Propolis Affects Pseudomonas aeruginosa Growth, Biofilm Formation, eDNA Release and Phenazine Production: Potential Involvement of Polyphenols

Abstract

Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic pathogen responsible for a wide range of clinical conditions, from mild infections to life-threatening nosocomial biofilm-associated diseases, which are particularly severe in susceptible individuals. The aim of this in vitro study was to assess the effects of an Albanian propolis on several virulence-related factors of P. aeruginosa, such as growth ability, biofilm formation, extracellular DNA (eDNA) release and phenazine production. To this end, propolis was processed using three different solvents and the extracted polyphenolic compounds were identified by means of high performance liquid chromatography coupled to electrospray ionization mass spectrometry (HPLC-ESI-MS) analysis. As assessed by a bioluminescence-based assay, among the three propolis extracts, the ethanol (EtOH) extract was the most effective in inhibiting both microbial growth and biofilm formation, followed by propylene glycol (PG) and polyethylene glycol 400 (PEG 400) propolis extracts. Furthermore, Pseudomonas exposure to propolis EtOH extract caused a decrease in eDNA release and phenazine production. Finally, caffeic acid phenethyl ester (CAPE) and quercetin decreased upon propolis EtOH extract exposure to bacteria. Overall, our data add new insights on the anti-microbial properties of a natural compound, such as propolis against P. aeruginosa. The potential implications of these findings will be discussed.

Propolis and its potential against SARS-CoV-2 infection mechanisms and COVID-19 disease

“…Propolis can be bacteriostatic and or bactericidal, depending on the concentration [ 197 ]. An ethanol extract of propolis inhibited microbial growth and biofilm formation by Pseudomonasaeruginosa [ 198 ]. The antibacterial properties of propolis make it a useful ingredient in a wound healing biofilm [ 199 ].…”

Antifungal and Antibacterial Effect of Propolis: A Comparative Hit for Food-Borne Pseudomonas, Enterobacteriaceae and Fungi

“…Some authors studied the mode of action of propolis towards Ps. aeruginosa and found that propolis impaired the growth, the production of biofilm and the capacity to release molecules, such as phenazines and eDNA with a possible role of complex phenols [39].…”

Effect of Ethanol Extracts of Propolis (EEPs) against Staphylococcal Biofilm—Microscopic Studies

“…The free extract and the one encapsulated in polymer nanoparticles both presented antimicrobial potential, with a minimum inhibitory concentration from 15.6 to 125 µg/mL and from 100 to 1560 µg/mL inhibiting biofilm formation by the S. aureus and Pseudomonas aeruginosa , respectively [ 30 ]. Propolis extracts also effectively eradicated biofilms formed by other dangerous bacteria, such as P. aeruginosa [ 30 , 31 , 32 ] and pathogenic fungi such as Candida spp. [ 33 , 34 , 35 ].…”