EVALUATION OF THE ANTIMICROBIAL ACTIVITY OF A BIFIDOBACTERIA MIX AGAINST ESCHERICHIA COLI O157:H7 UNDER AEROBIC CONDITIONS
A bifidobacteria mix (nine strains) was evaluated for its effect on the growth and survival of Escherichia coli O157:H7 (ATCC 43890) in 11% NFDM and MRS broth under the optimum growth conditions for E. coli O157:H7 growth (37¡ãC, aerobic). Preliminary experiments were conducted to obtain the growth curves of the 9 strains of bifidobacteria and E. coli O157:H7 and confirm the inhibitory effect of acidity on E. coli O157:H7 (pH of media adjusted to 3.8). Acid-adapted E. coli O157:H7 showed no difference in resistance toward bifidobacteria (P>0.05) when compared to the non-acid adapted one. Escherichia coli O157:H7 did not survive in the supernatant of the bifodbacteria mix collected after incubation (37¡ãC) with aerobic shaking (8 h). However, the pathogen was able to grow after the pH of the supernatant was adjusted to 6.50 (pH of fresh MRS broth). Results suggest that a high content of bifidobacteria has a strong inhibitory effect on E. coli O157:H7, in part due to the low pH. However, products from bifidobacteria may also exert inhibitory effects.
Advisor:Juan L. Silva; Charles H. White; M. Wes Schilling
School:Mississippi State University
School Location:USA - Mississippi
Source Type:Master's Thesis
Keywords:food science nutrition and health promotion
Date of Publication:04/28/2006