The objective of this study was to isolate, identify and characterize a collection of lytic bact... more The objective of this study was to isolate, identify and characterize a collection of lytic bacteriophages capable of infecting enterohaemorrhagic Escherichia coli (EHEC) serotypes. Phages were isolated from dairy and cattle feedlot manure using E. coli O157, O26 and O111 strains as hosts. Phages were enriched from faecal slurries by culture in 10× trypticase soy broth at 37°C overnight. Phage plaques were obtained by mixing the filtered culture supernatant with molten tryptone agar containing the phage E. coli host strain, pouring the inoculated agar on top of cooled TS agar and incubating the culture overnight. Phages were purified from plaques and screened against additional E. coli and EHEC strains by the efficiency of plating method (EOP). Phage CEV2, and five other phages previously isolated, were able to lyse all of the 15 O157 strains tested with EOP values consistently above 0·001. Two phages were found to be highly effective against strains of E. coli O157 through EOP tests and against O26 strains through spot tests, but not against the O serogroup 111 strains. A cocktail of eight phage that lyse E. coli O157 strains resulted in >5 log CFU ml(-1) reductions at 37°C. Multiplex-PCR revealed that none of these eight phages carried stx1, stx2, hlyA or eaeA genes. A cocktail of bacteriophages was capable of lysing most strains of two EHEC serotypes. This collection of phages can be combined and potentially used as an antimicrobial cocktail to inactivate E. coli strains from O serogroups 157 and 26 and reduce their incidence in the food chain.
Journal of The American College of Nutrition, Aug 1, 2001
Arabinogalactan (AG) is a non-digestible soluble dietary fiber that resists hydrolytic enzyme act... more Arabinogalactan (AG) is a non-digestible soluble dietary fiber that resists hydrolytic enzyme action and enters the large bowel intact where it is fermented by resident microflora. To determine whether AG has similar physiological properties to other soluble dietary fibers, we examined the effect of 15 and 30 g per day of a commercially available AG from Western Larch on several gastrointestinal and blood parameters. Gastrointestinal parameters included fecal microflora, fecal enzyme activity, fecal short-chain fatty acids, fecal pH, fecal weight, transit time and bowel frequency. Blood parameters included total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, Apo-A1, Apo-B, glucose and insulin. The study consisted of two three-week diet treatments with no washout period. Participants (n=20, 11 males, 9 females) consumed their usual diet in addition to 15 or 30 g AG in a beverage sweetened with aspartame as compared to their usual diet with the control beverage. Significant increases in total fecal anaerobes were observed with 15 g (p=0.01) and 30 g AG (p=0.001). A significant increase (p=0.02) in Lactobacillus spp. was observed when subjects consumed AG for a total of six weeks regardless of dose. There were no significant changes in other microflora, fecal enzyme activity, transit time, frequency, fecal weight, fecal pH and short-chain fatty acids. Fecal ammonia levels decreased with 15 g (p=0.001) and 30 g (p=0.002) AG. No significant changes in blood lipids or blood insulin were observed. These data suggest that dietary AG is easily incorporated into the diet, well tolerated in subjects and has some positive effects on fecal chemistry.
ABSTRACT Salmonella and Cronobacter are two bacteria of concern in powdered food ingredients with... more ABSTRACT Salmonella and Cronobacter are two bacteria of concern in powdered food ingredients with low water activity, due to their ability to remain viable for long periods of time. There is great interest in studying the survival of these bacteria in powdered foods, but discrepancies have been reported between broth-grown and lawn-grown bacterial cells and their thermal resistance and desiccation tolerance once inoculated onto powdered foods. The purpose of this study was to evaluate three different powdered food inoculation methods, two broth-grown and one lawn-grown. To evaluate these methods on three types of powdered food matrices, Salmonella enterica serovar Typhimurium LT2 (ATCC 700720), Salmonella surrogate Enterococcus faecium (NRRL B-2354), and Cronobacter sakazakii (ATCC 29544) were inoculated onto nonfat dry milk powder, organic soy flour, and all-purpose flour using one of the three previously developed inoculation methods. In the first broth-grown method, labeled broth-grown pelletized inoculation, a bacterial cell pellet was added to powdered foods directly and mixed with a sterile wooden stick. The second broth-grown method, labeled broth-grown spray inoculation, used a chromatography reagent sprayer to spray the bacterial cell suspension onto the powdered foods. The third inoculation method, lawn-grown liquid inoculation, made use of a spot inoculation and a stomacher to incorporate each bacterium into the powdered foods. Results indicated that the method of inoculation of each powder impacted repeatability and bacteria survivability postequilibration (4 to 6 days). Broth-grown spray inoculation, regardless of the powder and bacterium, resulted in the highest log reduction, with an average ∼1-log CFU/g reduction following equilibration. Broth-grown pelletized inoculation resulted in the second-highest log reduction (∼0.79 log CFU/g), and finally, lawn-grown liquid inoculation was the most stable inoculation method of the three, with ∼0.52-log CFU/g reduction. Overall, the results from this inoculation study demonstrate that inoculation methodologies impact the desiccation tolerance and homogeneity of C. sakazakii, E. faecium, and Salmonella Typhimurium LT2.
Inulin is a non-digestible oligosaccharide classified as a prebiotic, a substrate that promotes t... more Inulin is a non-digestible oligosaccharide classified as a prebiotic, a substrate that promotes the growth of certain beneficial microorganisms in the gut. We examined the effect of a 20 g day(-1) supplement of chicory inulin on stool weight, intestinal transit time, stool frequency and consistency, selected intestinal microorganisms and enzymes, fecal pH, short chain fatty acids and ammonia produced as by-products of bacterial fermentation. Twelve healthy male volunteers consumed a well-defined, controlled diet with and without a 20 g day(-1) supplement of chicory inulin (degree of polymerization (DP) ranging for 2-60), with each treatment lasting for 3 weeks in a randomized, double-blind crossover trial. Inulin was consumed in a low fat ice cream. No differences were found in flavor or appeal between the control and inulin-containing ice creams. Inulin consumption resulted in a significant increase in total anaerobes and Lactobacillus species and a significant decrease in ammonia levels and β-glucuronidase activity. Flatulence increased significantly with the inulin treatment. No other significant differences were found in bowel function with the addition of inulin to the diet. Thus, inulin is easily incorporated into a food product and has no negative effects on food acceptability. Twenty grams of inulin was well tolerated, but had minimal effects on measures of laxation in healthy, human subjects.
In an attempt to select streptococcal strains that could be used to accelerate the cheese ripenin... more In an attempt to select streptococcal strains that could be used to accelerate the cheese ripening process, we used ethyl methanesulfonate treatment to isolate Streptococcus lactis C2 temperature-sen- sitive mutants exhibiting normal growth patterns at 30 to 32°C but not at the highest cooking temperatures used in Cheddar cheese manufacture. Three classes of mutants isolated included: 1) mutants unable to grow and produce acid at 38 to 40°C; 2) mutants unable to grow at 38 to 40°C but that continued to produce acid at a rate similar to temperature-sensi- tive strains of S. cremoris; and 3) mutants that underwent lysis when the cells were shifted to 38 to 40°C, as evidenced by a decrease in optical density of the cell suspension and the concomitant release of the intracellular enzyme, phospho-~- galactosidase. The thermolytic variants could possibly be used to accelerate cheese ripening either by releasing their intracellular enzymes into the curd at an early stage in the cheese making process or by serving as a "delivery system" of ripening enzymes, the genes of which could be cloned into the thermolytic strains.
The objective of this study was to isolate, identify and characterize a collection of lytic bact... more The objective of this study was to isolate, identify and characterize a collection of lytic bacteriophages capable of infecting enterohaemorrhagic Escherichia coli (EHEC) serotypes. Phages were isolated from dairy and cattle feedlot manure using E. coli O157, O26 and O111 strains as hosts. Phages were enriched from faecal slurries by culture in 10× trypticase soy broth at 37°C overnight. Phage plaques were obtained by mixing the filtered culture supernatant with molten tryptone agar containing the phage E. coli host strain, pouring the inoculated agar on top of cooled TS agar and incubating the culture overnight. Phages were purified from plaques and screened against additional E. coli and EHEC strains by the efficiency of plating method (EOP). Phage CEV2, and five other phages previously isolated, were able to lyse all of the 15 O157 strains tested with EOP values consistently above 0·001. Two phages were found to be highly effective against strains of E. coli O157 through EOP tests and against O26 strains through spot tests, but not against the O serogroup 111 strains. A cocktail of eight phage that lyse E. coli O157 strains resulted in >5 log CFU ml(-1) reductions at 37°C. Multiplex-PCR revealed that none of these eight phages carried stx1, stx2, hlyA or eaeA genes. A cocktail of bacteriophages was capable of lysing most strains of two EHEC serotypes. This collection of phages can be combined and potentially used as an antimicrobial cocktail to inactivate E. coli strains from O serogroups 157 and 26 and reduce their incidence in the food chain.
Journal of The American College of Nutrition, Aug 1, 2001
Arabinogalactan (AG) is a non-digestible soluble dietary fiber that resists hydrolytic enzyme act... more Arabinogalactan (AG) is a non-digestible soluble dietary fiber that resists hydrolytic enzyme action and enters the large bowel intact where it is fermented by resident microflora. To determine whether AG has similar physiological properties to other soluble dietary fibers, we examined the effect of 15 and 30 g per day of a commercially available AG from Western Larch on several gastrointestinal and blood parameters. Gastrointestinal parameters included fecal microflora, fecal enzyme activity, fecal short-chain fatty acids, fecal pH, fecal weight, transit time and bowel frequency. Blood parameters included total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, Apo-A1, Apo-B, glucose and insulin. The study consisted of two three-week diet treatments with no washout period. Participants (n=20, 11 males, 9 females) consumed their usual diet in addition to 15 or 30 g AG in a beverage sweetened with aspartame as compared to their usual diet with the control beverage. Significant increases in total fecal anaerobes were observed with 15 g (p=0.01) and 30 g AG (p=0.001). A significant increase (p=0.02) in Lactobacillus spp. was observed when subjects consumed AG for a total of six weeks regardless of dose. There were no significant changes in other microflora, fecal enzyme activity, transit time, frequency, fecal weight, fecal pH and short-chain fatty acids. Fecal ammonia levels decreased with 15 g (p=0.001) and 30 g (p=0.002) AG. No significant changes in blood lipids or blood insulin were observed. These data suggest that dietary AG is easily incorporated into the diet, well tolerated in subjects and has some positive effects on fecal chemistry.
ABSTRACT Salmonella and Cronobacter are two bacteria of concern in powdered food ingredients with... more ABSTRACT Salmonella and Cronobacter are two bacteria of concern in powdered food ingredients with low water activity, due to their ability to remain viable for long periods of time. There is great interest in studying the survival of these bacteria in powdered foods, but discrepancies have been reported between broth-grown and lawn-grown bacterial cells and their thermal resistance and desiccation tolerance once inoculated onto powdered foods. The purpose of this study was to evaluate three different powdered food inoculation methods, two broth-grown and one lawn-grown. To evaluate these methods on three types of powdered food matrices, Salmonella enterica serovar Typhimurium LT2 (ATCC 700720), Salmonella surrogate Enterococcus faecium (NRRL B-2354), and Cronobacter sakazakii (ATCC 29544) were inoculated onto nonfat dry milk powder, organic soy flour, and all-purpose flour using one of the three previously developed inoculation methods. In the first broth-grown method, labeled broth-grown pelletized inoculation, a bacterial cell pellet was added to powdered foods directly and mixed with a sterile wooden stick. The second broth-grown method, labeled broth-grown spray inoculation, used a chromatography reagent sprayer to spray the bacterial cell suspension onto the powdered foods. The third inoculation method, lawn-grown liquid inoculation, made use of a spot inoculation and a stomacher to incorporate each bacterium into the powdered foods. Results indicated that the method of inoculation of each powder impacted repeatability and bacteria survivability postequilibration (4 to 6 days). Broth-grown spray inoculation, regardless of the powder and bacterium, resulted in the highest log reduction, with an average ∼1-log CFU/g reduction following equilibration. Broth-grown pelletized inoculation resulted in the second-highest log reduction (∼0.79 log CFU/g), and finally, lawn-grown liquid inoculation was the most stable inoculation method of the three, with ∼0.52-log CFU/g reduction. Overall, the results from this inoculation study demonstrate that inoculation methodologies impact the desiccation tolerance and homogeneity of C. sakazakii, E. faecium, and Salmonella Typhimurium LT2.
Inulin is a non-digestible oligosaccharide classified as a prebiotic, a substrate that promotes t... more Inulin is a non-digestible oligosaccharide classified as a prebiotic, a substrate that promotes the growth of certain beneficial microorganisms in the gut. We examined the effect of a 20 g day(-1) supplement of chicory inulin on stool weight, intestinal transit time, stool frequency and consistency, selected intestinal microorganisms and enzymes, fecal pH, short chain fatty acids and ammonia produced as by-products of bacterial fermentation. Twelve healthy male volunteers consumed a well-defined, controlled diet with and without a 20 g day(-1) supplement of chicory inulin (degree of polymerization (DP) ranging for 2-60), with each treatment lasting for 3 weeks in a randomized, double-blind crossover trial. Inulin was consumed in a low fat ice cream. No differences were found in flavor or appeal between the control and inulin-containing ice creams. Inulin consumption resulted in a significant increase in total anaerobes and Lactobacillus species and a significant decrease in ammonia levels and β-glucuronidase activity. Flatulence increased significantly with the inulin treatment. No other significant differences were found in bowel function with the addition of inulin to the diet. Thus, inulin is easily incorporated into a food product and has no negative effects on food acceptability. Twenty grams of inulin was well tolerated, but had minimal effects on measures of laxation in healthy, human subjects.
In an attempt to select streptococcal strains that could be used to accelerate the cheese ripenin... more In an attempt to select streptococcal strains that could be used to accelerate the cheese ripening process, we used ethyl methanesulfonate treatment to isolate Streptococcus lactis C2 temperature-sen- sitive mutants exhibiting normal growth patterns at 30 to 32°C but not at the highest cooking temperatures used in Cheddar cheese manufacture. Three classes of mutants isolated included: 1) mutants unable to grow and produce acid at 38 to 40°C; 2) mutants unable to grow at 38 to 40°C but that continued to produce acid at a rate similar to temperature-sensi- tive strains of S. cremoris; and 3) mutants that underwent lysis when the cells were shifted to 38 to 40°C, as evidenced by a decrease in optical density of the cell suspension and the concomitant release of the intracellular enzyme, phospho-~- galactosidase. The thermolytic variants could possibly be used to accelerate cheese ripening either by releasing their intracellular enzymes into the curd at an early stage in the cheese making process or by serving as a "delivery system" of ripening enzymes, the genes of which could be cloned into the thermolytic strains.
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Papers by Joellen Feirtag