Fresh fecal samples from healthy volunteers were examined for their content of theLactobacillus acidophiluscomplex (LAC). A two-step isolation method for fecal lactobacilli was developed and employed in this study. Isolates of lactobacilli were identified according to their restriction fragment length polymorphism (RFLP) of genes coding for ribosomal RNA. Our results suggested that all samples contain lactobacilli and the most dominant species of h uman fecal lactobacilli isL. paracasei.In addition, several strains of LAC were recovered from specimens of volunteers. Among six LAC species, namely, Al: L. acidophilus, A2: L. crispatus, A3: L. amylovorus, A4: L. gallinarum, B1: L. gassri, and B2: L. johnsonii, isolates classified into cluster B were recovered from 6 out of 15 volunteers; however isolates of cluster A were recovered from 3 of 15 volunteers. Four of 15 volunteers had strains ofL. gasseri, 3 of them had strains ofL. johnsonii, and strains ofL. amylovoruswere also isolated from specimens of 3 of 15 volunteers. These findings suggest that group B of LAC is the predominant cluster of LAC found in human feces andL. amylovoruswas the only species of cluster A found in this study. No volunteer with blood type O had LAC in the fecalLactobacillusflora.
The effects ofBifidobacterium longumBB536 (BB536) onEscherichia coliO157: H7 IPH9 (IPH9) were fist examined using germ-free mice mono-associated with BB536 (BB536-MA). Thirty-two days after oral challenge with a lethal dose of IPH9, all the non-associated germ-free mice (GF) died, but all the BB536-MA mice survived and the number of IPH9 in the feces was lower than that in GF mice. Second, co-culture experiments with BB536 and IPH 9 were performed. The number of IPH9 in the co-culture was less than 1% of that in mono-culture after 24 hr, and the verotoxin concentration also decreased. Culture of IPH9 under various conditions showed that lactate, acetate and the supernatant of BB536 culture had anti-O157 activities even when the pH was neutral, and the supernatant of BB536 culture had stronger inhibitory effects than lactate or acetate against the production of verotoxin. This efficient inhibition of verotoxin may suggest the presence of verotoxin-inhibitory factors in BB536 metabolites in addition to lactate and acetate.
Diet is the major source of cadmium for the non-smoking population. Currently, no method is available to remove cadmium from food products. Because the content of cadmium in the food is likely to continue to rise in the future, a new method for decontaminating foods is urgently needed. We assessed the ability of safe food grade lactic acid bacteria (LAB) to remove cadmium from an aqueous solution. At a concentration of 10μg/l up to 70% could be removed within 5 min, and up to 90% after 1 hr. At a concentration of 1000μg/l between 5 and 30% was removed after 5 min and between 20 ad 55% after 1 hr. Heat-treatment of the bacteria significantly enhanced the removal of Cd at 10 and 100μg/l, but not at 1000μg/l. Increased temperature (37deg;C), prolonged incubation (24 hr) and higher bacterial concentrations (5×109bacteria/ml) were found to increase the removal of Cd. LAB were shown to remove cadmium in a strain, temperature and concentration dependent manner. The results indicate that food grade LAB may provide a much needed means for decontamination of liquid foods. The practical feasibility of this approach deserves to be further investigated considering the importance of Cd removal from food.
Background: This study was designed to assess gut microflora changes in children in Finnish day-care centers (DCCs).Methods: Ninety-four children in four DCCs were randomised to receive a combination ofLactobacillus acidophilusLa 5 andBifidobacterium lactisBb 12 or placebo for six months. Faecal samples were collected monthly and during bouts of diarrhoea. The parents kept a daily record. These groups were similar to infections and antibiotic treatments during the last month before the study. Altogether 14/76 (18%) children developed diarrhoea, and 13 healthy children who did not were studied as controls from the same DCCs at the same time. The gut microflora of altogether 26 children was examined by fluorescent in situ hybridisation at the start of the study, and before and after diarrhoea. Results: Twelve of 26 subjects (46%) had initially an aberrant microflora as determined by high levels of clostridia, the remaining 14 (54%) had balanced microflora. In the group with aberrant microflora, 9/12 (75%) manifested diarrhoea during followup, whereas in the group with balanced microflora, 4/14 (29%) fell ill with diarrhoea (p= 0.04). Diarrhoea reduced the number of all bacteria for at least a month. Antibiotic therapies increased the numbers of bacteria, mostly the number of clostridia. The initial total number of bacteria in the probiotic group decreased significantly in the late follow-up samples;p= 0.0075, this being due to the stabilising effect of probiotics. During treatment with probiotics aberrant microflora tended to approach the pattern in balanced microflora. Conclusions: A smaller and more stable amount of bacteria in the gut microflora was associated with healthy outcome of children during the study. Not only infections and antibiotics caused disruption of the gut microflora; aberrance of the gut microflora itself seems to predispose a child to diarrhoea episodes and other infections. Probiotics reduced the aberrance.