Evaluation of resistance to low pH and bile salts of human Lactobacillus spp. isolates

Improvement effect of a next-generation probiotic L. plantarum-pMG36e-GLP-1 on type 2 diabetes mellitus via the gut-pancreas-liver axis

Next-generation probiotics (NGPs) are currently being investigated as therapeutic agents that impact the gut microbiota and disease development. Glucagon-like peptide-1 (GLP-1) shows an excellent therapeutic effect on diabetes, but has an extremely short half-life in vivo. Here, we constructed a novel and diabetes-specific NGP, the genetically engineered strain Lactobacillus plantarum (L. plantarum)-pMG36e-GLP-1, and evaluated its ameliorative effect on type 2 diabetes mellitus (T2DM) in artificially induced mice and transgenic mice. In vitro, L. plantarum-pMG36e-GLP-1 showed good genetic stability and probiotic characteristics. In the high-fat diet combined with streptozotocin (HFD/STZ)-induced T2DM mice, L. plantarum-pMG36e-GLP-1 relieved the diabetic symptoms, regulated the intestinal microbiota, and reduced the inflammatory reaction in the pancreatic tissue. Meanwhile, the apoptosis of pancreatic islet cells was inhibited, while islet tissue morphology repairs, islet β-cell proliferation, and insulin secretion were all promoted by L. plantarum-pMG36e-GLP-1. Furthermore, a similar effect of the engineered strain on diabetic symptoms and the pancreas was observed in db/db mice, and the metabolism of lipids in the liver was regulated. Together, the findings of this study confirmed the anti-hyperglycemic effect of the engineered strain L. plantarum-pMG36e-GLP-1, providing a promising approach for T2DM treatment.

Lactobacillus salivarius WZ1 Inhibits the Inflammatory Injury of Mouse Jejunum Caused by Enterotoxigenic Escherichia coli K88 by Regulating the TLR4/NF-κB/MyD88 Inflammatory Pathway and Gut Microbiota

Replacing antibiotics with probiotics has become an important way to safely and effectively prevent and treat some gastrointestinal diseases. This study was conducted to investigate whether Lactobacillus salivarius WZ1 (L.S) could reduce the inflammatory injury to the mouse jejunum induced by Escherichia coli (ETEC) K88. Forty Kunming mice were randomly divided into four groups with 10 mice in each group. From day 1 to day 14, the control group and the E. coli group were administered with normal saline each day, while the L.S group and the L.S + E. coli group were gavaged with Lactobacillus salivarius WZ1 1 × 108 CFU/mL each day. On the 15th day, the E. coli group and the L.S + E. coli group were intragastrically administered ETEC K88 1 × 109 CFU/mL and sacrificed 24 h later. Our results show that pretreatment with Lactobacillus salivarius WZ1 can dramatically protect the jejunum morphological structure from the changes caused by ETEC K88 and relieve the morphological lesions of the jejunum, inhibiting changes in the mRNA expressions of TNF-α, IL-1β and IL-6 and the protein expressions of TLR4, NF-κB and MyD88 in the intestinal tissue of mice caused by ETEC K88. Moreover, pretreatment with Lactobacillus salivarius WZ1 also increased the relative abundance of beneficial genera such as Lactobacillus and Bifidobacterium and decreased the abundance of harmful genera such as Ralstonia and Helicobacter in the gut. These results demonstrate that Lactobacillus salivarius WZ1 can inhibit the inflammatory damage caused by ETEC K88 in mouse jejunum by regulating the TLR4/NF-κB/MyD88 inflammatory pathway and gut microbiota.

A Novel Strain of Probiotic Leuconostoc citreum Inhibits Infection-Causing Bacterial Pathogens

Infectious diseases caused by bacteria are at risk of spreading and prolonging due to antimicrobial resistance. It is, therefore, urgently necessary to develop a more effective antibiotic alternative strategy to control pathogen spread. In general, probiotics have been recommended as a substitute for antibiotics that inhibit pathogens. This study was isolated and probiotic characteristics and antibacterial bacterial efficiency against various infection-causing pathogens were determined by different in vitro methods. A 16S rRNA sequence confirmed that the isolated strains belonged to a species of Leuconostoc citreum. L. citreum KCC-57 and KCC-58 produced various extracellular enzymes and fermented different carbohydrates. There was significant tolerance for both strains under the harsh conditions of the gastrointestinal tract (GIT). In addition, L. citreum KCC-57 and L. citreum KCC-58 showed significant auto-aggregations and hydrophobicity properties that varied with incubation time. Moreover, the cell-free secondary supernatant (CFS) of L. citreum KCC-57 and L. citreum KCC-58 inhibited growth of Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. According to a co-culture study, L. citreum KCC-57 and L. citreum KCC-58 were highly competitive for pathogen growth. L. citreum KCC-57 and L. citreum KCC-58 showed significant probiotic potential and strong antibacterial activities against different pathogens, suggesting that these strains could be used instead of antibiotics to control infectious pathogens.

Lead biosorption efficiency of Levilactobacillus brevis MZ384011 and Levilactobacillus brevis MW362779: A response surface based approach

Lead (Pb) is a substantial contaminant in the environment and a potent toxin for living organisms. Current study describes probiotic characteristics of Pb-biosorbing lactic acid bacteria (LAB), and response surface methodology (RSM) based optimization of physical conditions for maximum Pb biosorption. A total of 18 LAB, isolated from carnivore feces (n = 8) and human breast milk (n = 9), along with one reference strain Lactobacillus acidophilus ATCC4356 were included in the study. Pb biosorption was strain specific. Eight strains, demonstrating ≥ 70 % lead biosorption, were selected for further testing. The lactobacillus-Pb complex was found to be stable and strains had a negative surface charge. The strains displayed good probiotic properties with the survival rate of 71-90 % in simulated gastric environment, 36-69 % in intestinal condition (1.8 % bile salts) and 55-72 % hydrophobicity. On the basis of excellent probiotic ability, Levilactobacillus brevis MZ384011 and Levilactobacillus brevis MW362779 were selected for optimization of physical conditions of Pb biosorption through RSM. Maximum biosorption was observed at pH 6 in 60 min at a cell density of 1 g/L. L. brevis MZ384011 and L. brevis MW362779 are recommended for experimentation on Pb toxicity amelioration and safety evaluation in in-vivo setting.

Soluble peptidoglycan fragments produced by Limosilactobacillus fermentum with antiproliferative activity are suitable for potential therapeutic development: A preliminary report

Currently, the use of probiotic strains and their products represents a promising innovative approach as an antagonist treatment against many human diseases. Previous studies showed that a strain of Limosilactobacillus fermentum (LAC92), previously defined as Lactobacillus fermentum, exhibited a suitable amensalistic property. The present study aimed to purify the active components from LAC92 to evaluate the biological properties of soluble peptidoglycan fragments (SPFs). The cell-free supernatant (CFS) and bacterial cells were separated after 48 h of growth in MRS medium broth and treated for isolation of SPFs. Antimicrobial activity and proliferation analysis on the human cell line HTC116 were performed using technologies such as xCELLigence, count and viability, and clonogenic analysis. MALDI-MS investigation and docking analysis were performed to determine the molecular structure and hypothetical mode of action, respectively. Our results showed that the antimicrobial activity was mainly due to SPFs. Moreover, the results obtained when investigating the SPF effect on the cell line HCT116 showed substantial preliminary evidence, suggesting their significant cytostatic and quite antiproliferative properties. Although MALDI was unable to identify the molecular structure, it was subsequently revealed by analysis of the bacterial genome. The amino acid structure is called peptide 92. Furthermore, we confirmed by molecular docking studies the interaction of peptide 92 with MDM2 protein, the negative regulator of p53. This study showed that SPFs from the LAC92 strain exerted anticancer effects on the human colon cancer HCT116 cell line via antiproliferation and inducing apoptosis. These findings indicated that this probiotic strain might be a potential candidate for applications in functional products in the future. Further examination is needed to understand the specific advantages of this probiotic strain and improve its functional features to confirm these data. Moreover, deeper research on peptide 92 could increase our knowledge and help us understand if it will be possible to apply to specific diseases such as CRC.

Analysis and Characterization of Lactobacillus paragasseri and Lacticaseibacillus paracasei: Two Probiotic Bacteria that Can Degrade Intestinal Oxalate in Hyperoxaluric Rats

In the present study, we characterized the probiotic properties of two commercially available bacterial strains, Lactobacillus paragasseri UBLG-36 and Lacticaseibacillus paracasei UBLPC-87, and evaluated their ability to degrade oxalate in vitro and in a hyperoxaluria-induced nephrolithiasis rat model. UBLG-36 harboring two oxalate catabolizing genes, oxalyl coenzyme A decarboxylase (oxc) and formyl coenzyme A transferase (frc), was previously shown to degrade oxalate in vitro effectively. Here, we show that UBLPC-87, lacking both oxc and frc, could still degrade oxalate in vitro. Both these strains harbored several potential putative probiotic genes that may have conferred them the ability to survive in low pH and 0.3% bile, resist antibiotic stress, show antagonistic activity against pathogenic bacteria, and adhere to epithelial cell surfaces. We further evaluated if UBLG-36 and UBLPC-87 could degrade oxalate in vivo and prevent hyperoxaluria-induced nephrolithiasis in rats. We observed that rats treated with 4.5% sodium oxalate (NaOx) developed hyperoxaluria and renal stones. However, when pre-treated with UBLG-36 or UBLPC-87 before administering 4.5% NaOx, the rats were protected against several pathophysiological manifestations of hyperoxaluria. Compared to the hyperoxaluric rats, the probiotic pre-treated rats showed reduced urinary excretion of oxalate and urea (p < 0.05), decreased serum blood urea nitrogen and creatinine (p < 0.05), alleviated stone formation and renal histological damage, and an overall decrease in renal tissue oxalate and calcium content (p < 0.05). Taken together, both UBLG-36 and UBLPC-87 are effective oxalate catabolizing probiotics capable of preventing hyperoxaluria and alleviating renal damage associated with nephrolithiasis.

Probiotics in the Prevention of the Calcium Oxalate Urolithiasis

Nephrolithiasis ranks third among urological diseases in terms of prevalence, making up about 15% of cases. The continued increase in the incidence of nephrolithiasis is most probably due to changes in eating habits (high protein, sodium, and sugar diets) and lifestyle (reduced physical activity) in all developed countries. Some 80% of all kidney stones cases are oxalate urolithiasis, which is also characterized by the highest risk of recurrence. Frequent relapses of nephrolithiasis contribute to severe complications and high treatment costs. Unfortunately, there is no known effective way to prevent urolithiasis at present. In cases of diet-related urolithiasis, dietary changes may prevent recurrence. However, in some patients, the condition is unrelated to diet; in such cases, there is evidence to support the use of stone-related medications. Interestingly, a growing body of evidence indicates the potential of the microbiome to reduce the risk of developing renal colic. Previous studies have primarily focused on the use of Oxalobacterformigenes in patients with urolithiasis. Unfortunately, this bacterium is not an ideal probiotic due to its antibiotic sensitivity and low pH. Therefore, subsequent studies sought to find bacteria which are capable of oxalate degradation, focusing on well-known probiotics including Lactobacillus and Bifidobacterium strains, Eubacterium lentum, Enterococcus faecalis, and Escherichia coli.

Polysaccharide Hydrogels for the Protection of Dairy-Related Microorganisms in Adverse Environmental Conditions

Adverse environmental conditions are severely limiting the use of microorganisms in food systems, such as probiotic delivery, where low pH causes a rapid decrease in the survival of ingested bacteria, and mixed-culture fermentation, where stepwise changes and/or metabolites of individual microbial groups can hinder overall growth and production. In our study, model probiotic lactic acid bacteria (L. plantarum ATCC 8014, L. rhamnosus GG) and yeasts native to dairy mixed cultures (K. marxianus ZIM 1868) were entrapped in an optimized (cell, alginate and hardening solution concentration, electrostatic working parameters) Ca-alginate system. Encapsulated cultures were examined for short-term survival in the absence of nutrients (lactic acid bacteria) and long-term performance in acidified conditions (yeasts). In particular, the use of encapsulated yeasts in these conditions has not been previously examined. Electrostatic manufacturing allowed for the preparation of well-defined alginate microbeads (180–260 µm diameter), high cell-entrapment (95%) and viability (90%), and uniform distribution of the encapsulated cells throughout the hydrogel matrix. The entrapped L. plantarum maintained improved viabilities during 180 min at pH 2.0 (19% higher when compared to the free culture), whereas, L. rhamnosus appeared to be less robust. The encapsulated K. marxianus exhibited double product yields in lactose- and lactic acid-modified MRS growth media (compared to an unfavorable growth environment for freely suspended cells). Even within a conventional encapsulation system, the pH responsive features of alginate provided superior protection and production of encapsulated yeasts, allowing several applications in lacto-fermented or acidified growth environments, further options for process optimization, and novel carrier design strategies based on inhibitor charge expulsion.

Helicobacter pylori infection: from standard to alternative treatment strategies

Helicobacter pylori is the major component of the gastric microbiome of infected individuals and one of the aetiological factors of chronic gastritis, peptic ulcer disease and gastric cancer. The increasing resistance to antibiotics worldwide has made the treatment of H. pylori infection a challenge. As a way to overhaul the efficacy of currently used H. pylori antibiotic-based eradication therapies, alternative treatment strategies are being devised. These include probiotics and prebiotics as adjuvants in H. pylori treatment, antimicrobial peptides as alternatives to antibiotics, photodynamic therapy ingestible devices, microparticles and nanoparticles applied as drug delivery systems, vaccines, natural products, and phage therapy. This review provides an updated synopsis of these emerging H. pylori control strategies and discusses the advantages, hurdles, and challenges associated with their development and implementation. An effective human vaccine would be a major achievement although, until now, projects regarding vaccine development have failed or were discontinued. Numerous natural products have demonstrated anti-H. pylori activity, mostly in vitro, but further clinical studies are needed to fully disclose their role in H. pylori eradication. Finally, phage therapy has the potential to emerge as a valid alternative, but major challenges remain, namely the isolation of more H. pylori strictly virulent bacterio(phages).

Application of the Combination of Soybean Lecithin and Whey Protein Concentrate 80 to Improve the Bile Salt and Acid Tolerance of Probiotics

To improve the bile salt and acid tolerance of probiotics against gastrointestinal stresses, we investigated the effects of soybean lecithin and whey protein concentrate (WPC) 80 on the bile salt tolerance of Lacticaseibacillus paracasei L9 using a single-factor methodology, which was optimized using response surface methodology (RSM). The survival rate of L. paracasei L9 treated with 0.3% (w/v) bile salt for 2.5 h, and combined with soybean lecithin or WPC 80, was lower than 1%. After optimization, the survival rate of L. paracasei L9 incubated in 0.3% bile salt for 2.5 h reached 52.5% at a ratio of 0.74% soybean lecithin and 2.54% WPC 80. Moreover, this optimized method improved the survival rate of L. paracasei L9 in low pH condition and can be applied to other lactic acid bacteria (LAB) strains. Conclusively, the combination of soybean lecithin and WPC 80 significantly improved the bile salt and acid tolerance of LAB. Our study provides a novel approach for enhancing the gastrointestinal tolerance of LAB by combining food-derived components that have different properties.

The characteristics of lactic acid bacteria isolated from fermented food as potential probiotics

OBJECTIVES

This study aims to determine the characteristics of Lactobacillus acidophilus and Lactobacillus reuteri from fermented soursop fruit juice and cow's milk, respectively as probiotic candidate based on exposure to pH, bile salts, pathogenic bacteria, and antibiotics.

METHODS

In vitro studies were conducted to examine the resistance of Lactobacillus acidophilus and Lactobacillus reuteri in pH 2, 2.5, 3.2, and 7.2, resistance to bile salts, resistance to pathogenic bacteria (Escherichia coli, Staphylococcus aureus and Enterococcus faecalis) and antituberculosis antibiotics.

RESULTS

Viability of Lactobacillus acidophilus and Lactobacillus reuteri isolates remained unchanged (6.3 × 10⁷ CFU/mL and 5.03 × 10⁷ CFU/mL) at various acidic pH, and had a low survival rate in Ox gall 0.3% (bile salts). These isolates also showed antibacterial properties against pathogens in the gastrointestinal tract. Both of these bacteria are quite safe to be used together with ofloxacin, linezolid, moxifloxacin, and levofloxacin, antibiotic for tuberculosis therapy.

CONCLUSIONS

The results showed that Lactobacillus acidophilus and Lactobacillus reuteri from fermented soursop fruit juice and cow's milk respectively fulfilled the characteristics of probiotic and could potentially be used as adjunct therapy in tuberculosis drug-resistance.

Investigation on the Antibacterial Activity of Electronic Cigarette Liquids (ECLs): A Proof of Concept Study

BACKGROUND

The key ingredients of e-cigarettes liquid are commonly propane-1,2-diol (also called propylene glycol) and propane-1,2,3-triol (vegetal glycerol) and their antimicrobial effects are already established. The nicotine and flavors which are often present in e-liquids can interfere with the growth of some microorganisms.

OBJECTIVE

The effect of combining these elements in e-liquids is unknown. The aim of the study was to investigate the possible effects of these liquids on bacterial growth in the presence or absence of nicotine and flavors.

METHODS

Susceptibilities of pathogenic strains (Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, Escherichia coli, Enterococcus faecalis and Sarcina lutea) were studied by means of a multidisciplinary approach. Cell viability and antioxidant assays were also evaluated.

RESULTS

All e-liquids investigated showed antibacterial activity against at least one pathogenic strain. Higher activity was correlated to the presence of flavors and nicotine.

DISCUSSION

In most cases, the value of minimal bactericidal concentration is equal to the value of minimal inhibitory concentration showing that these substances have a bactericidal effect. This effect was observed in concentrations up to 6.25% v/v. Antioxidant activity was also correlated to the presence of flavors. Over time, the viability assay in human epithelial lung A549 cells showed a dose-dependent inhibition of cell growth.

CONCLUSION

Our results have shown that flavors considerably enhance the antibacterial activity of propane-1,2-diol and propane-1,2,3-triol. This study provides important evidence that should be taken into consideration in further investigative approaches, to clarify the different sensitivity of the various bacterial species to e-liquids, including the respiratory microbiota, to highlight the possible role of flavors and nicotine.

Impact of oral galenic formulations of Lactobacillus salivarius on probiotic survival and interactions with microbiota in human in vitro gut models

Health benefits of probiotics in humans essentially depend on their ability to survive during gastrointestinal (GI) transit and to modulate gut microbiota. To date, there is few data on the impact of galenic formulations of probiotics on these parameters. Even if clinical studies remain the gold standard to evaluate the efficacy of galenic forms, they stay hampered by technical, ethical and cost reasons. As an alternative approach, we used two complementary in vitro models of the human gut, the TNO gastrointestinal (TIM-1) model and the Artificial Colon (ARCOL), to study the effect of three oral formulations of a Lactobacillus salivarius strain (powder, capsule and sustained-release tablet) on its viability and interactions with gut microbiota. In the TIM-1 stomach, no or low numbers of bacteria were respectively released from the capsule and tablet, confirming their gastro-resistance. The capsule was disintegrated in the jejunum on average 76 min after administration while the core of sustained-release tablet was still intact at the end of digestion. Viability in TIM-1 was significantly influenced by the galenic form with survival percentages of 0.003±0.004%, 2.8±0.6% and 17.0±1.8% (n=3) for powder, capsule and tablet, respectively. In the ARCOL, the survival of the strain tended to be higher in the post-treatment phase with the tablet compared to capsule, but gut microbiota composition and activity were not differently modulated by the two formulations. In conclusion, the sustained-release tablet emerged as the formulation that most effectively preserved viability of the tested strain during GI passage. This study highlights the usefulness of in vitro gut models for the pre-screening of probiotic pharmaceutical forms. Their use could also easily be extended to the evaluation of the effects of food matrices and age on probiotic survival and activity during GI transit.

Insights on the Critical Parameters Affecting the Probiotic Viability During Stabilization Process and Formulation Development

Probiotics have gained a lot of interest in recent years as an alternative as well as adjuvant therapy for several conditions owing to their health benefits. These live microorganisms have proven efficacy for treating gut disorders, inflammation, bacterial vaginosis, hepatic and depressive disorders, and many more. There are conventional as well as non-conventional formulations available for the delivery of probiotics with the latter having fewer regulatory guidelines. The conventional formulations include the pharmaceutical formulations specifically designed to deliver an efficacious number of viable microorganisms. Studies have indicated 10⁸-10⁹ CFU/g as an ideal dose of probiotics for achieving health benefits, and hence, all the formulations must at least contain the said number of viable bacteria to show a therapeutic effect. The most crucial feature of probiotic formulations is that the bacteria are prone to several environmental and processing factors which all together reduce the viability of the bacteria in the final formulation. These factors include processing parameters like temperature, humidity, pressure, and storage conditions. Thus, the present review primarily focuses on the critical process parameters affecting the probiotic viability during stabilization process and formulation development. Understanding these factors prior to processing helps in delivering probiotics in the required therapeutic numbers at the target site.

Bacteriocins, A Natural Weapon Against Bacterial Contamination for Greater Safety and Preservation of Food: A Review

Nowadays, consumers have become increasingly attentive to human health and the use of more natural products. Consequently, the demand for natural preservatives in the food industry is more frequent. This has led to intense research to discover new antimicrobial compounds of natural origin that could effectively fight foodborne pathogens. This research aims to safeguard the health of consumers and, above all, to avoid potentially harmful chemical compounds. Lactobacillus is a bacterial genus belonging to the Lactic Acid Bacteria and many strains are defined GRAS, generally recognized as safe. These strains are able to produce substances with antibacterial activity against food spoilage bacteria and contaminating pathogens: the bacteriocins. The aim of this review was to focus on this genus and its capability to produce antibacterial peptides. The review collected all the information from the last few years about bacteriocins produced by Lactobacillus strains, isolated from clinical or food samples, with remarkable antimicrobial activities useful for being exploited in the food field. In addition, the advantages and disadvantages of their use and the possible ways of improvement for industrial applications were described.

In Vitro Anti-staphylococcal and Anti-inflammatory Abilities of Lacticaseibacillus rhamnosus from Infant Gut Microbiota as Potential Probiotic Against Infectious Women Mastitis

Infectious mastitis is the major cause of early weaning, depriving infants of breastfeeding benefits. It is associated with an inflammatory condition of the breast and lowered resistance to infection. Drug administration during lactation often being contra-indicated, it is therefore important to consider safe therapeutic alternatives to antibiotic and anti-inflammatory therapies, such as probiotics. In this study, we investigated in vitro the probiotic potential of thirteen Lacticaseibacillus (formerly Lactobacillus) rhamnosus strains isolated from the gut microbiota of breastfed healthy infants. Strains were assessed for their β-hemolytic activity, their resistance to antibiotics, and their antimicrobial activities against strains of Staphylococcus and Streptococcus, most often involved in women mastitis. Their immunomodulating abilities were also studied using in vitro stimulation of human immune cells. None of the strains exhibited β-hemolytic activity, and all of them were sensitive to ampicillin, penicillin, tetracycline, rifampicin, erythromycin, chloramphenicol, and imipenem but showed resistance to ceftazidime, trimethoprim/sulfamethoxazole, vancomycin, and cefotaxime, reported to be chromosomally encoded and not inducible or transferable. Four L. rhamnosus strains were selected for their large anti-staphylococcal spectrum: L. rhamnosus VR1-5 and L. rhamnosus VR3-1 inhibiting S. aureus, S. epidermis, and S. warneri and L. rhamnosus CB9-2 and L. rhamnosus CB10-5 exerting antagonistic effect against S. aureus and S. epidermis strains. Antimicrobial compounds released in cell-free supernatant showed proteinaceous nature and were thermoresistant. The immune modulatory analysis of the L. rhamnosus strains revealed two strains with significant anti-inflammatory potential, highlighted by strong induction of IL-10 and a weak pro-Th1 cytokine secretion (IL-12 and IFN-γ). L. rhamnosus CB9-2 combined a large anti-staphylococcal activity spectrum and a promising anti-inflammatory profile. This strain, used individually or in a mixture, can be considered as a probiotic candidate for the management of infectious mastitis during lactation.

Lactobacillus rhamnosus AD3 as a Promising Alternative for Probiotic Products

Lactobacillus strains dominate the vaginal habitat and they are associated with a lower risk of genital infections. In addition, they contribute to the conservation of the vaginal microbiota by producing postbiotic agents. Previous studies have shown that their predominance involves antimicrobial activity against urogenital pathologies. In this context, probiotics may improve treatment outcomes. The aim of this study was to evaluate the probiotic properties of lactobacilli strains of vaginal origin using a multidisciplinary approach. For this purpose, safety criteria, ability to resist at low pH and bile salts, antimicrobial activity, ability to produce biofilm, capacity to produce hydrogen peroxide and more importantly, auto-aggregation, co-aggregation (with Candida spp.) and adhesion to human cells were evaluated. The strains belonged to the species of L. crispatus, L. gasseri, L. rhamnosus and L. delbruckii. Among these, a strain of L. rhamnosus named AD3 showed the best probiotic properties. As probiotics are already in use in many clinical practice and there are no major safety concerns, L. rhamnosus AD3 showed promise in becoming a prevention and complementary treatment option for urogenital diseases. Indeed, these results suggest that strain L. rhamnosus AD3 is non-pathogenic and likely to be safe for human consumption. This study revealed the great amensalistic properties of a new L. rhamnosus strain which can aim to be used as probiotic in pharmaceutical applications.

Antimicrobial Efficacy of Five Probiotic Strains Against Helicobacter pylori

Treatment of Helicobacter pylori (H. pylori) infection is a challenge for clinicians. The large increase in drug-resistant strains makes the formulation of new therapeutic strategies fundamental. The frequent onset of side effects during antibiotic treatment (mainly due to intestinal dysbiosis) should not be underestimated as it may cause the interruption of treatment, failure of H. pylori eradication and clonal selection of resistant bacteria. Probiotic integration during antibiotic treatment can exert a dual function: a direct antagonistic effect on H. pylori and a balancing effect on dysbiosis. Therefore, it fulfills the definition of a new therapeutic strategy to successfully treat H. pylori infection. Data reported in literature give promising but discrepant results. Aim: To assess in vitro bacteriostatic and bactericidal activity of probiotic strains against H. pylori. Materials and methods: L. casei, L. paracasei, L. acidophilus, B. lactis and S. thermophilus strains were used. Agar well diffusion and time-kill curves were carried out to detect bacteriostatic and bactericidal activity, respectively. Results: All probiotic strains showed both bacteriostatic and bactericidal activity vs. H. pylori. Conclusions: Such findings prompted us to plan a protocol of treatment in which probiotics are given to infected patients in association with antibiotic therapy.

Lactobacillus casei LH23 modulates the immune response and ameliorates DSS-induced colitis via suppressing JNK/p-38 signal pathways and enhancing histone H3K9 acetylation

Probiotics are thought to have immunomodulatory functions, improve inflammatory disorders and treat inflammatory bowel disease (IBD).

Metabolic Characterization of Supernatants Produced by Lactobacillus spp. With in vitro Anti-Legionella Activity

Legionella pneumophila is an organism of public health interest for its presence in water supply systems and other humid thermal habitats. In this study, ten cell-free supernatants produced by Lactobacillus strains were evaluated for their ability to inhibit L. pneumophila strains isolated from hot tap water. Production of antimicrobial substances by Lactobacillus strains were assessed by agar well diffusion test on BCYE agar plates pre-inoculated with L. pneumophila. Cell-free supernatants (CFS) showed antimicrobial activity against all Legionella strains tested: L. rhamnosus and L. salivarius showed the highest activity. By means of a proton-based nuclear magnetic resonance (¹H-NMR) spectroscopy, we detected and quantified the Lactobacillus metabolites of these CFSs, so to gain information about which metabolic pathway was likely to be connected to the observed inhibition activity. A panel of metabolites with variations in concentration were revealed, but considerable differences among inter-species were not showed as reported in a similar work by Foschi et al. (2018). More than fifty molecules belonging mainly to the groups of amino acids, organic acids, monosaccharides, ketones, and alcohols were identified in the metabolome. Significant differences were recorded comparing the metabolites found in the supernatants of strains grown in MRS with glycerol and the same strains grown in MRS without supplements. Indeed, pathway analysis revealed that glycine, serine and threonine, pyruvate, and sulfur metabolic pathways had a higher impact when strains were grown in MRS medium with a supplement such as glycerol. Among the metabolites identified, many were amino acids, suggesting the possible presence of bacteriocins which could be linked to the anti-Legionella activity shown by cell-free supernatants.

Biological properties and production of bacteriocins-like-inhibitory substances by Lactobacillus sp. strains from human vagina

AIMS

The aim of this study was to characterize Lactobacillus strains for their biological properties and amensalistic activities against genital and nongenital pathogens.

METHODS AND RESULTS

For the purpose, some special characteristics (H₂ O₂ , biofilm and antimicrobial substances production) as well as safety properties of 112 lactobacilli were evaluated. All the strains had good amensalistic characteristics, in particular cell-free supernatants of 10 strains showed antibacterial activity against bacteria, as well as Candida sp. Moreover, these 10 strains were excellent biofilm producers.

CONCLUSIONS

These results provide evidence for the possible use as probiotics for vaginal co-therapy in case of dysbiosis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Recently, the problem of antibiotic resistance is constantly increasing, even though resources and energy are invested in order to increase knowledge on the mechanisms of action. Bacteriocins have a rapid mechanism of action, act at extremely low concentrations, are generally sensitive to proteases and they usually have a narrow killing spectrum; these characteristics reduce the possibility of the bacterium to develop resistance. This study is focused on the feasibility of a high production of antimicrobial substances and their characterization in order to be exploited as a therapeutic alterative or in co-therapy with antibiotics in case of vaginal dysbiosis.

Roles and applications of probiotic Lactobacillus strains

Lactobacilli are recognized as probiotics on account of their health-promoting effects in the host. The aim of this review is to summarize current knowledge of the mechanisms of the adaption factors and main functions of lactobacilli that exert health-promoting effects in the host and to discuss important applications in animal and human health. The adaption mechanisms of lactobacilli facilitate interactions with the host and directly contribute to the beneficial nutritional, physiological, microbiological, and immunological effects in the host. Besides, the application of probiotic lactobacilli will increase our understanding of practical uses based on the roles of these organisms in immunoregulation, antipathogenic activities, and enhancement of the epithelial barrier.

Addressing the Antibiotic Resistance Problem with Probiotics: Reducing the Risk of Its Double-Edged Sword Effect

Antibiotic resistance is a global public health problem that requires our attention. Indiscriminate antibiotic use is a major contributor in the introduction of selective pressures in our natural environments that have significantly contributed in the rapid emergence of antibiotic-resistant microbial strains. The use of probiotics in lieu of antibiotic therapy to address certain health conditions in both animals and humans may alleviate these antibiotic-mediated selective pressures. Probiotic use is defined as the actual application of live beneficial microbes to obtain a desired outcome by preventing diseased state or improving general health. Multiple studies have confirmed the beneficial effects of probiotic use in the health of both livestock and humans. As such, probiotics consumption is gaining popularity worldwide. However, concerns have been raised in the use of some probiotics strains that carry antibiotic resistance genes themselves, as they have the potential to pass the antibiotic resistance genes to pathogenic bacteria through horizontal gene transfer. Therefore, with the current public health concern on antibiotic resistance globally, in this review, we underscore the need to screen probiotic strains that are used in both livestock and human applications to assure their safety and mitigate their potential in significantly contributing to the spread of antibiotic resistance genes in our natural environments.

Potential role of probiotics in the management of gastric ulcer

Gastric ulcer is one of the most common chronic gastrointestinal diseases characterized by a significant defect in the mucosal barrier. Helicobacter pylori (H. pylori) infection and the frequent long-term use of non-steroidal anti-inflammatory drugs are major factors involved in gastric ulcer development. Acid inhibitors and antibiotics are commonly used to treat gastric ulcer. However, in the last few decades, the accumulating evidence for resistance to antibiotics and the side effects of antibiotics and acid inhibitors have drawn attention to the possible use of probiotics in the prevention and treatment of gastric ulcer. Probiotics are live microorganisms that when administered in adequate amounts confer health benefits on the host. Currently, the available experimental and clinical studies indicate that probiotics are promising for future applications in the management of gastric ulcers. This review aims to provide an overview of the general health benefits of probiotics on various systemic and gastrointestinal disorders with a special focus on gastric ulcer and the involved cellular and molecular mechanisms: i) Protection of gastric mucosal barrier; ii) upregulation of prostaglandins, mucus, growth factors and anti-inflammatory cytokines; iii) increased cell proliferation to apoptosis ratio; and iv) induction of angiogenesis. Finally, some of the available data on the possible use of probiotics in H. pylori eradication are discussed.

Labeling quality and molecular characterization studies of products containing Lactobacillus spp. strains

The objective of the study was to characterize at species level by phenotypic and different molecular methods the strains of Lactobacillus spp. used as constituents of five oral and four vaginal products. Susceptibilities to representative antibiotics were evaluated. In addition, total viable counts at mid and 3 months to deadline of shelf life, in the different formulations and the presence of eventual contaminant microorganisms were investigated.In all oral products the molecular characterization at species level of the strains of Lactobacillus spp. confirmed the strains stated on the label, except for one strain cited on the label as Lactobacillus casei, that our study characterized as Lactobacillus paracasei. In oral products total viable cell content complied with content claimed on the label. In three out four vaginal products (one product claimed "bacillo di Döderlein"), molecular characterization complied with the bacterial name stated on the label. Two vaginal products reported viable counts on the label that were confirmed by our study. The other vaginal products, which did not report bacterial counts on the label, showed a similar decrease of viable counts at different dates to deadline compared to the others. From all the tested products, contaminant microorganisms and acquired resistance to representative antibiotics by the probiotic strains were not detected.