Antagonistic Effects of Lactobacillus Isolates Against Diarrhogenic Escherichia coli

One of the bacterial pathogens implicated worldwide in intestinal illnesses is diarrheagenic Escherichia coli (DEC). This study was conducted to determine the antagonistic effects of Lactobacillus species isolated from soursop (Annona muricata) and pineapple (Ananas comosus) fruits against DEC isolates using agar well diffusion protocol. Lactobacillus species were isolated from a collection of pineapple and soursop fruits obtained from open markets in Benin City, Nigeria using culture-based methods. The antimicrobial-metabolites producing ability of Lactobacillus spp. were ascertained using a method described by the Association of Official Analytical Chemist (AOAC) methods and metabolites analyzed were lactic acid, hydrogen peroxide and diacetyl. Lactobacillus species that were isolated include: Lactobacillus plantarum and L. acidophilus from soursop; and L. acidophilus, L. casei, L. delbrueckii, L. plantarum were isolated from pineapple. The pineapple isolate - L. acidophilus showed a high antagonistic activity, with an inhibition zone of 18 mm. Lactobacillus delbrueckii and L. plantarum isolated from pineapple had an in-vitro concentration of hydrogen peroxide to be 23.70 g/l; diacetyl was 8.69 g/l and lactic acid concentration was 7.20 g/l, respectively. Results obtained from this study have shown that Lactobacillus species isolated from pineapple and soursop fruits are potential producers of antibacterial metabolites.