No abstract

Aims: The study of two human strains of Lactobacillus to be used as probiotics in the gastrointestinal tract. Methods and Results: The Lactobacillus acidophilus UO 001 and Lact. gasseri UO 002, were resistant to the gastrointestinal conditions (pH 2 and 3, presence of pepsin, pancreatin or bile salts), the resistance was enhanced in the presence of skimmed milk. Additionally, adhered to Caco-2 cells through glycoproteins in Lact. gasseri and carbohydrates in the case of Lact. acidophilus. These strains are able to inhibit the growth of certain enteropathogens: Salmonella, Listeria and Campylobacter without interfering with the normal microbiota of the gastrointestinal tract, as stated by using the mixed culture and the spot agar test. Finally, strongly adherent Lact. gasseri were found to inhibit the attachment of Escherichia coli O111 to intestinal Caco-2 cells under the condition of exclusion. Conclusions: These results indicate that the two strains of Lactobacillus from human origin present important properties for survival in, and colonization of, the gastrointestinal tract, that give them potential probiotic. Significance and Impact of the Study: Two strains of Lactobacillus isolated from human vagina of healthy premenopausal women could be promising candidates to be used in the preparation of probiotic products and for their use as health-promoting bacteria.

Three strains of Lactobacillus, identified asLactobacillus acidophilus, Lactobacillus gasseri, and Lactobacillus jensenii, were selected from among 70 isolates from the vaginas of healthy premenopausal women for properties relevant to mucosal colonization or antagonism. All three self-aggregated and adhered to epithelial vaginal cells, displacing well-known vaginal pathogens, such as G. vaginalis, and inhibiting the growth in vitro ofEscherichia coli and Streptococcus agalactiae. The surface components involved in self-aggregation appeared to be proteins for L. gasseri and lipoproteins for L. acidophilus and L. jensenii, as judged by susceptibility to treatment with appropriate degrading enzymes. The factors responsible for adherence to epithelial vaginal cells seemed to be glycoproteins (L. acidophilus and L. gasseri) and carbohydrate (L. jensenii). The receptors of the vaginal cells were glycolipids, which presumably were the targets of the competition observed between the lactobacilli and the pathogenic microbes.

S. 1997. Lactobacillus gasseri 2459, isolated from the human vagina, exhibits a strong autoaggregating phenotype. Filter-sterilized spent supernatants of this strain promote aggregation of Lact. plantarum LL441 and Enterococcus faecalis EF. Aggregation was abolished upon exposure of the cells to proteases and, in the case of Ent. faecalis, to metaperiodate, which suggests the involvement of cell-surface proteins and glycoproteins, respectively, in the aggregation phenotype. In accordance with this, a 75 kDa surface protein, and possibly another of approximately 94 kDa, appears in Lact. plantarum LL441 cultures incubated with Lact. gasseri culture supernatants. The diffusible aggregation promoting factor was purified from stationary phase culture supernatants and determined to be a 2 kDa hydrophilic peptide active at pH 3-4 and stable at neutral and acid pH. The activity was resistant to heat, chymotrypsin, chelating agents, triton X-100 and reducing agents, but sensitive to other proteases and SDS.

The characteristics required of lactobacilli as probioties are the following: beneficial function, easy cultivation, nonpathogenicity, adhesion, and population stability. Several studies have assessed the potential of lactobacilli in the prevention or treatment of certain genitourinary tract infections such as bacterial vaginosis, vaginitis, or urinary tract infections. The main goal of therapy with biotherapeutic agents should be to prevent overgrowth of a pathogen until such a time that the normal microbiota can be reestablished. The possibility of using lactobacilli is promising, especially in pregnant women and in the case of patients with recurrent genitourinary tract infections produced by strains with resistance to several antibiotics. In addition, probiotic therapy is considered as "natural" and without side effects in contrast with conventional pharmaceutical treatments, but there is a limited array of tested biotherapeutic agents and a lack of pharmacokinetic data.