Lactobacillus acidophilus modulates the virulence of Clostridium difficile

Environmental and Nutritional Parameters Modulating Genetic Expression for Virulence Factors of Clostridioides difficile

Clostridioides difficile infections (CDIs) continue to be a persistent healthcare concern despite newer antibiotic treatments, enhanced infection control practices, and preventive strategies focused on restoring the protective intestinal microbial barrier. Recent strides in gene sequencing research have identified many genes regulating diverse virulence factors for CDIs. These genes may be over- or under-expressed when triggered by various environmental and nutritional factors. The aims of this paper are to review the important genes involved in C. difficile pathogenesis and to identify modifiable environmental, nutritional, and other factors that may trigger the expression of these genes and thus offer new strategies to prevent CDIs.

Probiotics for Prevention and Treatment of Clostridium difficile Infection

Probiotics have been claimed as a valuable tool to restore the balance in the intestinal microbiota following a dysbiosis caused by, among other factors, antibiotic therapy. This perturbed environment could favor the overgrowth of Clostridium difficile, and in fact, the occurrence of C. difficile-associated infections (CDI) is increasing in recent years. In spite of the high number of probiotics able to in vitro inhibit the growth and/or toxicity of this pathogen, its application for treatment or prevention of CDI is still scarce since there are not enough well-defined clinical studies supporting efficacy. Only a few strains, such as Lactobacillus rhamnosus GG and Saccharomyces boulardii, have been studied in more extent. The increasing knowledge about the probiotic mechanisms of action against C. difficile, some of them reviewed here, makes promising the application of these live biotherapeutic agents against CDI. Nevertheless, more effort must be paid to standardize the clinical studies conducted to evaluate probiotic products, in combination with antibiotics, in order to select the best candidate for C. difficile infections.

Effect of feeding dairy calves with milk fermented with selected probiotic strains on occurrence of diarrhoea, carriage of pathogenic and zoonotic microorganisms and growth performance

Calf-diarrhoea is a major health problem in dairy calves and a primary reason for use of antimicrobials. We aimed to investigate the effect of feeding milk fermented with a combination of four probiotic bacterial strains to young-calves on; occurrence of diarrhoea and associated-pathogens (bacteria, virus and parasites), shedding of Salmonella Dublin and Campylobacter, occurrence of virulence genes linked to Clostridium perfringens, Enterotoxigenic Escherichia coli and shiga-toxin producing E. coli (STEC), as well as growth performance. For this, 143 new-born calves from three Danish dairy-farms were allocated into Treatment- (fed the fermented milk for the first 8-weeks-of-life) and Control-groups (fed regular farm-milk). Diarrhoea was observed in 18.6 % (Farm 1), 22.4 % (Farm 2) and 15.7 % (Farm 3) of the total registrations mainly within the first 3-weeks-of-life. C. perfringens was the most frequently detected pathogen. The treatment did not affect the occurrence of virulence genes linked to STEC and C. perfringens and, overall, their detection levels were very low/undetected. The statistical model applied found no significant effect of the treatment on prevalence of early-diarrhoea (≤ 3 weeks), late-diarrhoea (>3 weeks), occurrence of C. perfringens and Cryptosporidium parvum or levels of Campylobacter spp. Limited detection of the other pathogens and associated virulence-genes under study, did not allow for assessment of the impact of the treatment on their occurrence. Notably, the feeding-approach showed a significant detrimental effect on daily-weight-gain. The inefficacy of the treatment may be associated with the complexity of influencing factors under field conditions including management practices.

Revisiting the Intestinal Microbiome and Its Role in Diarrhea and Constipation

The gut microbiota represents a community of microorganisms (bacteria, fungi, archaea, viruses, and protozoa) that colonize the gut and are responsible for gut mucosal structural integrity and immune and metabolic homeostasis. The relationship between the gut microbiome and human health has been intensively researched in the past years. It is now widely recognized that gut microbial composition is highly responsible for the general health of the host. Among the diseases that have been linked to an altered gut microbial population are diarrheal illnesses and functional constipation. The capacity of probiotics to modulate the gut microbiome population, strengthen the intestinal barrier, and modulate the immune system together with their antioxidant properties have encouraged the research of probiotic therapy in many gastrointestinal afflictions. Dietary and lifestyle changes and the use of probiotics seem to play an important role in easing constipation and effectively alleviating diarrhea by suppressing the germs involved. This review aims to describe how probiotic bacteria and the use of specific strains could interfere and bring benefits as an associated treatment for diarrhea and constipation.

Biofilm Formation of Clostridioides difficile, Toxin Production and Alternatives to Conventional Antibiotics in the Treatment of CDI

Clostridioides difficile is considered a nosocomial pathogen that flares up in patients exposed to antibiotic treatment. However, four out of ten patients diagnosed with C. difficile infection (CDI) acquired the infection from non-hospitalized individuals, many of whom have not been treated with antibiotics. Treatment of recurrent CDI (rCDI) with antibiotics, especially vancomycin (VAN) and metronidazole (MNZ), increases the risk of experiencing a relapse by as much as 70%. Fidaxomicin, on the other hand, proved more effective than VAN and MNZ by preventing the initial transcription of RNA toxin genes. Alternative forms of treatment include quorum quenching (QQ) that blocks toxin synthesis, binding of small anion molecules such as tolevamer to toxins, monoclonal antibodies, such as bezlotoxumab and actoxumab, bacteriophage therapy, probiotics, and fecal microbial transplants (FMTs). This review summarizes factors that affect the colonization of C. difficile and the pathogenicity of toxins TcdA and TcdB. The different approaches experimented with in the destruction of C. difficile and treatment of CDI are evaluated.

Probiotics: insights and new opportunities for Clostridioides difficile intervention

Clostridioides difficile infection (CDI) is a life-threatening disease caused by the Gram-positive, opportunistic intestinal pathogen C. difficile. Despite the availability of antimicrobial drugs to treat CDI, such as vancomycin, metronidazole, and fidaxomicin, recurrence of infection remains a significant clinical challenge. The use of live commensal microorganisms, or probiotics, is one of the most investigated non-antibiotic therapeutic options to balance gastrointestinal (GI) microbiota and subsequently tackle dysbiosis. In this review, we will discuss major commensal probiotic strains that have the potential to prevent and/or treat CDI and its recurrence, reassess the efficacy of probiotics supplementation as a CDI intervention, delve into lessons learned from probiotic modulation of the immune system, explore avenues like genome-scale metabolic network reconstructions, genome sequencing, and multi-omics to identify novel strains and understand their functionality, and discuss the current regulatory framework, challenges, and future directions.

Anti-Quorum Sensing Activity of Probiotics: The Mechanism and Role in Food and Gut Health

Background: Quorum sensing (QS) is a cell-to-cell communication mechanism that occurs between inter- and intra-bacterial species and is regulated by signaling molecules called autoinducers (AIs). It has been suggested that probiotics can exert a QS inhibitory effect through their metabolites. Purpose: To provide an overview of (1) the anti-QS activity of probiotics and its mechanism against foodborne pathogenic and spoilage bacteria; (2) the potential role of the QS of probiotics in gut health; and (3) the impact of microencapsulation on QS. Results: Lactobacillus species have been extensively studied for their anti-QS activity and have been found to effectively disrupt QS in vitro. However, their effectiveness in a food matrix is yet to be determined as they interfere with the AI receptor or its synthesis. QS plays an important role in both the biofilm formation of probiotics and pathogenic bacteria. Moreover, in vitro and animal studies have shown that QS molecules can modulate cytokine responses and gut dysbiosis and maintain intestinal barrier function. In this scenario, microencapsulation was found to enhance AI activity. However, its impact on the anti-QS activity of probiotics and its underlying mechanism remains unclear. Conclusions: Probiotics are potential candidates to block QS activity in foodborne pathogenic and food spoilage bacteria. Microencapsulation increases QS efficacy. However, more research is still needed for the identification of the QS inhibitory metabolites from probiotics and for the elucidation of the anti-QS mechanism of probiotics (microcapsules and free cells) in food and the human gut.

Quorum-Sensing Inhibitors from Probiotics as a Strategy to Combat Bacterial Cell-to-Cell Communication Involved in Food Spoilage and Food Safety

Experience-based knowledge has shown that bacteria can communicate with each other through a cell-density-dependent mechanism called quorum sensing (QS). QS controls specific bacterial phenotypes, such as sporulation, virulence and pathogenesis, the production of degrading enzymes, bioluminescence, swarming motility, and biofilm formation. The expression of these phenotypes in food spoiling and pathogenic bacteria, which may occur in food, can have dramatic consequences on food production, the economy, and health. Due to the many reports showing that the use of conventional methods (i.e., antibiotics and sanitizers) to inhibit bacterial growth leads to the emergence of antibiotic resistance, it is necessary to research and exploit new strategies. Several studies have already demonstrated positive results in this direction by inhibiting autoinducers (low-molecular-weight signaling compounds controlling QS) and by other means, leading to QS inhibition via a mechanism called quorum quenching (QQ). Thus far, several QS inhibitors (QSIs) have been isolated from various sources, such as plants, some animals from aqueous ecosystems, fungi, and bacteria. The present study aims to discuss the involvement of QS in food spoilage and to review the potential role of probiotics as QSIs.

Lactobacilli, a Weapon to Counteract Pathogens through the Inhibition of Their Virulence Factors

To date, several studies have reported an alarming increase in pathogen resistance to current antibiotic therapies and treatments. Therefore, the search for effective alternatives to counter their spread and the onset of infections is becoming increasingly important.

Acetate reprograms gut microbiota during alcohol consumption

Liver damage due to chronic alcohol use is among the most prevalent liver diseases. Alcohol consumption frequency is a strong factor of microbiota variance. Here we use isotope labeled [1-13C] ethanol, metagenomics, and metatranscriptomics in ethanol-feeding and intragastric mouse models to investigate the metabolic impacts of alcohol consumption on the gut microbiota. First, we show that although stable isotope labeled [1-13C] ethanol contributes to fatty acid pools in the liver, plasma, and cecum contents of mice, there is no evidence of ethanol metabolism by gut microbiota ex vivo under anaerobic conditions. Next, we observe through metatranscriptomics that the gut microbiota responds to ethanol-feeding by activating acetate dissimilation, not by metabolizing ethanol directly. We demonstrate that blood acetate concentrations are elevated during ethanol consumption. Finally, by increasing systemic acetate levels with glyceryl triacetate supplementation, we do not observe any impact on liver disease, but do induce similar gut microbiota alterations as chronic ethanol-feeding in mice. Our results show that ethanol is not directly metabolized by the gut microbiota, and changes in the gut microbiota linked to ethanol are a side effect of elevated acetate levels. De-trending for these acetate effects may be critical for understanding gut microbiota changes that cause alcohol-related liver disease.

Do Probiotics Prevent Clostridium difficile-Associated Diarrhea?

Clostridium difficile is a bacterium that affects the gastrointestinal tract and is the leading cause of antibiotic-associated diarrhea. A wide range of probiotics has been studied and used to prevent or treat Clostridium difficile-associated diarrhea (CDAD). Probiotics are microorganisms with unique characteristics that suppress dangerous gut bacteria through several mechanisms. The main objective of this study is to evaluate the efficacy and safety of probiotics in the prevention of CDAD. In this literature review, we searched PubMed and Google Scholar databases to gather related articles depending on predetermined eligibility criteria and found 13 papers of different study designs. We found that probiotics have promising effects in preventing CDAD. Additionally, they were safe and well-tolerated. Further randomized clinical trials with larger sample sizes and various patient groups are needed to better understand the advantages of probiotics and recommend the best dose and duration of probiotic treatment.

Black Seed Oil, Bentonite Clay, and Probiotics: A Comprehensive Holistic Cure for Clostridium difficile Infection in a 2-Year-Old Female Child

There has been a rise in antibiotic resistance in secondary conditions such as Clostridium difficile (C. difficile) due to overuse of antibiotics. Oral antibiotics are used to treat C. difficile, which further disrupts the intestinal flora resulting in unwanted side effects. Naturopathic treatments often have fewer side effects and lower secondary infection risk than pharmaceutical interventions making them ideal for pediatric use. This case report describes the effective treatment of a pediatric clinical case of C. difficile using naturopathic and complementary alternative medicines (CAMs) including black seed oil (Nigella sativa), bentonite clay, and probiotics. A healthy two-year-old patient presented to a pediatrician with symptoms of, and subsequently confirmed, C. difficile after having been recently hospitalized and treated for a gluteal abscess and cellulitis using clindamycin, vancomycin, and piperacillin/tazobactam. Through a shared decision-making process, the patient's mother and providers developed a treatment plan for the C. difficile infection (CDI), which included black seed oil, bentonite clay, and Lactobacillus probiotics. No C. difficile was detected via stool immunoassay after 4 days of combined CAM therapy. Our results underscore the need for additional research regarding the effectiveness of naturopathic CAMs including black seed oil, bentonite clay, and probiotics as alternatives to antibiotic treatment of CDI in children.

Bacteriocin-Producing Probiotic Lactic Acid Bacteria in Controlling Dysbiosis of the Gut Microbiota

Several strains of lactic acid bacteria are potent probiotics and can cure a variety of diseases using different modes of actions. These bacteria produce antimicrobial peptides, bacteriocins, which inhibit or kill generally closely related bacterial strains and other pathogenic bacteria such as Listeria, Clostridium, and Salmonella. Bacteriocins are cationic peptides that kill the target cells by pore formation and the dissipation of cytosolic contents, leading to cell death. Bacteriocins are also known to modulate native microbiota and host immunity, affecting several health-promoting functions of the host. In this review, we have discussed the ability of bacteriocin-producing probiotic lactic acid bacteria in the modulation of gut microbiota correcting dysbiosis and treatment/maintenance of a few important human disorders such as chronic infections, inflammatory bowel diseases, obesity, and cancer.

Inhibition of Virulence Gene Expression in Salmonella Dublin, Escherichia coli F5 and Clostridium perfringens Associated With Neonatal Calf Diarrhea by Factors Produced by Lactic Acid Bacteria During Fermentation of Cow Milk

Diarrhea is a major health problem in neonatal and young calves worldwide. It can be caused by a variety of infectious agents, including the bacteria Salmonella enterica serovar Dublin (S. Dublin), enterotoxigenic Escherichia coli (ETEC), and Clostridium perfringens. Preventive alternatives to antibiotic treatment should be identified. As a first step toward this, the aim of the current study was to examine whether cell-free supernatants from cow milk fermented by lactic acid bacteria affects virulence-gene expression in strains of S. Dublin, ETEC E. coli F5 and C. perfringens. pH-neutralized, cell-free, spent medium of milk (nCFSM) fermented by 61 different lactic acid bacteria (LAB) and non-LAB starter cultures belonging to 17 genera was assayed for their effect on expression of important virulence factors (S. Dublin hilA, ssrB, ssaG, flhD, prgI, fliC; ETEC E. coli F5 fanC, estA, fim41a; C. perfringens cpa), when the bacteria were grown in the nCFSM. Screening was done using either a promoter-reporter expression system or RT-qPCR. nCFSM from Bifidobacterium longum BL-15955 and Limosilactobacillus reuteri LR-33016 downregulated the expression of fanC, fim41a and estA genes in the four tested ETEC E. coli F5 strains without affecting their growth, while mainly B. longum BL-15955 downregulated expression of cpa in the four tested strains of C. perfringens. nCFSM from the mixed cultures; NU-TRISH^® BY-Mild (Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus and Bifidobacterium BL-15954) and COMBO4 (Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus), as well as Lactobacillus helveticus CNRZ32 downregulated the tested virulence genes in the three tested strains of S. Dublin. To enable possible downregulation of the expression of virulence genes in all three target bacteria simultaneously, nCFSM was prepared from NU-TRISH^® By-Mild in combination with B. longum BL-15955 (i.e. a four-strain combination). The nCFSM from this combination downregulated the virulence genes expression in all the three species. In the future, NU-TRISH^® By-Mild and B. longum BL-15955 in combination could potentially be used for prevention of neonatal calf diarrhea caused by S. Dublin, E. coli F5, and C. perfringens, reducing the need for antimicrobial treatment, however, field studies are needed to prove that.

Antilisterial Potential of Lactic Acid Bacteria in Eliminating Listeria monocytogenes in Host and Ready-to-Eat Food Application

Listeriosis is a severe food borne disease with a mortality rate of up to 30% caused by pathogenic Listeria monocytogenes via the production of several virulence factors including listeriolysin O (LLO), transcriptional activator (PrfA), actin (Act), internalin (Int), etc. It is a foodborne disease predominantly causing infections through consumption of contaminated food and is often associated with ready-to-eat food (RTE) and dairy products. Common medication for listeriosis such as antibiotics might cause an eagle effect and antibiotic resistance if it is overused. Therefore, exploration of the use of lactic acid bacteria (LAB) with probiotic characteristics and multiple antimicrobial properties is increasingly getting attention for their capability to treat listeriosis, vaccine development, and hurdle technologies. The antilisterial gene, a gene coding to produce antimicrobial peptide (AMP), one of the inhibitory substances found in LAB, is one of the potential key factors in listeriosis treatment, coupled with the vast array of functions and strategies; this review summarizes the various strategies by LAB against L. monocytogenes and the prospect in development of a ‘generally regarded as safe’ LAB for treatment of listeriosis.

Potential role of probiotics in reducing Clostridioides difficile virulence: Interference with quorum sensing systems

Opportunistic pathogenic bacteria may cause disease after the normally protective microbiome is disrupted (typically by antibiotic exposure). Clostridioides difficile is one such pathogen having a severe impact on healthcare facilities and increasing costs of medical care. The search for new therapeutic strategies that are not reliant on additional antibiotic exposures are currently being explored. One such strategy is to disrupt the production of C. difficile virulence factors by interfering with quorum sensing (QS) systems. QS has been well studied in other bacteria, but our understanding in C. difficile is not so well understood. Some probiotic strains or combinations of strains have been shown to be effective in the treatment or primary prevention of C. difficile infections and may possess multiple mechanisms of action. One mechanism of probiotics might be the inhibition of QS, but their role has not been clearly defined yet. A literature search was conducted using standard databases (PubMed, Google Scholar) from database inception to August 2020. The objective of this paper is to update our understanding of how QS leads to toxin production by C. difficile, which is important in pathogenesis, and how QS inhibitors or probiotics may disrupt this pathway. We found two main QS systems for C. difficile (Agr and Lux systems) that are involved in C. difficile pathogenesis by regulating toxin production, motility and adherence. Probiotics and other QS inhibitors targeting QS systems may represent important new directions of therapy and prevention of CDI.

Current and Future Perspectives on the Role of Probiotics, Prebiotics, and Synbiotics in Controlling Pathogenic Cronobacter Spp. in Infants

Cronobacter species, in particular C. sakazakii, is an opportunistic bacterial pathogen implicated in the development of potentially debilitating illnesses in infants (<12months old). The combination of a poorly developed immune system and gut microbiota put infants at a higher risk of infection compared to other age groups. Probiotics and prebiotics are incorporated in powdered infant formula and, in addition to strengthening gut physiology and stimulating the growth of commensal gut microbiota, have proven antimicrobial capabilities. Postbiotics in the cell-free supernatant of a microbial culture are derived from probiotics and can also exert health benefits. Synbiotics, a mixture of probiotics and prebiotics, may provide further advantages as probiotics and gut commensals degrade prebiotics into short-chain fatty acids that can provide benefits to the host. Cell-culture and animal models have been widely used to study foodborne pathogens, but sophisticated gut models have been recently developed to better mimic the gut conditions, thus giving a more accurate representation of how various treatments can affect the survival and pathogenicity of foodborne pathogens. This review aims to summarize the current understanding on the connection between Cronobacter infections and infants, as well as highlight the potential efficacy of probiotics, prebiotics, and synbiotics in reducing invasive Cronobacter infections during early infancy.

Recent advances in the application of probiotic yeasts, particularly Saccharomyces, as an adjuvant therapy in the management of cancer with focus on colorectal cancer

Today, the increasing rate of cancer-related mortality, has rendered cancer a major global challenge, and the second leading cause of death worldwide. Conventional approaches in the treatment of cancer mainly include chemotherapy, surgery, immunotherapy, and radiotherapy. However, these approaches still come with certain disadvantages, including drug resistance, and different side effects such as gastrointestinal (GI) irritation (e.g., diarrhea, mucositis). This has encouraged scientists to look for alternative therapeutic methods and adjuvant therapies for a more proper treatment of malignancies. Application of probiotics as an adjuvant therapy in the clinical management of cancer appears to be a promising strategy, with several notable advantages, e.g., increased safety, higher tolerance, and negligible GI side effects. Both in vivo and in vitro analyses have indicated the active role of yeast probiotics in mitigating the rate of cancer cell proliferation, and the induction of apoptosis through regulating the expression of cancer-related genes and cellular pathways. Strain-specific anti-cancer activities of yeast probiotics strongly suggest that their administration along with the current cancer therapies may be an efficient method to reduce the side effects of these approaches. The main purpose of this article is to evaluate the efficacy of yeast probiotics in alleviating the adverse effects associated with cancer therapies.

Anti-virulence strategies for Clostridioides difficile infection: advances and roadblocks

Clostridioides difficile infection (CDI) is a common healthcare- and antibiotic-associated diarrheal disease. If mis-diagnosed, or incompletely treated, CDI can have serious, indeed fatal, consequences. The clinical and economic burden imposed by CDI is great, and the US Centers for Disease Control and Prevention has named the causative agent, C. difficile (CD), as an Urgent Threat To US healthcare. CDI is also a significant problem in the agriculture industry. Currently, there are no FDA-approved preventives for this disease, and the only approved treatments for both human and veterinary CDI involve antibiotic use, which, ironically, is associated with disease relapse and the threat of burgeoning antibiotic resistance. Research efforts in multiple laboratories have demonstrated that non-toxin factors also play key roles in CDI, and that these are critical for disease. Specifically, key CD adhesins, as well as other surface-displayed factors have been shown to be major contributors to host cell attachment, and as such, represent attractive targets for anti-CD interventions. However, research on anti-virulence approaches has been more limited, primarily due to the lack of genetic tools, and an as-yet nascent (but increasingly growing) appreciation of immunological impacts on CDI. The focus of this review is the conceptualization and development of specific anti-virulence strategies to combat CDI. Multiple laboratories are focused on this effort, and the field is now at an exciting stage with numerous products in development. Herein, however, we focus only on select technologies (Figure 1) that have advanced near, or beyond, pre-clinical testing (not those that are currently in clinical trial), and discuss roadblocks associated with their development and implementation.

The Effect of Athletes' Probiotic Intake May Depend on Protein and Dietary Fiber Intake

Studies investigating exercise-induced gut microbiota have reported that people who exercise regularly have a healthy gut microbial environment compared with sedentary individuals. In contrast, recent studies have shown that high protein intake without dietary fiber not only offsets the positive effect of exercise on gut microbiota but also significantly lowers the relative abundance of beneficial bacteria. In this study, to resolve this conundrum and find the root cause, we decided to narrow down subjects according to diet. Almost all of the studies had subjects on an ad libitum diet, however, we wanted subjects on a simplified diet. Bodybuilders who consumed an extremely high-protein/low-carbohydrate diet were randomly assigned to a probiotics intake group (n = 8) and a placebo group (n = 7) to find the intervention effect. Probiotics, comprising Lactobacillus acidophilus, L. casei, L. helveticus, and Bifidobacterium bifidum, were consumed for 60 days. As a result, supplement intake did not lead to a positive effect on the gut microbial environment or concentration of short-chain fatty acids (SCFAs). It has been shown that probiotic intake is not as effective as ergogenic aids for athletes such as bodybuilders with extreme dietary regimens, especially protein and dietary fiber. To clarify the influence of nutrition-related factors that affect the gut microbial environment, we divided the bodybuilders (n = 28) into groups according to their protein and dietary fiber intake and compared their gut microbial environment with that of sedentary male subjects (n = 15). Based on sedentary Korean recommended dietary allowance (KRDA), the bodybuilders′ intake of protein and dietary fiber was categorized into low, proper, and excessive groups, as follows: high-protein/restricted dietary fiber (n = 12), high-protein/adequate dietary fiber (n = 10), or adequate protein/restricted dietary fiber (n = 6). We found no significant differences in gut microbial diversity or beneficial bacteria between the high-protein/restricted dietary fiber and the healthy sedentary groups. However, when either protein or dietary fiber intake met the KRDA, gut microbial diversity and the relative abundance of beneficial bacteria showed significant differences to those of healthy sedentary subjects. These results suggest that the positive effect of exercise on gut microbiota is dependent on protein and dietary fiber intake. The results also suggest that the question of adequate nutrition should be addressed before supplementation with probiotics to derive complete benefits from the intervention.

A newly isolated E. thailandicus strain d5B with exclusively antimicrobial activity against C. difficile might be a novel therapy for controlling CDI

Colitis induced by C. difficile is one of the most common and costly healthcare-related infections for humans. Probiotics are one of the most promising approaches for controlling CDI. Here, we presented the isolation, safety, and probiotic property evaluation of a novel E. thailandicus strain, d5B, with effective antimicrobial activity against C. difficile. Strain d5B showed strong bactericidal effects on at least 54C. difficile strains. Safety tests showed that strain d5B was sensitive to clinically important antibiotics, and had no haemolytic and cytotoxic activities. Whole genomic analysis showed strain d5B only contained one aminoglycoside resistance gene located in the chromosome. Moreover, d5B was devoid of functional virulence genes. Finally, strain d5B exhibited probiotic properties, such as tolerance to the gastrointestinal tract, and adhered well to HT-29 cells. In conclusion, the E. thailandicus strain d5B should be investigated further for useful properties as a novel candidate probiotic for controlling CDI.

Controlling foodborne pathogens with natural antimicrobials by biological control and antivirulence strategies

Foodborne diseases represent a global health threat besides the great economic losses encountered by the food industry. These hazards necessitate the implementation of food preservation methods to control foodborne pathogens, the causal agents of human illnesses. Until now, most control methods rely on inhibiting the microbial growth or eliminating the pathogens by applying lethal treatments. Natural antimicrobials, which inhibit microbial growth, include traditional chemicals, naturally occurring antimicrobials, or biological preservation (e.g. beneficial microbes, bacteriocins, or bacteriophages). Although having great antimicrobial effectiveness, challenges due to the adaptation of foodborne pathogens to such control methods are becoming apparent. Such adaptation enables the survival of the pathogens in foods or food-contact environments. This imperative concern inspires contemporary research and food industry sector to develop technologies which do not target microbial growth but disarming microbial virulence factors. These technologies, referred to as "antivirulence", render the microbe non-capable of causing the disease with very limited or no opportunities for the pathogenic microorganisms to develop resistance. For the sake of safer and fresh-like foods, with no effect on the sensory properties of foods, a combination of two or more natural antimicrobials or with other stressors, is now widespread, to preserve foods. This review introduces and critically describes the traditional versus the emerging uses of natural antimicrobials for controlling foodborne pathogens in foods. Development of biological control strategies using natural antimicrobials proved to be effective in inhibiting microbial growth in foods and allowing improved food safety. In the meanwhile, discovery of new antivirulence agents could be a transformative strategy in food preservation in the far future.

The mechanisms and safety of probiotics against toxigenic clostridium difficile

INTRODUCTION

Toxigenic Clostridium difficile (C. difficile) is the main cause of antibiotic-associated diarrhea and can induce pseudomembranous colitis and infrequent toxic megacolon, which are potentially fatal. The standard antibiotic therapy for C. difficile infection (CDI) is limited by antibiotics' broad spectrum and further disruptive effects on indigenous microbiota. Probiotics may offer a prospective and alternative strategy for the prevention and treatment of CDI.

AREAS COVERED

In this article, the mechanisms implying the probiotic effect against C. difficile and the safety profile highlighting the patient groups with inappropriate application of probiotics were reviewed from 2015 to 2020.

EXPERT OPINION

Although many strains with ability against C. difficile have been reported, the usage of probiotics for CDI prevention and/or treatment is scarce since the number of clinical trials is not sufficient to prove probiotics' efficacy and safety in CDI treatment, especially for premature infant and immunocompromised patient. Especially, there are few well-defined clinical studies supporting safety of probiotics for CDI. A few strains from Lactobacillus and Saccharomyces genus have been studied more extensively than other probiotic strains through clinical trials for CDI. Thus, more clinical intervention studies regarding the benefit and the comprehensive safety assessments of probiotics for CDI are needed.

Microbiota in vitro modulated with polyphenols shows decreased colonization resistance against Clostridioides difficile but can neutralize cytotoxicity

While the knowledge on gut microbiota - C. difficile interactions has improved over the years, the understanding of the underlying mechanisms providing colonization resistance as well as preventative measures against the infection remain incomplete. In this study the antibiotic clindamycin and polyphenol extracts from pomegranate and blueberries were used individually and in combination to modulate fecal microbial communities in minibioreactor arrays (MBRA). Modulated communities were inoculated with C. difficile (ribotype 027). Subsequent 7-day periodical monitoring included evaluation of C. difficile growth and activity of toxins TcdA and TcdB as well as analysis of MBRA bacterial community structure (V3V4 16 S metagenomics). Polyphenols affected multiple commensal bacterial groups and showed different synergistic and antagonistic effects in combination with clindamycin. Exposure to either clindamycin or polyphenols led to the loss of colonization resistance against C. difficile. The successful growth of C. difficile was most significantly correlated with the decrease in Collinsella and Lachnospiraceae. Additionally, we demonstrated that Clostridium sporogenes decreased the activity of both C. difficile toxins TcdA and TcdB. The feature was shown to be common among distinct C. sporogenes strains and could potentially be applicable as a non-antibiotic agent for the alleviation of C. difficile infection.

Inhibitory effect of fidaxomicin on biofilm formation in Clostridioides difficile

Clostridioides difficile infection results from a disturbance of the normal microbial flora of the colon, allowing proliferation of C. difficile and toxin production by toxigenic strains. Fidaxomicin, a macrocyclic antibiotic that prevents RNA synthesis in C. difficile and inhibits spore formation, toxin production, and cell proliferation, is clinically effective in treating C. difficile infection. As recent studies have suggested that biofilm formation influences C. difficile colonization and infection in the colon, we undertook the present study to determine the effects of fidaxomicin on C. difficile biofilm formation. Sub-minimum inhibitory concentrations (MICs) of fidaxomicin inhibited biofilm formation by C. difficile UK027 and delayed planktonic growth. Sub-MICs of vancomycin did not inhibit biofilm formation or affect planktonic growth. In C. difficile UK027 exposed to sub-MICs of fidaxomicin, mRNA expression of biofilm-related flagellin gene fliC was slightly increased compared with that of other biofilm-related genes (pilA1, cwp84, luxS, dccA, and spo0A). In conclusion, this study indicates that sub-MICs of fidaxomicin inhibit C. difficile UK027 biofilm formation by influencing cell growth and fliC transcription.

Proteobiotics as a new antimicrobial therapy

Antibiotic resistance is a major concern for healthcare. The emergence of resistant bacteria has contributed to an increase in cost, morbidity, and mortality rates of patients. There is evidence to suggest that the inhibition of bacteria's virulence strategies would downregulate their pathogenesis and stop infections while also preventing more resistance. This concept became the backbone of many studies in the arena of human microbiome. Through probiotic studies, novel compounds were discovered that possessed antimicrobial activity. These have become labeled as proteobiotics, i.e. metabolites from probiotics. Proteobiotics have demonstrated the ability to interrupt bacteria cell-to-cell communication. Currently, there is one approved product containing proteobiotic technologies for swine showing positive outcomes.

Microbe-microbe interactions during Clostridioides difficile infection

Clostridioides difficile is the leading cause of hospital-acquired gastrointestinal infections and a major public health burden in the United States. C. difficile infection causes a spectrum of disease from mild diarrhea to severe complications such as pseudomembranous colitis, toxic megacolon and death. This broad range of disease is only partially explained by bacterial genetic factors, host genetics, comorbidities and previous drug exposures. Another important factor is the gut microbiome, the disruption of which results in a loss of colonization resistance to C. difficile. Here, we review how gut microbiota and their metabolites impact C. difficile virulence and influence disease.

Effect of soybean oligopeptide on the growth and metabolism of Lactobacillus acidophilus JCM 1132

Soybean protein (Pro) and soybean oligopeptide (Pep) were subjected to simulated digestion in vitro to study the effect of Pep on the growth and metabolism of Lactobacillus acidophilus JCM 1132. First, the molecular weight distribution differences of samples before and after digestion were compared, and the samples were used to replace the nitrogen source components in the culture media. Then, the viable cell numbers, lactic acid and acetic acid content, differential metabolites, and metabolic pathways during the culturing process were measured. Results showed that the digested soybean oligopeptide (dPep) was less efficient than MRS medium in promoting the growth, but by increasing the content of the intermediates during the tricarboxylic acid (TCA) cycle, its metabolic capacity was significantly improved. Besides, due to the low molecular weight of dPep, it can be better transported and utilized. And dPep significantly strengthened the amino acid metabolism and weakened the glycerol phospholipid metabolism, so the ability of dPep in promoting the growth and metabolism of Lactobacillus acidophilus JCM 1132 is higher than the digested soybean protein (dPro).

Exploring the effect of soybean oligopeptide on the growth and metabolism of Lactobacillus acidophilus JCM 1132 by metabolomics.

Antibacterial Activity of Bifidobacterium breve Against Clostridioides difficile

Bifidobacterium breve (YH68) is widely used in the fields of food fermentation and biomedicine. In this study, we explored the antibacterial activity of the cell free culture supernatant (CFCS) of YH68 against Clostridioides difficile ATCC 9689 (CD) by measuring multiple indexes, including the growth, spores production, toxin A/B production, and the expression levels of the tcdA and tcdB genes of CD. In addition, we examined the changes in major cellular functional groups, structures, permeability, integrity, and the proton motive force (PMF) of the cytoplasmic membrane. The results showed that double-dilution ratio of YH68-CFCS (3 × 10⁹ CFU/mL) was the MIC value. The cell density, spores production, and the toxin production of CD treated with YH68-CFCS were lower than that of the control (p < 0.05). In addition, the gene expression levels of tcdA and tcdB in CD treated with YH68-CFCS were significant downregulated (p < 0.05). Marked differences were observed in the cell membrane and cell wall by a FT-IR spectroscopy and SEM. Analysis of the cell membrane permeability and integrity of the CD cells revealed that YH68-CFCS induced the leakage of a large amount of intracellular K⁺, inorganic phosphate, ATP, nucleic acids and proteinaceous substances. Furthermore, PMF analysis indicated that there was a significant change in Δψ and ΔpH. These findings demonstrated that the antibacterial activity of YH68-CFCS against CD involved the inhibition of growth, spore production, toxin production, and virulence genes expression; a consumption of PMF in the cytoplasmic membrane, the formation of pore in the cell membrane, together with the enhanced cell membrane permeability; and, eventually, cell completely disintegration.

Downregulation of Salmonella Virulence Gene Expression During Invasion of Epithelial Cells Treated with Lactococcus lactis subsp. cremoris JFR1 Requires OppA

Invasion of Salmonella into host intestinal epithelial cells requires the expression of virulence genes. In this study, cell culture models of human intestinal cells (mucus-producing HT29-MTX cells, absorptive Caco-2 cells, and combined cocultures of the two) were used to determine the effects of Lactococcus lactis subsp. cremoris treatments (exopolysaccharide producing and nonproducing strains) on the virulence gene expression of Salmonella Typhimurium and its mutant lacking the oligopeptide permease subunit A (ΔoppA). During the course of epithelial cell (HT29-MTX, Caco-2, and combined) infection by Salmonella Typhimurium DT104, improved barrier function was reflected by increased transepithelial electrical resistance in cells treated with both strains of L. lactis subsp. cremoris. In addition, virulence gene expression was downregulated, accompanied with lower numbers of invasive bacteria into epithelial cells in the presence of L. lactis subsp. cremoris treatments. Similarly, virulence gene expression of Salmonella was also suppressed when coincubated with overnight cultures of both L. lactis subsp. cremoris strains in the absence of epithelial cells. However, in medium or in the presence of cell cultures, Salmonella lacking the OppA permease function remained virulent. HT29-MTX cells and combined cultures stimulated by Salmonella Typhimurium DT104 showed significantly lower secretion levels of pro-inflammatory cytokine IL-8 after treatment with L. lactis subsp. cremoris cell suspensions. Contrarily, these responses were not observed during infection with S. Typhimurium ΔoppA. Both the exopolysaccharide producing and nonproducing strains of L. lactis subsp. cremoris JFR1 exhibited an antivirulence effect against S. Typhimurium DT104 although no significant difference between the two strains was observed. Our results show that an intact peptide transporter is essential for the suppression of Salmonella virulence genes which leads to the protection of the barrier function in the cell culture models studied.

High sporulation and overexpression of virulence factors in biofilms and reduced susceptibility to vancomycin and linezolid in recurrent Clostridium [Clostridioides] difficile infection isolates

Clostridium [Clostridioides] difficile infection (CDI) is one of the leading causes of diarrhea associated with medical care worldwide, and up to 60% of patients with CDI can develop a recurrent infection (R-CDI). A multi-species microbiota biofilm model of C. difficile was designed to evaluate the differences in the production of biofilms, sporulation, susceptibility to drugs, expression of sporulating (sigH, spo0A), quorum sensing (agrD1, and luxS), and adhesion-associated (slpA and cwp84) pathway genes between selected C. difficile isolates from R-CDI and non-recurrent patients (NR-CDI). We obtained 102 C. difficile isolates from 254 patients with confirmed CDI (66 from NR-CDI and 36 from R-CDI). Most of the isolates were biofilm producers, and most of the strains were ribotype 027 (81.374%, 83/102). Most C. difficile isolates were producers of biofilm (100/102), and most were strongly adherent. Sporulation was higher in the R-CDI than in the NR-CDI isolates (p = 0.015). The isolates from R-CDI patients more frequently demonstrated reduced susceptibility to vancomycin than isolates of NR-CDI patients (27.78% [10/36] and 9.09% [6/66], respectively, p = 0.013). The minimum inhibitory concentrations for vancomycin and linezolid against biofilms (BMIC) were up to 100 times and 20 times higher, respectively, than the corresponding planktonic MICs. Expression of sigH, spo0A, cwp84, and agrD1 was higher in R-CDI than in NR-CDI isolates. Most of the C. difficile isolates were producers of biofilms with no correlation with the ribotype. Sporulation was greater in R-CDI than in NR-CDI isolates in the biofilm model of C. difficile. The R-CDI isolates more frequently demonstrated reduced susceptibility to vancomycin and linezolid than the NR-CDI isolates in both planktonic cells and biofilm isolates. A higher expression of sporulating pathway (sigH, spo0A), quorum sensing (agrD1), and adhesion-associated (cwp84) genes was found in R-CDI than in NR-CDI isolates. All of these factors can have effect on the recurrence of the infection.

Inhibition of Clostridium difficile in Mice Using a Mixture of Potential Probiotic Strains Enterococcus faecalis NM815, E. faecalis NM915, and E. faecium NM1015: Novel Candidates to Control C. difficile Infection (CDI)

This study is aimed at the isolation, identification, and characterization of potential probiotic strains capable of inhibiting Clostridium difficile in vitro and in vivo. Twenty isolates were isolated from infant fecal samples and screened against C. difficile using their cell-free supernatant. Only three isolates showed maximum inhibition from 56.05 to 60.60%, thus they were characterized for probiotic properties and safety. The results obtained approved their tolerance to the gastrointestinal tract conditions and safety profile. They were identified by sequencing 16S rRNA as Enterococcus faecalis NM815, E. faecalis NM915, and Enterococcus faecium NM1015. For in vivo evaluation, a viable mixture of these three strains (10⁹ CFU/mL) was administrated to a group of mice (treated group) in daily dose for 14 days, then followed by challenge with viable C. difficile (10⁵ CFU/mL) in daily dose for 7 days, then a second administration of a viable mixture of the three strains was done daily for 7 days. In addition, the control group was administered PBS buffer only and the untreated group received PBS buffer instead of the probiotic mixture before and after the challenge with C. difficile. The results obtained from histological analysis confirmed the effectiveness of our three potential probiotic strains which expressed inhibition of C. difficile and maintained the structural integrity of the liver and intestinal cells.

Evaluation of protective effect of Lactobacillus acidophilus La-5 on toxicity and colonization of Clostridium difficile in human epithelial cells in vitro

Clostridium difficile infection is a range of toxin - mediated intestinal diseases that is often acquired in hospitals and small communities in developed countries. The main virulence factors of C. difficile are two exotoxins, toxin A and toxin B, which damage epithelial cells and manifest as colonic inflammation and mild to severe diarrhea. Inhibiting C. difficile adherence, colonization, and reducing its toxin production could substantially minimize its pathogenicity and lead to faster recovery from the disease. This study investigated the efficacy of probiotic secreted bioactive molecules from Lactobacillus acidophilus La-5, in decreasing C. difficile attachment and cytotoxicity in human epithelial cells in vitro. L. acidophilus La-5 cell-free supernatant (La-5 CFS) was used to treat the hypervirulent C. difficile ribotype 027 culture with subsequent monitoring of cytotoxicity and adhesion. In addition, the effect of pretreating cell lines with La-5 CFS in protecting cells from the cytotoxicity of C. difficile culture filtrate or bacterial cell attachment was examined. La-5 CFS substantially reduced the cytotoxicity and cytopathic effect of C. difficile culture filtrate on HT-29 and Caco-2 cells. Furthermore, La-5 CFS significantly reduced attachment of the C. difficile bacterial cells on both cell lines. It was also found that pretreatment of cell lines with La-5 CFS effectively protected cell lines from cytotoxicity and adherence of C. difficile. Our study suggests that La-5 CFS could potentially be used to prevent and cure C. difficile infection and relapses.

Postnatal Administration of Lactobacillus rhamnosus HN001 Ameliorates Perinatal Broad-Spectrum Antibiotic-Induced Reduction in Myelopoiesis and T Cell Activation in Mouse Pups

SCOPE

This study addresses whether administration of Lactobacillus rhamnosus HN001 could mitigate the effects of a compromised gut microbiota on the composition of mature leukocytes and granulocyte-macrophage progenitor cells (GMPs) in newborn mice.

METHODS AND RESULTS

Pregnant dams receive oral broad-spectrum antibiotics, which dramatically decrease the gut microbial composition analyzed by 16S rRNA sequencing. Perinatal antibiotic treatment decreases the proportions of bone marrow (BM) GMPs (postnatal day (PND2): 0.5% vs 0.8%, PND4: 0.2% to 0.6%) and mature granulocytes (33% vs 24% at PND2), and spleen granulocytes (7% vs 17% at PND2) and B cells (PND2:18% vs 28%, PND4:11% vs 22%). At PND35, T helper (Th) cells (20% vs 14%) and cytotoxic T (Tc) cells (10% vs 8%) decrease in the spleen. Oral administration of L. rhamnosus HN001 to neonatal pups (PND1-7) restores the antibiotic-induced changes of GMPs and granulocytes in BM and spleen, and further increases splenic granulocytes in control pups. At PND35, splenic proportions of B and Th but not Tc cells are restored.

CONCLUSION

Postnatal administration of a single bacterial strain efficiently restores granulopoiesis and most T cell activation in neonatal mice that suffer from a perinatal antibiotic-induced compromised gut microbiota at birth.

An Engineered Synthetic Biologic Protects Against Clostridium difficile Infection

Morbidity and mortality attributed to Clostridium difficile infection (CDI) have increased over the past 20 years. Currently, antibiotics are the only US FDA-approved treatment for primary C. difficile infection, and these are, ironically, associated with disease relapse and the threat of burgeoning drug resistance. We previously showed that non-toxin virulence factors play key roles in CDI, and that colonization factors are critical for disease. Specifically, a C. difficile adhesin, Surface Layer Protein A (SlpA) is a major contributor to host cell attachment. In this work, we engineered Syn-LAB 2.0 and Syn-LAB 2.1, two synthetic biologic agents derived from lactic acid bacteria, to stably and constitutively express a host-cell binding fragment of the C. difficile adhesin SlpA on their cell-surface. Both agents harbor conditional suicide plasmids expressing a codon-optimized chimera of the lactic acid bacterium's cell-wall anchoring surface-protein domain, fused to the conserved, highly adherent, host-cell-binding domain of C. difficile SlpA. Both agents also incorporate engineered biocontrol, obviating the need for any antibiotic selection. Syn-LAB 2.0 and Syn-LAB 2.1 possess positive biophysical and in vivo properties compared with their parental antecedents in that they robustly and constitutively display the SlpA chimera on their cell surface, potentiate human intestinal epithelial barrier function in vitro, are safe, tolerable and palatable to Golden Syrian hamsters and neonatal piglets at high daily doses, and are detectable in animal feces within 24 h of dosing, confirming robust colonization. In combination, the engineered strains also delay (in fixed doses) or prevent (when continuously administered) death of infected hamsters upon challenge with high doses of virulent C. difficile. Finally, fixed-dose Syn-LAB ameliorates diarrhea in a non-lethal model of neonatal piglet enteritis. Taken together, our findings suggest that the two synthetic biologics may be effectively employed as non-antibiotic interventions for CDI.

Probiotics for Prevention and Treatment of Clostridium difficile Infection

Probiotics have been claimed as a valuable tool to restore the balance in the intestinal microbiota following a dysbiosis caused by, among other factors, antibiotic therapy. This perturbed environment could favor the overgrowth of Clostridium difficile and, in fact, the occurrence of C. difficile-associated infections (CDI) is being increasing in recent years. In spite of the high number of probiotics able to in vitro inhibit the growth and/or toxicity of this pathogen, its application for treatment or prevention of CDI is still scarce since there are not enough well-defined clinical studies supporting efficacy. Only a few strains, such as Lactobacillus rhamnosus GG and Saccharomyces boulardii have been studied in more extent. The increasing knowledge about the probiotic mechanisms of action against C. difficile, some of them reviewed here, makes promising the application of these live biotherapeutic agents against CDI. Nevertheless, more effort must be paid to standardize the clinical studied conducted to evaluate probiotic products, in combination with antibiotics, in order to select the best candidate for C. difficile infections.

Evaluation of Lactic Acid Bacteria on the Inhibition of Vibrio parahaemolyticus Infection and Its Application to Food Systems

This study tested the effect of lactic acid bacteria (LAB) inhibition on Vibrio parahaemolyticus BCRC (Bioresource Collection and Research Center) 10806 and BCRC 12865 in a food model. MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assays indicated that Caco-2 cells were not damaged after a two-hour treatment with lactic acid bacteria (LAB) and V. parahaemolyticus. The LAB cell culture and supernatant effectively inhibited the growth of V. parahaemolyticus in a food model. ELISA (Enzyme-linked immunosorbent assay) results indicated the significant inhibition of TNF-α; IL-1β; and IL-6; but Lactobacillus plantarum PM 222 and L. plantarum LP 735 did not significantly affect IL-8 levels. Real-time polymerase chain reaction (PCR) results indicated that LAB could inhibit the mRNA expression of proinflammatory cytokines IL-8; IL-6; and TNF-α; which were induced by V. parahaemolyticus. After rat-received LAB; the expression levels of TNF-α; IL-6; and IL-8 in the serum decreased significantly. In intestinal histology; the rat that received L. plantarum PM 222 and L. plantarum LP 010 was able to alleviate the intestinal villi damage caused by V. parahaemolyticus; which also helped reduce cell apoptosis. In conclusion; our results indicate that LAB can inhibit inflammatory responses caused by V. parahaemolyticus and can effectively inhibit the growth of V. parahaemolyticus in food products.

Using murine colitis models to analyze probiotics-host interactions

Probiotics are defined as 'live microorganisms which when administered in adequate amounts confer a health benefit on the host'. So, to consider a microorganism as a probiotic, a demonstrable beneficial effect on the health host should be shown as well as an adequate defined safety status and the capacity to survive transit through the gastrointestinal tract and to storage conditions. In this review, we present an overview of the murine colitis models currently employed to test the beneficial effect of the probiotic strains as well as an overview of the probiotics already tested. Our aim is to highlight both the importance of the adequate selection of the animal model to test the potential probiotic strains and of the value of the knowledge generated by these in vivo tests.

Potential Probiotic Microorganisms in Kefir

Probiotic microorganisms are defined as living microorganisms that provide health benefits on the host when administered in adequate amounts. The benefits include improvement of microbial balance immune system and oral health, provision of cholesterol-lowering effect, and antimicrobial activity against a wide variety of bacteria and some fungi. Kefir microbiota contains active living microorganisms. Many researches were carried out that potential probiotic bacteria such as Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus kefir, Lactobacillus kefiranofaciens, Leuconostoc mesenteroides, or yeasts like microorganisms such as Saccharomyces cerevisiae, Kluyveromyces lactis, and Kluyveromyces marxianus were isolated from kefir grains. This chapter presents the data both on the probiotic bacteria isolated from kefir grains or kefir and the probiotic properties of kefir produced with these microorganisms.

Molecules produced by probiotics prevent enteric colibacillosis in pigs

BACKGROUND

With the advent of antimicrobial resistance in animal pathogens, novel methods to combat infectious diseases are being sought. Among these, probiotics have been proposed as a means of promoting animal health but problems with their use has been reported. Research has demonstrated that bioactive molecules produced during the growth of certain probiotics interfere with bacterial cell-to-cell communication, which consequently results in an attenuation of virulence in a number of pathogens, including E. coli. The objective of this study was to determine the efficacy of the bioactive molecules, termed proteobiotics, produced by Lactobacillus acidophilus in preventing enterotoxigenic E, coli (ETEC) infection in pigs, which is the etiological agent for enteric colibacillosis, a common disease of nursing and young pigs.

RESULTS

To achieve this, piglets were fed a preparation of the bioactive at four levels: 0, 0.5×, 1.0× and 2.0× for 7 days prior to challenge with E. coli K88. There were 36 pigs (18 gilts and 18 barrows) per treatment, resulting in 144 piglets in total for the study. Each pen had 6 piglets (3 gilts and 3 barrows). Only piglets with no physical abnormality or conditions were used in the trial and intact male piglets and ridglings were excluded. The bioactive continued to be fed to the pigs post-challenge. Based of fecal and demeanour scores, pigs fed the low and high dose of the proteobiotic were significanlty less likely to show symptoms of illness than pigs fed no bioactive. While not being significant, the weight gain of pigs given the proteobiotics was improved. At day 4 following challenge, almost 50% of piglets that did not receive the proteobiotic were shedding ETEC in their feces, compared with about 15% of animals receiving the supplement. There was also an indication that the proteobiotics reduced colonization of the ileum by E. coli K88 and improved gut health.

CONCLUSION

This study indicates that the bioactive molecules produced by L. acidophilus reduces incidence of enteric colibacillosis in pigs and their use on farms would help to reduce antibiotic use.

Two Lactobacillus Species Inhibit the Growth and α-Toxin Production of Clostridium perfringens and Induced Proinflammatory Factors in Chicken Intestinal Epithelial Cells in Vitro

Clostridium perfringens is the causative pathogen of avian necrotic enteritis. Lactobacillus spp. are well-characterized probiotics with anti-microbial and immune-modulatory activities. In the present study, we investigated the effects of L. acidophilus and L. fermentum on the growth, α-toxin production and inflammatory responses of C. perfringens. In in vitro culture experiments, both lactobacilli inhibited the growth of C. perfringens (P < 0.01), accompanied with a decrease in pH (P < 0.01). Supernatants from lactobacilli cultures also suppressed the growth of C. perfringens during 24 h of incubation (P < 0.01), but this inhibitory effect disappeared after 48 h. Both lactobacilli decreased the α-toxin production of C. perfringens (P < 0.01) without influencing its biomass, and even degraded the established α-toxin (P < 0.01). Lower environmental pH reduced the α-toxin production as well (P < 0.01). Preincubation with L. acidophilus decreased the attachment of C. perfringens to cells (P < 0.01) with the cell cytotoxicity being unaffected. Both lactobacilli pretreatment reduced the up-regulation of proinflammatory factors, peptidoglycan (PGN) receptors and nuclear factor kappa B (NF-κB) p65 in C. perfringens-challenged chicken intestinal epithelial cells (P < 0.05). In conclusion, L. acidophilus and L. fermentum inhibited the pathological effects of C. perfringens in vitro conditions.

Beneficial Effect of Bifidobacterium longum ATCC 15707 on Survival Rate of Clostridium difficile Infection in Mice

Clostridium difficile infection (CDI) is the main cause of hospital-acquired diarrhea that can cause colitis or even death. The medical-treatment cost and deaths caused by CDI are increasing annually worldwide. New approaches for prevention and treatment of these infections are needed, such as the use of probiotics. Probiotics, including Bifidobacterium spp. and Lactobacillus, are microorganisms that confer a health benefit to the host when administered in adequate amounts. The effect of Bifidobacterium longum ATCC 15707 on infectious disease caused by C. difficile 027 was investigated in a mouse model. The survival rates for mice given the pathogen alone, and with live cells, or dead cells of B. longum were 40, 70, and 60%, respectively. In addition, the intestinal tissues of the B. longum-treated group maintained structural integrity with some degree of damage. These findings suggested that B. longum ATCC 15707 has a function in repressing the infectious disease caused by C. difficile 027.

A common bacterial metabolite elicits prion-based bypass of glucose repression

Robust preference for fermentative glucose metabolism has motivated domestication of the budding yeast Saccharomyces cerevisiae. This program can be circumvented by a protein-based genetic element, the [GAR⁺] prion, permitting simultaneous metabolism of glucose and other carbon sources. Diverse bacteria can elicit yeast cells to acquire [GAR⁺], although the molecular details of this interaction remain unknown. Here we identify the common bacterial metabolite lactic acid as a strong [GAR⁺] inducer. Transient exposure to lactic acid caused yeast cells to heritably circumvent glucose repression. This trait had the defining genetic properties of [GAR⁺], and did not require utilization of lactic acid as a carbon source. Lactic acid also induced [GAR⁺]-like epigenetic states in fungi that diverged from S. cerevisiae ~200 million years ago, and in which glucose repression evolved independently. To our knowledge, this is the first study to uncover a bacterial metabolite with the capacity to potently induce a prion.

DOI:http://dx.doi.org/10.7554/eLife.17978.001

We communicate with each other using speech, writing and physical gestures. But how do bacteria, yeast and other single-celled microbes communicate? In 2014, researchers reported a new example of communication between bacteria and yeast in which the bacteria send a chemical message that has a very long-lasting effect on how the yeast grow in certain environments. This in turn also affected the ability of the bacteria to survive in these environments. The identity of the chemical message produced by the bacteria, however, was not known.

Garcia, Dietrich et al. – including one of the researchers from the previous study – used biochemical and genetic approaches to identify the chemical message. The experiments show that the message is a molecule called lactic acid, which is very common in nature and is produced by many bacteria. Garcia, Dietrich et al. found out how much lactic acid is needed to alter the growth of brewer’s yeast, and which genes in yeast are involved in responding to the message from the bacteria. Further experiments suggest that the ability of yeast and bacteria to communicate using lactic acid is likely to have existed for hundreds of millions of years.

The next step following this work will be to identify other chemical messages used by microbes. The human body is packed with billions of bacterial cells, and in some cases yeast can also take up residence. A future challenge will be to find out if bacteria and yeast inside the human body are able to communicate with each other in ways that could affect our health.

DOI:http://dx.doi.org/10.7554/eLife.17978.002

Mathematical model of LsrR-binding and derepression in Escherichia coli K12

Quorum sensing (QS) enables bacterial communication and collective behavior in response to self-secreted signaling molecules. Unlocking its genetic regulation will provide insight towards understanding its influence on pathogenesis, formation of biofilms, and many other phenotypes. There are few datasets available that link QS-mediated gene expression to its regulatory components and even fewer mathematical models that incorporate known mechanistic detail. By integrating these data with annotated sequence information, mathematical inferences can be pieced together that shed light on regulatory structure. A first principles model, developed here for the E. coli QS system, builds on known mechanistic detail and is used to develop a working model of LuxS-regulated (Lsr) activity. That is, our model is meant to discriminate among hypothetical mechanisms governing lsr transcriptional regulation. Our simulations are in qualitative agreement with experimentally observed data. Importantly, our results point to the importance of transcriptional regulator, LsrR, cycling on genetic control. We also found several experimental observations in E. coli and homologous systems that were not explained by current mechanistic understanding. For example, by comparing simulations with reports of the integrating host factor in Aggrigatibacter actinomycetemcomitans, we conclude that additional transcriptional components are likely involved. An iterative process of simulation and experiment, therefore, is needed to inform new experiments and incorporate new model detail, the benefit of which will more rapidly validate mechanistic understanding.

Probiotic Saccharomyces boulardii CNCM I-745 prevents outbreak-associated Clostridium difficile-associated cecal inflammation in hamsters

C. difficile infection (CDI) is a common debilitating nosocomial infection associated with high mortality. Several CDI outbreaks have been attributed to ribotypes 027, 017, and 078. Clinical and experimental evidence indicates that the nonpathogenic yeast Saccharomyces boulardii CNCM I-745 (S.b) is effective for the prevention of CDI. However, there is no current evidence suggesting this probiotic can protect from CDI caused by outbreak-associated strains. We used established hamster models infected with outbreak-associated C. difficile strains to determine whether oral administration of live or heat-inactivated S.b can prevent cecal tissue damage and inflammation. Hamsters infected with C. difficile strain VPI10463 (ribotype 087) and outbreak-associated strains ribotype 017, 027, and 078 developed severe cecal inflammation with mucosal damage, neutrophil infiltration, edema, increased NF-κB phosphorylation, and increased proinflammatory cytokine TNFα protein expression. Oral gavage of live, but not heated, S.b starting 5 days before C. difficile infection significantly reduced cecal tissue damage, NF-κB phosphorylation, and TNFα protein expression caused by infection with all strains. Moreover, S.b-conditioned medium reduced cell rounding caused by filtered supernatants from all C. difficile strains. S.b-conditioned medium also inhibited toxin A- and B-mediated actin cytoskeleton disruption. S.b is effective in preventing C. difficile infection by outbreak-associated via inhibition of the cytotoxic effects of C. difficile toxins.

Effect of Bifidobacterium upon Clostridium difficile Growth and Toxicity When Co-cultured in Different Prebiotic Substrates

The intestinal overgrowth of Clostridium difficile, often after disturbance of the gut microbiota by antibiotic treatment, leads to C. difficile infection (CDI) which manifestation ranges from mild diarrhea to life-threatening conditions. The increasing CDI incidence, not only in compromised subjects but also in traditionally considered low-risk populations, together with the frequent relapses of the disease, has attracted the interest for prevention/therapeutic options. Among these, probiotics, prebiotics, or synbiotics constitute a promising approach. In this study we determined the potential of selected Bifidobacterium strains for the inhibition of C. difficile growth and toxicity in different carbon sources. We conducted co-cultures of the toxigenic strain C. difficile LMG21717 with four Bifidobacterium strains (Bifidobacterium longum IPLA20022, Bifidobacterium breve IPLA20006, Bifidobacterium bifidum IPLA20015, and Bifidobacterium animalis subsp. lactis Bb12) in the presence of various prebiotic substrates (Inulin, Synergy, and Actilight) or glucose, and compared the results with those obtained for the corresponding mono-cultures. C. difficile and bifidobacteria levels were quantified by qPCR; the pH and the production of short chain fatty acids was also determined. Moreover, supernatants of the cultures were collected to evaluate their toxicity using a recently developed model. Results showed that co-culture with B. longum IPLA20022 and B. breve IPLA20006 in the presence of short-chain fructooligosaccharides, but not of Inulin, as carbon source significantly reduced the growth of the pathogen. With the sole exception of B. animalis Bb12, whose growth was enhanced, the presence of C. difficile did not show major effects upon the growth of the bifidobacteria. In accordance with the growth data, B. longum and B. breve were the strains showing higher reduction in the toxicity of the co-culture supernatants.

Screening of Bifidobacteria and Lactobacilli Able to Antagonize the Cytotoxic Effect of Clostridium difficile upon Intestinal Epithelial HT29 Monolayer

Clostridium difficile is an opportunistic pathogen inhabiting the human gut, often being the aetiological agent of infections after a microbiota dysbiosis following, for example, an antibiotic treatment. C. difficile infections (CDI) constitute a growing health problem with increasing rates of morbidity and mortality at groups of risk, such as elderly and hospitalized patients, but also in populations traditionally considered low-risk. This could be related to the occurrence of virulent strains which, among other factors, have high-level of resistance to fluoroquinolones, more efficient sporulation and markedly high toxin production. Several novel intervention strategies against CDI are currently under study, such as the use of probiotics to counteract the growth and/or toxigenic activity of C. difficile. In this work, we have analyzed the capability of twenty Bifidobacterium and Lactobacillus strains, from human intestinal origin, to counteract the toxic effect of C. difficile LMG21717 upon the human intestinal epithelial cell line HT29. For this purpose, we incubated the bacteria together with toxigenic supernatants obtained from C. difficile. After this co-incubation new supernatants were collected in order to quantify the remnant A and B toxins, as well as to determine their residual toxic effect upon HT29 monolayers. To this end, the real time cell analyser (RTCA) model, recently developed in our group to monitor C. difficile toxic effect, was used. Results obtained showed that strains of Bifidobacterium longum and B. breve were able to reduce the toxic effect of the pathogen upon HT29, the RTCA normalized cell-index values being inversely correlated with the amount of remnant toxin in the supernatant. The strain B. longum IPLA20022 showed the highest ability to counteract the cytotoxic effect of C. difficile acting directly against the toxin, also having the highest capability for removing the toxins from the clostridial toxigenic supernatant. Image analysis showed that this strain prevents HT29 cell rounding; this was achieved by preserving the F-actin microstructure and tight-junctions between adjacent cells, thus keeping the typical epithelium-like morphology. Besides, preliminary evidence showed that the viability of B. longum IPLA20022 is needed to exert the protective effect and that secreted factors seems to have anti-toxin activity.