Inhibition of non-O157 Shiga toxin Escherichia coli in African fermented foods by probiotic bacteria

Abstract

Non-O157 Shiga toxin producing Escherichia coli (STEC) serotypes are increasingly being associated with outbreaks of foodborne infections and illness. This study evaluated the in vitro probiotic characteristics of Lactobacillus plantarum strain B411 and dominant lactic acid bacteria (LAB) isolated from traditional African fermented maize gruel (ogi). Subsequently, the effects of acid adaption and those potential probiotic bacteria on the growth and survival of non-O157 STEC strains in fermented goat s milk and traditional African fermented cereal-based foods were investigated. Two of the 14 lactic acid bacteria (LAB) strains that were isolated from ogi together with L. plantarum strain B411 possess hydrophobic cell surface with ability to coaggregate with pathogens as well as antimicrobial activities against non-O157 STEC strains and E. coli ATCC 25922. The three strains with in vitro probiotic attributes also exhibited high level of adhesion to Caco-2 cells and the two LAB strains from ogi spontaneous fermentation were genetically similar to other reported potential probiotic bacteria. Though prior adaptation to acid enhanced acid tolerance of non-O157 STEC strains in Brain Heart Infusion (BHI) broth at low pH, it was detrimental to the survival in fermented goat s milk. The growth of both acid adapted (AA) and non-acid adapted (NAA) non-O157 STEC strains was not inhibited by the single strain potential probiotic L. plantarum B411 in fermented goat s milk. However, combination of yoghurt starter culture and potential probiotic L. plantarum B411 for the fermentation of the goat s milk had a bacteriostatic effect on the NAA non-O157 STEC strains while the growth of AA non-O157 STEC strains were substantially inhibited. Non-O157 Shiga toxin producing Escherichia coli (STEC) serotypes are increasingly being associated with outbreaks of foodborne infections and illness. This study evaluated the in vitro probiotic characteristics of Lactobacillus plantarum strain B411 and dominant lactic acid bacteria (LAB) isolated from traditional African fermented maize gruel (ogi). Subsequently, the effects of acid adaption and those potential probiotic bacteria on the growth and survival of non-O157 STEC strains in fermented goat s milk and traditional African fermented cereal-based foods were investigated. Two of the 14 lactic acid bacteria (LAB) strains that were isolated from ogi together with L. plantarum strain B411 possess hydrophobic cell surface with ability to coaggregate with pathogens as well as antimicrobial activities against non-O157 STEC strains and E. coli ATCC 25922. The three strains with in vitro probiotic attributes also exhibited high level of adhesion to Caco-2 cells and the two LAB strains from ogi spontaneous fermentation were genetically similar to other reported potential probiotic bacteria. Though prior adaptation to acid enhanced acid tolerance of non-O157 STEC strains in Brain Heart Infusion (BHI) broth at low pH, it was detrimental to the survival in fermented goat s milk. The growth of both acid adapted (AA) and non-acid adapted (NAA) non-O157 STEC strains was not inhibited by the single strain potential probiotic L. plantarum B411 in fermented goat s milk. However, combination of yoghurt starter culture and potential probiotic L. plantarum B411 for the fermentation of the goat s milk had a bacteriostatic effect on the NAA non-O157 STEC strains while the growth of AA non-O157 STEC strains were substantially inhibited. Non-O157 Shiga toxin producing Escherichia coli (STEC) serotypes are increasingly being associated with outbreaks of foodborne infections and illness. This study evaluated the in vitro probiotic characteristics of Lactobacillus plantarum strain B411 and dominant lactic acid bacteria (LAB) isolated from traditional African fermented maize gruel (ogi). Subsequently, the effects of acid adaption and those potential probiotic bacteria on the growth and survival of non-O157 STEC strains in fermented goat s milk and traditional African fermented cereal-based foods were investigated. Two of the 14 lactic acid bacteria (LAB) strains that were isolated from ogi together with L. plantarum strain B411 possess hydrophobic cell surface with ability to coaggregate with pathogens as well as antimicrobial activities against non-O157 STEC strains and E. coli ATCC 25922. The three strains with in vitro probiotic attributes also exhibited high level of adhesion to Caco-2 cells and the two LAB strains from ogi spontaneous fermentation were genetically similar to other reported potential probiotic bacteria. Though prior adaptation to acid enhanced acid tolerance of non-O157 STEC strains in Brain Heart Infusion (BHI) broth at low pH, it was detrimental to the survival in fermented goat s milk. The growth of both acid adapted (AA) and non-acid adapted (NAA) non-O157 STEC strains was not inhibited by the single strain potential probiotic L. plantarum B411 in fermented goat s milk. However, combination of yoghurt starter culture and potential probiotic L. plantarum B411 for the fermentation of the goat s milk had a bacteriostatic effect on the NAA non-O157 STEC strains while the growth of AA non-O157 STEC strains were substantially inhibited. Non-O157 Shiga toxin producing Escherichia coli (STEC) serotypes are increasingly being associated with outbreaks of foodborne infections and illness. This study evaluated the in vitro probiotic characteristics of Lactobacillus plantarum strain B411 and dominant lactic acid bacteria (LAB) isolated from traditional African fermented maize gruel (ogi). Subsequently, the effects of acid adaption and those potential probiotic bacteria on the growth and survival of non-O157 STEC strains in fermented goat s milk and traditional African fermented cereal-based foods were investigated. Two of the 14 lactic acid bacteria (LAB) strains that were isolated from ogi together with L. plantarum strain B411 possess hydrophobic cell surface with ability to coaggregate with pathogens as well as antimicrobial activities against non-O157 STEC strains and E. coli ATCC 25922. The three strains with in vitro probiotic attributes also exhibited high level of adhesion to Caco-2 cells and the two LAB strains from ogi spontaneous fermentation were genetically similar to other reported potential probiotic bacteria. Though prior adaptation to acid enhanced acid tolerance of non-O157 STEC strains in Brain Heart Infusion (BHI) broth at low pH, it was detrimental to the survival in fermented goat s milk. The growth of both acid adapted (AA) and non-acid adapted (NAA) non-O157 STEC strains was not inhibited by the single strain potential probiotic L. plantarum B411 in fermented goat s milk. However, combination of yoghurt starter culture and potential probiotic L. plantarum B411 for the fermentation of the goat s milk had a bacteriostatic effect on the NAA non-O157 STEC strains while the growth of AA non-O157 STEC strains were substantially inhibited. Non-O157 Shiga toxin producing Escherichia coli (STEC) serotypes are increasingly being associated with outbreaks of foodborne infections and illness. This study evaluated the in vitro probiotic characteristics of Lactobacillus plantarum strain B411 and dominant lactic acid bacteria (LAB) isolated from traditional African fermented maize gruel (ogi). Subsequently, the effects of acid adaption and those potential probiotic bacteria on the growth and survival of non-O157 STEC strains in fermented goat s milk and traditional African fermented cereal-based foods were investigated. Two of the 14 lactic acid bacteria (LAB) strains that were isolated from ogi together with L. plantarum strain B411 possess hydrophobic cell surface with ability to coaggregate with pathogens as well as antimicrobial activities against non-O157 STEC strains and E. coli ATCC 25922. The three strains with in vitro probiotic attributes also exhibited high level of adhesion to Caco-2 cells and the two LAB strains from ogi spontaneous fermentation were genetically similar to other reported potential probiotic bacteria. Though prior adaptation to acid enhanced acid tolerance of non-O157 STEC strains in Brain Heart Infusion (BHI) broth at low pH, it was detrimental to the survival in fermented goat s milk. The growth of both acid adapted (AA) and non-acid adapted (NAA) non-O157 STEC strains was not inhibited by the single strain potential probiotic L. plantarum B411 in fermented goat s milk. However, combination of yoghurt starter culture and potential probiotic L. plantarum B411 for the fermentation of the goat s milk had a bacteriostatic effect on the NAA non-O157 STEC strains while the growth of AA non-O157 STEC strains were substantially inhibited.