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A total of 74 Streptococcus thermophilus isolates collected between 1948 and 2005 from different environments were investigated to assess erythromycin, clindamycin, streptomycin, gentamicin, tetracycline and ampicillin susceptibility by means of microdilution, Etest and disk diffusion methods. For this purpose a new S. thermophilus Susceptibility test Medium (SSM) was developed. This medium allowed a better identification of strains with atypical tetracycline resistance. The recipe is a mixed formulation of Iso-Sensitest medium (90% v/v) and M17 medium (10% v/v) supplemented with lactose (0.5% w/v). The overall agreement of the techniques was good with exception of tetracycline, for which Etest provided lower MICs than the microdilution method. Most strains were susceptible to all the antibiotics tested while a few erythromycin, tetracycline and streptomycin resistant strains were detected.

Microbiological risk in the first part of life is endowed with peculiar features when compared to the same risk in adulthood. The purpose of this review is to highlight these age-related traits. While pathogens harmful for neonates and infants have been reviewed, less attention has been paid to the role played by the infant gut as battle field between pathogens and protecting bacteria or between pathogens and the immune system. Immediately after birth a race for colonizing the gut begins; the main tool for neonates to select good bacteria is represented by mother's milk. Quite surprisingly, this milk carries potentially harmful bacteria, but antibodies, oligosaccharides and the whole breast milk composition provide a powerful selective tool. Nevertheless this selective action is deeply influenced by the type and/or time (i.e. premature) of delivery or in premature subjects; recent data also show that breast milk could have a different potential in selecting bacterial species. The hygienic conditions of parents and, more generally, of the surrounding environment play a role in the selection of the intestinal biota of infants. It is then possible to group neonates according to the composition of the microbiota. Results of ecological studies suggest that neonates with a different microbiota could have a different microbiological risk.

The minimum inhibitory concentrations (MICs) of six antibiotics with activity against gram-positive bacteria (ampicillin, clindamycin, erythromycin, gentamicin, streptomycin, and tetracycline) were determined by microdilution and the Etest in 121 Lactobacillus plantarum strains of plant and dairy origin. MIC values for all antibiotics varied widely between strains. The analysis of both absolute MICs and their distribution was used to define new susceptibility-resistance cutoff values for all antibiotics, except for streptomycin. Based on these new cutoffs, the studied strains were nearly all identified as either susceptible (ampicillin, clindamycin, erythromycin, and gentamicin) or intrinsically resistant (streptomycin). The exceptions were four strains with MICs for tetracycline higher than the cutoff point (64 microg ml(1)); these were suspected to harbor acquired resistance determinants.

With the aim of developing new functional foods, a traditional product, the table olive, was used as a vehicle for incorporating probiotic bacterial species. Survival on table olives of Lactobacillus rhamnosus (three strains), Lactobacillus paracasei (two strains), Bifidobacterium bifidum (one strain), and Bifidobacterium longum (one strain) at room temperature was investigated. The results obtained using a selected olive sample demonstrated that bifidobacteria and one strain of L. rhamnosus (Lactobacillus GG) showed a good survival rate, with a recovery of about 10(6) CFU g(-1) after 30 days. The Lactobacillus GG population remained unvaried until the end of the experiment, while a slight decline (to about 10(5) CFU g(-1)) was observed for bifidobacteria. High viability, with more than 10(7) CFU g(-1), was observed throughout the 3-month experiment for L. paracasei IMPC2.1. This strain, selected for its potential probiotic characteristics and for its lengthy survival on olives, was used to validate table olives as a carrier for transporting bacterial cells into the human gastrointestinal tract. L. paracasei IMPC2.1 was recovered from fecal samples in four out of five volunteers fed 10 to 15 olives per day carrying about 10(9) to 10(10) viable cells for 10 days.

Background: Exclusive enteral nutrition (EN) is an established primary therapy for pediatric Crohn's disease (CD). The mechanism of action of such treatment is still conjectural. The aim of the present study was to investigate if EN-induced remission is associated with modification of the fecal microflora in CD., Methods: Stool samples were collected from 5 healthy children and adolescents over a period of 3 months, and from 9 children and adolescents with active CD. To induce disease remission, children with CD received a course of exclusive EN for 8 weeks with a polymeric formula (Modulen IBD, Nestlè). At the end of the course of exclusive EN, children returned to a free diet but continued to take 40% of the daily caloric intake as polymeric formula. Fecal microflora was analyzed by 16S ribosomal DNA polymerase chain reaction and temperature gradient gel electrophoresis (TGGE) with direct visual comparison of band profiles of PCR products., Results: In 8 of 9 children, the exclusive EN alone induced disease remission. In 1 child, it was necessary to add steroids to the exclusive EN course to achieve remission. In all children with CD, analysis of gel band distribution revealed profound modification of the fecal microflora after exclusive EN. Variations of band distribution corresponding to different bacterial species were observed also in children on partial EN and required time to achieve stability of the band profile. In contrast, control healthy children showed a host-specific and stable TGGE profile over time., Conclusion: These data suggest that a possible mechanism of action of EN in inducing disease remission in CD is the capacity of modification of gut microflora. Possible explanations of such capacity are both low residue and prebiotic properties of the polymeric liquid formula.

Probiotics are live micro-organisms that when administered in adequate amounts confer a health benefit on the host. Consumption of yoghurt has been shown to induce measurable health benefits linked to the presence of live bacteria. A number of human studies have clearly demonstrated that yoghurt containing viable bacteria (Streptococcus thermophilus and Lactobacillus delbrueckii sp. bulgaricus) improves lactose digestion and eliminates symptoms of lactose intolerance. Thus, these cultures clearly fulfil the current concept of probiotics.

We tested the therapeutic relevance of auto aggregation in lactobacilli by comparing the effect on DSS induced colitis of viable Lactobacillus crispatus M247, isolated from healthy humans, to L. crispatus MU5, an isogenic spontaneous mutants of M247, the latter lacking the auto aggregation phenotype which allows the adhesion to human mucus. Aggregating L. crispatus M247, but not the non-aggregating MU5, was retrievable from mice feces and adherent to the colonic mucosa. Daily administration of L. crispatus M247, but not heat killed L. crispatus M247 or aggregation deficient L. crispatus MU5, dose-dependently reduced the severity of DSS colitis. Indeed, L. crispatus MU5 administered in a 30% sucrose solution, known to restore the aggregation phenotype, had a protective effect comparable to mice receiving L. crispatus M247. These results indicate that a surface-mediated property such as aggregation may play a pivotal role in the protective effects obtained by dietary supplementation with L. crispatus M247 during colitis.

The development of intestinal microflora in newborns is strictly related to the kind of feeding. Breast-fed infants, unlike the bottle-fed ones, have an intestinal ecosystem characterized by a strong prevalence of bifidobacteria and lactobacilli. Data available so far in the literature show that, among the numerous substances present in human milk, oligosaccharides have a clear prebiotic effect. They are quantitatively one of the main components of human milk and are only partially digested in the small intestine, so they reach the colon, where they stimulate selectively the development of bifidogenic flora. Such results have been recently proved both by characterization of oligosaccharides in breast-fed infant feces and by the study of intestinal microflora using new techniques of molecular analysis, confirming that human milk oligosaccharides represent the first prebiotics in humans.

Background: Use of synbiotic preparations as dietary supplement is believed to be a valid approach to restore and maintain colonic microflora. However, only few papers have been published on the assessment of these food supplements and none of them have used molecular biology techniques to evaluate the effects of the probiotic components., Methods: Twelve healthy volunteers were recruited. Faecal samples were taken before and at various time points during the administration period and at day 3 in the post-treatment period. Stool culture were performed and amplified ribosomal DNA restriction analysis was used to detect L. paracasei, the major bacterial component of the synbiotic products., Results: An increase of at least 1 log of L. paracasei-like bacteria was observed in all subjects. An increase of as much as 3 log was seen in subjects who had a low number of L. paracasei-like lactobacilli at the baseline. The counts of L. paracasei-like lactobacilli were found to persist for at least 3 days after discontinuation of intake in healthy volunteers in 7 subjects. Genetic analysis showed that the maiority of vancomicin insensitive lactobacilli were real L. paracasei, as the strains administered with the tested product., Conclusion: This study has shown that the strains of L paracasei administered with a synbiotic dietary supplement are able to survive through the gastrointestinal tract and to persist for at least a few days. It was also shown the efficacy of a synbiotic preparation to positively affect the microflora of healthy volunteers.

Lactobacillus helveticus CNRZ 892 contains a surface layer (S-layer) composed of protein monomers of 43 kDa organized in regular arrays. The gene encoding this protein (slpH) has been cloned in Escherichia coli and sequenced. slpH consists of 440 codons and is preceded by a ribosome-binding site (RBS) and followed by a putative rho-independent terminator. Indeed, Northern analysis revealed that slpH is a monocistronic gene. The gene is preceded by a possible promotor of which the -35 and -10 hexanucleotides are separated by 17 nt. By primer extension analysis the transcription start site was mapped at 7 nt downstream of the -10 sequence while the deduced amino acid sequence of SlpH shows a leader peptide of 30 aa. The slpH gene has been amplified by PCR and the fragment, carrying the complete gene from the RBS to the stop codon, has been cloned in a lactococcal gene expression vector downstream of promoter P32. Lactococcus lactis MG1363 carrying the resulting plasmid produced and secreted an S-layer monomer with the same molecular mass as the authentic L. helveticus CNRZ 892 SlpH, as judged by SDS-PAGE. Immunoelectron microscopy revealed that SlpH was bound to the lactococcal cell walls in small clumps and accumulated in the growth medium as small sheets.