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Clostridium difficile infection (CDI) is the most common identifiable cause of diarrhoea in hospitalized patients. Current therapies rely on the administration of metronidazole or vancomycin, which reduce vegetative populations of C. difficile in the bowel. Recurrence of the disease when treatment with these antibiotics ceases indicates that metronidazole and vancomycin affect not only C. difficile but also commensal populations that normally mediate competitive exclusion. Fidaxomicin is a new antibiotic that inhibits C. difficile. Our study shows that fidaxomicin had little effect on the composition of the faecal microbiota in terms of its major phylogenetic clusters. Notably, clostridial clusters XlVa and IV, and Bifidobacterium, were much less affected by fidaxomicin compared to vancomycin treatment. These findings help to explain the substantially reduced rates of relapse following treatment of CDI with fidaxomicin in recent clinical trials. DOI 10.1099/mic.0.042010-0

Members of the genus Lactobacillus are common inhabitants of the proximal gastrointestinal tract of animals such as mice, rats, chickens and pigs, where they form epithelial biofilms. Little is known about the traits that facilitate biofilm formation and gut colonization. This study investigated the ecological role of a glucosyltransferase (GtfA) and inulosucrase (Inu) of Lactobacillus reuteri TMW 1.106 and a fructosyltransferase (FtfA) of L. reuteri LTH5448. In vitro experiments using isogenic mutants revealed that GtfA was essential for sucrose-dependent autoaggregation of L. reuteri TMW1.106 cells under acidic conditions, while inactivation of Inu slowed the formation of cell aggregates. Experiments using an in vitro biofilm assay showed that GtfA and Inu contributed to biofilm formation of L. reuteri TMW1.106. Experiments using ex-Lactobacillus-free mice revealed that the ecological performance of the inu mutant, but not of the gtfA or ftfA mutant, was reduced in the gastrointestinal tract when in competition with the parental strain. In the absence of competition, the gtfA mutant showed delayed colonization of the murine gut relative to the wild-type. In addition, the gtfA mutant showed reduced ecological performance in competition experiments with Lactobacillus johnsonii #21. From the evidence provided in this study we conclude that GtfA and Inu confer important ecological attributes of L. reuteri TMW1.106 and contribute to colonization of the mouse gastrointestinal tract.

Comparative studies are carried out on two Campylobacter jejuni strains, T1016 and Pstau, in relation to their prevalence in human infections and on poultry meat in a specific geographical area of New Zealand. The strain comparisons have used an in vitro cell invasion assay, microarray-based comparative genomic hybridization, flagellin A (FlaA) characteristics obtained from amino acid sequences, and competitive-exclusion experiments with chickens.

A study was conducted to measure the impact on the gut microbiota of rats of the consumption of diets supplemented with beta-glucans extracted from barley flour. The results show that HV beta-glucan could produce a prebiotic effect in the ceca of rats, at least under the specific dietary conditions that were used.

The physiological and ecological role for the luxS gene in Lactobacillus reuteri 100-23C is defined by constructing a luxS mutant by insertional mutagenesis. The results show that LuxS influences important ecological attributes of L. reuteri 100-23C, the consequences of which are niche specific.

Culture-based enumeration of selected bacterial populations, monitoring of the bifidobacterial species and strain composition by nucleic acid-based methods were used for measuring the impact of the consumption of three biscuits per day, containing oligosaccharide on the fecal microbiota of humans. Physiological methods may prove to be more informative as compared to the phylogenetic approach during the analysis of the gut ecosystem.

Researchers describe a PCR technique based on the transaldolase gene in Bifidobacterium coupled with denaturing gradient gel electrophoresis that can distinguish between species. This is possible because bifidobacteria produce 14 or more different types of transaldolase. Because they produce different electrophoretic patterns, the transaldolase genes must have variable sequences.

Researchers describe the development of PCR primers specific for Lactobacillus, Pediococcus, Leuconostoc, and Weissella. Lactic acid bacteria make up less than 1% of the intestinal microflora, and are not easily detectable using universal PCR primers.

Research demonstrates that intestinal Lactobacillus accumulates bile acids as shown by the accumulation of cholic acid. Data indicate that the acid uptake is mediated by the transmembrane proton gradient.

The influence of different functional elements of plasmid pGT232, which is indigenous in Lactobacillus reuteri 100-23, on maintaining recombinant plasmids in L. reuteri populations in vitro and in vivo is discussed. The plasmid replicates via the rolling-circle mechanism. The reconstituted lactobacillus-free (RLF) mouse is the experimental animal model for the preliminary studies. Stable maintenance of the pGR232-derived plasmids in the lactobacillus population in vivo required an additional 1.0-kb sequence having a putative single-strand replication origin (SSO). The SSO of pGT232 is throught to be novel and acts in an orientation-specific manner.

Microbiological research shows that strains of the microorganisms lactobacilli and bifidobacteria found in human feces vary in number. Pulsed-field gel electrophoresis and ribotyping experiments were used to select that the most common strains for immunological studies. Immunological analysis suggests that antibodies react to the organism's genus and not its strain.

An endo-1,3-1,4-beta-glucanase gene from Bacillus macerans has been cloned and expressed in Lactobacillus reuteri. The lactobacilli secreted the beta-glucanase gene which means that B. macerans secretion signals can be recognized by Lactobacillus cells. The beta-glucanase gene could be used to synthesize heterologous peptides of L. reuteri. A new promoter probe vector for L. reuteri can be made from the synthesis of plasmid pNCKH113.

Bifidobacteria count is more stable as compared to lactobacillus count in the fecal samples of two humans studied over a period of one year. The presence of five bifidobacteria strains is seen throughout the study period, of which one strain is predominant. The second subject harbors five to six bifidobacterial strains, the composition of which varies throughout the study period. However, one lactobacillus strain is numerically dominant in both the humans for the complete study period.

Streptococcus (S) gordonii has a hexa-heptapeptide permease uptake system with a high degree of genetic similarity to that found in S. pneumoniae. The S. gordonii system differs only in its binding-protein requirements. Specifically, the cytoplasmic-membrane bound lipoproteins HppA, HppG and HppH were found to be necessary for peptide utilization in the bacterium, whenever the peptides to be processed had five to seven amino acid residues. HppA and HppH, in particular, were crucial to oligopeptide uptake.

Four DNA probes were constructed by cloning at random from Lactobacillus DNA in plasmid vector pBR322. These DNA probes hybridized to DNA from Lacotobacillus acidophilus O. Two of these DNA probes, pSR1 and pSR2, comprised vector and plasmid DNA inserts while the other two, pSR3 and pSR4, consisted of vector and chromosomally obtained inserts. These probes were employed to determine strain O in digestive tract samples of piglets. The piglets were inoculated 24 hours before the culture was taken from them. The probes did not hybridize to the DNA in these piglets.

Ribotyping is used to determine the stability of ribotypes to distinguish Lactobacillus strains present in the digestive track. Ribotyping helps distinguish 54 Lactobacillus strains comprising 11 strains of Type Culture collections and 1 strain of Escherichia coli. Stability of ribotypes of four strains of Lactobacilli present in the digestive track of mice is detected, and it is revealed that within a period of twenty two months, a ribotype pattern can vary.

Examination of the activity of bile salt hydrolase isolated from five Lactobacillus strains of murine origin reveals the range of activities of these enzymes. Colonization of Lactobacillus strains in the murine gastrointestinal tract does not require the production of bile salt hydrolase. Presence of lactobacilli exerts no influence on the growth rate of mice.

Real-time quantitative PCR assay targeting a 16S-23S intergenic space region sequence is designed for measuring the sizes of populations of Lactobacillus salivarius present in ileal digesta collected from broiler chickens. Stocking densities have not affected the numbers of Lactobacillus salivarius cells in the ileum, whereas a diet containing meat and bone meal has reduced the size of the Lactobacillus salivarius populations relative to that of chickens given the controlled diet.

Thirty-eight isolates of Lactobacillus gallinarum cultured from the crops of broiler chickens are screened for the presence of genes encoding S-layer proteins. The results provide a basis for the investigation of gene duplication and sequence variation as mechanisms by which bacterial strains of the same species can share the same habitat.

The construction of a bacterial artificial chromosomes (BAC) library using DNA extracted directly from the large-bowel microbiota of BALB/c mice is described. The library consisting of 5,760 clones with an average insert size of 55 kbp is screened for the production of enzymes that degrade lichenin, a 1,3-1,4-beta-glucan.

The identification and characterization of a gene encoding a large surface protein (Lsp) and the testing of insertional mutants of the lsp gene and of the three in vivo-induced genes for ecological performance in the reconstituted Lactobacillius-free (RLF) mouse gut is discussed. It is found that homologues of lsp and msrB are present in the genomes of several strains of Lactobacillus and may play an important role in the maintenance of these bacteria in gut ecosystems.

Lactobacilli, member of a lactic acid bacteria, is useful in the production of dairy products. Lactobacilli is a model for research for biomedical applications as well as acquiring of knowledge of cell formation in the gut ecosystem of microorganisms.

The microflora of the crop was investigated throughout the broiler production period using PCR combined with denaturing gradient gel electrophories and selective bacteriological culture of lactobacilli followed by amplified ribosomal DNA restriction analysis. The results provide knowledge of the Lactobacillus microflora in the crops of birds of different ages nucleic acid-based methods of detection and identification.

Research describes development of a method based on in vivo expression technology for the detection of genes of lactobacilli induced in the murine gut and their functionality. The in vivo expression system is plasmid-based and consists of two reporter genes that identify the induction of specific genes in the gastrointestinal tract.

Research examines the composition of the bacterial community with respect to ileal contents of 7-, 14-, 21-, and 35-day-old broiler chickens fed with different dietary fat sources and subtherapeutic concentrations of the growth promoters salinomycin and avilamycin in bacteriological cultures. Results show that the microflora composition is age dependent and influenced by dietary fat source and antibiotics.

Spectrofluorometry helps determine concentration of conjugated and unconjugated bile acid in the small bowel contents and portal serum samples from mice with and without lactobacilli as gastrointestinal inhabitants. Mice containing lactobacilli and bile salt hydrolase activity in gastrointestinal tracts exhibit higher amounts of unconjugated bile acids in small bowel content compared to animals lacking lactobacilli. Lactobacillus-produced bile salt hydrolase is active under conditions existing in proximal bowel of mice.