Influence of a combination of two potential probiotic strains, Lactobacillus rhamnosus IMC 501® and Lactobacillus paracasei IMC 502® on bowel habits of healthy adults

Aims: This study aims to investigate the effect of different kinds of food products enriched with a combination of two potential probiotic strains, Lactobacillus rhamnosus IMC 501^® and Lactobacillus paracasei IMC 502^®, on bowel habits of healthy adults. Methods and Results: Fifty healthy volunteers took part in a double‐blind placebo probiotic feeding study (25 fed probiotics, 25 fed placebo) for 12 weeks. Each volunteer ingested daily one or more food products enriched with a combination of the two potential probiotic strains (probiotic group) or the same food products without the probiotics (control group). Faecal samples were collected before, at the end and 2 weeks later the intervention period, and some of the main groups of faecal bacteria were enumerated by plate count and real‐time PCR. Questionnaires on bowel habits were submitted to volunteers. After the intervention, a significant increase in faecal lactobacilli and bifidobacteria were observed in the probiotic group, and stool frequency and stool volume were higher in the probiotic group than in the placebo group. Conclusions: Daily consumption of food products enriched with the two potential probiotic strains, Lact. rhamnosus IMC 501^® and Lact. paracasei IMC 502^®, contributes to improve intestinal microbiota with beneficial properties and enhances bowel habits of healthy adults. Significance and Impact of the Study: The study revealed that Lact. rhamnosus IMC 501^® and Lact. paracasei IMC 502^® exert a positive effect, in terms of improved bowel habits, on healthy adults.     

Lactobacillus plantarum AS1 binds to cultured human intestinal cell line HT-29 and inhibits cell attachment by enterovirulent bacterium Vibrio parahaemolyticus

Aim: Lactobacillus plantarum AS1 was incubated with HT‐29 adenocarcinoma cell line to assess its adhesion potency and examined for its inhibitory effect on the cell attachment by an enterovirulent bacterium Vibrio parahaemolyticus. Methods and Results: Lactobacillus plantarum AS1 attached efficiently to HT‐29 cells as revealed by scanning electron microscopy and bacterial adhesion assay. Lactobacillus plantarum AS1 significantly reduced V. parahaemolyticus attached to HT‐29 cells by competition, exclusion and displacement mode. Lactobacillus plantarum AS1 seems to adhere to human intestinal cells via mechanisms that involve different combinations of carbohydrate and protein factors on the bacteria and eukaryotic cell surface. Conclusion: Strain Lact. plantarum AS1 inhibits the cell attachment of a pathogen V. parahaemolyticus by steric hindrance mechanism. Also, antibacterial factors such as bacteriocins, lactic acid and exopolysaccharides could be involved. Significance and Impact of the Study: The ability to inhibit the adhesion of V. parahaemolyticus to intestinal cell line warrants further investigation to explore the use of probiotic strain Lact. plantarum AS1 in the management of gastroenteritis caused by V. parahaemolyticus.     

Butanol production from corncob residue using Clostridium beijerinckii NCIMB 8052

Aims: Not all lactic acid bacteria possess the ability to confer health benefits for the host. Thus, it becomes necessary to screen and characterize numerous strains to obtain ideal probiotics. Here, two Lactobacillus plantarum strains (CECT 7315 and CECT 7316) were isolated and characterized. Methods and Results: In vitro and in vivo tests were carried out for demonstrating the abilities as probiotics of CECT 7315/CECT 7316 Lact. plantarum strains. Both strains showed high ability to survive at gastro‐intestinal tract conditions and to adhere to intestinal epithelial cells, as well as great inhibitory activity against a wide range of enteropathogens and ability to induce the production of anti‐inflammatory cytokine IL‐10. Conclusions: Lactobacillus plantarum CECT 7315/CECT 7316 because of their potential probiotic properties could be excellent candidates for being tested in clinical trials aimed to demonstrate beneficial effects on human health. Significance and Impact of the Study: Probiotics are live micro‐organisms that confer a health benefit for the host. However, not all the lactic acid bacteria possess the ability to confer health benefits for the host. In this study, two Lact. plantarum strains (CECT 7315 and CECT 7316) were isolated and characterized to demonstrate their excellent qualities as potential probiotic strains.     

Comparison of Campylobacter jejuni isolates from human, food, veterinary and environmental sources in Iceland using PFGE, MLST and fla-SVR sequencing

Aims: To evaluate the probiotic properties of strains isolated from smoked salmon and previously identified as bacteriocin producers. Methods and Results: Strains Lactobacillus curvatus ET06, ET30 and ET31, Lactobacillus fermentum ET35, Lactobacillus delbrueckii ET32, Pediococcus acidilactici ET34 and Enterococcus faecium ET05, ET12 and ET88 survived conditions simulating the gastrointestinal tract (GIT) and produced bacteriocins active against several strains of Listeria monocytogenes, but presented very low activity against other lactic acid bacteria (LAB). Cell‐free supernatants containing bacteriocins, added to 3‐h‐old cultures of L. monocytogenes 603, suppressed growth over 12 h. Auto‐aggregation was strain‐specific, and values ranged from 7·2% for ET35 to 12·1% for ET05. Various degrees of co‐aggregation with L. monocytogenes 603, Lactobacillus sakei ATCC 15521 and Enterococcus faecalis ATCC 19443 were observed. Adherence of the bacteriocinogenic strains to Caco‐2 cells was within the range reported for Lactobacillus rhamnosus GG, a well‐known probiotic. The highest levels of hydrophobicity were recorded for Lact. curvatus (61·9–64·6%), Lact. fermentum (78·9%), Lact. delbrueckii (43·7%) and Ped. acidilactici (51·3%), which are higher than the one recorded for Lact. rhamnosus GG (53·3%). These strains were highly sensitive to several antibiotics and affected by several drugs from different generic groups in a strain‐dependent manner. Conclusions: Smoked salmon is a rich source of probiotic LAB. All strains survived conditions simulating the GIT and produced bacteriocins active against various pathogens. Adherence to Caco‐2 cells was within the range reported for Lact. rhamnosus GG, a well‐known probiotic. In addition, the high hydrophobicity readings recorded define the strains as good probiotics. Significance and Impact of the Study: Smoked salmon contains a number of different probiotic LAB and could be marketed as having a potential beneficial effect.     

Isolation and characterization of bacteriocin‐producing bacteria from the intestinal microbiota of elderly Irish subjects

Aims

To isolate and characterize bacteriocins produced by predominant species of lactic acid bacteria from faeces of elderly subjects.

Methods and Results

Screening over 70 000 colonies, from faecal samples collected from 266 subjects, using the indicator organisms Lactobacillus bulgaricus LMG 6901 and Listeria innocua DPC 3572, identified 55 antimicrobial‐producing bacteria. Genomic fingerprinting following ApaI digestion revealed 15 distinct strains. The antimicrobial activities associated with 13 of the 15 strains were sensitive to protease treatment. The predominant antimicrobial‐producing species were identified as Lactobacillus salivarius, Lactobacillus gasseri, Lactobacillus acidophilus, Lactobacillus crispatus and Enterococcus spp. A number of previously characterized bacteriocins, including ABP‐118 and salivaricin B (from Lact. salivarius), enterocin B (Enterococcus faecium), lactacin B (Lact. acidophilus), gassericin T and a variant of gassericin A (Lact. gasseri), were identified. Interestingly, two antimicrobial‐producing species, not generally associated with intestinally derived microorganisms were also isolated: Lactococcus lactis producing nisin Z and Streptococcus mutans producing mutacin II.

Conclusion

These data suggest that bacteriocin production by intestinal isolates against our chosen targets under the screening conditions used was not frequent (0·08%).

Significance and Impact of the Study

The results presented are important due to growing evidence indicating bacteriocin production as a potential probiotic trait by virtue of strain dominance and/or pathogen inhibition in the mammalian intestine.     

Inhibitory effect of oral Lactobacillus against oral pathogens

Aims: To determine the inhibitory effect of oral Lactobacillus against putative oral pathogens. Methods and Results: Total 357 strains comprising 10 species of oral Lactobacillus, Lactobacillus fermentum (195), Lactobacillus salivarius (53), Lactobacillus casei (20), Lactobacillus gasseri (18), Lactobacillus rhamnosus (14), Lactobacillus paracasei (12), Lactobacillus mucosae (12), Lactobacillus oris (12), Lactobacillus plantarum (11) and Lactobacillus vaginalis (10) were used as producer strains. Inhibitory effect against a panel of indicators, periodontitis‐ and caries‐related pathogens, was assessed. Most oral Lactobacillus was able to inhibit the growth of both periodontitis‐ and caries‐related pathogens. The strongest inhibitory activity was associated with Lact. paracasei, Lact. plantarum, Lact. rhamnosus, Lact. casei and Lact. salivarius. Lactobacillus SD1–SD6, representing the six species with the strong inhibitory effect, inhibited growth of Streptococcus mutans ATCC 25175 in the biofilm model. Also, it was demonstrated that growth of Strep. mutans was inhibited in a mixture with Lact. paracasei SD1. The inhibition was enhanced in acidic condition and 5% glucose. Conclusions: The results have shown that oral Lactobacillus SD1–SD6 showed a strong inhibitory effect against Strep. mutans and Streptococcus sobrinus, as well as, Gram‐negative periodontal pathogens Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans. Significance and Impact of the Study: The results indicated that Lactobacillus may be of benefit as probiotics for the prevention of oral diseases.     

Survival of silage lactic acid bacteria in the goat gastrointestinal tract as determined by denaturing gradient gel electrophoresis

Aims: To determine the survival rate of silage lactic acid bacteria (LAB) in the ruminant gastrointestinal tract. Methods and Results: Wilted Italian ryegrass (Lolium multiflorum Lam.) silage (containing 1·9 × 10⁶ CFU LAB g^?1) was fed ad libitum to three goats equipped with rumen cannulae. Silage was given alone or with concentrates at a 1 : 1 ratio on a dry matter basis. Rumen fluid was then obtained 2, 4 and 8 h after the morning feeding. Denaturing gradient gel electrophoresis was performed to compare LAB communities in silage, rumen fluid and faeces. The LAB detected in the wilted silage included Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus murinus and Lactobacillus sakei. Bands indicative of Lact. murinus were detected in either the rumen fluid or faeces, whereas the bands indicative of Lact. plantarum, Lact. brevis and Lact. sakei were not. Although the rumen fluid LAB counts and volatile fatty acid concentrations were higher in goats fed silage plus concentrates compared with those fed silage alone, the LAB communities themselves remained unaffected. Sampling times and goat‐to‐goat variations did not affect the LAB communities found in the rumen fluid. Conclusion: LAB communities found in the gut are not remarkably affected by the consumption of silage LAB, even when the silage is accompanied by concentrates that facilitate gut fermentation. Significance and Impact of the Study: Although silage can improve probiotic function, it may be difficult for silage LAB to survive the digestive process in the ruminant gastrointestinal tract.     

Linoleate isomerase activity occurs in lactic acid bacteria strains and is affected by pH and temperature

Aims: To investigate the ability of lactic acid bacteria (LAB) to convert linoleic acid (LA) and α‐linolenic acid (α‐LNA) to conjugated linoleic acid (CLA) and conjugated linolenic acid (CLNA), respectively. To assess pH and temperature influences on CLA and CLNA production by Lactobacillus sakei LMG 13558. Methods and Results: A screening of 48 LAB yielded one Lactobacillus curvatus, five Lactobacillus plantarum and four Lact. sakei strains displaying linoleate isomerase (LAI) activity. CLNA conversion percentages varied largely (1–60%). CLA conversion, occurring in three strains, was lower (2–5%). The LAI gene sequences of the ten LAI‐positive strains shared 75–99% identity with the LAI gene sequence of a Lact. plantarum AS1.555. At pH 6·2, CLA and CLNA production by Lact. sakei LMG 13558 was higher at 30°C than at 20 and 25°C. At pH 5·5 (30°C) or 37°C (pH 6·2), LA was not converted and α‐LNA only slightly converted. Conclusions: LAB show strain‐dependent LAI activity. Production of CLA and CLNA is affected by pH and temperature, as shown for Lact. sakei LMG 13558. Significance and Impact of the Study: Several LAB produce CLA and/or CLNA, as shown for Lact. sakei and Lact. curvatus for the first time. These findings offer potential for the manufacturing of fermented functional foods.     

Probiotic characterization of Lactiplantibacillus plantarum HOM3204 and its restoration effect on antibiotic-induced dysbiosis in mice

The purpose of this study was to evaluate the probiotic characteristics of Lactiplantibacillus plantarum HOM3204 isolated from homemade pickled cabbage and to examine its restoration effect on antibiotic-induced dysbiosis in mice. Lact. plantarum HOM3204 tolerated simulated gastric and intestinal juices with a 99·38% survival rate. It also showed strong adhesion ability (3·45%) to Caco-2 cells and excellent antimicrobial activity against foodborne pathogens in vitro. For safety (antibiotic susceptibility) of this strain, it was susceptible to all the tested seven antibiotics. Lact. plantarum HOM3204 had good stability during storage, especially in cold and frozen conditions. Furthermore, Lact. plantarum HOM3204 significantly restored the gut microbiota composition by increasing the abundance of Lactobacilli and Bifidobacteria and decreasing Enterococci, and improved antioxidative function by raising the concentrations of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) in serum of antibiotic-induced dysbiosis in mice. These results suggest that Lact. plantarum HOM3204 could be a potential probiotic as a functional food ingredient.     

Characterization of lactic acid bacteria from musts and wines of three consecutive vintages of Ribeira Sacra

Aims: This study was designed to isolate and characterize the lactic acid microbiota of the musts and wines of a young denomination of origin area, Ribeira Sacra in north‐west Spain. Methods and Results: Over three consecutive years (2007, 2008 and 2009), we examined musts and wines from four cellars in different zones of the region. Through biochemical and genetic tests, 459 isolates of lactic acid bacteria (LAB) were identified as the following species: Lactobacillus alvei (0·7%), Lactobacillus brevis (1·7%), Lactobacillus frumenti (0·9%), Lactobacillus kunkeei (12%), Lactobacillus plantarum (6·5%), Lactobacillus pentosus (0·9%), Lactococcus lactis ssp. lactis (3%), Leuconostoc citreum (0·7%), Leuconostoc fructosum (synon. Lactobacillus fructosum) (3·7%), Leuconostoc mesenteroides ssp. mesenteroides (2·8%), Leuconostoc pseudomesenteroides (0·2%), Oenococcus oeni (59%), Pediococcus parvulus (7%) and Weisella paramesenteroides (synon. Leuconostoc paramesenteroides) (0·9%). Of these species, O. oeni was the main one responsible for malolactic fermentation (MLF) in all cellars and years with the exception of Lact. plantarum, predominant in 2007, in one cellar, and Lact. brevis, Lact. frumenti and Ped. parvulus coexisting with O. oeni in one cellar in 2009. Different strains (84) of LAB species (14) were identified by biochemical techniques (API strips, the presence of plasmids, enzyme activities and MLF performance) and molecular techniques (PCR). All assays were carried out with every one of the 459 isolates. To select candidates for use as culture starters, we assessed malolactic, β‐glucosidase and tannase activities, the presence of genes involved in biogenic amine production and plasmid content. Conclusions: A high diversity of LAB is present in the grape musts of Ribeira Sacra but few species are responsible for MLF; however, different strains of such species are involved in the process. As far as we are aware, this is the first report of Lact. frumenti thriving in wine. Significance and Impact of the Study: Information on LAB populations in must and wine is presented. A large collection of well‐characterized strains of LAB are available as starter cultures to winemakers.     

Heterologous protein secretion by Lactobacillus plantarum using homologous signal peptides

Aims: To test seven selected putative signal peptides from Lactobacillus plantarum WCFS1 in terms of their ability to drive secretion of two model proteins in Lact. plantarum, and to compare the functionality of these signal peptides with that of well‐known heterologous signal peptides (Usp45, M6). Methods and Results: Signal peptide functionality was assessed using a series of modular derivatives of the pSIP vectors for peptide pheromone‐controlled high‐level gene expression in lactobacilli. Several of the constructs with homologous signal peptides yielded similar or higher reporter protein activities than constructs with heterologous signal peptides. Two of the homologous signal peptides (Lp_0373 and Lp_0600) appeared as especially promising candidates for directing secretion, as they were among the best performing with both reporter proteins. Conclusions: We have identified homologous signal peptides for high‐level secretion of heterologous proteins in Lact. plantarum. With the model proteins, some of these performed better than commonly used heterologous signal peptides. Significance and Impact of the Study: The homologous signal peptides tested out, in this study, could be useful in food‐grade systems for secretion of interesting proteins in Lact. plantarum. The constructed modular secretion vectors are easily accessible for rapid signal peptide screening.     

Comparison of alternatives to in‐feed antimicrobials for the prevention of clinical necrotic enteritis

Aims: The capacity for Lactobacillus johnsonii and an organic acid (OA) blend to prevent Clostridium perfringens‐induced clinical necrotic enteritis (NE) in chickens was studied. Methods and Results: Cobb 500 birds were allocated into six groups (n = 25 birds/pen, eight pens/treatment); Unchallenged, Challenged, Antimicrobial (zinc bacitracin (ZnB)/monensin), OA, probiotic Lact. johnsonii and probiotic sham (Phosphate–buffered saline). All birds were challenged with Eimeria spp. and Cl. perfringens except for unchallenged controls. Birds fed antimicrobials were protected from NE development as indicated by maintenance of body weight, low mortality and clostridium levels, and decreased intestinal macroscopic lesion scores compared to challenged controls (P < 0·05). Lactobacillus johnsonii‐fed birds had reduced lesion scores, whilst OA‐fed birds had decreased Cl. perfringens levels. Both Lact. johnsonii and OA‐fed birds had improved feed efficiency between days 0 and 28 compared to challenged controls; however, mortality and body weights were not improved by either treatment. Microbial profiling indicated that the challenge procedure significantly altered the jejunal microbiota. The microbiota of antimicrobial‐fed birds was significantly different from all other groups. Conclusions: Whilst Lact. johnsonii and OA altered specific intestinal parameters, significant protection against NE was not observed. Significance and Impact of the Study: Lactobacillus johnsonii and OA did not prevent NE; however, some improvements were evident. Other related treatments, or combinations of these two treatments, may provide greater protection.     

The Effects of Limosilactobacillus reuteri LR-99 Supplementation on Body Mass Index,Social Communication,Fine Motor Function,and Gut Microbiome Composition in Individuals with Prader–Willi Syndrome: a Randomized Double-Blinded Placebo-Controlled Trial

Prader–Willi syndrome (PWS) is a rare genetic disorder associated with developmental delay, obesity, and neuropsychiatric comorbidities. Limosilactobacillus reuteri (Lactobacillus reuteri, Lact. reuteri) has demonstrated anti-obesity and anti-inflammatory effects in previous studies. In the present study, we aim to evaluate the effects of Lact. reuteri supplementation on body mass index (BMI), social behaviors, and gut microbiota in individuals with PWS. We conducted a 12-week, randomized, double-blind, placebo-controlled trial in 71 individuals with PWS aged 6 to 264 months (64.4 ± 51.0 months). Participants were randomly assigned to either receive daily Lact. reuteri LR-99 probiotic (6 × 10¹⁰ colony forming units) or a placebo sachet. Groupwise differences were assessed for BMI, ASQ-3, and GARS-3 at baseline, 6 weeks, and 12 weeks into treatment. Gut microbiome data was analyzed with the QIIME2 software package, and predictive functional profiling was conducted with PICRUSt-2. We found a significant reduction in BMI for the probiotic group at both 6 weeks and 12 weeks relative to the baseline (P < 0.05). Furthermore, we observed a significant improvement in social communication and interaction, fine motor function, and total ASQ-3 score in the probiotics group compared to the placebo group (P < 0.05). Altered gut microbiota was observed in the probiotic group to favor weight loss and improve gut health. The findings suggest a novel therapeutic potential for Lact. reuteri LR-99 probiotic to modulate BMI, social behaviors, and gut microbiota in Prader–Willi syndrome patients, although further investigation is warranted.

Trial registration Chinese Clinical Trial Registry: ChiCTR1900022646

     

Effect of riboflavin‐producing bacteria against chemically induced colitis in mice

Aim

To assess the anti‐inflammatory effect associated with individual probiotic suspensions of riboflavin‐producing lactic acid bacteria (LAB) in a colitis murine model.

Methods and Results

Mice intrarectally inoculated with trinitrobenzene sulfonic acid (TNBS) were orally administered with individual suspensions of riboflavin‐producing strains: Lactobacillus (Lact.) plantarum CRL2130, Lact. paracasei CRL76, Lact. bulgaricus CRL871 and Streptococcus thermophilus CRL803; and a nonriboflavin‐producing strain or commercial riboflavin. The extent of colonic damage and inflammation and microbial translocation to liver were evaluated. iNOs enzyme was analysed in the intestinal tissues and cytokine concentrations in the intestinal fluids. Animals given either one of the four riboflavin‐producing strains showed lower macroscopic and histologic damage scores, lower microbial translocation to liver, significant decreases of iNOs+ cells in their large intestines and decreased proinflammatory cytokines, compared with mice without treatment. The administration of pure riboflavin showed similar benefits. Lact. paracasei CRL76 accompanied its anti‐inflammatory effect with increased IL‐10 levels demonstrating other beneficial properties in addition to the vitamin production.

Conclusion

Administration of riboflavin‐producing strains prevented the intestinal damage induced by TNBS in mice.

Significance and Impact of the Study

Riboflavin‐producing phenotype in LAB represents a potent tool to select them for preventing/treating IBD.     

Improvement of the fermentation performance of Lactobacillus plantarum by the flavanol catechin is uncoupled from its degradation

Aims: To determine the influence of the flavanol catechin on key metabolic traits for the fermentation performance of Lactobacillus plantarum strain RM71 in different media and to evaluate the ability of this strain to catabolize catechin. Methods and Results: Growth monitoring and time course of sugar consumption data tracking in chemically defined medium (CDM), revealed that growth of Lact. plantarum strain RM71 upon catechin was characterized by a noticeable shorter lag period, outcome of earlier sugar consumption and lactic acid production courses. Catechin gave rise to higher cell densities compared to controls because of an increased extension of sugar utilization. Fermentation of media relevant for practical fermentation processes with Lact. plantarum strain RM71 showed that catechin sped up malic acid decarboxylation, which besides quicker and extended consumption of several sugars, resulted in faster and higher lactic acid production and growth. Spectrophotometric evaluation of catechin by HPLC‐DAD and the lack of catechin concentration‐dependent effects showed that the observed stimulations were uncoupled from catechin catabolism by Lact. plantarum. Conclusions: The flavanol catechin stimulated the growth of Lact. plantarum strain RM71 by promoting quicker sugar consumption, increasing the extension of sugar utilization and stimulating malic acid decarboxylation. These stimulations are uncoupled from catechin catabolism as Lact. plantarum did not catabolize it during fermentation. Significance and Impact of the Study: This study, for the first time, examined the influence of the flavanol catechin on the fermentation performance of a Lact. plantarum strain in several media under different fermentation conditions. The information could be relevant to control the production and obtain high‐quality food products fermented by this micro‐organism.     

Effect of biosynthetic intermediates and citrate on the phenyllactic and hydroxyphenyllactic acids production by Lactobacillus plantarum CRL 778

Aim: To evaluate the influence of biosynthetic precursors, intermediates and electron acceptors on the production of antifungal compounds [phenyllactic acid (PLA) and hydroxyphenyllactic acid (OH‐PLA)] by Lactobacillus plantarum CRL 778, a strain isolated from home‐made sourdough. Methods and Results: Growth of fermentative activity and antifungal compounds production by Lact. plantarum CRL 778 were evaluated in a chemically defined medium (CDM) supplemented with biosynthetic precursors [phenylalanine (Phe), tyrosine (Tyr)], intermediates [glutamate (Glu), alpha‐ketoglutarate (α‐KG)] and electron acceptors [citrate (Cit)]. Results showed that the highest PLA production (0·26 mmol l^?1), the main antifungal compound produced by Lact. plantarum CRL 778, occurred when greater concentrations of Phe than Tyr were present. Both PLA and OH‐PLA yields were increased 2‐folds when Cit was combined with α‐KG instead of Glu at similar Tyr/Phe molar ratio. Similarly, glutamate dehydrogenase (GDH) activity was significantly (P < 0·01) stimulated by α‐KG and Cit in Glu‐free medium. Conclusion: Phe was the major stimulant for PLA formation; however, Cit could increase both PLA and OH‐PLA synthesis by Lact. plantarum CRL 778 probably due to an increase in oxidized NAD⁺. This effect, as well as the GDH activity, was enhanced by α‐KG and down regulated by Glu. Significance and Impact of the Study: This is the first study where the role of Glu and GDH activity in the PLA and OH‐PLA synthesis was evidenced in sourdough lactic acid bacteria (LAB) using a CDM. These results contribute to the knowledge on the antifungal compounds production by sourdough LAB with potential applications on the baked goods.     

Isolation and phenotypic characterization of Lactobacillus casei and Lactobacillus paracasei bacteriophage-resistant mutants

Aims: To isolate and characterize bacterial strains derived from Lactobacillus casei and Lactobacillus paracasei strains and resistant to phage MLC‐A. Methods and Results: Two of nine assayed strains rendered resistant mutants with recovery efficiencies of 83% (Lact. paracasei ATCC 27092) and 100% (Lact. casei ATCC 27139). DNA similarity coefficients (RAPD–PCR) confirmed that no significant genetic changes occurred while obtaining resistant mutants. Neither parent nor mutant strains spontaneously released phages. Phage‐resistant mutants were tested against phages PL‐1, J‐1, A2 and MLC‐A8. Lactobacillus casei ATCC 27092 mutants showed, overall, lower phage resistance than Lact. paracasei ATCC 27092 ones, but still higher than that of the parent strain. Lactobacillus paracasei ATCC 27092 mutants moderately adsorbed phage MLC‐A only in calcium presence, although their parent strain successfully did it with or without calcium. Adsorption rates for Lact. casei ATCC 27139 and its mutants were highly influenced by calcium. Again, phage adsorption was higher on the original strain. Conclusions: Several isolates derived from two Lact. casei and Lact. paracasei strains showed resistance to phage MLC‐A but also to other Lact. casei and Lact. paracasei phages. Significance and Impact of the Study: This study highlights isolation of spontaneous bacteriophage‐resistant mutants from Lact. casei and Lact. paracasei as a good choice for use in industrial rotation schemes.     

Protective effect of Lactobacillus casei strain Shirota against lethal infection with multi-drug resistant Salmonella enterica serovar Typhimurium DT104 in mice

Aims: The anti‐infectious activity of lactobacilli against multi‐drug resistant Salmonella enterica serovar Typhimurium DT104 (DT104) was examined in a murine model of an opportunistic antibiotic‐induced infection. Methods and Results: Explosive intestinal growth and subsequent lethal extra‐intestinal translocation after oral infection with DT104 during fosfomycin (FOM) administration was significantly inhibited by continuous oral administration of Lactobacillus casei strain Shirota (LcS), which is naturally resistant to FOM, at a dose of 10⁸ colony‐forming units per mouse daily to mice. Comparison of the anti‐Salmonella activity of several Lactobacillus type strains with natural resistance to FOM revealed that Lactobacillus brevis ATCC 14869^T, Lactobacillus plantarum ATCC 14917^T, Lactobacillus reuteri JCM 1112^T, Lactobacillus rhamnosus ATCC 7469^T and Lactobacillus salivarius ATCC 11741^T conferred no activity even when they obtained the high population levels almost similar to those of the effective strains such as LcS, Lact. casei ATCC 334^T and Lactobacillus zeae ATCC 15820^T. The increase in concentration of organic acids and maintenance of the lower pH in the intestine because of Lactobacillus colonization were correlated with the anti‐infectious activity. Moreover, heat‐killed LcS was not protective against the infection, suggesting that the metabolic activity of lactobacilli is important for the anti‐infectious activity. Conclusion: These results suggest that certain lactobacilli in combination with antibiotics may be useful for prophylaxis against opportunistic intestinal infections by multi‐drug resistant pathogens, such as DT104. Significance and Impact of the Study: Antibiotics such as FOM disrupt the metabolic activity of the intestinal microbiota that produce organic acids, and that only probiotic strains that are metabolically active in vivo should be selected to prevent intestinal infection when used clinically in combination with certain antibiotics.     

Atopic dermatitis‐mitigating effects of new Lactobacillus strain,Lactobacillus sakei probio 65 isolated from Kimchi

Aims

Atopic dermatitis (AD) is an inflammatory skin disease. Probiotics have been reported to modulate immune responses and thus are now being suggested as potential treatments for allergies. In this study, we investigated the inhibitory effects of Lactobacillus sakei probio 65 isolated from Kimchi on artificially inducing AD in NC/Nga mice.

Methods and Results

Oral administration of viable or heat‐inactivated Lact. sakei probio 65 improved the condition of skin and reduced scratching frequency. Serum levels of IgE and cutaneous T‐cell‐attracting chemokine (CTACK) were significantly decreased by this therapy. Dead Lact. sakei probio 65 also decreased IL‐4 and IL‐6 serum concentrations. Moreover, both live and dead Lact. sakei probio 65 inhibited the expression of Thymus and activation‐regulated chemokine and CTACK in AD‐like skin lesions. The increased levels of Foxp3 expression in the lesional skin and ears were also suppressed by Lact. sakei probio 65. In addition, Lact. sakei probio 65 inhibited β‐hexosaminidase release and the secretion of IL‐4, TNF‐α and IL‐6 from RBL‐2H3 cells.

Conclusions

Oral treatment with both viable and heat‐inactivated Lact. sakei probio 65 inhibits skin inflammation and AD‐like skin lesions, as well as mast cell activation.

Significance and Impact of the Study

Lactobacillus sakei probio 65 has an inhibitory effect on atopic dermatitis‐like skin lesions and may represent an effective new anti‐inflammatory agent.