Indigenous Reduction of Multi-drug Resistant Bacterial Pathogens in a Natural Uncontrolled Fermented Milk Ecosystem

Abstract

Raw milk and its products have been questioned for microbiological safety. However, Dahi: an artisanally fermented milk product that is yet microbiologically unexplored is popularly known for therapeutic uses in public. Aiming safety and therapeutic assessment of dahi, samples of raw milk and dahi were analyzed for microbiology and bacterial pathogens. The pathogens were also evaluated for antibiotic resistance. Further dahi samples were assessed for antipathogen effect. The total bacterial count of raw milk was between 3.80 × 1002 to 2.97 × 1007 and the total fungal count was 2.50 × 1001 to 4.90 × 1002 whereas the total bacterial and fungal count of Dahi was 3.00 × 1001 to 4.05 × 1009 and 2.00 × 1001 to 5.30 × 1007. The bacterial population of the Dahi was found dominated by lactic acid bacteria. In milk samples, E. coli was detected as 38%, S. aureus 28%, L. monocytogenes 3%, Salmonella 42% and Pseudomonas spp 31%. In Dahi samples, their percentages were 7%, 10%, 7%, 8% and 2% respectively. The detected pathogens were found resistant to different antibiotics, especially to third and fourth generations of cephalosporin and other beta-lactam drugs. When assessed in vitro, the low incidence of pathogens in the Dahi samples was associated with its inhibitory effect against pathogens. Dahi samples also inhibited the growth of antibiotic resistance ATCC strains. The inhibitory activity of the Dahi is due to the changes that occur during fermentation but are not correlated to the pH of the Dahi.