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Two genes, bshA and bshB, encoding bile salt hydrolase enzymes (EC 3.5.1.24) were identified in the genome sequence of Lactobacillus acidophilus NCFM. Targeted inactivation of these genes via chromosomal insertion of an integration vector demonstrated different substrate specificities for these two enzymes.
OBJECTIVE: To select a probiotic bacteria that would reduce serum lipids in hypercholesterolaemic volunteers. DESIGN: A strain of lactobacillus was selected for its ability to metabolise cholesterol under varying conditions in vitro. Freeze-dried Lactobacillus acidophilus or placebo were then given in a double-blind randomised crossover study to volunteers with high cholesterols. SUBJECTS: A total of 80 volunteers with elevated cholesterols. INTERVENTIONS: Volunteers were randomly allocated to receive either two capsules containing freeze-dried L. acidophilus 3 x 10(10) CFU or placebo three times a day for 6 weeks. After a 6-week washout period, volunteers were crossed over to another 6 weeks of capsules. Serum lipids were measured at the beginning and end of each interventional period. RESULTS: L. acidophilus was able to reduce cholesterol and survive in an acid and bile environment. No changes in anthropomorphic measurements or in dietary records were seen between the baseline and final records or between the two sets of baseline records. There were no changes in serum lipids seen throughout the study. CONCLUSION: Despite the ability in vitro for L. acidophilus to reduce cholesterol, no effect was seen in volunteers.
A total of 205 Grey Leghorn chicks were hatched germfree for separate trials to determine the effects of Lactobacillus acidophilus treatment on pathogenic Salmonella typhimurium and Staphlococcus aureus. Prophylactic and therapeutic treatments with L. acidophilus were administered either before or after the pathogens were introduced. Prophylactic treatments significantly reduced chick mortality (P less than .01) and shedding of the pathogens (P less than .05). The L. acidophilus prophylactic treatments were also effective qualitatively in reducing the isolation of S. typhimurium and Staph. aureus from crop contents but not, to a great extent, from cecal or rectal contents of gnotobiotic chicks at postmortem. The average surface pH values for the crop, proventriculus, duodenum, cecum, and rectum for gnotobiotic chicks were 5.43, 5.02, 6.18, 6.56, and 6.71, respectively. The L. acidophilus treatments did not significantly affect surface pH of the various segments of the intestinal tract.
In addition to a high antimicrobial activity toward infective agents of some diseases of the human gastrointestinal tract, Lactobacillus acidophilus Ke-10 also had an immunomodulatory effect in physiological experiments both in vivo and in vitro. This strain of lactic acid bacteria was found to be able to restore the proliferation reaction of lymphocytes and their capacity to produce interleukin-2 (IL-2) in rats with a model radiation-induced immune deficiency.
Four human Lactobacillus acidophilus strains were tested for their ability to adhere onto human enterocyte like Caco-2 cells in culture. The LA 1 strain exhibited a high calcium independent adhesive property. This adhesion onto Caco-2 cells required a proteinaceous adhesion promoting factor, which was present in the spent bacterial broth culture supernatant. LA 1 strain also strongly bound to the mucus secreted by the homogeneous cultured human goblet cell line HT29-MTX. The inhibitory effect of LA 1 organisms against Caco-2 cell adhesion and cell invasion by a large variety of diarrhoeagenic bacteria was investigated. As a result, the following dose dependent inhibitions were obtained: (a) against the cell association of enterotoxigenic, diffusely adhering and enteropathogenic Escherichia coli, and Salmonella typhimurium; (b) against the cell invasion by enteropathogenic Escherichia coli, Yersinia pseudotuberculosis, and Salmonella typhimurium. Incubations of L acidophilus LA 1 before and together with enterovirulent E coli were more effective than incubation after infection by E coli.
Lactobacillus acidophilus, like many other bacteria, harbors a surface layer consisting of a protein (S(A)-protein) of 43 kDa. S(A)-protein could be readily extracted and crystallized in vitro into large crystalline patches on lipid monolayers with a net negative charge but not on lipids with a net neutral charge. Reconstruction of the S-layer from crystals grown on dioleoylphosphatidylserine indicated an oblique lattice with unit cell dimensions (a=118 A; b=53 A, and gamma=102 degrees ) resembling those determined for the S-layer of Lactobacillus helveticus ATCC 12046. Sequence comparison of S(A)-protein with S-proteins from L. helveticus, Lactobacillus crispatus and the S-proteins encoded by the silent S-protein genes from L. acidophilus and L. crispatus suggested the presence of two domains, one comprising the N-terminal two-thirds (SAN), and another made up of the C-terminal one-third (SAC) of S(A)-protein. The sequence of the N-terminal domains is variable, while that of the C-terminal domain is highly conserved in the S-proteins of these organisms and contains a tandem repeat. Proteolytic digestion of S(A)-protein showed that SAN was protease-resistant, suggesting a compact structure. SAC was rapidly degraded by proteases and therefore probably has a more accessible structure. DNA sequences encoding SAN or Green Fluorescent Protein fused to SAC (GFP-SAC) were efficiently expressed in Escherichia coli. Purified SAN could crystallize into mono and multi-layered crystals with the same lattice parameters as those found for authentic S(A)-protein. A calculated S(A)-protein minus SAN density-difference map revealed the probable location, in projection, of the SAC domain, which is missing from the truncated SAN peptide. The GFP-SAC fusion product was shown to bind to the surface of L. acidophilus, L. helveticus and L. crispatus cells from which the S-layer had been removed, but not to non-stripped cells or to Lactobacillus casei.
Lactobacillus acidophilus, Saccharomyces boulardii and Escherichia coli are probiotic strains used individually to protect against enteropathogenic agents. In order to determine if a synergistic effect of the individual protective mechanisms ordinarily attributed to each of these biotherapeutic agents is possible, we orally administered Lact. acidophilus H2B20, S. boulardii and E. coli EMO (LSE) to germfree mice. Ten days after colonization of the digestive tract, groups of animals associated (experimental) or not (control) with LSE were challenged orally with streptomycin resistant (Sfr) or streptomycin sensitive (Sfs) Shigella flexneri strains or Salmonella enteritidis subsp. typhimurium. Bacterial counts in faeces from experimental mice showed that the Sfr strain was eliminated 11 d after challenge while Sfs and S. enteritidis subsp. typhimurium colonized the digestive tract and continued to be present at high population levels (108 CFU g-1 of faeces), which is similar to that observed in control animals. All possible di- and monoassociations of the three probiotics with gnotobiotic mice were also performed before experimental oral infection with Sfr. The data showed that antagonism was obtained only when E. coli EMO was present. Different sensitivity of Sh. flexneri Sfr and Sfs to E. coli EMO antagonism could be explained by the different generation times between Sfr and Sfs, as shown by colonization kinetic experiments in the digestive tract of gnotobiotic mice.
Candida albicans grew at pH 4.6 or above in nutrient broth containing 5% glucose but was retarded at pH 7.7 by filtrates of Lactobacillus acidophilus grown in casitone broth. Vaginal implantation of nonfermented acidophilus milk, yogurt, or low-fat milk for preventing recurrence of monilia vaginitis subsequent to treatment with Nystatin was studied with 30 women. Reinfections within 3 mo according to product received were: no milk product, 3; yogurt, 1; nonfermented acidophilus milk, 1; and low-fat milk, 0.
Campylobacter pylori has been implicated as a causative factor in acid-peptic disease. Lactobacillus acidophilus is known to inhibit the growth of pathogens in the human gastrointestinal tract. We recovered C. pylori from gastric antral biopsies of seven patients with acid-peptic disease; the isolates were then cultured in brucella broth. The effect of L. acidophilus (cultured in DeMan-Rogosa-Sharpe broth) on the growth of C. pylori was tested by a mixed culture technique. L. acidophilus inhibited the growth of all seven isolates of C. pylori in vitro. All these isolates were also inhibited by the L. acidophilus culture supernatant (brucella blood agar cup technique) obtained at or after 48 h of incubation. Inhibition of C. pylori growth was also observed with 1 and 3% lactic acid but not with 0.5 and 1% hydrogen peroxide, the L. acidophilus sonic extract, or a citrate-phosphate buffer (pH 4.0). We conclude that the inhibitory action of L. acidophilus on C. pylori is dependent on an extracellular secretory product, probably lactic acid. This inhibitory effect may be of therapeutic relevance in patients with C. pylori-positive acid-peptic disease.
Effects of skim milk and its fermented product by Lactobacillus acidophilus on plasma and liver triglyceride and cholesterol levels were examined in diet-induced hypertriglyceridemic rats. Male Sprague-Dawley rats at 4 weeks of age were fed a hypertriglyceridemic diet that contained 20% coconut oil, 17.5% fructose, and 17.5% sucrose for 14 days. The test diet was supplemented with either 20% skim milk powder or 20% powder of skim milk fermented by L. acidophilus SBT 2062. Hypertriglyceridemia was observed in the control group, but plasma cholesterol levels were not increased. Skim milk suppressed the elevation of plasma triglyceride levels, while its fermented product had no significant effect. Both dairy products prevented the elevation of liver triglyceride and cholesterol levels, but had no effect on plasma cholesterol levels.
The relationships among growth in the presence of bile, deconjugation of sodium taurocholate, and assimilation of cholesterol by 19 cultures of Lactobacillus acidophilus were examined. Cultures of L. acidophilus were grown at 37 degrees C in lactobacilli MRS broth supplemented with sodium thioglycollate, sodium taurocholate, and cholesterol (cholesterol phosphatidyl choline micelles). Deconjugation activity was maximum in the late exponential phase of growth, which also coincided with maximum assimilation of cholesterol. Considerable variation existed among cultures in their ability to grow in the presence of bile, to deconjugate sodium taurocholate, and to assimilate cholesterol. However, statistical analyses revealed no significant correlations.
An S-layer (surface regular array) was found in the cell wall from six out of ten strains of Lactobacillus acidophilus examined by electron microscopic observations. All of the six strains which were shown to carry the S-layers belonged to the deoxyribonucleic acid (DNA) homology group A, but not to B, which had been classified by Johnson et al (Int. J. Syst. Bacteriol. 30: 53-68, 1980). On the other hand, the other four strains which possessed no S-layers were in the homology group B. The apparent molecular weights of the S-layer proteins ranged from 41 to 49 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Of the S-layer proteins from the six strains, three were susceptible to chemical cleavage with N-chlorosuccinimide, giving different peptide maps. All of the six S-layer proteins were fragmented by limited proteolysis with Staphylococcus aureus V8 protease, and gave markedly different peptide patterns by the subsequent peptide mapping analysis, except that the peptide maps of the S-layer proteins from the two strains which were in the same subgroup were identical.
The combination of PFGE and hybridization approaches was used to study the genome of Lactobacillus acidophilus neotype strain ATCC 4356. PFGE analysis of chromosomal DNA after digestion with each of the rare-cutting restriction enzymes I-CeuI, NotI, CspI, SmaI, ApaI and SgrAI allowed the size of the circular chromosome of L. acidophilus to be estimated at 2.061 Mbp. The physical map contained 86 restriction sites for the six enzymes employed, with intervals between the sites varying from 1 to 88 kbp (approximately 0.05-4.3 % of the chromosome). Based on the physical map, a genetic map was constructed via Southern blot analyses of L. acidophilus DNA using specific gene probes. A total of 73 probes representing key genes, including 12 rRNA (rrn) genes, were positioned on the latter map. Mapping analysis also indicated the presence of four rrn operons (rrnA-D) on the chromosome, each containing a single copy of each of the three rrn genes 16S (rrl), 23S (rrs) and 5S (rrf). Operon rrnD was inverted in orientation with respect to the others and contained a long 16S-23S intergenic spacer region with tRNAIle and tRNAAla genes, whereas the other operons contained a short spacer lacking any tRNA genes. The high-resolution physical/genetic map constructed in this study provides a platform for genomic and genetic studies of Lactobacillus species and for improving industrial and probiotic strains.
Lactobacillus acidophilus 74-2, which is used in probiotic products, was administered, with fructo-oligosaccharide in a milk-based product, to the second vessel (duodenum/jejunum) of the SHIME reactor, an in vitro simulation of the human intestinal microbial ecology. The main focus of this study was to monitor the changes of the population density of selected bacterial species in the intestine and the changes of metabolic activities during the supplementation of L. acidophilus and fructooligosaccharide in the SHIME reactor. Interestingly, the addition of L. acidophilus 74-2 with fructooligosaccharide gave rise to an increase of bifidobacteria. Moreover, major positive changes occurred in the production of volatile fatty acids: a strong upward trend was observed especially in the case of butyric acid and propionic acid. Furthermore a noticeable increase of beta-galactosidase activity was monitored, while the activity of beta-glucuronidase, generally considered undesirable, declined.
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To compare and assess ingestion of yogurt that contained live Lactobacillus acidophilus with pasteurized yogurt as prophylaxis for recurrent bacterial vaginosis (BV) and candidal vaginitis, we designed a crossover trial during which patients were examined monthly for candidal infection and BV while they were receiving either a pasteurized yogurt or a yogurt that contained live L acidophilus. Forty-six patients in 2 groups of 23 were randomly assigned to each of the study groups. At least 28 (61%) participated during the first 4 months of the study. Seven patients completed the entire study protocol. We concluded that daily ingestion of 150 mL of yogurt, enriched with live L acidophilus, was associated with an increased prevalence of colonization of the rectum and vagina by the bacteria, and this ingestion of yogurt may have reduced episodes of BV.
Recent work with a mouse model of Trichomonas vaginalis infection indicated that estrogenized BALB/c mice that were preinfected with Lactobacillus acidophilus showed a greater duration of T. vaginalis infection as compared to a control group of mice that were not treated with L. acidophilus. To examine the interaction between T. vaginalis and L. acidophilus further we performed in vitro competitive growth assays between the 2 species. Although the addition of L. acidophilus to the T. vaginalis cultures slowed the growth of the protozoa, the added bacteria did not increase trichomonad death. However, T. vaginalis had a deleterious effect on L. acidophilus growth in combined cultures when compared to matched controls. Using an initial inoculum of 10(5)/ml, at 40 hr the control L. acidophilus concentrations had grown to 1.3 x 10(7)/ml. However, in combined culture with T. vaginalis, L. acidophilus concentrations at 40 hr had fallen to 7.8 x 10(5)/ml and 6.1 x 10(4)/ml for the 10:1 (T. vaginalis at 10(4)) and 1:1 (T. vaginalis at 10(5) test ratios, respectively (P < 0.01). This demonstrates that T. vaginalis can cause the concentration of L. acidophilus to fall in vitro and may explain why the concentration of L. acidophilus in the vagina falls in trichomoniasis.