Propolis ethanolic extract has double-face in vitro effect on the planktonic growth and biofilm formation of some commercial probiotics

Ibrahim Alfarrayeh; Csaba Fekete; Zoltán Gazdag; Gábor Papp

doi:10.1016/j.sjbs.2020.11.047

Propolis ethanolic extract has double-face in vitro effect on the planktonic growth and biofilm formation of some commercial probiotics

Saudi J Biol Sci. 2021 Jan;28(1):1033-1039. doi: 10.1016/j.sjbs.2020.11.047. Epub 2020 Nov 17.

Authors

Ibrahim Alfarrayeh¹, Csaba Fekete¹, Zoltán Gazdag¹, Gábor Papp¹

Affiliation

¹ Department of General and Environmental Microbiology, University of Pécs, Faculty of Sciences, Pécs, Hungary.

Abstract

This study investigated the in vitro effect of propolis ethanolic extract (PEE) on planktonic growth and biofilm forming abilities of five commercial probiotics (Enterol, Protexin, Normaflore, BioGaia and Linex). Broth microdilution method was used to investigate the susceptibility of the microbes of five commercial probiotics to PEE. Crystal violet assay was used for the quantitative assessment of biofilm formation and mature biofilm eradication tests. Effect of PEE on autoaggregation ability and swarming motility of Normaflore microbes was determined. Planktonic forms of probiotics showed varied susceptibilities with minimal inhibitory concentration values in the range of 100-800 µg/mL of PEE. However, low PEE concentrations significantly enhanced the planktonic growth of Linex and BioGaia microbes. Biofilm studies revealed that Enterol and Protexin were non-biofilm formers, while BioGaia, Linex and Normaflore showed weak biofilms, which were inhibited by 12.5, 25, and 800 µg/mL of PEE, respectively. PEE revealed double-face effect on the biofilms of Normaflore and Linex, which were enhanced at low concentrations of PEE and inhibited at higher concentrations. Interestingly, Normaflore biofilms were shifted from weak to strong biofilms at low PEE concentrations (12.5, 25, and 50 µg/mL). In conclusion, PEE has strain dependent controversial effects on the planktonic growth and biofilm forming ability of the tested probiotics, although high concentrations have inhibitory effect on all of them, low concentrations may have strain dependent prebiotic effect.

Keywords: Antimicrobial; Biofilm; Dysbiosis; Food preservative; MIC, Minimal Inhibitory Concentration; PBS, Phosphate-Buffered Saline; PEE, Propolis Ethanolic Extract; Probiotic; Propolis.