Characterization of bacteriocin production in Lactobacillus spp. isolated from mother's milk

Oral administration of Lactobacillus plantarum expressing aCD11c modulates cellular immunity alleviating inflammatory injury due to Klebsiella pneumoniae infection

BACKGROUND

Klebsiella pneumoniae (KP), responsible for acute lung injury (ALI) and inflammation of the gastrointestinal tract, is a zoonotic pathogen that poses a threat to livestock farming worldwide. Nevertheless, there is currently no validated vaccine to prevent KP infection. The development of mucosal vaccines against KP using Lactobacillus plantarum (L. plantarum) is an effective strategy.

RESULTS

Firstly, the L. plantarum strains NC8-pSIP409-aCD11c' and NC8-pLc23-aCD11c were constructed via homologous recombination to express the aCD11c protein either inducibly or constitutively. Both NC8-pSIP409-aCD11c' and NC8-pLc23-aCD11c strains could enhance the adhesion and invasion of L. plantarum on bone marrow-derived dendritic cells (BMDCs), and stimulate the activation of BMDCs compared to the control strain NC8-pSIP409 in vitro. Following oral immunization of mice with NC8-pSIP409-aCD11c' and NC8-pLc23-aCD11c, the cellular, humoral, and mucosal immunity were significantly improved, as evidenced by the increased expression of CD4+ IL-4+ T cells in the spleen, IgG in serum, and secretory IgA (sIgA) in the intestinal lavage fluid (ILF). Furthermore, the protective effects of L. plantarum against inflammatory damage caused by KP infection were confirmed by assessing the bacterial loads in various tissues, lung wet/dry ratio (W/D), levels of inflammatory cytokines, and histological evaluation, which influenced T helper 17 (Th17) and regulatory T (Treg) cells in peripheral blood and lung.

CONCLUSIONS

Both the inducible and constitutive L. plantarum strains NC8-pSIP409-aCD11c' and NC8-pLc23-aCD11c have been found to stimulate cellular and humoral immunity levels and alleviate the inflammatory response caused by KP infection. These findings have provided a basis for the development of a novel vaccine against KP.

Analysis of Human Milk Microbiota in Northern Greece by Comparative 16S rRNA Sequencing vs. Local Dairy Animals

Milk is a biological fluid with a dynamic composition of micronutrients and bioactive molecules that serves as a vital nutrient source for infants. Milk composition is affected by multiple factors, including genetics, geographical location, environmental conditions, lactation phase, and maternal nutrition, and plays a key role in dictating its microbiome. This study addresses a less-explored aspect, comparing the microbial communities in human breast milk with those in mature milk from species that are used for milk consumption. Since mature animal milk is used as a supplement for both the infant (formula) and the child/adolescent, our main aim was to identify shared microbial communities in colostrum and mature human milk. Using 16S rRNA metagenomic sequencing, we focused on characterizing the milk microbiota in the Northern Greek population by identifying shared microbial communities across samples and comparing the relative abundance of prevalent genera. We analyzed ten human milk samples (from five mothers), with five collected three days postpartum (colostrum) and five collected thirty to forty days postpartum (mature milk) from corresponding mothers. To perform an interspecies comparison of human milk microbiota, we analyzed five goat and five bovine milk samples from a local dairy industry, collected fifty to seventy days after birth. Alpha diversity analysis indicated moderate diversity and stability in bovine milk, high richness in goat milk, and constrained diversity in breast milk. Beta diversity analysis revealed significant distinctions among mammalian species, emphasizing both presence/absence and abundance-based clustering. Despite noticeable differences, shared microbial components underscore fundamental aspects across all mammalian species, highlighting the presence of a core microbiota predominantly comprising the Proteobacteria, Firmicutes, and Actinobacteriota phyla. At the genus level, Acinetobacter, Gemella, and Sphingobium exhibit significant higher abundance in human milk compared to bovine and goat milk, while Pseudomonas and Atopostipes are more prevalent in animal milk. Our comparative analysis revealed differences and commonalities in the microbial communities of various mammalian milks and unraveled the existence of a common fundamental milk core microbiome. We thus revealed both species-specific and conserved microbial communities in human, bovine, and goat milk. The existence of a common core microbiome with conserved differences between colostrum and mature human milk underscores fundamental similarities in the microbiota of milk across mammalian species, which could offer valuable implications for optimizing the nutritional quality and safety of dairy products as well as supplements for infant health.

Metagenome-mining indicates an association between bacteriocin presence and strain diversity in the infant gut

BACKGROUND

Our knowledge about the ecological role of bacterial antimicrobial peptides (bacteriocins) in the human gut is limited, particularly in relation to their role in the diversification of the gut microbiota during early life. The aim of this paper was therefore to address associations between bacteriocins and bacterial diversity in the human gut microbiota. To investigate this, we did an extensive screening of 2564 healthy human gut metagenomes for the presence of predicted bacteriocin-encoding genes, comparing bacteriocin gene presence to strain diversity and age.

RESULTS

We found that the abundance of bacteriocin genes was significantly higher in infant-like metagenomes (< 2 years) compared to adult-like metagenomes (2-107 years). By comparing infant-like metagenomes with and without a given bacteriocin, we found that bacteriocin presence was associated with increased strain diversities.

CONCLUSIONS

Our findings indicate that bacteriocins may play a role in the strain diversification during the infant gut microbiota establishment.

In Vitro Evaluation of Commercial Probiotic Products Containing Streptococcus salivarius K12 by Assessment of Probiotic Viability and Inhibitory Potency against Respiratory Pathogens

Upper respiratory infections (URI) are the most frequent illnesses, especially in children. The majority of those infections are prescribed broad-spectrum antibiotics, which are associated with various side effects and with the increase in multi-drug-resistant strains. A promising alternative approach is the administration of the probiotic strain Streptococcus salivarius K12 (SSK12) that colonizes the upper respiratory tract (URT) and produces the salivaricins A2 and B, which strongly antagonize the growth of key respiratory pathogens. However, since for food supplements no quality controls of the active probiotic ingredient are mandatory, the efficacy of commercial products containing SSK12 may vary. This study aimed to investigate the in vitro efficacy of several commercial SSK12-containing probiotics, positioned for the prevention of respiratory infections. The parameters evaluated to determine the in vitro efficacy included the viability of the probiotic bacterial strain and the minimum inhibitory dilution (MID) of the probiotic, determined by the agar spot method, against the pathogenic/potential pathogenic bacterial strains Streptococcus pyogenes FF22 and Micrococcus luteus T18. All tests were carried out both 12 and 24 months after manufacturing (AM) for each commercial product. The viability ranged from 9 × 108 to 4.4 × 109 CFU/serving at 12 months AM and from 8.5 × 107 to 2.8 × 109 CFU/serving at 24 months AM. The MID was, in general, positively correlated with the probiotic bacterium viability and varied between the commercial products, ranging from 10−5 to 10−7 at 12 months AM and from 10−4 to 10−7 at 24 months AM. Moreover, the inhibition zones related to the two indicator strains were variable in diameter for different products. The high variation of the in vitro efficacy of commercial products containing SSK12 may explain the different results reported in the literature regarding the clinical benefits of these preparations, and the determination of this parameter may be useful to evaluate the quality of probiotic products containing this bacterial strain.

Oral or intranasal immunization with recombinant Lactobacillus plantarum displaying head domain of Swine Influenza A virus hemagglutinin protects mice from H1N1 virus

BACKGROUND

Swine influenza A virus (swIAV) is a major concern for the swine industry owing to its highly contagious nature and acute viral disease. Currently, most commercial swIAV vaccines are traditional inactivated virus vaccines. The Lactobacillus plantarum-based vaccine platform is a promising approach for mucosal vaccine development. Oral and intranasal immunisations have the potential to induce a mucosal immune response, which confers protective immunity. The aim of this study was to evaluate the probiotic potential and adhesion ability of three L. plantarum strains. Furthermore, a recombinant L. plantarum strain expressing the head domain of swIAV antigen HA1 was constructed and evaluated for its ability to prevent swIAV infection.

RESULTS

The three L. plantarum strains isolated from healthy pig faecal samples maintained the highest survival rate when incubated at pH 3 and at bile salt concentration of 0.3%. They also showed high adherence to intestinal cells. All three L. plantarum strains were monitored in live mice, and no major differences in transit time were observed. Recombinant L. plantarum expressed swIAV HA1 protein (pSIP401-HA1-ZN-3) and conferred effective mucosal, cellular and systemic immune responses in the intestine as well as in the upper respiratory airways of mice. In conclusion, the oral and intranasal administration of L. plantarum strain pSIP401-HA1-ZN-3 in mice induced mucosal immunity and most importantly, provided protection against lethal influenza virus challenge.

CONCLUSION

In summary, these findings suggest that the engineered L. plantarum strain pSIP401-HA1-ZN-3 can be considered as an alternative approach for developing a novel vaccine during an swine influenza A pandemic.

Human milk microbiota: what did we learn in the last 20 years?

Human milk (HM) is the gold standard for infant nutrition during the first months of life. Beyond its nutritional components, its complex bioactive composition includes microorganisms, their metabolites, and oligosaccharides, which also contribute to gut colonization and immune system maturation. There is growing evidence of the beneficial effects of bacteria present in HM. However, current research presents limited data on the presence and functions of other organisms. The potential biological impacts on maternal and infant health outcomes, the factors contributing to milk microbes' variations, and the potential functions in the infant's gut remain unclear. This review provides a global overview of milk microbiota, what the actual knowledge is, and what the gaps and challenges are for the next years.

Characterization of Streptococcus salivarius as New Probiotics Derived From Human Breast Milk and Their Potential on Proliferative Inhibition of Liver and Breast Cancer Cells and Antioxidant Activity

Breast milk is well known as the abundant source of beneficial bacteria. A new alternative source of human probiotic origin from breast milk is in demand and currently of interest for both the functional food industry and biopharmaceuticals. The aim in this study was to investigate the anticancer and antioxidant efficacies of the new potential probiotics isolated from human breast milk. Three strains of lactic acid bacteria (LAB) have shown their potential probiotic criteria including antimicrobial activity, non-hemolytic property, and survival in acid and bile salt conditions. These strains showed high abilities on cell surface hydrophobicity, auto-aggregation, and co-aggregation. The genera identification by 16S rRNA sequencing and comparison revealed that they were Streptococcus salivarius BP8, S. salivarius BP156, and S. salivarius BP160. The inhibition of liver cancer cells (HepG2) and breast cancer cells (MCF-7) proliferation by these probiotic strains using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was 44.83–59.65 and 29.85–37.16%, respectively. The probiotic action mode was inducted via apoptotic mechanisms since they stimulate the liver and breast cancer cell death through DNA fragmentation and positive morphological changes by acridine orange (AO) and propidium iodide (PI) staining. The antioxidant activity of these probiotics in the form of intact cells, cell free supernatant (CFS), and heat-killed cells was evaluated by a 2,2–diphenyl–1–picrylhydrazyl (DPPH) assay, resulting in the scavenging activity rates of 16.93–25.43, 15.47–28.03, and 13.67–23.0%, respectively. These S. salivarius probiotic strains protected the L929 mouse fibroblasts against oxidative stress with very high survival rates at 94.04–97.77%, which was significantly higher (P < 0.05) than L-ascorbic acid at 75.89–78.67% in the control groups. The results indicated that S. salivarius BP8 and S. salivarius BP160 probiotic strains could be applied as functional foods or new alternative bioprophylactics for treating liver and breast cancers.

Isolation and phenotypic and genotypic characterization of the potential probiotic strains of Lactobacillus from the Iranian population

Among different causes of inflammatory bowel disease (IBD), the imbalance of the gut microbiome (dysbiosis) is one of the main reasons for the development of the disease. Probiotics are live microorganisms that can maintain gut microbiota by different mechanisms. We aimed to isolate and characterize the potential probiotic strains of Lactobacillus from the Iranian population. This cross-sectional study was conducted on faecal samples of 83 volunteer individuals living in Guilan Province, North Iran. The primary identification of Lactobacillus strains was performed by standard microbiological tests and confirmed by amplification of 16s rRNA specific primers. The acid and bile salt tolerance were assessed for all recovered strains. Also, the presence of 3 bacteriocins encoding genes was investigated by the PCR method. Totally, 42 samples were positive for Lactobacillus species. Acid and bile resistance assay showed that 67% and 33% of strains were resistant to acid and bile salt stress, respectively. Therefore, we found out that 28% of our Lactobacillus strains have the ability for resistance to acid and bile conditions. PCR results revealed that the prevalence of gassericin A, plantaricin S, lactacin bacteriocin genes were 16.6%, 12%, and 9.5%, respectively. Meanwhile, 5 out of 12 Lactobacillus strains that were resistant to acid and bile conditions contained one of the gassericin or plantaricin bacteriocins. We isolated 42 potential probiotic strains of Lactobacillus, of which the results of 5 strains were more promising and can be considered as potential probiotics sources for future functional products.

Interesting probiotic traits of mother's milk Lactobacillus isolates; from bacteriocin to inflammatory bowel disease improvement

AIMS AND BACKGROUND

Lactobacillus spp. are an important element in breast milk. This component has a beneficial effect on the composition of the intestinal microflora and the intestinal immune system. The aim of this study was to isolate and identify Lactobacillus strains in breast milk and evaluate some of their probiotic properties, such as presence of bacteriocin genes, adhesion to HT-29 cell line, competition with enteropathogens in cell culture, and effect on serum level of lipids and digestive enzymes, and mice model of inflammatory bowel disease (IBD).

MATERIALS AND METHODS

A total of 323 lactic acid bacteria (LAB) were isolated from breast milk samples of healthy mothers with the age ranges from 21 to 45 years old. These isolates were subjected to phenotypic and molecular experiments. The frequency of bacteriocin genes was determined by polymerase chain reaction (PCR). Adhesion of Lactobacillus isolates to HT-29 cells was measured based on the number of attached bacterial cells in 20 fields of the light microscopy. Competition test was done by colony count and real-time PCR procedures. Five strongly adhesive Lactobacillus strains were selected and administered orally to the treatment groups. After 8 days, the serum level of digestive enzymes and improvement in induced IBD, and after 14 days, the serum level of lipids (triglycerides, total cholesterol, HDL, and LDL) in treated mice were surveyed compared to the control groups.

RESULTS

Based on the phenotypic and molecular experiments, L. casei, L. plantarum, L. rhamnosus, and L. acidophilus strains were isolated and identified in the breast milk samples. The highest frequency of bacteriocin genes belonged to Plantaricin B (100%), followed by Plantaricin D (84.7%), Plantaricin G (84.7%), and Plantaricin EF (54.3%). Also, 71.8% of the isolates were strongly adhesive, 21.8% were non-adhesive, and 6.4% were adhesive. Lactobacillus strains had a significant effect on the displacement of enteropathogens. The in vitro cholesterol-removing ability of L. casei (L1), L. casei (L2), L. casei (L3), L. plantarum (L4), and L. rhamnosus (L5) was 3.5, 31.5, 21.3, 18.7, and 27.3%, respectively. The serum level of total cholesterol in the L. plantarum (L4) group as well as LDL in the L. casei (L3) (p = .0108) and L. rhamnosus (L5) (p = .0206) groups decreased significantly compared to the control group. The serum level of lipase increased in all the treatment groups compared to the control group, which was significant in the L. plantarum (L4) group (p = .0390). Disease activity index (DAI) scores were improved significantly in L. casei (L3) group compared to the IBD control group (p < .0001).

CONCLUSION

It could be concluded that lactobacilli strains isolated from the breast milk samples had good probiotic properties, such as presence of bacteriocin genes, attaching to enterocyte-like HT-29 cells, competing with intestinal pathogens, lowering cholesterol, and improving IBD. Thus, after further studies, they could be considered as probiotic strains.

Human Milk Microbiota in an Indigenous Population Is Associated with Maternal Factors, Stage of Lactation, and Breastfeeding Practices

BACKGROUND

Human milk contains a diverse community of bacteria that are modified by maternal factors, but whether these or other factors are similar in developing countries has not been explored. Our objective was to determine whether the milk microbiota was modified by maternal age, BMI, parity, lactation stage, subclinical mastitis (SCM), and breastfeeding practices in the first 6 mo of lactation in an indigenous population from Guatemala.

METHODS

For this cross-sectional study, Mam-Mayan indigenous mothers nursing infants aged <6 mo were recruited. Unilateral human milk samples were collected (n = 86) and processed for 16S rRNA sequencing at the genus level. Microbial diversity and relative abundance were compared with maternal factors [age, BMI, parity, stage of lactation, SCM, and 3 breastfeeding practices (exclusive, predominant, mixed)] obtained through questionnaires.

RESULTS

Streptococcus was the most abundant genus (33.8%), followed by Pseudomonas (18.7%) and Sphingobium (10.7%) but relative abundance was associated with maternal factors. First, Lactobacillus and Streptococcus were more abundant in early lactation whereas the common oral (Leptotrichia) and environmental (Comamonas) bacteria were more abundant in established lactation. Second, Streptococcus,Lactobacillus,Lactococcus,Leuconostoc, and Micrococcus had a higher abundance in multiparous mothers compared with primiparous mothers. Third, a more diverse microbiota characterized by a higher abundance of lactic acid bacteria (Lactobacillus,Leuconostoc, and Lactococcus), Leucobacter, and Micrococcus was found in mothers with a healthy BMI. Finally, distinct microbial communities differed by stage of lactation and by exclusive, predominant, or mixed breastfeeding practices.

CONCLUSION

Milk bacterial communities in an indigenous community were associated with maternal factors. Higher microbial diversity was supported by having a healthy BMI, the absence of SCM, and by breastfeeding. Interestingly, breastfeeding practices when assessed by lactation stage were associated with distinct microbiota profiles.

Evaluation of in vitro and in vivo potential of Bacillus subtilis MBTDCMFRI Ba37 as a candidate probiont in fish health management

Bacillus subtilis MBTDCMFRI Ba37 (B. subtilis Ba37), an antibacterial strain isolated from the tropical estuarine habitats of Cochin, was evaluated for in vitro and in vivo potential, and its application as a candidate probiont in fish health management. B. subtilis Ba37 was characterized using their morphological and biochemical properties. It exhibited exoenzymatic activities, tolerance to various physiological conditions and a wide spectrum of antibacterial activity against aquaculture pathogens such as Vibrio and Aeromonas. In co-culture assay, B. subtilis Ba37 inhibited Vibrio anguillarum O1 (V. anguillarum O1) even with the initial cell count of 10⁴ CFUmL^-1. Cytotoxicity assay performed using the cell free supernatant (CFS) of B. subtilis Ba37 revealed its non toxic nature. A twenty one days of feeding trial was conducted in juveniles of Etroplus suratensis (E.suratensis) by administrating B. subtilis Ba37 to evaluate its efficacy on growth, immune parameters and antioxidant enzyme activities. Overall the supplementation of B. subtilis Ba37 enhanced significantly (P < 0.05) the survival rate, weight gain, specific growth (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER), and feed efficiency (FE) of the fed animals as compared with the control. The immune parameters and antioxidant activities such as total protein, alkaline phosphatase (ALP), superoxide dismutase (SOD) and catalase were also improved significantly (P < 0.05) while serum alanine aminotransferase (SGOT) and serum aspartate aminotransferase (SGPT) activities were decreased slightly than the control. After fifteen days of challenge test, the fish fed with B. subtilis Ba37 showed higher relative percentage survival (RPS) than the control. Thus the study indicated the advantages of B. subtilis Ba37 to be used as a candidate probiont, which could be effectively utilized in managing diseases in aquaculture systems and to improve the health of the host.

Probiotic characteristics of Lactobacillus strains isolated from cheese and their antibacterial properties against gastrointestinal tract pathogens

In the present study, four Lactobacillus strains from the cheese were analyzed for its probiotic potential against enteropathogenic bacteria. The probiotic properties of the selected strains were also analyzed and the selected bacterial strains showed high tolerance in bile salts and organic acid. The strain L. plantarum LP049 showed maximum survival rate (92 ± 4.2% and 93.3 ± 2%) after 3 h of treatment at 0.25% (w/v) bile salts and 0.25% (w/v) organic acid concentrations. The ability of the Lactobacillus strains to adhere to human epithelial cells (HT-29 cell lines) was evaluated and L. plantarum LP049 showed maximum adhesion property (19.2 ± 1.1%) than other tested strains. The Lactobacillus strains produced lactic acid at various concentrations. Compared with other strains, maximum level of lactic acid (3.1 g/L), hydrogen peroxide (4.31 mM) and bacteriocin (31 AU/mg) was detected in LB049. The inhibitory activity of culture supernatant against various bacterial pathogens was observed. The zone of inhibition ranged between 6 ± 2 mm and 23 ± 2 mm. The cell free extract showed activity against, Escherichia coli (ATCC 10536), Salmonella enteritidis (ATCC 13076), Shigella flexneri (ATCC 29903), and Enterococcus faecium (ATCC 8459). Consequently, L. plantarum LP049 may be considered as a potential candidate for the production of novel bioactive metabolites for therapeutic and bio-protective applications.

Protective effects of Lactobacillus plantarum against chronic alcohol-induced liver injury in the murine model

Long-term alcohol consumption causes liver injuries such as alcoholic hepatitis, fatty liver, and endotoxemia. Some probiotics were demonstrated to exert beneficial effects in the gastrointestinal tract. The present study was aimed to evaluate the protective effects of Lactobacillus plantarum CMU995 against alcohol-induced liver injury. The mice were orally administered L. plantarum CMU995 for 1 week, followed by the administration of alcohol and different tested substances daily for 6 weeks. The liver injury was examined by measuring the levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), malondialdehyde (MDA), anti-oxidative enzyme, endotoxin, inflammatory cytokines, and lipid accumulation in the liver or serum among different groups. L. plantarum CMU995 exhibited beneficial effects on alcohol-induced liver injury via reduction in the serum concentration of AST, ALT, cholesterol, triglycerides, endotoxin, TNF-α, IL-1β, and oxidative stress. Furthermore, we also found that the levels of glutathione (GSH), superoxide dismutase (SOD), and intestinal tight junction protein zonula occludens-1 (ZO-1) were considerably higher in L. plantarum CMU995-fed groups when compared with placebo group. Meanwhile, the protective effects were demonstrated biological gradients as controversial dose-dependent. We speculate that L. plantarum CMU995 inhibited the migration of alcohol-derived endotoxin into the blood and liver, thereby improving the intestinal barrier. The present evidence may provide a novel microbiota-based strategy to prevent the alcohol-induced liver injury.