Protection activity of a novel probiotic strain of Bacillus subtilis against Salmonella Enteritidis infection

Probiotic evaluation, adherence capability and safety assessment of Lactococcus lactis strain isolated from an important herb "Murraya koenigii"

Lactic acid bacteria (LAB) isolated from medicinal herb Murraya koenigii, commonly known as curry leaf, which promotes the growth and maintenance of gut microbiota, were studied for their probiotic potential. The key objective of this research was to isolate and evaluate probiotic characteristics, test adherence capabilities, and confirm their safety. Lactococcus lactis (MKL8), isolated from Murraya koenigii, was subjected to in vitro analysis to assess its resistance to the gastric environment, ability to adhere Caco-2 cells, anti-microbial activity, hydrophobicity, auto-aggregation, and safety profiling through MTT assay and hemolytic. MKL8 exhibited growth at 0.5% phenol concentrations (> 80%) and was able to survive in conditions with high bile concentrations (> 79%) and a relatively low pH (72%-91%). It shows high tolerance to high osmotic conditions (> 73%) and simulated gastric juice (> 72%). Additionally, MKL8 demonstrated strong hydrophobicity (85%), auto-aggregation (87.3%-91.7%), and adherence to Caco-2 cells. Moreover, it had an inhibitory effect against pathogens too. By performing the hemolytic and MTT assays, the non-toxicity of MKL8 isolate was examined, and it exhibited no harmful characteristics. Considering MKL8's resistance to gastrointestinal tract conditions, high surface hydrophobicity, non-toxicity, and ability to inhibit the tested pathogens, it can be concluded that MKL8 demonstrated promising probiotic properties and has potential for use in the food industry.

Identification of differentially expressed genes and metabolism signaling pathway in the spleen of broilers supplemented with probiotic Bacillus spp

Probiotics are essential in the body's nutrients, improving the ratio of meat to meat, immune response, and preventing diseases. In this study, RNA-sequencing (RNA-seq) was used to identify the differentially expressed genes (DEGs), enriched related pathways, and Gene Ontology (GO) terms among blank negative control (NC), supplemented with Bacillus spp. (BS) and commercial probiotic (PC) groups after a 42-day fed supplementation. The results showed that 2005, 1356, and 2189 DEGs were significantly altered in BS vs. NC, PC vs NC, and BS vs PC groups, respectively. On the other hand, 9 DEGs were further validated by qRT-PCR, indicating that the qRT-PCR and RNA-Seq results were more consistent. Therefore, the GO and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of DEGs showed that the DEGs were mainly enriched to metabolism signalling pathways (alpha-linolenic acid metabolism, linoleic acid metabolism, tryptophan metabolism, tyrosine metabolism, ether lipid metabolism, and metabolic pathway, etc) and immune response pathways (cytokine-cytokine receptor interaction, MAPK signalling pathway, and intestinal immune network for IgA production, neuroactive ligand-receptor interaction etc). These results will provide a better understanding of the role of probiotics in chicken development and provide basic information on the genetic development of chickens.

Salmonellosis: An Overview of Epidemiology, Pathogenesis, and Innovative Approaches to Mitigate the Antimicrobial Resistant Infections

Salmonella is a major foodborne pathogen and a leading cause of gastroenteritis in humans and animals. Salmonella is highly pathogenic and encompasses more than 2600 characterized serovars. The transmission of Salmonella to humans occurs through the farm-to-fork continuum and is commonly linked to the consumption of animal-derived food products. Among these sources, poultry and poultry products are primary contributors, followed by beef, pork, fish, and non-animal-derived food such as fruits and vegetables. While antibiotics constitute the primary treatment for salmonellosis, the emergence of antibiotic resistance and the rise of multidrug-resistant (MDR) Salmonella strains have highlighted the urgency of developing antibiotic alternatives. Effective infection management necessitates a comprehensive understanding of the pathogen's epidemiology and transmission dynamics. Therefore, this comprehensive review focuses on the epidemiology, sources of infection, risk factors, transmission dynamics, and the host range of Salmonella serotypes. This review also investigates the disease characteristics observed in both humans and animals, antibiotic resistance, pathogenesis, and potential strategies for treatment and control of salmonellosis, emphasizing the most recent antibiotic-alternative approaches for infection control.

Probiotics as an Alternative to Antibiotics: Genomic and Physiological Characterization of Aerobic Spore Formers from the Human Intestine

A total of thirty-two aerobic spore former strains were isolated from intestinal samples of healthy children and analyzed for their hemolytic and antibiotic-resistant activities. Four strains selected as non-hemolytic and sensitive to all antibiotics recommended as relevant by regulatory agencies were short-listed and evaluated for their in silico and in vitro probiotic potentials. The four selected strains were assigned to the Bacillus velezensis (MV4 and MV11), B. subtilis (MV24), and Priestia megaterium (formerly Bacillus megaterium) (MV30) species. A genomic analysis indicated that MV4, MV11, and MV24 contained a homolog of the gene coding for the fibrinolytic enzyme nattokinase while only MV30 encoded a glutamic acid decarboxylase essential to synthesize the neurotransmitter GABA. All four strains contained gene clusters potentially coding for new antimicrobials, showed strong antioxidant activity, formed biofilm, and produced/secreted quorum-sensing peptides able to induce a cytoprotective stress response in a model of human intestinal (HT-29) cells. Altogether, genomic and physiological data indicate that the analyzed strains do not pose safety concerns and have in vitro probiotic potentials allowing us to propose their use as an alternative to antibiotics.

Bacillus Co-culture Inhibits Quorum Sensing in Pseudomonas aeruginosa

Pseudomonas aeruginosa is a widespread source of hospital-acquired infections and a top priority antibiotic-resistant pathogen as it has developed robust immunity to most traditional antibiotics. Quorum sensing (QS) enables P. aeruginosa to modulate virulence functions and is important for pathogenesis. QS relies on the production and perception of autoinducing chemical signal molecules. Acyl-homoserine lactones are the key autoinducer molecules that mediate P. aeruginosa-associated QS, and N-(3-oxododecanoyl)-L-homoserine lactone (3-O-C12-HSL) and N-butyryl-L-homoserine lactone (C4-HSL) are the two types. This study aimed to identify potential quenching targets of QS pathways that may reduce the chances of resistance developing in P. aeruginosa using co-culture approaches. In co-cultures, Bacillus reduced the production of 3-O-C12-HSL/C4-HSL signal molecules by inactivating acyl- homoserine lactone-based QS to inhibit important virulence factor expression. Moreover, Bacillus is subject to complex crosstalk with other regulatory systems, such as the integrated QS system and the Iqs system. The results showed that blocking one or more QS pathways was insufficient to reduce infection with multidrug resistant P. aeruginosa.

Bacillus subtilis isolates from camel milk as probiotic candidates

Recently Bacillus spp. has gained much attention as potential probiotics due to the production of resistant cells. So, this research is purposeful for evaluation of probiotic characteristics of Bacillus isolates from camel milk as a suitable source for growth and isolation of microorganisms that can be candidate to be used as probiotic. First, forty-eight colonies were screened by using morphological and biochemical analysis. Among the isolates, two of them were recognized as Bacillus subtilis CM1 and CM2 by partial 16SrRNA sequencing that, probiotic potentials of them were evaluated. Both of them, in the preliminary safety screening, were found negative for hemolysis and lecithinase activity. Also, in vitro characteristics such as acid, bile salts and artificial gastric juice resistant, cell surface hydrophobicity, auto-aggregation, antioxidant characteristics, and adherent capability to HT-29 cells were determined for them approximately in the range of other probiotic strains. Two strains were susceptible to various antibiotics and enterotoxigenic activities were not detected by PCR which means isolated Bacillus strains could be classified as safe. Altogether, results demonstrate that Bacillus CM1 and CM2 strains could have the potential of consideration as probiotics, however more extensive in vitro/vivo studies are needed.

Nutrient Availability and Biofilm Polysaccharide Shape the Bacillaene-Dependent Antagonism of Bacillus subtilis against Salmonella Typhimurium

Salmonella enterica is one of the most common foodborne pathogens and, due to the spread of antibiotic resistance, new antimicrobial strategies are urgently needed to control it. In this study, we explored the probiotic potential of Bacillus subtilis PS-216 and elucidated the mechanisms that underlie the interactions between this soil isolate and the model pathogenic strain S. Typhimurium SL1344. The results reveal that B. subtilis PS-216 inhibits the growth and biofilm formation of S. Typhimurium through the production of the pks cluster-dependent polyketide bacillaene. The presence of S. Typhimurium enhanced the activity of the PpksC promoter that controls bacillaene production, suggesting that B. subtilis senses and responds to Salmonella. The level of Salmonella inhibition, overall PpksC activity, and PpksC induction by Salmonella were all higher in nutrient-rich conditions than in nutrient-depleted conditions. Although eliminating the extracellular polysaccharide production of B. subtilis via deletion of the epsA-O operon had no significant effect on inhibitory activity against Salmonella in nutrient-rich conditions, this deletion mutant showed an enhanced antagonism against Salmonella in nutrient-depleted conditions, revealing an intricate relationship between exopolysaccharide production, nutrient availability, and bacillaene synthesis. Overall, this work provides evidence on the regulatory role of nutrient availability, sensing of the competitor, and EpsA-O polysaccharide in the social outcome of bacillaene-dependent competition between B. subtilis and S. Typhimurium. IMPORTANCE Probiotic bacteria represent an alternative for controlling foodborne disease caused by Salmonella enterica, which constitutes a serious concern during food production due to its antibiotic resistance and resilience to environmental stress. Bacillus subtilis is gaining popularity as a probiotic, but its behavior in biofilms with pathogens such as Salmonella remains to be elucidated. Here, we show that the antagonism of B. subtilis is mediated by the polyketide bacillaene and that the production of bacillaene is a highly dynamic trait which depends on environmental factors such as nutrient availability and the presence of competitors. Moreover, the production of extracellular polysaccharides by B. subtilis further alters the influence of these factors. Hence, this work highlights the inhibitory effect of B. subtilis, which is condition-dependent, and the importance of evaluating probiotic strains under conditions relevant to the intended use.

Priestia flexa KS1: A new bacterial strain isolated from human faeces implicated in mucin degradation

The human gut acts as a habitat for diverse microbial communities, including mucin utilizers that play a significant role in host health and diseases. In this study, a gram-positive, rod-shaped mucin degrading bacterium was isolated from human faeces that belonged to the Priestia flexa species. Priestia isolate was analyzed for mucin-degrading ability and found that the KS1 strain could grow on mucin as the sole carbon source. The experimental results of the mucolytic zone around the colony and a 58% decrease in carbohydrate concentration confirmed the ability of Priestia to degrade mucin. The intracellular and extracellular glycosidase assay data supported the above results suggesting the ability of P. flexa to produce glycan hydrolysis enzymes that convert complex mucin oligosaccharide chains into simple glycans. The survival ability of the KS1 strain in simulated gastrointestinal conditions revealed that it could tolerate low pH (≥ 50% cell viability at pH 1.0) and 0.5% bile salt concentration (≥ 85% cell viability). The strain showed low hydrophobicity towards n-hexadecane (26.51 ± 0.92%) and xylene (21.71 ± 0.54%). Moreover, the KS1 culture was resistant to cefixime, clavulanic acid/ceftazidime, nafallin, methicillin, trimethoprim, kanamycin, and nalidixic antibiotic. Our results highlight the isolation of P. flexa KS1 strain that degrade mucin under in vitro conditions and show its better acclimatization within the GI environment. Further studies are required to unearth the molecular mechanisms involved in the degradation of mucin oligosaccharides in the human gut, advancing our understanding of health and disease.

Bioactive Earthworm Peptides Produced by Novel Protease-Producing Bacillus velezensis PM 35 and Its Bioactivities on Liver Cancer Cell Death via Apoptosis, Antioxidant Activity, Protection Against Oxidative Stress, and Immune Cell Activation

Earthworms have long been used as traditional medicine. The purposes of this research were to create bioactive peptides from the unique Amynthas arenulus earthworm (PAAEs) and test their potentials on liver cancer bioprophylactic activity, antioxidant, oxidative stress protection, and immune cell activation. This earthworm had a high protein content ratio, at 55.39%. Besides, PM 35 is one out of 58 bacteria isolated from the earthworm carcasses that exhibited the highest protease and yield protein production which was chosen as the protease-producing bacteria to hydrolyze the protein. The genera were identified by 16S rRNA and 16S–23S rRNA comparison and confirmed as Bacillus velezensis PM 35. The response surface methodology was applied to optimize these hydrolysis parameters, i.e., the enzyme/substrate (E/S) concentration ratio [1%–3% (v/v)] and time (1–3 h) of the hydrolyzing earthworm’s proteins. The optimal hydrolyzing conditions were 3% (v/v) of E/S concentration ratio and 3 h of hydrolysis time, which found protein-hydrolysate yield (24.62%) and degree of hydrolysis (85.45%) as the highest. After being challenged in the gastrointestinal tract-resistant model, these PAAEs (MW <3 and 3–5 kDa) induced liver cancer cell (HepG2) death via apoptotic action modes (cell morphological change and DNA fragmentation). The PAAEs (MW <3 kDa) exhibited significant antioxidant activity via DPPH, ABTS, and FRAP with IC₅₀ values of 0.94, 0.44, and 6.34 mg/ml, respectively. The PAAEs (MW < 3 kDa) were non-cytotoxic and protected the mouse fibroblast cells (L929) against oxidative stress. These PAAEs (MW < 3 kDa, 0.2 mg/ml) stimulated the B lymphocytes (122.3%), and T lymphocytes (126.7%) proliferation. This research suggests that PAAEs can be used in a variety of applications, especially in the food and pharmaceutical industries.

Effects of Clostridium butyricum on intestinal environment and gut microbiome under Salmonella infection

Salmonellosis causes massive economic losses globally every year. Especially in poultry, numerous drug-resistant bacteria have emerged; thus, it is imperative to find alternatives to antibiotics. As a probiotic, Clostridium butyricum (C. butyricum) provides the latest strategy for inhibiting the proliferation of Salmonella. This study aimed to evaluate the effects of C. butyricum on intestinal environment and gut microbiome under Salmonella infection. In this study, we modeled the infection of Salmonella using specific pathogen-free (SPF) chicks and found that the use of C. butyricum directly reduced the number of Salmonella colonizations in the spleen and liver. It also alleviated the histopathological changes of the liver, spleen, and cecum caused by Salmonella Enteritidis (S. Enteritidis). In addition, S. Enteritidis increased the expression of pro-inflammatory IL-6 in the cecum on day 6 postinfection. Interestingly, we found that C. butyricum changed PPAR-γ transcript levels in the cecum on day 6 postinfection. Analysis of the chick gastrointestinal microbiome showed that Salmonella infection increased the relative abundance of Subdoligranulum variabile. Further analysis found that Salmonella challenge significantly reduced the relative abundance of Faecalibacterium prausnitzii and C. butyricum increased the relative abundance of anaerobic bacteria in the gut on day 6 postinfection. Moreover, early supplementation of C. butyricum restored the epithelial hypoxia in S. Enteritidis infection in chicks. The results suggest that C. butyricum restores epithelial hypoxia caused by S. Enteritidis, improves the stability of intestinal flora, and inhibits the proliferation of Salmonella.

Bioprophylactic potential of novel human colostrum probiotics via apoptotic induction of colon cancer cells and cell immune activation

The potential and modes of action of novel human colostrum probiotics were investigated with the aim of studying their application as an alternative in the bioprophylactic and biotherapy of colon cancer. A total of 218 isolates of Gram-positive rod and cocci bacteria obtained from the colostrum of 50 healthy lactating females were collected. Beneficial probiotic criteria from these isolates, which included growth inhibition against seven foodborne pathogens (Helicobacter pylori, Escherichia coli, Salmonella Enteritidis, Salmonella Typhimurium, Staphylococcus aureus, Bacillus cereus and Listeria monocytogenes), no blood haemolysis and tolerance to acid and bile salt conditions, resulted in only eight probiotic bacteria successfully inhibiting the proliferation of colon cancer cells at rates of 32.47-61.21%. Two probiotic bacteria with higher anticancer efficacy (Streptococcus salivarius CP163 and S. salivarius CP208) were identified using 16S rRNA sequences. High rates of cell surface hydrophobicity, autoaggregation and coaggregation were obtained from both probiotics. The probiotic mode of action involved synergic probiotic adhesion to colon cancer cells that triggered SCFA bioproduction. Apoptotic induction of colon cancer cell death through caspase-2 activity, DNA fragmentation and morphological change as assessed by AO/PI staining were also observed. Immune stimulation by S. salivarius CP163 and S. salivarius CP208 resulted in B and T-cell lymphocyte activation. This study suggests that these novel human colostrum probiotics could be applied as a functional food to facilitate a bioprophylactic strategy in colon cancer.

Long-chain glucomannan supplementation modulates immune responsiveness, as well as intestinal microbiota, and impacts infection of broiler chickens with Salmonella enterica serotype Enteritidis

The zoonotic pathogen Salmonella enterica serotype Enteritidis (SE) causes severe disease in young chickens. Restriction on antibiotic use requires alternative SE control strategies such as nutritional solutions to improve the resistance of chickens. In this study, chickens were fed long-chain glucomannan (GM) or standard diet and challenged with SE at seven days of age. During 21 days post-infection (dpi), we determined numbers and responsiveness of natural killer (NK) and T cells in ileum and spleen, and SE-specific antibody titers in serum. Microbiota compositions in ileum and caeca were determined, as well as correlations of these with numbers and function of immune cells. Some of the samples in the control group had numerically higher CFUs than the GM-treated group. In addition, the relative abundance of SE based on DNA assessment was significantly lower at 21 dpi upon GM supplementation. At 3 dpi, numbers of intraepithelial NK cells were significantly higher, while activation of intraepithelial NK cells (7 dpi), numbers of intraepithelial cytotoxic CD8⁺ T cells (14 dpi) and SE-specific antibodies (14 dpi) were numerically higher. Furthermore, relative abundance of the commensal lactic acid bacteria (LAB) significantly increased with GM supplementation post-infection. Higher relative abundance of streptococci was associated with reduced SE in ileal and caecal contents at 21 dpi. Relative abundance of streptococci negatively correlated with SE counts and positively correlated with NK cell activation and SE-specific antibodies, which suggests involvement of the commensal LAB in NK cell responsiveness. These results indicate that GM supplementation modulates the immune system, intestinal microbiota and impacts SE infection of young chickens.

In vitro probiotic and safety attributes of Bacillus spp. isolated from beebread, honey samples and digestive tract of honeybees Apis mellifera

Bacillus species isolated from honeybee Apis mellifera gut, honey and bee bread samples were characterized for their in vitro probiotic and safety attributes. Alpha and γ haemolytic cultures were tested for their antibiotic resistance, antibacterial spectrum, acid and bile tolerance, adhesion ability (auto-aggregation, co-aggregation and hydrophobicity) and phenol tolerance. Safety criteria included evaluation of virulence genes and cytotoxicity percentages. Bacillus isolates inhibited both Gram-positive and Gram-negative pathogens including Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis and Streptococcus mutans, while none could inhibit Listeria monocytogenes. Among the isolates, Bacillus subtilis ZH05, ZB03 and ZG025 showed resistance to most of the tested antibiotics and were considered unsafe. B. subtilis (4) and B. licheniformis (1) tolerated acidic pH and bile conditions, never the less were more tolerant in simulated intestinal conditions vis-a-vis gastric conditions. In 0·5% phenol concentrations, B. licheniformis ZH02 showed highest growth, while, B. subtilis ZG029 demonstrated highest auto-aggregation (65 ± 4·6) and hydrophobicity (23 ± 3·6) percentages (P < 0·05). The isolates lacked virulence genes (hblA, hblC, hblD, nhe, cytK and ces), and their cytotoxic percentage on Caco-2 cell lines was ˂15%. Overall, honeybees appear to be a good source of Bacillus species exhibiting typical in vitro probiotic properties, which could be of commercial interest.

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.

Indian oil sardine (Sardinella longiceps) gut derived Bacillus safensis SDG14 with enhanced probiotic competence for food and feed applications

Probiotics are considered as functional food as they provide health benefits along with traditional nutrition. Spore forming probiotic Bacillus are of commercial interest than Lactic Acid Bacillus due to their relatively lower cost of production and higher survivability. In the present study we identified the bacterial strain SDG14 isolated from Indian oil Sardine by Average Nucleotide Identity of whole genome sequence. The whole genome of SDG14 was also explored for pathogenicity, the presence of genes responsible for probiotic traits such as spore formation, resistance to host gastrointestinal tract conditions, adhesion to intestinal mucosa, interference in pathogen survival, expression of bacteriocins, oxidative and other stress responses, absorption of nutrition, production of essential amino acids and vitamins. Wet lab experiments for probiotic characterization were also conducted. The organism was confirmed to be Bacillus safensis SDG14. The possible pathogenicity of the organism was also ruled out by in silico analysis. Bacillus safensis SDG14 was able to survive at pH 3 and bile salt concentration of 0.5% (w/v). The adhesion index of Bacillus safensis SDG14 on HEp-2 was 36.82 ± 5.93 and 45.54 ± 9.55 respectively after 60 and 90 min of incubation and self aggregation percentage was 18.4 ± 0.48% after 3 h. Bacillus safensis SDG14 produced bacteriocin and co-aggregated with E. coli, Salmonella Typhimurium and Pseudomonas aeruginosa. The genomic data supported the findings of wet lab study and vice versa. Bacillus safensis SDG14 was proved to be a non-pathogenic, spore forming, pH and bile salt resistant, bacteriocin, amino acid and vitamin producing probiotic with proposed food and feed applications.

Effect of dietary direct-fed microbial and yeast cell walls on cecal digesta microbiota of layer chicks inoculated with nalidixic acid resistant Salmonella Enteritidis

Salmonella enterica serovar Enteritidis (SE) has consistently been the most common serotype associated with the foodborne Salmonellosis worldwide. In this study, the effect of a dietary direct-fed microbial (DFM) and yeast cell walls (YCW) under a challenge of nalidixic acid resistant SE strain using layer chicks has been investigated. A total of 160 newly hatched Dekalb White female chicks were randomly assigned into 2 experimental groups (80 birds/treatment), control group (CON) and treatment group (DY). Chicks were fed ad libitum a non–medicated-corn-soy based diet and DY was supplemented with the combination of DFM and YCW. At 8 days of age, 2.1 × 10⁹ CFU/bird of the SE was given to all chicks by oral administration. On 3 days postinoculation (dpi), 20 chicks/group were euthanized and all cecal contents were collected for analysis. On 6, 10, and 14 dpi, the cecal contents were sampled from 16 chicks per group. The number of SE in the cecal contents was counted using culture-based methods. A 16S rRNA-based microbiota analysis was performed for additional microbial profiling. The CON and DY showed difference (P ≤ 0.05) in β diversity throughout the trial. Prevalence of SE in cecal contents was lower (P ≤ 0.05) in DY across all time-points. Lower abundance of Salmonella spp. was also shown in DY by liner discriminant analysis effect size (LEfSe). DY increased (P ≤ 0.05) diversity of bacterial species in the cecal contents in DY at 10 and 14 dpi. For the SE challenged birds, SE reduction in DY was observed at 3 dpi and until the end of the trial at 14 dpi confirming a numerically larger difference between groups as well as an increase in bacterial species diversity in DY. It could be hypothesized that the SE reduction shown immediately after the challenge and the greater SE reduction shown after 10 dpi may be the synergistic effect of the combined feed additives.

Isolation and Characterization of Probiotic Bacillus subtilis MKHJ 1-1 Possessing L-Asparaginase Activity

The purpose of this study was to isolate functional Bacillus strains from Korean fermented soybeans and to evaluate their potential as probiotics. The L-asparaginase activity of MKHJ 1-1 was the highest among 162 Bacillus strains. This strain showed nonhemolysis and did not produce β-glucuronidase. Among the nine target bacteria, MKHJ 1-1 inhibited the growth of Escherichia coli, Pseudomonas aeruginosa, Shigella sonnei, Shigella flexneri, Klebsiella pneumoniae, Staphylococcus aureus, and Bacillus cereus. 16S rRNA gene sequence analysis resulted in MKHJ 1-1 identified as Bacillus subtilis subsp. stercoris D7XPN1. As a result of measuring the survival rate in 0.1% pepsin solution (pH 2.5) and 0.3% bile salt solution for 3 h, MKHJ 1-1 exhibited high acid resistance and was able to grow in the presence of bile salt. MKHJ 1-1 showed outstanding autoaggregation ability after 24 h. In addition, its coaggregation with pathogens was strong. Therefore, MKHJ 1-1 is a potential probiotic with L-asparaginase activity and without L-glutaminase activity, suggesting that it could be a new resource for use in the food and pharmaceutical industry.

Interaction between the probiotic Bacillus subtilis and Salmonella Typhimurium in Caco-2 cell culture

Background and Objectives:

Bacillus probiotics have been recently considered in biotechnological researches, and food additives. The present study was aimed to investigate the effects of Bacillus subtilis probiotics (PY79 and ATCC 6633) and their metabolites on Salmonella Typhimurium in Caco-2 cells.

Materials and Methods:

Cytotoxicity of B. subtilis ATCC 6633 crude supernatant (CS) was evaluated by 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. S. Typhimurium invasion assay was performed in the presence of the probiotics. Cell viability, apoptosis, and necrosis were evaluated in presence of S. Typhimurium, B. subtilis strains, and CS (4%, 8%) using flow cytometry.

Results:

Results showed a significant reduction in the invasive ability of S. Typhimurium to Caco-2 cells by employing B. subtilis probiotics, and CS (p < 0.05). The less invasion was indicated in B. subtilis PY79 and Salmonella co-cultural group. Furthermore, the cell survival rates, and apoptosis/necrosis were respectively increased and decreased in co-culture groups (p < 0.05).

Conclusion:

Hence, it seems that B. subtilis strains could be suggested as beneficial candidates to overcome the invasion and cytotoxicity of Salmonella on the intestinal cells. However, additional in vivo models are suggested to validate our results.

Bacillus subtilis and lactic acid bacteria improve the growth performance and blood parameters and reduce Salmonella infection in broilers

Aim

The aim of the study was to determine the potentials and effects of Bacillus subtilis and lactic acid bacteria (LAB) as probiotics on broiler growth, health, and Salmonella infection.

Materials and Methods

To evaluate the inoculum size applicable for broilers, 1-day-old broilers were orally fed fresh cultures of single strains and a B. subtilis KKU213/Pediococcus pentosaceus NP6 mixture at 10⁸ and 10¹² colony-forming unit (CFUs)/mL/chick. The body weight gain (BWG), Salmonella contamination level and total Bacillus and LAB abundances in the crop and intestine were measured. Subsequently, 1-day-old broilers were orally fed of KKU213, CH403, and Pediococcus acidilactici SH8 at 10¹⁰ CFUs/mL, followed by inulin. After 35 days, the BWG, Bacillus and LAB abundances in the cecum, blood parameters, and KKU213 colonization were assessed.

Results

The broilers fed single strains or KKU213+NP6 exhibited a higher BWG and a higher crop LAB abundance than the controls (p<0.05). Probiotic feeding decreased the intestinal Salmonella abundance and correspondingly increased the LAB abundance. The broilers fed the mixed culture (KKU213+CH403+SH8) followed by prebiotics showed lower mortality, higher blood high-density lipoprotein levels, and lower blood uric acid levels than the controls (p<0.0004). Probiotic feeding significantly increased the Bacillus and LAB counts (p<0.05). A CE330 isolate obtained from the cecum after 35 days of KKU213 feeding was closely related to B. subtilis KKU213.

Conclusion

B. subtilis KKU213 is a potent probiotic strain that can survive, colonize and reduce Salmonella infection in broilers and improve their growth and health. This strain, combined with different LAB can act synergistically in the gut and promote broiler growth.

Isolation, selection and evaluation of Bacillus spp. as potential multi-mode probiotics for poultry

Bacillus based probiotics are becoming relevant as alternatives to antibiotics used in poultry production and in other animal husbandry. This study describes the isolation of 48 Bacillus spp. candidates, from chickens and chicken environments, for use as potential probiotics in poultry production. These isolates, plus a further 18, were tested in a comprehensive in vitro screening regime that was specifically designed to select the best isolates that satisfied multiple modes of action desirable for commercial poultry probiotics. This screening programme involved the evaluation of the ability of the isolates to survive and grow in the limiting conditions of the chicken gastrointestinal tract. Only 11 of the isolates fulfilled these criteria; hence, they were further evaluated for the ability to adhere to epithelial cells, produce extracellular enzymes, and to demonstrate antagonistic activity against selected pathogens of significant importance in poultry production. Of these, a total of 6 isolates were selected, due to their all-round probiotic capability. Identification by 16S RNA sequencing confirmed these isolates as B. subtilis and B. velezensis, identities which are generally regarded as safe. The Bacillus isolates reported in our study exhibit strong all-inclusive probiotic effects and can potentially be formulated as a probiotic preparation for poultry production.

Recent Advances in the Physiology of Spore Formation for Bacillus Probiotic Production

Spore-forming probiotic bacteria have received a wide and constantly increasing scientific and commercial interest. Among them, Bacillus species are the most studied and well-characterized Gram-positive bacteria. The use of bacilli as probiotic products is expanding especially rapidly due to their inherent ability to form endospores with unique survivability and tolerance to extreme environments and to produce a large number of valuable metabolites coupled with their bio-therapeutic potential demonstrating immune stimulation, antimicrobial activities and competitive exclusion. Ease of Bacillus spp. production and stability during processing and storage make them a suitable candidate for commercial manufacture of novel foods or dietary supplements for human and animal feeds for livestock, especially in the poultry and aquaculture industries. Therefore, the development of low-cost and competitive technologies for the production of spore-forming probiotic bacteria through understanding physiological peculiarities and mechanisms determining the growth and spore production by Bacillus spp. became necessary. This review summarizes the recent literature and our own data on the physiology of bacilli growth and spore production in the submerged and solid-state fermentation conditions, focusing on the common characteristics and unique properties of individual bacteria as well as on several approaches providing enhanced spore formation.

Imidazole and Methoxybenzylamine Growth Inhibitors Reduce Salmonella Persistence in Tomato Plant Tissues

HIGHLIGHTS

Small molecules (SMs) 1, 3, 4, and 5 are novel growth inhibitors of Salmonella enterica. These SMs are not toxic to tomato plant tissues including fruits. Combining biocontrol agents and SMs enhanced the control of Salmonella in infected plants. These SMs may be safe bactericides against Salmonella and phytopathogens in produce.

The effects of probiotic Bacillus coagulans on the cytotoxicity and expression of alpha toxin gene of Clostridium perfringens type A

Around the world, Clostridium perfringens type A is known to be a common foodborne pathogen. Therefore, the control and treatment of food poisoning caused by this pathogen are important. This study investigated, in vitro, the effects of Bacillus coagulans and its culture extracts on alpha toxin gene expression, growth inhibition, cytotoxicity, and apoptosis induced by C. perfringens spore, germinated spore and its enterotoxin. Flow cytometry was used to evaluate the apoptosis rate, and MTT test was used to evaluate cytotoxicity. Minimum inhibitory concentration was also used to measure the percentage of inhibition in the broth medium. Finally, RT-qPCR was used to evaluate alpha toxin gene expression. The results showed that the B. coagulans culture extract was able to inhibit the growth of the germinated spore of C. perfringens. Moreover, treating the extract with pepsin can reduce growth in the broth medium. MTT and flow cytometry showed that both B. coagulans and its extract can significantly reduce the cytotoxicity and apoptosis rate induced by C. perfringens type A. In addition, it was shown that the co-culture of B. coagulans and C. perfringens decreases alpha toxin gene expression. The findings of this study indicate that B. coagulans, with growth inhibition and reduced expression of alpha toxin in C. perfringens, can reduce the cytotoxicity and apoptosis rate induced on HT-29 cells.

Bacillus subtilis in broiler diets with different levels of energy and protein

The present study evaluated the impacts of Bacillus subtilis (BAS) inclusion in broiler diets with standard nutrient content or nutrient deficiency (ND) on growth performance (GP) and nutrient digestibility. The 42 d experiment consisted of 6 experimental diets, a diet with standard nutrient content, and 2 diets with different levels of energy and protein deficiency, without or with BAS. At the end of experiment, apparent ileal digestibility coefficients (AIDC) of starch, crude protein (CP), and gross energy (GE) were determined. Furthermore, impacts of BAS supplementation in standard diets on gut histomorphology, bacterial metabolic activity, and composition were evaluated. Performance and AIDC data were subjected to ANOVA using GLM procedure with a 3 (nutrient levels) × 2 (BAS presence/absences) factorial arrangement of treatments. Gut histomorphology and microbiology data, obtained from broilers fed standard diets without (S) and with BAS (SB), were assessed by an independent Student's t-test. The ND in diets was effective enough to cause nutritional stress and negatively affect performance. Inclusion of BAS in both types of diet improved GP, which was due to the fact that adding BAS in these diets led to improvements in AIDC of CP, starch, and GE (P ≤ 0.05). Comparing only 2 experimental groups, S and SB, revealed no impact on bacterial composition and metabolism in the ileum and cecum, except a reduction in ileal lactobacilli number for SB group. Adding BAS to standard diet reduced crypt depth (CD) and increased villus length to CD ratio in the duodenum, whereas it had no impact on other histomorphological variables in the duodenum, jejunum, and ileum. In conclusion, supplementation of broiler diets with probiotic BAS can positively affect growth performance and nutrient digestibility and this positive impact might even be more pronounced in nutrient-deficient diets. However, the extent of the alleviating ability of BAS in nutrient-deficient diets as well as the biological mechanisms for such a phenomenon needs to be studied further.

Effect of dietary Bacillus coagulans supplementation on growth performance and immune responses of broiler chickens challenged by Salmonella enteritidis

This study was conducted to evaluate the protective efficacy of dietary Bacillus coagulans (B. coagulans) supplementation in birds receiving Salmonella enteritidis (SE). Two hundred and forty 1-day-old Cobb broilers were randomly assigned to 2 × 2 factorial arrangements of treatments with 2 levels of dietary B. coagulans (0 or 400 mg/kg) and 2 levels of SE challenge (0 or 1 × 109 SE between d 9 to 11). Results showed that SE infection did not affect growth performance, but caused intestinal inflammation and barrier function impairment by reducing intestinal goblet cells and beneficial bacteria numbers, increasing cecal Salmonella colonization and liver Salmonella invasion, downregulating jejunal mucin-2 (at 7 and 17 d post-infection, DPI), TLR2 (at 7 and 17 DPI), TLR4 (at 17 DPI), TNFSF15 (at 7 and 17 DPI) gene mRNA levels, and upregulating jejunal IFN-γ mRNA levels (at 17 DPI) compared to uninfected birds. Moreover, SE infection also elevated the concentration of jejunal anti-Salmonella IgA and sera anti-Salmonella IgG compared to uninfected birds. However, chickens received B. coagulans diets showed significant increase in body weight gain and weight gain to feed intake ratio from d 15 to 21, alkaline phosphatase activity (at 7 DPI), cecal Lactobacilli and Bifidobacterium numbers (at 7 DPI; at 17 DPI), villous height: crypt ratio (at 17 DPI), and goblet cell numbers (at 7 and 17 DPI), whereas exhibiting reduced jejunal crypt depth (at 17 DPI), cecal Escherichia coli (at 7, 17, and 31 DPI), and Salmonella (at 7 and 17 DPI) levels compared with the non-supplemented birds, regardless of SE infection. In addition, B. coagulans supplement upregulated lysozyme mRNA levels (at 17 DPI), downregulated IFN-γ mRNA levels (at 7 and 17 DPI), showed an increased trend in Fowlicidin-2 mRNA levels (at 7 DPI) and a reduced trend in liver Salmonella load compared to the non-supplemented control. These data indicated that B. coagulans has a protective effect in SE infected broilers.

Antibiotic-Resistant Salmonella in the Food Supply and the Potential Role of Antibiotic Alternatives for Control

Salmonella enterica is one of the most ubiquitous enteropathogenic bacterial species on earth, and comprises more than 2500 serovars. Widely known for causing non-typhoidal foodborne infections (95%), and enteric (typhoid) fever in humans, Salmonella colonizes almost all warm- and cold-blooded animals, in addition to its extra-animal environmental strongholds. The last few decades have witnessed the emergence of highly virulent and antibiotic-resistant Salmonella, causing greater morbidity and mortality in humans. The emergence of several Salmonella serotypes resistant to multiple antibiotics in food animals underscores a significant food safety hazard. In this review, we discuss the various antibiotic-resistant Salmonella serotypes in food animals and the food supply, factors that contributed to their emergence, their antibiotic resistance mechanisms, the public health implications of their spread through the food supply, and the potential antibiotic alternatives for controlling them.

Antioxidant and immune-enhancing effects of probiotic Lactobacillus plantarum 200655 isolated from kimchi

Probiotic properties including antioxidant and immune-enhancing effects of Lactobacillus plantarum 200655 isolated from kimchi were evaluated. The tolerance of three strains (L. plantarum 200655, L. plantarum KCTC 3108, and L. rhamnosus GG to bile salts (0.3% oxgall, 24 h) was similar, and L. plantarum 200655 showed the highest tolerance to gastric juice (0.3% pepsin, 3 h). All strains presented similar autoaggregation ability. L. plantarum 200655 showed higher cell surface hydrophobicity and adhesion ability on HT-29 cells. L. plantarum 200655 did not produce β-glucuronidase and was sensitive to ampicillin, tetracycline, chloramphenicol, and doxycycline. Additionally, L. plantarum 200655 showed the highest antioxidant effects in DPPH and ABTS radical scavenging, and β-carotene bleaching assays. RAW 264.7 cells treated with L. plantarum 200655 produced more nitric oxide, induced nitric oxide synthase, and cytokine related to immune-enhancing effects such as interleukin-1β and interleukin-6. Therefore, L. plantarum 200655 could be useful as a probiotic strain for older people.

Effects of intranasal administration with Bacillus subtilis on immune cells in the nasal mucosa and tonsils of piglets

The nasal mucosa is the body's first barrier against pathogens entering through the respiratory tract. The respiratory immune system of pigs has more similarities with humans than the mouse respiratory system does, and so was selected as the animal model in the present study. To evaluate the effects of Bacillus subtilis as a potential probiotic to stimulate local immune responses, piglets were intranasally administered with Dylight 488-labeled B. subtilis (WB800-green fluorescent protein). The results revealed that B. subtilis was able to reach the lamina propria of the nasal mucosa, nasopharyngeal tonsils and soft palate tonsils. Piglets were subsequently administered intranasally with B. subtilis (WB800) at 3, 12 and 28 days. The results revealed that, following administration with B. subtilis, the number of dendritic cells, immunoglobulin A⁺ B cells and T cells in the nasal mucosa and tonsils significantly increased (P<0.05). No obvious differences were observed in the morphological structure following B. subtilis administration. There were no statistical differences were observed in the expression of interleukin (IL)-1β, tumor necrosis factor-α and IL-8 mRNA between the B. subtilis treated group and the control group in the nasal mucosa, nasopharyngeal tonsil or soft palate tonsil. Toll-like receptor (TLR)-2 and TLR-9 mRNA expression in the tonsils was significantly increased following B. subtilis administration compared with the control group (P<0.05). The results demonstrate that B. subtilis administration increases the number of immune cells in the nasal mucosa and tonsils of piglets and stimulates nasal mucosal and tonsillar immunity. The present study lays the foundation for further study into the intranasal administration of B. subtilis in humans to enhance the immunity of human nasal mucosa to respiratory diseases.

Bacillus probiotics: an alternative to antibiotics for livestock production

The use of probiotics as feed supplements in animal production has increased considerably over the last decade, particularly since the ban on antibiotic growth promoters in the livestock sector. Several Bacillus sp. are attractive for use as probiotic supplements in animal feed due to their ability to produce spores. Their heat stability and ability to survive the low pH of the gastric barrier represent an advantage over other probiotic micro-organisms. This review discusses important characteristics required for selection of Bacillus probiotic strains and summarizes the beneficial effect of Bacillus-based feed additives on animal production. Although the mechanism of action of Bacillus probiotics has not been fully elucidated, they are effective in improving the growth, survival and health status of terrestrial and aquatic livestock. Bacillus strains also have utility in bioremediation and can reduce nitrogenous waste, thereby improving environmental conditions and water quality. Finally, recent innovative approaches for using Bacillus spores in various applications are discussed.

Draft Genome Sequences of Bacillus subtilis Strain DKU_NT_01 Isolated from Traditional Korean Food Containing Soybean (Chung-gook-jang)

Here, we report the whole-genome sequence of Bacillus subtilis strain DKU_NT_01 isolated from traditional Korean food containing soybean (chung-gook-jang). The de novo genome of Bacillus subtilis strain DKU_NT_01 has one contig and G+C content of 55.4%, is 4,954,264 bp in length, and contains 5,011 coding sequences (CDSs).

The effects of probiotic Bacillus subtilis on the cytotoxicity of Clostridium perfringens type a in Caco-2 cell culture

Background

Some Bacillus strains have recently been identified for potential use as probiotics and food additives. The present study evaluated the antimicrobial effects of Bacillus subtilis ATCC 6633 and its metabolite on the enterotoxin and vegetative cells, spore and germinated spore of Clostridium perfringens type A in Caco-2 cells.

Results

We used flow cytometry and MTT assays to evaluate the cytotoxicity effect of treatments. According to the results, the most cell survival was found in the 4% crude antimicrobial substance (CAS) with the vegetative form of C. perfringens among co-cultured groups. Furthermore, the apoptosis and necrosis in co-cultured groups were significantly decreased (P < 0.05).

Conclusion

The present results suggested the crucial role of the current probiotic in the control of various forms of C. perfringens type A which was investigated for the first time. Also, the majority of treatments showed higher cell viability in flow cytometry compared to the MTT assay.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-017-1051-1) contains supplementary material, which is available to authorized users.

Probiotic engineering: towards development of robust probiotic strains with enhanced functional properties and for targeted control of enteric pathogens

There is a growing concern about the increase in human morbidity and mortality caused by foodborne pathogens. Antibiotics were and still are used as the first line of defense against these pathogens, but an increase in the development of bacterial antibiotic resistance has led to a need for alternative effective interventions. Probiotics are used as dietary supplements to promote gut health and for prevention or alleviation of enteric infections. They are currently used as generics, thus making them non-specific for different pathogens. A good understanding of the infection cycle of the foodborne pathogens as well as the virulence factors involved in causing an infection can offer an alternative treatment with specificity. This specificity is attained through the bioengineering of probiotics, a process by which the specific gene of a pathogen is incorporated into the probiotic. Such a process will subsequently result in the inhibition of the pathogen and hence its infection. Recombinant probiotics offer an alternative novel therapeutic approach in the treatment of foodborne infections. This review article focuses on various strategies of bioengineered probiotics, their successes, failures and potential future prospects for their applications.

Bacillus subtilis Improves Immunity and Disease Resistance in Rabbits

Probiotics such as Lactobacillus and Bifidobacterium have been successfully used to promote growth and prevent diseases. Previous reports have demonstrated that Bacillus subtilis (B. subtilis) was a potential probiotic for animals. In this research, 180 B. subtilis were isolated from the soil, identified, and investigated in vitro. Furthermore, five B. subtilis were selected and mixed to investigate their effect on growth performance, immune response, intestine microbiota, and disease resistance in rabbits. Rabbits with a diet of 106 CFU g-1 mixed B. subtilis exhibited the best growth performance and higher serum IgG and IgA than controls (P < 0.05). Moreover, dairy with B. subtilis can promote the balance of intestinal flora. The major proinflammatory factor and β-defensin were upregulated compared with the controls. After 7 weeks of feeding, the survival rate of the rabbits fed with B. subtilis was significantly higher than those in the control groups postinfected with Escherichia coli. At the same time, this study detected higher expression of β-defensin and reduced bacteria contents of the heart and cecal contents from the diet mixed with B. subtilis compared with the control groups. In conclusion, dietary supplementation with B. subtilis for rabbits could improve growth performance, intestinal homeostasis, and immune organ index and enhance innate immune response as well as disease resistance. These findings showed that the induction of β-defensin by B. subtilis might be an interesting new therapeutic strategy to strengthen innate defense mechanisms.

Can Bacteriotherapy Using Commercially Available Probiotics, Prebiotics, and Organic Acids Ameliorate the Symptoms Associated With Runting-Stunting Syndrome in Broiler Chickens?

Runting-stunting syndrome (RSS) in poultry has been known for more than 40 years, but the precise etiology remains unknown and a licensed vaccine is consequently not currently available. In order to mitigate the symptoms associated with RSS, a series of experiments was performed to investigate whether a combined bacteriotherapeutic treatment consisting of probiotics, prebiotics, and organic acids could influence the outcome of this disease. Initially two groups of commercial broiler chickens were either left uninoculated or inoculated with filtrate from homogenized intestines of RSS-affected broiler chickens. One group from each of these two challenge groups was treated, with a bacteriotherapeutic regimen. After 12 days chickens were euthanatized, the body weight was measured, and duodenal lesions were enumerated. Five consecutive broiler chicken flocks were then raised either on litter from RSS-affected birds or on fresh wood shavings. Treatment had no beneficial effect on the number and severity of intestinal lesions. There appeared to be a significant build-up of RSS agent(s) in poultry litter, with each consecutive flock placement, independent of bacteriotherapeutic treatment, as more individuals exhibited intestinal lesions on built-up litter in RSS-affected houses (28.9% vs. 44%). While treatment did not appear to consistently reduce intestinal lesions, it did significantly improve the mean body weights (P<0.05) and uniformity of 12-day-old chickens placed on reused litter in houses in which RSS-infected birds were previously raised. A combination of litter management and bacteriotherapy may be needed to ameliorate the adverse effects of RSS on intestinal health and body weight in broiler chickens.