Volume: 5, 2026
5th International PhD Students’ Conference at the University of Life Sciences in Lublin, Poland:
ENVIRONMENT – PLANT – ANIMAL – PRODUCT
Abstract number: H018
DOI: https://doi.org/10.24326/ICDSUPL5.H018
Published online: 22 April 2026
Evaluation of the safety and probiotic properties of Enterococcus faecalis isolates
Angelika Śliwka*, Kinga Zdybel and Magdalena Polak-Berecka
Department of Biotechnology, Microbiology and Human Nutrition, University of Life Sciences in Lublin, 8 Skromna St., 20-704 Lublin, Poland
* Corresponding author: angelika.sliwka@up.edu.pl
Microorganisms play an important role in the development of the infant gut microbiota and may influence host health. In this study, ten Enterococcus faecalis strains were isolated from human milk samples and evaluated for their safety and probiotic potential. Due to the dual role of this species as both a commensal and an opportunistic pathogen, careful safety assessment is required before considering its application as a probiotic. The analyzed parameters included hemolytic activity, gelatinase production, antibiotic susceptibility, survival under low pH conditions, cell surface hydrophobicity assessed by the microbial adhesion to hydrocarbons (MATH) assay using n-hexadecane, and autoaggregation ability. Three out of ten isolates exhibited virulence-associated traits, including partial hemolysis or gelatinase activity, and were excluded from further analysis. The remaining strains were non-hemolytic and gelatinase-negative, indicating acceptable preliminary safety.
Antibiotic susceptibility testing revealed strain-dependent variability, with several isolates showing resistance to selected antibiotics, particularly macrolides (azithromycin) and fluoroquinolones (ofloxacin), while others, such as strain EF1, remained fully susceptible. All selected strains demonstrated the ability to survive under acidic conditions, suggesting their potential to withstand gastrointestinal passage. Additionally, several isolates exhibited high cell surface hydrophobicity and strong autoaggregation ability, which are associated with enhanced adhesion to intestinal surfaces. In particular, strains EF9 and EF10 showed the highest hydrophobicity, while EF3, EF7, and EF10 demonstrated the strongest autoaggregation capacity. Overall, the results indicate that selected human milk-derived Enterococcus faecalis strains, particularly EF1, EF9, and EF10, represent promising candidates for further investigation as probiotics. These findings highlight the importance of strain-level evaluation in identifying safe and functionally relevant probiotic microorganisms.
Keywords: acid tolerance; antibiotic susceptibility; autoaggregation; cell surface properties; human milk isolates
How to cite
Śliwka A., Zdybel K., Polak-Berecka M., 2026. Evaluation of the safety and probiotic properties of Enterococcus faecalis isolates. In: 5th International PhD Students’ Conference at the University of Life Sciences in Lublin, Poland: Environment – Plant – Animal – Product. https://doi.org/10.24326/ICDSUPL5.H018