In vitro evaluation of the probiotic potential of bacteriocin producer Lactobacillus sakei 1

Bacteriocins attenuate Listeria monocytogenes-induced intestinal barrier dysfunction and inflammatory response

Bacteriocins have the potential to effectively improve food-borne infections or gastrointestinal diseases and hold promise as viable alternatives to antibiotics. This study aimed to explore the antibacterial activity of three bacteriocins (nisin, enterocin Gr17, and plantaricin RX-8) and their ability to attenuate intestinal barrier dysfunction and inflammatory responses induced by Listeria monocytogenes, respectively. Bacteriocins have shown excellent antibacterial activity against L. monocytogenes without causing any cytotoxicity. Bacteriocins inhibited the adhesion and invasion of L. monocytogenes on Caco-2 cells, lactate dehydrogenase (LDH), trans-epithelial electrical resistance (TEER), and cell migration showed that bacteriocin improved the permeability of Caco-2 cells. These results were attributed to the promotion of tight junction proteins (TJP) assembly, specifically zonula occludens-1 (ZO-1), occludin, and claudin-1. Furthermore, bacteriocins could alleviate inflammation by inhibiting the mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) pathways and reducing the secretion of interleukin-6 (IL-6), interleukin-1 β (IL-1β) and tumor necrosis factor α (TNF-α). Among three bacteriocins, plantaricin RX-8 showed the best antibacterial activity against L. monocytogenes and the most pronounced protective effect on the intestinal barrier due to its unique structure. Based on our findings, we hypothesized that bacteriocins may inhibit the adhesion and invasion of L. monocytogenes by competing adhesion sites. Moreover, they may further enhance intestinal barrier function by inhibiting the expression of L. monocytogenes virulence factors, increasing the expression of TJP and decreasing the secretion of inflammatory factors. Therefore, bacteriocins will hopefully be an effective alternative to antibiotics, and this study provides valuable insights into food safety concerns. KEY POINTS: • Bacteriocins show excellent antibacterial activity against L. monocytogenes • Bacteriocins improve intestinal barrier damage and inflammatory response • Plantaricin RX-8 has the best protective effect on Caco-2 cells damage.

Functional and probiotic characterization of Ligilactobacillus salivarius CPN60 isolated from calf faeces and its appraisal in rats

Emerging concern about the emergence of antimicrobial resistance has limited the use of antibiotics in calves. Hence, there is a need to find suitable alternatives to antibiotics to manage gastrointestinal infections in neonatal calves. The objective of the present study was to develop a probiotic of calf-origin for its potential application in calf nutrition. Accordingly, 69 lactic acid bacteria (LAB) strains were isolated from faeces of newborn calves, out of which 10 strains were short-listed for further in vitro testing based on the aggregation time and cell surface hydrophobicity. The results of acid-, bile- and phenol-tolerance tests indicated that out of the ten strains, the isolate CPN60 had better resistance to these adverse conditions likely to be encountered in the gastrointestinal tract. The isolate also showed an optimal ability to produce biofilm. Further assessments reiterated its superiority in terms of co-aggregation and antagonistic activity against pathogenic strains of Escherichia coli. Subsequently, the isolate was identified through 16S rRNA sequencing and sequence homology and designated as Ligilactobacillus salivarius CPN60. The candidate probiotic was evaluated in vivo using 48 male (5 weeks old) Wistar rats, divided into two equal groups viz. control (CON) and probiotic (PRO). During the 4-weeks feeding trial, the PRO group rats were gavaged with one mL culture of L. salivarius CPN60 equivalent to 10⁸ CFU/rat. The in vivo trial results indicated better nutrient utilization efficiency and growth performance (p < 0.001) of the PRO group of rats. The probiotic supplementation improved the faecal concentration of lactate (p < 0.001) and individual as well as total short-chain fatty acids (p < 0.001) production. The cell-mediated immune response, assessed as a delayed-type hypersensitivity reaction to phytohaemagglutinin-P, was improved (p < 0.001) in PRO compared to the CON rats. It is concluded that the calf-origin probiotic L. salivarius CPN60, in addition to possessing all the in vitro functional attributes of a candidate probiotic, also has desirable potential for its future use in young calves to promote gut health and immunity.

Evaluation of Probiotic Characteristics of Newly Isolated Lactic Acid Bacteria from Dry-Aged Hanwoo Beef

Dry aging is a traditional method that improves meat quality, and diverse microbial communities are changed during the process. Lactic acid bacteria (LAB) are widely present in fermented foods and has many beneficial effects, such as immune enhancement and maintenance of intestinal homeostasis. In this study, we conducted metagenomic analysis to evaluate the changes in the microbial composition of dry-aged beef. We found that lactic acid bacterial strains were abundant in dry-aged beef including Lactobacillus sakei and Enterococcus faecalis. We investigated their abilities in acid and bile tolerance, adhesion to the host, antibiotic resistance, and antimicrobial activity as potential probiotics, confirming that L. sakei and E. faecalis strains had remarkable capability as probiotics. The isolates from dry-aged beef showed at least 70% survival under acidic conditions in addition to an increase in the survival level under bile conditions. Antibiotic susceptibility and antibacterial activity assays further verified their effectiveness in inhibiting all pathogenic bacteria tested, and most of them had low resistance to antibiotics. Finally, we used the Caenorhabditis elegans model to confirm their life extension and influence on host resistance. In the model system, 12D26 and 20D48 strains had great abilities to extend the nematode lifespan and to improve host resistance, respectively. These results suggest the potential use of newly isolated LAB strains from dry-aged beef as probiotic candidates for production of fermented meat.

A time-lagged association between the gut microbiome, nestling weight and nestling survival in wild great tits

Natal body mass is a key predictor of viability and fitness in many animals. While variation in body mass and therefore juvenile viability may be explained by genetic and environmental factors, emerging evidence points to the gut microbiota as an important factor influencing host health. The gut microbiota is known to change during development, but it remains unclear whether the microbiome predicts fitness, and if it does, at which developmental stage it affects fitness traits. We collected data on two traits associated with fitness in wild nestling great tits Parus major: weight and survival to fledging. We characterised the gut microbiome using 16S rRNA sequencing from nestling faeces and investigated temporal associations between the gut microbiome and fitness traits across development at Day-8 (D8) and Day-15 (D15) post-hatching. We also explored whether particular microbial taxa were 'indicator species' that reflected whether nestlings survived or not. There was no link between mass and microbial diversity on D8 or D15. However, we detected a time-lagged relationship where weight at D15 was negatively associated with the microbial diversity at D8, controlling for weight at D8, therefore reflecting relative weight gain over the intervening period. Indicator species analysis revealed that specificity values were high and fidelity values were low, suggesting that indicator taxa were primarily detected within either the survived or not survived groups, but not always detected in birds that either survived or died. Therefore these indicator taxa may be sufficient, but not necessary for determining either survival or mortality, perhaps owing to functional overlap in microbiota. We highlight that measuring microbiome-fitness relationships at just one time point may be misleading, especially early in life. Instead, microbial-host fitness effects may be best investigated longitudinally to detect critical development windows for key microbiota and host traits associated with neonatal weight. Our findings should inform future hypothesis testing to pinpoint which features of the gut microbial community impact on host fitness, and when during development this occurs. Such confirmatory research will shed light on population level processes and could have the potential to support conservation.

Studies on host-foodborne bacteria in intestinal three-dimensional cell culture model indicate possible mechanisms of interaction

Spheroids of intestinal cells (Caco-2) were used to evaluate the adhesion/invasion ability of Listeria monocytogenes (pathogen) and Lactobacillus sakei 1 (potential probiotic). Besides, transcriptomic analyses of Caco-2 cells in three dimensional cultures were done, with the aim of revealing possible host-foodborne bacteria interactions. Result of adhesion assay for L. monocytogenes in Caco-2 spheroids was 22.86 ± 0.33%, but it was stimulated in acidic pH (4.5) and by the presence of 2% sucrose (respectively, 32.56 ± 1.35% and 33.25 ± 1.26%). Conversely, the invasion rate of L. monocytogenes was lower at pH 4.5, in comparison with non-stressed controls (18.89 ± 1.05% and 58.65 ± 0.30%, respectively). L. sakei 1 adhered to Caco-2 tridimensional cell culture (27.30 ± 2.64%), with no invasiveness. There were 19 and 21 genes down and upregulated, respectively, in tridimensional Caco-2 cells, upon infection with L. monocytogenes, which involved immunity, apoptosis; cytoprotective responses, cell signalling-regulatory pathways. It was evidenced despite activation or deactivation of several pathways in intestinal cells to counteract infection, the pathogen was able to hijack many host defense mechanisms. On the other hand, the probiotic candidate L. sakei 1 was correlated with decreased transcription of two genes in Caco-2 cells, though it stimulated the expression of 14 others, with diverse roles in immunity, apoptosis, cytoprotective response and cell signalling-regulatory pathways. Our data suggest the use of tridimensional cell culture to mimic the intestinal epithelium is a good model for gathering broad information on the putative mechanisms of interaction between host and bacteria of importance for food safety, which can serve as a basis for further in-depth investigation.

Spontaneously Fermented Fruiting Bodies of Agaricus bisporus as a Valuable Source of New Isolates of Lactic Acid Bacteria with Functional Potential

The aim of the investigation was the identification and initial study of lactic acid bacteria (LAB) isolated from spontaneously fermented (at 28 °C for 5 days) fruiting bodies of white button mushrooms (Agaricus bisporus). The isolated LAB were preliminarily characterized applying the MALDI-TOF Biotyper. Moreover, further phenotypical, genotypical characteristics as well as some functional and technological properties of the selected microorganisms (including the ability to produce exopolysaccharides, cell hydrophobicity, resistance to low pH, and bile salt) were also analyzed. Among autochthonous LAB (isolated from the tested mushroom raw material), Leuconostoc mesenteroides predominated in spontaneously fermented A. bisporus, while Lactiplantibacillus paraplantarum, Lactiplantibacillus plantarum, and Lactococcus lactis were less abundant. The highest dynamics of acidification of the mushroom material were exhibited by isolates EK55 and EK4 that, after 24 h of incubation, were able to decrease the pH of the raw material up to 5.06 ± 0.021 and 5.17 ± 0.015, respectively. Furthermore, the analysis of bacterial cell hydrophobicity indicated that the highest values of this parameter were noted for L. plantarum isolates EK12 (29.59 ± 0.7%), EK55 (28.75 ± 0.551%), and EK5 (27.33 ± 1.516%). It was revealed some of the analyzed LAB (especially isolates L. plantarum EK55 and L. paraplantarum EK4) exhibited functional and technological potential that might be used in the formulation of novel starter cultures.

Isolation of acid tolerant lactic acid bacteria and evaluation of α-glucosidase inhibitory activity

In this study, lactic acid bacteria strains (LABs) were isolated from Korean traditional fermented food and examined as potential probiotics using in vitro methods. Ten LAB strains survived in de Man, Rogosa and Sharpe broth adjusted to pH 2.5 were tested for resistance to acidic conditions and bile, antimicrobial activity, and α-glucosidase inhibitory activity. Among them, strain MBEL1397 showed antimicrobial activity against Bacillus cereus and exhibited survival rates of over 97% in acidic and bile conditions. The α-glucosidase inhibitory activity was 3.91 ± 0.25%, corresponding to approximately 2.3 times higher than that of acarbose. MBEL1397 was susceptible to ampicillin, erythromycin, and penicillin G and identified as Lactobacillus sakei. It was deposited to Korean Collection for Type Culture (KCTC) as KCTC14037BP. In conclusion, these results demonstrate that L. sakei MBEL1397 might be prominent probiotics with potential hypoglycemic effects.

Lactobacillus spp. impair the ability of Listeria monocytogenes FBUNT to adhere to and invade Caco-2 cells

OBJECTIVES

The objective of this study was to evaluate the ability of Lactobacillus curvatus CRL705, CRL1532, and CRL1533 and Lactobacillus sakei CRL1613 to survive under simulated gastrointestinal conditions. Moreover, a microencapsulation approach was proposed to improve gastrointestinal survival. Finally, experiments were performed to demonstrate that Lactobacillus spp. can modulate the ability of Listeria monocytogenes FBUNT to adhere to and invade Caco-2 cells.

RESULTS

Lactobacillus strains were encapsulated in alginate beads to enhance the survival of bacteria under in vitro gastrointestinal conditions. All strains hydrolyzed bile salts using chenodeoxycholic acid as a substrate and adhered to Caco-2 cells. Cell-free supernatants (CFSs) showed antimicrobial activity against L. monocytogenes as demonstrated by agar diffusion assays. The average percentages of L. monocytogenes adhesion decreased from 67.74 to 41.75 and 38.7% in the presence of 50 and 90% (v/v), respectively, for all CFSs tested. The highest concentrations of CFSs completely inhibited the L. monocytogenes invasion of Caco-2 cells.

CONCLUSIONS

The studied Lactobacillus strains have protective effects against the adhesion and invasion of L. monocytogenes FBUNT. Alginate encapsulation of these bacteria improved gastrointestinal tolerance such that they could be further studied as potential probiotics against intestinal pathogenic bacteria.

Growth, detection and virulence of Listeria monocytogenes in the presence of other microorganisms: microbial interactions from species to strain level

Like with all food microorganisms, many basic aspects of L. monocytogenes life are likely to be influenced by its interactions with bacteria living in close proximity. This pathogenic bacterium is a major concern both for the food industry and health organizations since it is ubiquitous and able to withstand harsh environmental conditions. Due to the ubiquity of Listeria monocytogenes, various strains may contaminate foods at different stages of the supply chain. Consequently, simultaneous exposure of consumers to multiple strains is also possible. In this context even strain-to-strain interactions of L. monocytogenes play a significant role in fundamental processes for the life of the pathogen, such as growth or virulence, and subsequently compromise food safety, affect the evolution of a potential infection, or even introduce bias in the detection by classical enrichment techniques. This article summarizes the impact of microbial interactions on the growth and detection of L. monocytogenes primarily in foods and food-associated environments. Furthermore it provides an overview of L. monocytogenes virulence in the presence of other microorganisms.

The Influence of Probiotic Lactobacilli and Flaxseed on the Health of Weaned Piglets and Metabolism of Polyunsaturated Fatty Acids (PUFAs)

This study investigated for 14 days post-weaning, the influence of dietary supplementation of synbiotics in the form of probiotic cheeses containing cultures of L. plantarum and L. fermentum and crushed flaxseed (source of ω-3 polyunsaturated fatty acids — PUFAs and fibre) on 36 commercial piglets originating from an infected herd (Coronavirus and E. coli) during the critical period of weaning. We focused on the health and metabolism of PUFAs in this critical period of a piglet’s life. The dietary supplementation positively affected: the overall health state of weaners, reduced diarrhoea by 29 % by 14 days post-weaning and significantly increased the counts of lactic acid bacteria, bifidobacteria and the production of volatile fatty acids. The PUFA concentrations in the m. biceps femoris of the piglets were analysed by gas chromatography. High levels of ω-3 alpha-linolenic acid (ALA) in flaxseed increased significantly the level of ALA, eicosapentaenic acid (EPA) and docosahexaenic acid (DHA) in the pig muscles on days 7 and 14 post-weaning. The levels of ω-6 linolenic acid (LA) were less affected by the diet, but were increased on day 14 post-weaning, while the conversion products of LA, and arachidonic acid (AA), were decreased on days 7 and 14. The increased level of dietary ALA favoured the activity of Δ-6-desaturase for the conversion of ALA to EPA and DHA, at the expense of AA synthesis from LA. The ability of synbiotics to incorporate high levels of DHA in the pig muscles appear prospective for improving the nutritional properties of pork and reducing the occurrence of civilization diseases in consumers of this product of animal origin.

Synbiotics suppress the release of lactate dehydrogenase, promote non-specific immunity and integrity of jejunum mucosa in piglets

The aim of our experiment was to study how synbiotics are able to deal with the problems of post‐weaning piglets. Lactobacillus plantarum – Biocenol^TM LP96 (CCM 7512), Lactobacillus fermentum – Biocenol^TM LF99 (CCM 7514) and flaxseed (rich in n‐3 polyunsaturated fatty acids) were administered to 36 conventional piglets from a problematic breed with confirmed presence of enterotoxigenic Escherichia coli and Coronavirus. The experimental piglets were supplied with probiotic cheeses and crushed flax‐seed in the period starting 10 days before weaning and lasting up to 14 days post‐weaning. Piglets in the control group were supplied only control cheese. The impact of such additives on the release of lactate dehydrogenase (LDH; spectroscopic and electrophoretic assay), alteration of immunity (index of metabolic activity), jejunum histology (light microscopy), and health of conventional piglets from a problematic breed (monitoring of hematology, consistency and moisture of feces and body temperature) were examined. We found significant decrease in LDH leakage in the blood serum and tissue extracts, indicating better cell membrane integrity in the individual organs of animals. Probiotics and flaxseed applied together seem to be a good source of nutrients to improve the immune status and the integrity of jejunum mucosa during infection. © 2015 Japanese Society of Animal Science

In vitro protective effect of lactic acid bacteria on Listeria monocytogenes adhesion and invasion of Caco-2 cells

The adhesion of Listeria monocytogenes to intestinal endothelial cells is a crucial step in the infection process, which is not well understood. In this study, we evaluated the potential ability of bacteriocin-producing Enterococcus faecium, Leuconostoc mesenteroides and Lactobacillus sakei strains to prevent the adhesion and invasion of eukaryotic cells by ten different L. monocytogenes isolates. The results showed that E. faecium 130 co-cultured with L. monocytogenes was the most effective in preventing infection of Caco-2 cells, as the vast majority of isolates showed significantly lower adhesion counts and invasion rates below the quantification limit of the method (<30 cfu/plate). L. sakei 1 was the least effective strain in preventing L. monocytogenes infection; only one isolate presented a lower adhesion rate and two isolates reduced the invasion rate of Caco-2 cells. Fluorescence in situ hybridisation (FISH) assay was shown to be an effective tool to illustrate and identify species in co-culture with L. monocytogenes during the adhesion process to Caco-2 cells.

Postbiotic activities of lactobacilli-derived factors

Probiotics are alive nonpathogenic microorganisms present in the gut microbiota that confer benefits to the host for his health. They act through molecular and cellular mechanisms that contrast pathogen bacteria adhesion, enhance innate immunity, decrease pathogen-induced inflammation, and promote intestinal epithelial cell survival, barrier function, and protective responses. Some of these beneficial effects result to be determined by secreted probiotic-derived factors that recently have been identified as "postbiotic" mediators. They have been reported for several probiotic strains but most available literature concerns Lactobacilli. In this review, we focus on the reported actions of several secretory products of different Lactobacillus species highlighting the available mechanistic data. The identification of soluble factors mediating the beneficial effects of probiotics may present an opportunity not only to understand their fine mechanisms of action, but also to develop effective pharmacological strategies that could integrate the action of treatments with live bacteria.

Pyrosequencing analysis of microbiota reveals that lactic acid bacteria are dominant in Korean flat fish fermented food, gajami-sikhae

The gajami-sikhae, traditional Korean cuisine fermented with flat fish, samples were collected from eight different manufacturers (GS1–GS8). We employed pyrosequencing method to analyze the bacterial communities of the gajami-sikhae samples. Family- and genus-level analyses indicated that the bacterial community compositions of GS3 and GS6 were distinct from those of the rest. The species-level structures of bacterial communities of the gajami-sikhae samples except for GS3 and GS6 featured Lactobacillus sakei as the most abundant species. Leuconostoc mesenteroides was revealed as the most dominant species among the bacterial community of GS6 and the bacterial community of GS3 was composed of various lactic acid bacteria. We employed a culture-based method to isolate beneficial strains from the gajami-sikhae samples. However, most of the 47 selected colonies were identified as Bacillus subtilis and Bacillus amyloliquefaciens. This study indicated that gajami-sikhae was mainly composed of many beneficial lactic acid bacteria.

Listeria monocytogenes: survival and adaptation in the gastrointestinal tract

The foodborne pathogen Listeria monocytogenes has the capacity to survive and grow in a diverse range of natural environments. The transition from a food environment to the gastrointestinal tract begins a process of adaptation that may culminate in invasive systemic disease. Here we describe recent advances in our understanding of how L. monocytogenes adapts to the gastrointestinal environment prior to initiating systemic infection. We will discuss mechanisms used by the pathogen to survive encounters with acidic environments (which include the glutamate decarboxylase and arginine deiminase systems), and those which enable the organism to cope with bile acids (including bile salt hydrolase) and competition with the resident microbiota. An increased understanding of how the pathogen survives in this environment is likely to inform the future design of novel prophylactic approaches that exploit specific pharmabiotics; including probiotics, prebiotics, or phages.

Role of endogenous microbiota, probiotics and their biological products in human health

Although gut diseases such as inflammatory bowel disease, mucositis and the alimentary cancers share similar pathogenetic features, further investigation is required into new treatment modalities. An imbalance in the gut microbiota, breached gut integrity, bacterial invasion, increased cell apoptosis to proliferation ratio, inflammation and impaired immunity may all contribute to their pathogenesis. Probiotics are defined as live bacteria, which when administered in sufficient amounts, exert beneficial effects to the gastrointestinal tract. More recently, probiotic-derived factors including proteins and other molecules released from living probiotics, have also been shown to exert beneficial properties. In this review we address the potential for probiotics, with an emphasis on probiotic-derived factors, to reduce the severity of digestive diseases and further discuss the known mechanisms by which probiotics and probiotic-derived factors exert their physiological effects.