Native Lactobacillus fermentum, Lactobacillus plantarum and Lactobacillus acidophilus Strains from Traditional Sri Lankan Buffalo Curd Reveal Significant Strain-Specific Antagonistic Potential Against Listeria monocytogenes NCTC 11994

Abstract

The excessive use of antibiotics to control foodborne pathogens has contributed to the emergence of antibiotic-resistant Listeria monocytogenes, posing a significant global public health concern. In response to this challenge, the present study aimed to evaluate the potential of native Lactobacillus species as natural antibacterial agents against L. monocytogenes. Cell-free supernatants (CFS) of nine Lactobacillus strains comprising L. plantarum, L. fermentum, and L. acidophilus isolated from traditionally fermented buffalo curd in Sri Lanka were tested for antagonistic activity against L. monocytogenes NCTC 11994 using the agar well diffusion method on Brain Heart Infusion (BHI) agar. Among the tested strains, L. plantarum T3b showed no inhibition, whereas the remaining eight strains demonstrated varying degrees of antagonistic activity, with inhibition zones ranging between 10.77 mm and 14.10 mm, indicating a strain-specific antibacterial effect. These findings highlight the potential of traditional Sri Lankan buffalo curd as a source of native Lactobacillus strains with a functional probiotic characteristic and natural bio-preservative properties. The study contributes to the growing body of evidence supporting the use of beneficial microbes as biological alternatives for controlling foodborne pathogens and emphasizes the value of indigenous fermented foods in public health and food safety strategies.