Survival and retention of the probiotic Lactobacillus casei LAFTI�L26 in the gastrointestinal tract of the mouse

Bacteriocins: potentials and prospects in health and agrifood systems

Bacteriocins are highly diverse, abundant, and heterogeneous antimicrobial peptides that are ribosomally synthesized by bacteria and archaea. Since their discovery about a century ago, there has been a growing interest in bacteriocin research and applications. This is mainly due to their high antimicrobial properties, narrow or broad spectrum of activity, specificity, low cytotoxicity, and stability. Though initially used to improve food quality and safety, bacteriocins are now globally exploited for innovative applications in human, animal, and food systems as sustainable alternatives to antibiotics. Bacteriocins have the potential to beneficially modulate microbiota, providing viable microbiome-based solutions for the treatment, management, and non-invasive bio-diagnosis of infectious and non-infectious diseases. The use of bacteriocins holds great promise in the modulation of food microbiomes, antimicrobial food packaging, bio-sanitizers and antibiofilm, pre/post-harvest biocontrol, functional food, growth promotion, and sustainable aquaculture. This can undoubtedly improve food security, safety, and quality globally. This review highlights the current trends in bacteriocin research, especially the increasing research outputs and funding, which we believe may proportionate the soaring global interest in bacteriocins. The use of cutting-edge technologies, such as bioengineering, can further enhance the exploitation of bacteriocins for innovative applications in human, animal, and food systems.

Bacteriocins as a new generation of antimicrobials: toxicity aspects and regulations

In recent decades, bacteriocins have received substantial attention as antimicrobial compounds. Although bacteriocins have been predominantly exploited as food preservatives, they are now receiving increased attention as potential clinical antimicrobials and as possible immune-modulating agents. Infections caused by antibiotic-resistant bacteria have been declared as a global threat to public health. Bacteriocins represent a potential solution to this worldwide threat due to their broad- or narrow-spectrum activity against antibiotic-resistant bacteria. Notably, despite their role in food safety as natural alternatives to chemical preservatives, nisin remains the only bacteriocin legally approved by regulatory agencies as a food preservative. Moreover, insufficient data on the safety and toxicity of bacteriocins represent a barrier against the more widespread use of bacteriocins by the food and medical industry. Here, we focus on the most recent trends relating to the application of bacteriocins, their toxicity and impacts.

Lactobacillus fermentum strains of dairy-product origin adhere to mucin and survive digestive juices

Introduction. There is an ever present need to isolate and characterize indigenous bacterial strains with potential probiotic health benefits for humans.Aim. Lactobacillus fermentum of dairy origin was focused because of its propensity to adhere to the intestinal glycoprotein, mucin.Methodology. The lactobacillus strains were screened for mucin adhesion, resistance to low pH and bile, autoaggregation, hydrophobicity, and survival in an in vitro digestion model. The cholesterol-lowering and oxalate-degrading effects of selected strains were also determined. Safety was assessed for haemolytic, mucinolytic and gelatinase activity, biogenic amine production, antibiotic resistance and phenol resistance. Expression of the 32-mmub adhesion-related gene was also measured following strain exposure to simulated gastrointestinal tract (GIT) digestion.Results. The selected mucin-adhesive strains were tolerant to acid (pH 3.0) and bile (0.25 %) and demonstrated >85 % survival following simulated human digestion in the presence of milk. The digestive treatment did not affect the adhesive potential of PL20, and PL27, regardless of the food matrix. The simulated digestion had less effect on their adhesion than on the type strain and it also did not correlate with the mmub gene expression level as determined by qPCR. The selected strains exhibited cholesterol removal (36-44 %) and degraded oxalate (66-55 %). Neither of these strains exhibited undesirable characteristics.Conclusion. These preliminary findings suggest a functionality in the two strains of L. fermentum with high colonization potential on GIT mucosal membranes and possible health-promoting effects. This prima facie evidence suggests the need for further studies to test these probiotic candidates as live biotherapeutic agents in vivo.

Suppression of bacteriocin resistance using live, heterospecific competitors

Rapidly spreading antibiotic resistance has led to the need for novel alternatives and sustainable strategies for antimicrobial use. Bacteriocins are a class of proteinaceous anticompetitor toxins under consideration as novel therapeutic agents. However, bacteriocins, like other antimicrobial agents, are susceptible to resistance evolution and will require the development of sustainable strategies to prevent or decelerate the evolution of resistance. Here, we conduct proof-of-concept experiments to test whether introducing a live, heterospecific competitor along with a bacteriocin dose can effectively suppress the emergence of bacteriocin resistance in vitro. Previous work with conventional chemotherapeutic agents suggests that competition between conspecific sensitive and resistant pathogenic cells can effectively suppress the emergence of resistance in pathogenic populations. However, the threshold of sensitive cells required for such competitive suppression of resistance may often be too high to maintain host health. Therefore, here we aim to ask whether the principle of competitive suppression can be effective if a heterospecific competitor is used. Our results show that a live competitor introduced in conjunction with low bacteriocin dose can effectively control resistance and suppress sensitive cells. Further, this efficacy can be matched by using a bacteriocin-producing competitor without any additional bacteriocin. These results provide strong proof of concept for the effectiveness of competitive suppression using live, heterospecific competitors. Currently used probiotic strains or commensals may provide promising candidates for the therapeutic use of bacteriocin-mediated competitive suppression.

Bacteriocins - a viable alternative to antibiotics?

Solutions are urgently required for the growing number of infections caused by antibiotic-resistant bacteria. Bacteriocins, which are antimicrobial peptides produced by certain bacteria, might warrant serious consideration as alternatives to traditional antibiotics. These molecules exhibit significant potency against other bacteria (including antibiotic-resistant strains), are stable and can have narrow or broad activity spectra. Bacteriocins can even be produced in situ in the gut by probiotic bacteria to combat intestinal infections. Although the application of specific bacteriocins might be curtailed by the development of resistance, an understanding of the mechanisms by which such resistance could emerge will enable researchers to develop strategies to minimize this potential problem.

The dual role of bacteriocins as anti- and probiotics

Bacteria employed in probiotic applications help to maintain or restore a host's natural microbial floral. The ability of probiotic bacteria to successfully outcompete undesired species is often due to, or enhanced by, the production of potent antimicrobial toxins. The most commonly encountered of these are bacteriocins, a large and functionally diverse family of antimicrobials found in all major lineages of Bacteria. Recent studies reveal that these proteinaceous toxins play a critical role in mediating competitive dynamics between bacterial strains and closely related species. The potential use of bacteriocin-producing strains as probiotic and bioprotective agents has recently received increased attention. This review will report on recent efforts involving the use of such strains, with a particular focus on emerging probiotic therapies for humans, livestock, and aquaculture.

Investigation of the immunomodulatory effects of Lactobacillus casei and Bifidobacterium lactis on Helicobacter pylori infection

BACKGROUND

Lactobacillus and Bifidobacterium species have shown beneficial effects in the treatment of Helicobacter pylori infection; however, the mechanisms behind such effects are not fully understood. In this study, we have investigated the immunomodulatory effects of probiotics in a mouse model of H. pylori infection.

MATERIALS AND METHODS

H. pylori-infected C57BL/6 mice were treated with L. casei L26, B. lactis B94, or no probiotics for 5 weeks, respectively. Mice not infected with H. pylori were included as normal controls. Gastric histology, protein levels of interleukin (IL)-1beta, IL-10, IL-12/23p40, and H. pylori colonization density in the gastric tissues, as well as H. pylori-specific antibodies were examined.

RESULTS

In mice receiving L. casei L26 and B. lactis B94, gastric neutrophil infiltration and IL-1beta were significantly decreased and IL-10 was significantly increased as compared with mice receiving no probiotics. In mice receiving B. lactis B94, IL-12/23p40 was significantly increased and H. pylori IgG was significantly reduced as compared with mice receiving no probiotics. No significant difference of H. pylori colonization was observed among the three groups of mice.

CONCLUSION

The reduced level of IL-1beta and neutrophil infiltration observed in mice infected with H. pylori following treatment with L. casei L26 and B. lactis B94 resulted from a modulation of immune response rather than a decrease of H. pylori colonization. Furthermore, B. lactis B94 has the intrinsic ability to promote a Th1 immune response through an increase in IL-12/IL-23.

Prebiotics enhance survival and prolong the retention period of specific probiotic inocula in an in vivo murine model

AIM

To identify novel prebiotics that could be used to maintain persistence of three representative probiotic strains in vivo.

METHODS AND RESULTS

Test mice were treated with prebiotics soybean oligosaccharide (SOS), fructooligosaccharide (FOS) or inulin, followed by probiotics Lactobacillus acidophilus LAFTI L10 (L10), Bifidobacterium lactis LAFTI B94 (B94) or Lactobacillus casei L26 LAFTI (L26). Faecal samples were then collected and analysed using selective medium and PCR analysis to determine the presence of the probiotic strains. In contrast to the control groups, in mice fed prebiotics, the survival and retention time of the test probiotics was increased extensively. SOS and FOS prolonged the retention period of L10 from 24 to 30 h. Of the three prebiotics, FOS gave the best result with B94, prolonging the retention period from 3 to > or =10 days. Of the three prebiotics, inulin gave the best result for L26, prolonging the retention period from 2 to > or =6 days.

CONCLUSIONS

The prebiotics SOS, FOS and inulin significantly enhance survival and prolong the retention period of L10, B94 and L26 in vivo.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our results demonstrate the potential use of FOS, inulin and SOS as prebiotics in conjunction with the probiotic strains L10, B94 and L26 for new synbiotic products.

Evidence for in vitro anti-genotoxicity of cheese non-starter lactobacilli

The inhibition of direct acting DNA reactive agents by 63 non-starter lactobacilli isolated from raw ewes milk cheeses was examined by short-term assay (SOS-Chromotest) and compared with already characterized starter lactobacilli. The screening revealed strains active against the nitroarene 4-nitroquinoline-1-oxide (NQO) and the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in different species of the genus Lactobacillus (L. rhamnosus, L. casei, L. plantarum, L. brevis, Lactobacillus spp.). It was proved that the anti-genotoxicity was strain-dependent, and always associated with spectroscopic modification of genotoxins. The frequency of strains inhibiting nitroarene genotoxicity was comparable for non-starter and starter lactobacilli, whereas inhibition of the alkylating agent was largely predominant in non-starter isolates. Seventeen strains presented inhibitory activity against both genotoxins. DNA RAPD-PCR performed with M13, Pro-Up and RPO2 primers on the lactobacilli under examination showed genetic diversity in these strains. The non-starter isolates clustered in seven groups and the strains presenting a high degree of activity against 4-nitroquinoline-1-oxide clustered in a single group with a similarity around 75%. Interestingly, the strains with anti-genotoxic properties also showed acid-bile tolerance, indicating that the autochthonous lactobacilli which survive cheese ripening may also reach the gut as viable cells and could prevent genotoxin DNA damage to enterocytes, as is desirable for probiotic bacteria.