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.
Highlights
The gastrointestinal tract is colonized by large number of microorganisms (Lin and Zhang, 2017) which have several health benefits for the host, such as the improvement of intestinal health, harvesting energy, competitive exclusion and antimicrobial activity against pathogens and immune modulation (Thursby and Abbreviations: propolis ethanolic extract (PEE), Propolis Ethanolic Extract; minimal inhibitory concentration (MIC), Minimal Inhibitory Concentration; PBS, Phosphate-Buffered Saline.Production and hosting by ElsevierJuge, 2017)
To get more inside to the unique and interesting response of Normaflore microbes to the PEE treatment, the effect of PEE on their mature biofilms was investigated
With respect to planktonic cells which were found in the suspension above the biofilm, PEE revealed a dose-dependent inhibitory effect on their growth (Fig. 2)
Summary
The gastrointestinal tract is colonized by large number of microorganisms (Lin and Zhang, 2017) which have several health benefits for the host, such as the improvement of intestinal health, harvesting energy, competitive exclusion and antimicrobial activity against pathogens and immune modulation (Thursby and Abbreviations: PEE, Propolis Ethanolic Extract; MIC, Minimal Inhibitory Concentration; PBS, Phosphate-Buffered Saline.Production and hosting by ElsevierJuge, 2017). Dysbiosis may develop as temporary or chronic clinical symptoms, or it could be asymptomatic but may increase susceptibility for many diseases, including intestinal, metabolic and brain disorders (Blumstein et al, 2014). This problem can be solved by using probiotics, which have the ability to recolonize the gut, improve its normal microbiota and enhance overall health (Gill and Guarner, 2004; Puebla-Barragan and Reid, 2019). Biofilm form of growth of probiotics is considered an advantageous property, since it could resist the environmental conditions, support longer persistence in the gut of the host and prevent colonization by pathogenic microorganisms (Salas-Jara et al, 2016)
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