Evaluation of antibacterial effect of probiotic filtrate combination against common food borne pathogens

Abstract

newline In the present study, a total of 200 food samples in four different categories (dairy newlineproducts, vegetable, fruit and poultry products) were selected for isolation of food borne newlinepathogens. By using the conventional method, 191 food borne pathogens were isolated. newlineThe isolates were identified by morphological, biochemical and molecular newlinecharacterization, in which 57 were identified as Escherichia coli, 51 isolates were newlineStaphylococcus aureus, 38 isolates were Shigella dysenteriae and 45 isolates were newlineSalmonella typhi. Against the isolates, antibacterial activity of probiotic cultures newlineLacticaseibacillus casei and Bifidobacterium bifidum was studied. In probiotic newlinepotential evaluation, both the selected probiotic cultures showed survival in all tested newlineconcentrations of bile (0.5%, 1.0%, 1.5% and 2%), NaCl (1-10%) and phenol (0.1- newline0.4%). The growth of selected cultures showed a negative tendency towards increasing newlineconcentrations of probiotic potential parameters. In the tested pH ranges (pH 1 to pH newline10) Lacticaseibacillus casei showed survival in the pH range of 3 to 8 while newlineBifidobacterium bifidum showed survival with pH 3 to pH 7. In both cases, the optimum newlinepH for growth was pH 7. Both the probiotic culture was able to grow at all tested newlinetemperatures (25ºC, 30ºC, 37ºC and 40ºC). The antibacterial property of probiotic newlineculture in alone form was studied by the agar overlay method whereas the agar well newlinediffusion method was used to study the antibacterial property of mixed probiotic filtrate. newlineThe filtrate was prepared by centrifugation. In both cases, the highest inhibition was newlinerecorded against Escherichia coli while the lowest inhibition was recorded against newlineShigella dysenteriae. The zone of inhibition (in mm) was recorded grater (40 mm newlineagainst Escherichia coli and 30 mm against Shigella dysenteriae) with mixed probiotic newlinefiltrate as compared to the alone form of culture (32 mm against Escherichia coli and newline14 mm against Shigella dysenteriae). In combination form, antibiotics were combined newline