biofilm formation by a reference A. baumannii strain and by several clinical isolates, including four multidrug-resistant isolates. Furthermore, the antibiofilm activity of curcumin (the most active flavonoid) was greater than that of the well-known biofilm inhibitor gallium nitrate. Curcumin inhibited pellicle formation and the surface motility of A. baumannii . Interestingly, curcumin also showed antibiofilm activity against Candida albicans and mixed cultures of C. albicans and A. baumannii . In silico molecular docking of the biofilm response regulator BfmR showed that the binding efficacy of flavonoids with BfmR was correlated with antibiofilm efficacy. In addition, curcumin treatment diminished A. baumannii virulence in an in vivo Caenorhabditis elegans model without cytotoxicity. The study shows curcumin and other flavonoids have potential for controlling biofilm formation by and the virulence of A. baumannii .

The interference of Moringa oleifera leaf extracts to modulate quorum sensing-facilitated virulence factors

“…This finding is in accordance with another study (Ikalinus et al 2015) suggesting phytochemical screening of M. oleifera leaves showed positive results for all the mentioned compounds, except for saponins. Some of the phytochemicals, such as flavonoids, harbor significant disruption properties for biofilm formation (Raorane et al 2019). In the present study, the MLE showed Gram-negative bacterial inhibition at the lowest concentration of 10 mg/mL (Table 2).…”

Candida spp./Bacteria Mixed Biofilms

“…Its chronic infections endure predominantly due to its ability to form biofilms resistant to conventional drugs and to fragile host immune systems. A report disclosed the antibiofilm and antivirulence ability of the three most active flavonoids, fisetin, phloretin, and curcumin, against A. baumannii [146]. The antibiofilm activity was dose dependent, and curcumin had the highest activity, when compared with gallium nitrate (a biofilm inhibitor), inhibiting pellicle formation and the surface motility of A. baumannii.…”

In Vitro Anti-Biofilm Activity of Curcumin Nanoparticles in Acinetobacter baumannii: A Culture-Based and Molecular Approach

“…Curcumin is an unstable, reactive, nonbioavailable compound, while it is an established therapeutic agent and is effective against various strains of Gram-negative and Gram-positive pathogens. Its mode of action at the molecular level has not been established, but it is thought to disrupt bacterial membranes (14). On the other hand, the formation of biofilms has been indicated that can be controlled by coating surfaces with nanoparticles (25).…”

“…It has been shown the inactivation of CsuE results in the prevention of pili production and the formation of biofilms. This indicates that the CsuA/BABCDE system plays a prominent role in the initial stage of biofilm formation (14).…”