Characterization and Antimicrobial Potential of Enterococcus faecium Isolates from Raw Bovine Milk and Yoghurt

Arafat, Hussam H.; Shoulkamy, M. A.; Imam, M. M.; Ali, Amany M.A

doi:10.21608/sjdfs.2025.361742.1223

	Characterization and Antimicrobial Potential of Enterococcus faecium Isolates from Raw Bovine Milk and Yoghurt
Scientific Journal for Damietta Faculty of Science
Volume 15, Issue 2, August 2025, Page 83-93 PDF (1.22 MB)
Document Type: Original articles
DOI: 10.21608/sjdfs.2025.361742.1223
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Authors
Hussam H. Arafat ¹; M. A. Shoulkamy²; M. M. Imam²; Amany M.A Ali ²
¹Department of Botany &amp; Microbiology, Faculty of Science, Minia University, Minia City- 61519, Egypt
²Department of Botany & Microbiology, Faculty of Science, Minia University, Minia City- 61519, Egypt
Abstract
This study focuses on the isolation of enterococci, a subset of lactic acid bacteria (LAB). The study involves the identification of these isolates through morphological, biochemical, as well as molecular identification using 16S rRNA gene sequencing methods, alongside an exploration of their antimicrobial efficacy. Three isolates were obtained from milk and yoghurt samples, identified as Enterococcus faecium. Tolerance of the isolates to bile salts (up to 40%) and mild acidity (pH=4.5), makes them survive in guts and thus applicable as probiotics. The cell-free supernatants (CFSs) derived from these isolates exhibited significant antibacterial activity where inhibition zones reached 9.3-10.33 mm against Proteus vulgaris, Staphylococcus aureus and Staphylococcus albus; while zones recorded against Pseudomonas aeruginosa, Serratia marcescens, Klebsiella pneumonia and Escherichia coli, reached 3-8.3 mm. By contrast, they showed no efficacy against fungi. Notably, the antimicrobial activity of CFSs was maintained at various temperatures, including autoclaving conditions (121 °C). The isolates displayed tolerance across a wide pH range (2.5-9.5), with enhanced activity observed at acidic pH levels compared to basic ones. Heat and pH stability of supernatants encourage their use as bio-preservatives.
Keywords
Enterococcus faecium; Biochemical characterization; 16S rRNA; Antimicrobial activity


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