Intra-individual diversity and similarity of salivary and faecal microbiota

In the present study, polyphasic analysis [cultivation, combined with the fingerprinting of individual isolates, and denaturing gradient gel electrophoresis (DGGE)] was applied to study whether similar features concerning the diversity and temporal stability of selected bacterial groups could be detected intra-individually in two different niches - the oral cavity and the colon - from ten adult volunteers consuming probiotics. The predominant bacterial microbiota, Clostridium coccoides-Eubacterium rectale group and bifidobacterial populations, were generally stable in salivary and faecal samples, with the greater diversity seen in faeces. Furthermore, different species predominated at the two different sites. Lactobacillus group DGGE profiles were unstable, yet the intra-individual profiles from faecal and salivary samples collected at the same time resembled each other. The ingested probiotic product did not affect the stability of the bacterial groups studied. The culture-based analysis showed that most subjects harboured identical indigenous Lactobacillus genotypes in saliva and faeces (Lactobacillus rhamnosus, Lactobacillus gasseri, Lactobacillus paracasei and Lactobacillus plantarum group). Thus, identical indigenous lactobacilli were able to inhabit both ends of the orogastrointestinal tract, whereas the composition of the other bacterial groups studied varied between the two sites.

Inhibition of proliferation in colon cancer cell lines and harmful enzyme activity of colon bacteria by Bifidobacterium adolescentis SPM0212

In this study, we assessed the anticancer activity and bacterial enzyme inhibition of Bifidobacterium adolescentis SPM0212. B. adolescentis SPM0212 inhibited the proliferation of three human colon cancer cell lines: HT-29, SW 480, and Caco-2. SPM0212 also dose-dependently inhibited TNF-á production and changes in cellular morphology. B. adolescentis SPM0212 inhibited harmful fecal enzymes, including â-glucuronidase, â-glucosidase, tryptophanase, and urease. Thus, B. adolescentis SPM0212 exerts an anticancer effect and inhibits harmful fecal enzymes.

[Application of the methods of molecular systematics to classification and identification of bacteria of the genus Bifidobacterium]

The methods of molecular systematics currently used in the classification and identification of bifidobacteria are reviewed. The sequencing of the 16S rRNA gene and some other genes considered to be phylogenetic markers is a universal and effective approach to taxonomic characterization of members of the genus Bifidobacterium and to reliable identification of new isolates. Various techniques of obtaining DNA fingerprints (PFGE, RAPD, rep-PCR) are widely used for solving particular problems in identifying bifidobacteria. Bacteria of the genus Bifidobacterium are important organisms in biotechnology and medicine. The research into molecular systematics of bifidobacteria provides a basis not only for the solution of taxonomic problems, but also for monitoring of individual species in the environment and for more detailed study of the genetics and ecology of this group of microorganisms.

Metascardovia criceti Gen. Nov., Sp. Nov., from hamster dental plaque

A novel microorganism, Metascardovia criceti gen. nov., sp. nov., was isolated from dental plaque of golden hamsters fed with a high-carbohydrate diet. The three isolated strains, OMB104, OMB105, and OMB107, were Gram-positive, facultative anaerobic rods that lacked catalase activity. Analyses of the partial 16S rRNA and heat-shock protein 60 (HSP60) gene sequences of these isolates indicated that they belonged to the family Bifidobacteriaceae. However, in contrast to Bifidobacterium, one of the genera under this family, these isolates grew under aerobic conditions, and the DNA G + C contents were lower (53 mol%) than those of Bifidobacterium. On the basis of phylogenetic analyses using phenotypic characterization, and partial 16S rRNA and HSP60 gene sequences data, we propose a novel taxa, Metascardovia criceti for OMB105(T) (type strain=JCM 13493(T)=DSM 17774(T)) for this newly described isolate.

[Substrate phase state and time factor in variability of human fecal microbiota]

Effects of substrate phase state and time factor on variability of human fecal microbiota were studied. It was shown that microecological system of native feces was characterized by marked time-dependent variability. It is unstable and begins to destruct after 24 hours of cultivation. The most sensitive elements of the system were bifidobacteria and Escherichia coli. Change of phase state of biotope eliminated the effect of factor limiting the microecosystem development, which allowed species of obligate and transitory microflora to freely colonize the growth substrate and interact with each other. The mentioned facts demonstrate that fecal microbiota exists in the environment of excess of growth substrate, which colonization is limited by cluster structure of biotope of native feces. It was concluded that phase state of growth substrate and duration of cultivation are important factors determining the population variability of fecal microbiota.

From bacterial genome to functionality; case bifidobacteria

The availability of complete bacterial genome sequences has significantly furthered our understanding of the genetics, physiology and biochemistry of the microorganisms in question, particularly those that have commercially important applications. Bifidobacteria are among such microorganisms, as they constitute mammalian commensals of biotechnological significance due to their perceived role in maintaining a balanced gastrointestinal (GIT) microflora. Bifidobacteria are therefore frequently used as health-promoting or probiotic components in functional food products. A fundamental understanding of the metabolic activities employed by these commensal bacteria, in particular their capability to utilize a wide range of complex oligosaccharides, can reveal ways to provide in vivo growth advantages relative to other competing gut bacteria or pathogens. Furthermore, an in depth analysis of adaptive responses to nutritional or environmental stresses may provide methodologies to retain viability and improve functionality during commercial preparation, storage and delivery of the probiotic organism.

Differences in the composition of intestinal Bifidobacterium species and the development of allergic diseases in infants in rural Japan

BACKGROUND

Bifidobacterium is a dominant genus in the intestinal microbiota of infants and comprises many different species. A series of studies performed in northern Europe showed differences in the composition of Bifidobacterium species between allergic infants and healthy controls. Additional studies are needed to confirm this observation.

OBJECTIVE

To investigate the composition of fecal Bifidobacterium species in allergic infants and healthy controls in Japan, using molecular methods.

METHODS

Full-term born babies were followed up to 6 months of age at a local hospital in rural Japan. The presence or absence of allergy was determined based on allergic symptoms and skin prick tests. Fecal Bifidobacterium species in allergic infants (n=10), and healthy controls (n=16) were evaluated using nine Bifidobacterium species-specific or group-specific primers based on 16S rDNA sequences at 1, 3, and 6 months of age.

RESULTS

The number of the infants in whom no Bifidobacterium species could be found was four (15.4%) at 1 month, two (7.7%) at 3 months, and one (3.3%) at 6 months of age, all of whom were healthy controls. At 1 month of age, allergic infants had a higher prevalence f the Bifidobacterium catenulatum group than healthy controls (60.0% vs. 6.3%, P<0.01). At 6 months of age, allergic infants had a higher prevalence of B. bifidum than healthy controls (70.0% vs. 12.5%, P<0.01). These differences were not related to feeding method.

CONCLUSIONS

Our results in infants in rural Japan support the hypothesis that a compositional difference in intestinal Bifidobacterium species may be associated with the development of allergy in early infancy, although the responsible species might vary among countries or races.

Bifidobacterium pseudocatenulatum is associated with atopic eczema: a nested case-control study investigating the fecal microbiota of infants

BACKGROUND

Exposure to specific bacterial bowel commensals may increase/reduce the risk of atopic diseases.

OBJECTIVE

To compare fecal bacterial communities of young infants with/without eczema.

METHODS

Nested case-control study. Infants age 3 to 6 months with eczema (cases, n = 37) and without (controls, n = 24) were matched for sex, age, feeding (breast/bottle/mixed/solids), ethnicity. Information was collected on maternal/infant antibiotic exposure, feeding, gastrointestinal symptoms, family history of allergy. Eczema severity scoring was used (Severity Scoring of Atopic Dermatitis index). Samples were taken for determination of allergen-specific serum IgE (cases) and urinary/fecal eosinophilic protein X. Gastrointestinal permeability was measured. The compositions of fecal bacterial communities were analyzed (culture-independent, nucleic acid-based analyses).

RESULTS

There was no difference in overall profiles of fecal bacterial communities between cases and controls. Family history of allergy increased likelihood of bifidobacteria detection (history, 86%; no history, 56%; P = .047); breast-fed infants were more likely to harbor Bifidobacterium bifidum (odds ratio, 5.19; 95% CI, 1.47-18.36; P = .01). Bifidobacterium pseudocatenulatum was detected more commonly in feces of non-breast-fed children (odds ratio, 5.6; 95% CI, 1.3-24.3; P = .02) and children with eczema (eczema, 26%; no eczema, 4%; P = .04). There were no significant associations between clinical measurements and detection of B pseudocatenulatum.

CONCLUSION

Presence of B pseudocatenulatum in feces was associated with eczema and with exclusive formula-feeding; B bifidum was associated with breast-feeding.

Quantitative assessment of faecal bifidobacterial populations by real-time PCR using lanthanide probes

AIM

To develop real-time quantitative PCR methods, based on the use of probes labelled with a stable fluorescent lanthanide chelate, for the quantification of different human faecal bifidobacterial populations.

METHODS AND RESULTS

The designed quantitative PCR assays were found to be specific for the corresponding Bifidobacterium species or groups (Bifidobacterium longum group, Bifidobacterium catenulatum group, Bifidobacterium adolescentis, Bifidobacterium breve, Bifidobacterium angulatum, Bifidobacterium bifidum and Bifidobacterium dentium). The detection limits of the methodologies used ranged between 2 x 10(5) and 9 x 10(3) cells g(-1) of faeces. The applicability of the developed assays was tested by analysing 20 human faecal samples. Bif. longum group was found to be the qualitatively and quantitatively predominant bifidobacterial group.

CONCLUSIONS

The real-time PCR procedures developed here are specific, accurate, rapid and easy methods for the quantification of Bifidobacterium groups or species in human faecal samples.

SIGNIFICANCE AND IMPACT OF THE STUDY

The developed procedures will facilitate rapid and objective counting of large numbers of samples increasing our knowledge on the role of gut bifidobacterial microbiota in health and disease. This will contribute to the efficient use of intestinal bacterial assays in research, food and pharmaceutical development as well as in the assessment of dietary management of diseases.

Imbalance in intestinal microflora constitution could be involved in the pathogenesis of inflammatory bowel disease

Since genetically engineered animal models of inflammatory bowel disease (IBD) do not develop colitis under germ-free conditions, the intestinal microflora is thought to be one of the most important environmental factors associated with IBD. To understand the involvement of intestinal microflora in the pathogenesis of IBD, we analyzed the constituents of intestinal microflora in IBD. Faecal samples from 73 patients with ulcerative colitis (UC) and 23 patients with Crohn's disease (CD) were analyzed by quantitative PCR using 16S rRNA gene-targeted group-specific primers for Bacteroides fragilis group, Bifidobacterium, Clostridium coccoides groups, Clostridium leptum subgroup, Atopobium cluster, and seven species of Bacteroides. We analyzed the distribution of the predominant microflora by fluorescence in situ hybridization (FISH) using group-specific probes. We also examined the concentration of faecal organic acids produced by intestinal microflora. Contrary to previous reports, we found that the B. fragilis group was significantly decreased in the faeces of patients with IBD. Moreover, B. vulgatus was the predominant microflora in healthy controls and relatively decreased among IBD patients. Most of the microflora adhering to the colonic mucosa surrounding the mucus layer comprised C. coccoides group and Bifidobacterium. B. fragilis group mainly inhabited the faeces, but did not adhere to or invade the mucosa. The concentrations of propionic and butyric acids in the faeces were significantly decreased in patients with IBD. These findings indicate that IBD is not caused by a specific intestinal bacterial cluster or species and that disordered intestinal microflora could be involved in the pathogenesis of IBD.

Mucosa-associated bacterial diversity in relation to human terminal ileum and colonic biopsy samples

Little is known about bacterial communities that colonize mucosal surfaces in the human gastrointestinal tract, but they are believed to play an important role in host physiology. The objectives of this study were to investigate the compositions of these populations in the distal small bowel and colon. Healthy mucosal tissue from either the terminal ileum (n = 6) or ascending (n = 8), transverse (n = 8), or descending colon (n = 4) of 26 patients (age, 68.5 +/- 1.2 years [mean +/- standard deviation]) undergoing emergency resection of the large bowel was used to study these communities. Mucosa-associated eubacteria were characterized by using PCR-denaturing gradient gel electrophoresis (DGGE), while real-time PCR was employed for quantitative analysis. Mucosal communities were also visualized in situ using confocal laser scanning microscopy. DGGE banding profiles from all the gut regions exhibited at least 45% homology, with five descending colon profiles clustering at ca. 75% concordance. Real-time PCR showed that mucosal bacterial population densities were highest in the terminal ileum and that there were no significant differences in overall bacterial numbers in different parts of the colon. Bifidobacterial numbers were significantly higher in the large bowel than in the terminal ileum (P = 0.006), whereas lactobacilli were more prominent in the distal large intestine (P = 0.019). Eubacterium rectale (P = 0.0004) and Faecalibacterium prausnitzii (P = 0.001) were dominant in the ascending and descending colon. Site-specific colonization in the gastrointestinal tract may be contributory in the etiology of some diseases of the large intestine.

Molecularly assessed shifts of Bifidobacterium ssp. and less diverse microbial communities are characteristic of 5-year-old allergic children

The composition of intestinal microbiota and the Bifidobacterium group community in 20 allergic and 20 nonallergic 5-year-old children was visualized by PCR-denaturing gradient gel electrophoresis (DGGE). The number of dominant bands in the DGGE profiles was smaller in allergic children than in nonallergic children (P<0.001). Allergic children mainly formed a single group upon cluster analysis, whereas nonallergic children were divided between four different groups. In allergic children the Bifidobacterium adolescentis species prevailed, and in nonallergic children the Bifidobacterium catenulatum/pseudocatenulatum prevailed (P=0.01 and P=0.01, respectively). The less diverse composition of intestinal microbiota and prevalence of particular species of Bifidobacterium were characteristic of allergic children even at the age of 5 years.

Taxonomy of Lactobacilli and Bifidobacteria

Genera Lactobacillus and Bifidobacterium include a large number of species and strains exhibiting important properties in an applied context, especially in the area of food and probiotics. An updated list of species belonging to those two genera, their phylogenetic relationships and other relevant taxonomic information are reviewed in this paper. The conventional nature of taxonomy is explained and some basic concepts and terms will be presented for readers not familiar with this important and fast-evolving area, which importance is often underestimated. The analysis of biodiversity and its cataloguing, i.e. taxonomy, constitute the basis for applications and scientific communication: reliable identification and correct naming of bacterial strains are not only primary aims of taxonomic studies, but also fundamental elements in an applied context, for the tracking of probiotic strains and a non fraudulent labelling of fermented milks and pharmaceutical products containing probiotic microorganisms. A number of resources freely available have been listed and their use is suggested for people concerned with different aspects of taxonomy. Some perspectives in taxonomy have been outlined, in particular considering the role of culture independent analyses to reveal the still unknown and uncultured microorganisms. Finally, the impact of the availability of whole-genome sequences in taxonomy is briefly explained: they have already begun to give insights on bacterial evolution, which will surely have implications on taxonomy, even if the analysis of data for lactic acid bacteria is still limited to few species.

Safety assessment of dairy microorganisms: Propionibacterium and Bifidobacterium

The genera Propionibacterium and Bifidobacterium are clustered in the class Actinobacteria and form the anaerobic branch of coryneform bacteria. The dairy propionibacteria comprising four species P. freudenreichii, P. acidipropionici, P. jensenii and P. thoenii are industrially important as starter cultures in hard-cheese ripening and recently also as protective bio-preservatives and probiotics. These four species are considered as safe whereas cutaneous Propionibacterium species (also named "acnes group") are pathogens. In contrast, bifidobacteria in fermented dairy products and milk powder are exclusively used as probiotics; selected strains of several species (out of more than thirty) contribute to this task. It has been only rarely found that commensal bifidobacteria have been connected with certain dental and other infections. Consequently, only one single species, Bifidobacterium dentium, is recognized as pathogenic. Genome sequence analysis of Bifidobacterium longum and molecular biological analysis of other probiotic strains confirmed so far the absence of virulence and pathogenecity factors. However, tetracycline resistance genes tet(W), although probably not easy transferable, were found in Bifidobacterium strains, also in Bifidobacterium animalis subsp. lactis, the worldwide most used industrial strain. Conclusively, strains from the Propionibacterium and Bifidobacterium species in dairy food generally represent so far no health hazards.

Classification of a moderately oxygen-tolerant isolate from baby faeces as Bifidobacterium thermophilum

Background

Bifidobacteria are found at varying prevalence in human microbiota and seem to play an important role in the human gastrointestinal tract (GIT). Bifidobacteria are highly adapted to the human GIT which is reflected in the genome sequence of a Bifidobacterim longum isolate. The competitiveness against other bacteria is not fully understood yet but may be related to the production of antimicrobial compounds such as bacteriocins. In a previous study, 34 Bifidobacterium isolates have been isolated from baby faeces among which six showed proteinaceous antilisterial activity against Listeria monocytogenes. In this study, one of these isolates, RBL67, was further identified and characterized.

Results

Bifidobacterium isolate RBL67 was classified and characterized using a polyphasic approach. RBL67 was classified as Bifidobacterium thermophilum based on phenotypic and DNA-DNA hybridization characteristics, although 16S rDNA analyses and partial groEL sequences showed higher homology with B. thermacidophilum subsp. porcinum and B. thermacidophilum subsp. thermacidophilum, respectively. RBL67 was moderately oxygen-tolerant and was able to grow at pH 4 and at a temperature of 47°C.

Conclusion

In order to assign RBL67 to a species, a polyphasic approach was used. This resulted in the classification of RBL67 as a Bifidobacterium thermophilum strain. To our knowledge, this is the first report about B. thermophilum isolated from baby faeces since the B. thermophilum strains were related to ruminants and swine faeces before. B. thermophilum was previously only isolated from animal sources and was therefore suggested to be used as differential species between animal and human contamination. Our findings may disapprove this suggestion and further studies are now conducted to determine whether B. thermophilum is distributed broader in human faeces. Furthermore, the postulated differentiation between human and animal strains by growth above 45°C is no longer valid since B. thermophilum is able to grow at 47°C. In our study, 16S rDNA and partial groEL sequence analysis were not able to clearly assign RBL67 to a species and were contradictory. Our study suggests that partial groEL sequences may not be reliable as a single tool for species differentiation.

Isolation and molecular characterization of a cryptic plasmid from Bifidobacterium longum

An isolate from the fecal samples of children was identified as Bifidobacterium longum. A plasmid isolated from it pBIFA24 was 4,892 bp with three open reading frames, ORFI, ORFII, and ORFIII. ORFI encoded a replication protein involved in a rolling-circle replication mechanism, and three sets of tandem repeat sequences featuring iteron structure were identified. Secondary structure prediction analysis of ORFII suggested it was a transmembrane protein. ORFIII showed high amino acid sequence identity with some mobilization proteins and contained an oriT sequence.

Description of a new species, Bifidobacterium crudilactis sp. nov., isolated from raw milk and raw milk cheeses

A new Bifidobacterium species is described based on the study of ten Gram-positive strains with fructose-6-phosphate phosphoketolase activity. They are part of a phenotypic group comprising 141 strains isolated from raw milk and raw milk cheeses in French raw milk cheese factories. This group was separated by a numerical analysis based on API 50CH, API 32A tests and growth at 46 degrees C. A strong similarity of 16S rRNA sequences (99.8%) was shown between strain FR62/b/3(T) and Bifidobacterium psychraerophilum LMG 21775(T). However, low DNA-DNA relatedness was observed between their DNAs (31%). The new isolates are able to grow at low temperatures (all ten strains up to 5 degrees C) and strain FR62/b/3(T) grows under aerobic conditions, as does B. psychraerophilum. However, contrary to B. psychraerophilum, they do not ferment L-arabinose, D-xylose, arbutin or melezitose, but they do acidify lactose. The DNA G+C content of FR62/b/3(T) is 56.4mol%. Therefore, the name Bifidobacterium crudilactis sp. nov. is proposed, with its type strain being FR62/b/3(T) (=LMG 23609(T)=CNCM I-3342(T)).

Assessment of lipopolysaccharide-binding activity of Bifidobacterium and its relationship with cell surface hydrophobicity, autoaggregation, and inhibition of interleukin-8 production

This study was performed to screen probiotic bifidobacteria for their ability to bind and neutralize lipopolysaccharides (LPS) from Escherichia coli and to verify the relationship between LPS-binding ability, cell surface hydrophobicity (CSH), and inhibition of LPS-induced interleukin-8 (IL-8) secretion by HT-29 cells of the various bifidobacterial strains. Ninety bifidobacteria isolates from human feces were assessed for their ability to bind fluorescein isothiocyanate (FITC)-labeled LPS from E. coli. Isolates showing 30-60% binding were designated LPS-high binding (LPS-H) and those with less than 15% binding were designated LPS-low binding (LPS-L). The CSH, autoaggregation (AA), and inhibition of LPS-induced IL-8 release from HT-29 cells of the LPS-H and LPS-L groups were evaluated. Five bifidobacteria strains showed high levels of LPS binding, CSH, AA, and inhibition of IL-8 release. However, statistically significant correlations between LPS binding, CSH, AA, and reduction of IL-8 release were not found. Although we could isolate bifidobacteria with high LPS-binding ability, CSH, AA, and inhibition of IL-8 release, each characteristic should be considered as strain dependent. Bifidobacteria with high LPS binding and inhibition of IL-8 release may be good agents for preventing inflammation by neutralizing Gram-negative endotoxins and improving intestinal health.

Screening of exopolysaccharide-producing Lactobacillus and Bifidobacterium strains isolated from the human intestinal microbiota

Using phenotypic approaches, we have detected that 17% of human intestinal Lactobacillus and Bifidobacterium strains could be exopolysaccharide (EPS) producers. However, PCR techniques showed that only 7% harbored genes related to the synthesis of heteropolysaccharides. This is the first work to screen the human intestinal ecosystem for the detection of EPS-producing strains.

Reagentless identification of human bifidobacteria by intrinsic fluorescence

A new identification method for bifidobacteria species from the human gastrointestinal tract was developed based on the measurement and statistical analysis of the intrinsic fluorescence of aromatic amino acids (AAA) and nucleic acids (NA), following their excitation at 250 nm. The model was constructed by recording the fluorescence spectra of 53 Bifidobacterium strains of 10 different species, including the corresponding type strains, and validated by analyzing the spectra data from nine further problem strains. Principal components analysis (PCA) and factorial discriminant analysis (FDA) of the results showed the technique to distinguish between the isolates at the species level; the Bifidobacterium pseudolongum subspecies (globosum and pseudolongum) could also be distinguished. The proposed method provides a powerful, inexpensive and convenient means of rapidly identifying intestinal bifidobacteria, which could be of help for large probiotic surveys.

Rapid identification of Lactobacillus and Bifidobacterium in probiotic products using multiplex PCR

Lactic acid bacteria (LAB) are beneficial for the gastrointestinal tract and reinforce immunity in human health. Recently, many functional products using the lactic acid bacteria have been developed. Among these LAB, Lactobacillus acidophilus, Lactobacillus rhamnosus, Bifidobacterium longum, and Bifidobacterium bifidum are frequently used for probiotic products. In order to monitor these LAB in commercial probiotic products, a multiplex PCR method was developed. We designed four species-specific primer pairs for multiplex PCR from the 16S rRNA, 16S-23S rRNA intergenic spacer region, and 23S rRNA genes in Lactobacillus acidophilus, Lactobacillus rhamnosus, Bifidobacterium longum, and Bifidobacterium bifidum. Using these primer pairs, 4 different LAB were detected with high specificity in functional foods. We suggest that the multiplex PCR method developed in this study would be an efficient tool for simple, rapid, and reliable identification of LAB used as probiotic strains.

Intra-specific composition and succession of Bifidobacterium longum in human feces

Intra-species analysis of pulsed field gel electrophoresis (PFGE) on human fecal Bifidobacterium longum isolates revealed that a majority of 12 Japanese subjects harbored strains of unique PFGE types or subtypes over a 68-week period, suggesting that "indigenous"Bifidobacterium strains remain stable for a considerable time in each individual intestinal microbiota.

Analysis of bifidobacterial evolution using a multilocus approach

Bifidobacteria represent one of the most numerous groups of bacteria found in the gastrointestinal tract of humans and animals. In man, gastrointestinal bifidobacteria are associated with health effects and for this reason they are often used as functional ingredients in food and pharmaceutical products. Such applications may benefit from or require a clear and reliable bifidobacterial species identification. The increasing number of available bacterial genome sequences has provided a large amount of housekeeping gene sequences that can be used both for identification of bifidobacterial species as well as for understanding bifidobacterial evolution. In order to assess their relative positions in the evolutionary process, fragments from seven conserved genes, clpC, dnaB, dnaG, dnaJ1, purF, rpoC and xfp, were sequenced from each of the currently described type strains of the genus Bifidobacterium. The results demonstrate that the concatenation of these seven gene sequences for phylogenetic purposes allows a significant increase in the discriminatory power between taxa.

Antibiotic susceptibility of Bifidobacterium thermophilum and Bifidobacterium pseudolongum isolates from animal sources

The widespread use of antimicrobial substances has led to resistant populations of microorganisms in several ecosystems. In animal husbandry, the application of antibiotics has contributed to resistance development in pathogenic and commensal bacteria. These strains or their resistance genes can be spread along several ecological routes, including the food chain. Antibiotic resistance is important in terms of the safety of industrial strains, such as probiotics for food and feed. Bifidobacterium thermophilum and Bifidobacterium pseudolongum are known to comprise the major part of the bifidobacterial microbiota in the gut and feces of cattle and pigs. In this study, the antimicrobial susceptibility in bifidobacterial isolates of these species was investigated. Isolates from the beef and pork production chain were identified and typed to strain level, and the antimicrobial susceptibility level was tested to a set of antibiotics. Isolates with low susceptibility levels were screened by PCR for already described resistance genes. Strains atypically resistant to clindamycin, erythromycin, and tetracycline were determined. The resistance genes tet(O), tet(W), and erm(X) were detected in the bifidobacterial species that were examined.

Identification and differentiation of Lactobacillus, Streptococcus and Bifidobacterium species in fermented milk products with bifidobacteria

The aim of this study was to identify and discriminate bacteria contained in commercial fermented milks with bifidobacteria by the use of amplified ribosomal DNA restriction analysis (ARDRA) and randomly amplified polymorphic DNA (RAPD) techniques. ARDRA of the 16S rDNA gene and RAPD were performed on 13 Lactobacillus strains, 13 Streptococcus and 13 Bifidobacterium strains isolated from commercial fermented milk. Lactobacillus delbrueckii, Streptococcus thermophilus and Bifidobacterium animalis isolates were identified by genus- and species-PCR and also, they were differentiated at genus and species level by ARDRA using MwoI restriction enzyme. The ARDRA technique allowed for the discrimination among these three related genus with the use of only one restriction enzyme, since distinctive profiles were obtained for each genus. Therefore it can be a simple, rapid and useful method for routine identification. Also, RAPD technique allowed the discrimination of all bacteria contained in dairy products, at genus- and strain-level by the performance of one PCR reaction.