Antimicrobial potential of probiotic or potentially probiotic lactic acid bacteria, the first results of the international European research project PROPATH of the PROEUHEALTH cluster

Characterization of lactic acid bacteria isolated from the poultry intestinal environment with anti-Salmonella activity in vitro

The purpose of this research was the genotypic identification of lactic acid bacteria (LAB), isolated from the gastrointestinal tract (GIT) of healthy adult birds, and the study of their safety regarding antibiotic resistance, physiological and functional properties involved in the colonization of the GIT of poultry, and Salmonella exclusion, as members of a potential mixed probiotic supplement for poultry. The nucleotidic sequence from Lactobacillus crispatus P1, L. animalis L3, and Enterococcus faecium CRL 1385 (ex-J96) showed 100, 99.8, and 99.3% identity with L. crispatus DSM 20584 T, Ligilactobacillus salivarius ATCC 11741 T, and E. faecium ATCC 19434 T, respectively. These strains showed no resistance to relevant antibiotics usually administered to animals proposed by the European Food Safety Authority. They could endure the detrimental conditions of the gastrointestinal tract (pH 2.6 and oxgall 0.1 and 0.4% w/v). In an ex vivo assay, the LAB showed high adherence to the three sections of the GIT, reaching values higher than 70%. The adhesion to mucus was strain-dependent: L. crispatus CRL 1453 evidenced the highest adhesion (> 19%) while Lig. salivarius subsp. salivarius CRL 1417 and E. faecium CRL 1385 adhered to a lower extent (> 9 and 2%, respectively). Moreover, the LAB elicited remarkable anti-Salmonella activity, taking into account that they could inhibit elevated counts of different Salmonella serovars, especially the host-specific serovars S. Gallinarum and S. Pullorum (up to 8 log CFU/mL decrease in Salmonella counts).

Applying Differential Neural Networks to Characterize Microbial Interactions in an Ex Vivo Gastrointestinal Gut Simulator

The structure of mixed microbial cultures—such as the human gut microbiota—is influenced by a complex interplay of interactions among its community members. The objective of this study was to propose a strategy to characterize microbial interactions between particular members of the community occurring in a simulator of the human gastrointestinal tract used as the experimental system. Four runs were carried out separately in the simulator: two of them were fed with a normal diet (control system), and two more had the same diet supplemented with agave fructans (fructan-supplemented system). The growth kinetics of Lactobacillus spp., Bifidobacterium spp., Salmonella spp., and Clostridium spp. were assessed in the different colon sections of the simulator for a nine-day period. The time series of microbial concentrations were used to estimate specific growth rates and pair-wise interaction coefficients as considered by the generalized Lotka-Volterra (gLV) model. A differential neural network (DNN) composed of a time-adaptive set of differential equations was applied for the nonparametric identification of the mixed microbial culture, and an optimization technique was used to determine the interaction parameters, considering the DNN identification results and the structure of the gLV model. The assessment of the fructan-supplemented system showed that microbial interactions changed significantly after prebiotics administration, demonstrating their modulating effect on microbial interactions. The strategy proposed here was applied satisfactorily to gain quantitative and qualitative knowledge of a broad spectrum of microbial interactions in the gut community, as described by the gLV model. In the future, it may be utilized to study microbial interactions within mixed cultures using other experimental approaches and other mathematical models (e.g., metabolic models), which will yield crucial information for optimizing mixed microbial cultures to perform certain processes—such as environmental bioremediation or modulation of gut microbiota—and to predict their dynamics.

Influence of Dietary Factors on Helicobacter pylori and CagA Seroprevalence in Bulgaria

The aim of this study was to assess the association between some dietary factors and prevalence of H. pylori infection or strain virulence in 294 adult asymptomatic blood donors. Methods. Seroprevalence was evaluated using ELISA. Logistic regression was used. Results. Anti-H. pylori IgG prevalence was 72.4%, and CagA IgG seroprevalence was 49.3%. In the multivariate analyses, the frequent (>5 days per week) honey consumption was associated with both reduced H. pylori seroprevalence OR, 0.68 with 95% confidence interval (CI), 0.473-0.967 and reduced CagA IgG seroprevalence OR, 0.65 with 95% CI, 0.486-0859. Frequent (>5 days per week) yoghurt consumption also was associated with lower H. pylori virulence of the strains (CagA IgG OR, 0.56 with 95% CI, 0.341-0.921). Smoking and consumption of the other dietary factors resulted in no significant differences in the prevalence of H. pylori IgG and CagA IgG within the subject groups. Conclusion. To the best of our knowledge, this is the first report revealing reverse associations between honey or yoghurt consumption and CagA IgG prevalence as well as between frequent honey consumption and lower prevalence of the H. pylori infection. Regular honey and yoghurt consumption can be of value as a supplement in the control of H. pylori therapy.

Reduction of Escherichia coli O157:H7 in Fresh Spinach, using lactic acid bacteria and chlorine as a multihurdle intervention

A 12-day shelf life study was conducted at 7 degrees C to determine whether Escherichia coli O157:H7 on spinach can be controlled effectively by selected strains of lactic acid bacteria (LAB) alone or in combination with chlorine as a multihurdle intervention. The multihurdle intervention consisted of both LAB and chlorine and was applied to spinach as a rinse and evaluated in comparison to LAB alone and chlorine and water rinses. Reductions achieved by all treatments also were compared with those observed for an inoculated control. The spinach was inoculated by submersion in a solution containing an E. coli O157:H7 cocktail at 1.0 x 10(6) CFU/ml. LAB were applied postharvest at a concentration of 2.0 x 10(8) CFU/ml, and 200 ppm of chlorine was used for the chlorine rinse. All spinach samples were packaged in commercial packaging, held in a retail display case, and tested for E. coli O157:H7 on days 0, 1, 3, 6, 9, and 12 using the Neo-Grid filtration system and CHROMagar. Survival of LAB throughout the shelf life also was determined. Significant reductions in pathogen populations were achieved by water (P = 0.0008), LAB (P < 0.0001), chlorine (P < 0.0001), and multihurdle (P < 0.0001) treatments when compared with controls. The multihurdle treatment produced the greatest reduction from control populations, a reduction of 1.91 log CFU/ml. This reduction was significantly greater than that achieved with water (P < 0.0001), LAB (P = 0.0025), and chlorine (P < 0.0001) alone, indicating that the application of chlorine and LAB is most effective as a combination treatment. The results obtained from this study indicate that the industry standard chlorine wash may be more effective when applied in combination with LAB.

Anti-Helicobacter pylori activity of Lactobacillus delbrueckii subsp. bulgaricus strains: preliminary report

AIMS

To evaluate the activities of six Lactobacillus delbrueckii subsp. bulgaricus (LB) strains against 30 Helicobacter pylori strains by agar-well diffusion method.

METHODS AND RESULTS

LB cultures [4 x 10(8)-4 x 10(9) CFU ml(-1)) either were prepared in milk at their native pH, 3.8-5.0, or were adjusted to pH 6.4-7.7. At low and neutralized pH, LB strains inhibited the growth by 40-86.7% and 16.7-66.7% of H. pylori strains, respectively. LB activity was strain-dependent. At low and neutralized pH, one and five H. pylori strains, respectively, were not inhibited by any LB strain. LB2 and LB3, taken together, were active against most metronidazole and clarithromycin resistant strains.

CONCLUSIONS

All LB strains inhibited a number of H. pylori strains, including also antibiotic resistant strains. LB activity was strain-dependent and better at low pH. At low pH values, the most active LB strains were LB1, LB2 and LB3, inhibiting 86.7% of H. pylori strains, while at neutralized pH values, the most active LB strains were LB2 and LB3, inhibiting 53.3 and 66.7% of H. pylori strains, respectively.

SIGNIFICANCE AND IMPACT OF THE STUDY

LB could be utilized in the treatment or prophylaxis of H. pylori infection and warrants clinical investigations.

Lactobacillus fermentum ACA-DC 179 displays probiotic potential in vitro and protects against trinitrobenzene sulfonic acid (TNBS)-induced colitis and Salmonella infection in murine models

Lactobacillus fermentum ACA-DC 179, Lactobacillus plantarum ACA-DC 287 and Streptococcus macedonicus ACA-DC 198 were studied for their probiotic potential. Firstly, strains were screened for antimicrobial activity towards a broad range of target strains, including lactic acid bacteria, food spoilage and pathogenic bacteria. L. fermentum ACA-DC 179 was active against five streptococci, including the two pathogenic strains Streptococcus oralis LMG 14532T and Streptococcus pneumoniae LMG 14545T. S. macedonicus ACA-DC 198 was active against the majority of the strains tested, including not only lactic acid bacteria but also many food spoilage or pathogenic species. The three potential probiotic strains were found to survive variably at pH 2.5 and were unaffected by bile salts. Only S. macedonicus ACA-DC 198 exhibited bile salt hydrolase activity, while none of the strains was haemolytic. Moreover, strains exhibited variable susceptibility towards commonly used antibiotics. L. plantarum ACA-DC 287 and S. macedonicus ACA-DC 198 induced the secretion of the pro-inflammatory cytokines IL-12, IFN-gamma and TNF-alpha by human peripheral blood mononuclear cells. Also elevated levels of the anti-inflammatory IL-10 were observed with L. fermentum ACA-DC 179. This strain consequently was found to significantly reduce colitis in a TNBS-induced colitis mouse model. Furthermore, L. fermentum ACA-DC 179 was successfully applied in an experimental Salmonella-infection mouse model. To conclude, strain L. fermentum ACA-DC 179 possesses desirable probiotic properties, such as antimicrobial activity and immunomodulation in vitro, which were confirmed in vivo by the use of animal models.

The Lactobacillus plantarum strain ACA-DC287 isolated from a Greek cheese demonstrates antagonistic activity in vitro and in vivo against Salmonella enterica serovar Typhimurium

AIMS

The purpose of this study was to investigate the antibacterial activity of the Xynotyri cheese isolate Lactobacillus plantarum ACA-DC287 using a set of in vitro and in vivo assays.

METHODS AND RESULTS

The co-culture of L. plantarum strain ACA-DC287 and Salmonella enterica serovar Typhimurium strain SL1344 results in the killing of the pathogen. The killing activity was produced mainly by non-lactic acid molecule(s) that were present in the cell-free culture supernatant of the L. plantarum strain ACA-DC287. The culture of the L. plantarum strain ACA-DC287 inhibited the penetration of S. typhimurium SL1344 into cultured human enterocyte-like Caco-2/TC7 cells. In conventional mice infected with S. typhimurium SL1344, the intake of L. plantarum strain ACA-DC287 results in a decrease in the levels of Salmonella associated with intestinal tissues or those present in the intestinal contents. In germ-free mice, the L. plantarum strain ACA-DC287 colonized the gastrointestinal tract.

CONCLUSIONS

The L. plantarum strain ACA-DC287 strain exerts anti-Salmonella activity similar that of the established probiotic strains Lactobacillus rhamnosus GG, Lactobacillus casei Shirota YIT9029 and Lactobacillus johnsonii La1.

SIGNIFICANCE AND IMPACT OF THE STUDY

The observation that a selected cheese Lactobacillus strain exerted antibacterial activity that was similar to those of probiotic Lactobacillus strains, is of interest for the use of this strain as an adjunct strain for the production of health-giving cheeses.

Kinetic analysis of the antibacterial activity of probiotic lactobacilli towards Salmonella enterica serovar Typhimurium reveals a role for lactic acid and other inhibitory compounds

Six Lactobacillus strains including commercial probiotic ones (L. acidophilus IBB 801, L. amylovorus DCE 471, L. casei Shirota, L. johnsonii La1, L. plantarum ACA-DC 287 and L. rhamnosus GG) were investigated, through batch fermentations under controlled conditions, for their capacity to inhibit Salmonella enterica serovar Typhimurium SL1344. All lactobacilli displayed strong antibacterial activity toward this Gram-negative pathogen and significantly inhibited invasion of the pathogen into cultured human enterocyte-like Caco-2/TC7 cells. By studying the production kinetics of antibacterial activity and applying the appropriate acid and pH control samples during a killing assay, we were able to distinguish between the effect of lactic acid and other inhibitory compounds produced. The antibacterial activity of L. acidophilus IBB 801, L. amylovorus DCE 471, L. casei Shirota and L. rhamnosus GG was solely due to the production of lactic acid. The antibacterial activity of L. johnsonii La1 and L. plantarum ACA-DC 287 was due to the production of lactic acid and (an) unknown inhibitory substance(s). The latter was (were) only active in the presence of lactic acid. In addition, the lactic acid produced was responsible for significant inhibitory activity upon invasion of Salmonella into Caco-2/TC7 cells.