Antibacterial effect of postbiotics derived from Lactobacillus acidophilus against mastitis causing pathogens

Abstract

The current study evaluated the antibacterial efficacy of postbiotics derived from probiotic Lactobacillus acidophilus (strain UBLA-34) against two major mastitis-causing pathogens, S. aureus and S. agalactiae. The postbiotic was prepared by culturing L. acidophilus in MRS broth followed by heat inactivation, ultrasonication, centrifugation, filtration and lyophilization. Antibacterial activity was assessed using disc diffusion method. Preliminary trials were conducted to select the concentration of postbiotics. Based on the results, 600,700 and 800 mg/mL of postbiotics were selected for studying the antibacterial effect. The results demonstrated a concentration-dependent antibacterial effect against both pathogens. For S. aureus, zones of inhibition (ZOI) measured were 13.58 ± 0.30, 17.16 ± 0.33 and 19.25 ± 0.11 mm at postbiotic concentrations of 600, 700 and 800 mg/mL respectively. The minimum inhibitory concentration (MIC) was identified as 450 mg/mL (ZOI: 10.17 ± 0.25 mm). Similarly, S. agalactiae exhibited ZOIs of 14.83 ± 0.33, 17.92 ± 0.24 and 19.25 ± 0.11 mm for the respective concentrations.  The MIC was found to be 450 mg/mL (ZOI: 11.00 ± 0.26 mm). Comparative analysis indicated that S. agalactiae displayed slightly higher susceptibility at lower concentrations of postbiotics than S. aureus. The findings underscore the potential of L. acidophilus-derived postbiotics as natural antibacterial agents against mastitis causing pathogens. Thus postbiotics offer a promising alternative strategy for mastitis management amidst rising concerns of antibiotic resistance.