Molecular characterization of Lactococcus lactis subspecies in milk and milk products and studying their inhibitory effects on some aerobic and anaerobic bacteria | ||
| Microbes and Infectious Diseases | ||
| Articles in Press, Accepted Manuscript, Available Online from 24 October 2025 | ||
| Document Type: Original Article | ||
| DOI: 10.21608/mid.2025.423199.3207 | ||
| Authors | ||
| Heba A.M. Zahran1; Mona Hussein Abdel-Rahim2; Ehsan Mahmoud Hassan2; Aliaa M.A. Ghandour* 2 | ||
| 1Department of Veterinary Microbiology and Immunology, Faculty of Veterinary Medicine, Badr University in Assiut, Assiut, Egypt | ||
| 2Department of Medical Microbiology and Immunology, Faculty of Medicine, Assiut University, Egypt | ||
| Abstract | ||
| Background: Lactococcus lactis are Gram-positive ovoid lactic acid bacteria (LAB) widely used as bio-preservatives in milk and dairy products. Objectives: To isolate and identify Lactococcus lactis from milk and dairy products collected in Assiut City over a six-month period (January–June 2024), and to assess the inhibitory effects of its subspecies against selected resistant aerobic and anaerobic bacteria. Methods: A cross-sectional study was conducted on 200 random samples (80 raw milk, 60 yoghurts, 60 cheese) cultured on M17 agar. Biochemical identification involved xylose fermentation and growth in 4% and 6.5% NaCl, while PCR confirmed identification genotypically. Antimicrobial activity was tested using agar well diffusion method. Results: Lc. lactis was detected in 67.5% of milk, 41.7% of cheese, and 33.3% of yoghurt samples. PCR confirmed a 29% overall prevalence: 28.5% Lc. lactis subsp. lactis and 0.5% Lc. lactis subsp. cremoris. The highest frequency of Lc. lactis subsp. lactis occurred in milk. Lc. lactis Subsp. lactis showed strong inhibition of MRSA, CoNS, and C. perfringens but not Gram-negative bacteria, whereas Lc. lactis subsp. cremoris inhibited MRSA and CoNS only. Conclusion: Lactococcus lactis are prevalent in milk and dairy products in Assiut City and exhibit notable antibacterial activity, supporting their potential application as natural bio-preservatives in the dairy industry. | ||
| Keywords | ||
| Lactococcus lactis; milk; dairy products; PCR | ||
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