In Vitro Evaluation of Antimicrobial Activity of Lactic Acid Bacteria against Clostridium difficile

Evaluating the antibacterial, antibiofilm, and anti-toxigenic effects of postbiotics from lactic acid bacteria on Clostridium difficile

Background and Objectives

The most common cause of healthcare-associated diarrhea is Clostridium difficile infection (CDI), which causes severe and recurring symptoms. The increase of antibiotic-resistant C. difficile requires alternate treatments. Postbiotics, metabolites produced by probiotics, fight CDI owing to their antibacterial capabilities. This study aims to evaluate the antibacterial, antibiofilm, and anti-toxigenic potential of postbiotics in combating CDI.

Materials and Methods

GC-MS evaluated postbiotics from Bifidobacterium bifidum and Lactobacillus plantarum. Disk diffusion and broth microdilution determined C. difficile antibacterial inhibition zones and MICs. Microtiter plates assessed antibiofilm activity. MTT assay evaluated postbiotics anti-viability on HEK293. ELISA testing postbiotic detoxification of toxins A and B. Postbiotics were examined for tcdA and tcdB genes expression using real-time PCR.

Results

The most identified B. bifidum and L. plantarum postbiotic compounds were glycolic acid (7.2%) and butyric acid (13.57%). B. bifidum and L. plantarum displayed 13 and 10 mm inhibition zones and 2.5 and 5 mg/ml MICs against C. difficile. B. bifidum reduced biofilm at 1.25 mg/ml by 49% and L. plantarum by 31%. MTT assay showed both postbiotics had little influence on cell viability, which was over 80%. The detoxification power of postbiotics revealed that B. bifidum decreased toxin A and B production more effectively than L. plantarum, and also their related tcdA and tcdB genes expression reduction were statistically significant (p < 0.05).

Conclusion

Postbiotics' ability to inhibit bacterial growth, biofilm disruption, and toxin reduction makes them a promising adjunctive for CDI treatment and a good solution to pathogens' antibiotic resistance.

Probiotic Potential of Lactobacillus and Enterococcus Strains Isolated From the Faecal Microbiota of Critically Endangered Hangul Deer (Cervus hanglu hanglu): Implications for Conservation Management

The mammalian gut microbiota plays a crucial role in promoting host health, and lactic acid bacteria (LAB) are commonly employed as probiotics for their beneficial effects. The Hangul deer (Cervus hanglu hanglu), a critically endangered red deer subspecies found in the Indian subcontinent, requires meticulous health management for its conservation. This pioneering study aimed to isolate, identify, and evaluate the in-vitro probiotic functional properties of LAB strains from the faeces of Hangul deer. A total of 27 LAB strains were isolated and identified using 16S rDNA gene sequencing, followed by comprehensive probiotic characterization and safety assessment. Remarkably, four species exhibited robust resistance and survivability against varying pH levels and bile salts, along with high aggregation and co-aggregation capacities. Notably, Lactobacillus acidophilus and Enterococcus mundtii strains displayed antibacterial activities. Safety assessment revealed the absence of hemolytic activity and virulence genes in all four strains. Antibiotic susceptibility testing showed that Lactobacillus acidophilus and Enterococcus casseliflavus were susceptible to all tested antibiotics, while Enterococcus mundtii exhibited resistance to clindamycin, and Enterococcus gallinarum exhibited resistance to erythromycin. These findings suggest that the isolated LAB strains possess advantageous probiotic characteristics and hold potential as dietary supplements for promoting the health and disease management of Hangul deer.

Antagonistic properties of Lactiplantibacillus plantarum MYSVB1 against Alternaria alternata: a putative probiotic strain isolated from the banyan tree fruit

Alternaria alternata, a notorious phytopathogenic fungus, has been documented to infect several plant species, leading to the loss of agricultural commodities and resulting in significant economic losses. Lactic acid bacteria (LAB) hold immense promise as biocontrol candidates. However, the potential of LABs derived from fruits remains largely unexplored. In this study, several LABs were isolated from tropical fruit and assessed for their probiotic and antifungal properties. A total of fifty-five LABs were successfully isolated from seven distinct fruits. Among these, seven isolates showed inhibition to growth of A. alternata. Two strains, isolated from fruits: Ficus benghalensis, and Tinospora cordifolia exhibited promising antifungal properties against A. alternata. Molecular identification confirmed their identities as Lactiplantibacillus plantarum MYSVB1 and MYSVA7, respectively. Both strains showed adaptability to a wide temperature range (10-45°C), and salt concentrations (up to 7%), with optimal growth around 37 °C and high survival rates under simulated gastrointestinal conditions. Among these two strains, Lpb. plantarum MYSVB1 demonstrated significant inhibition (p < 0.01) of the growth of A. alternata. The inhibitory effects of cell-free supernatant (CFS) were strong, with 5% crude CFS sufficient to reduce fungal growth by >70% and complete inhibition by 10% CFS. Moreover, the CFS was inhibitory for both mycelial growth and conidial germination. CFS retained its activity even after long cold storage. The chromatographic analysis identified organic acids in CFS, with succinic acid as the predominant constituent, with lactic acid, and malic acid in descending order. LAB strains isolated from tropical fruits showed promising probiotic and antifungal properties, making them potential candidates for various applications in food and agriculture.

Green biorefinery of shrimp shell waste for α-chitin and high-value co-products through successive fermentation by co-lactic acid bacteria and proteolytic fungus

Green biorefinery process was conducted to extract α-chitin and high-value co-products from shrimp shell waste through microbial fermentation using mature coconut water (MCW) as a sole nutrient source. Symbiotic co-lactic acid fermentation (Co-LAF) by Lactobacillus plantarum and Streptococcus thermophilus produced higher levels of lactic acid (LA) and protease activity than their mono-cultures, which led to greater demineralization (DM) and deproteinization (DP) of shrimp shell powder (SSP). After optimizing Co-LAF through Response Surface Methodology and successive fermentation by an acid-active proteolytic fungus Rhizopus oligosporus, the highest DM of 94.0 ± 0.91 % and DP of 86.7 ± 0.1 % were achieved. Based on FT-IR, XRD, and SEM analysis, the bio-extracted chitin had similar structural characteristics to commercial α-chitin but with better quality. These strategies not only contribute to environmentally-friendly and cost-effective extraction of α-chitin (303 ± 18 mg/g-SSP), but also co-produce LA (57.18 ± 0.89 g/L), acid protease (4.33 ± 0.5 U/mL), bio-calcium (277 ± 12 mg-CaSO4/g-SSP), protein hydrolysate (268 ± 5 mg/g-SSP), and pigments (28.78 ± 1.56 µg/g-SSP).

Novel Wild-Type Pediococcus and Lactiplantibacillus Strains as Probiotic Candidates to Manage Obesity-Associated Insulin Resistance

As the food and pharmaceutical industry is continuously seeking new probiotic strains with unique health properties, the aim of the present study was to determine the impact of short-term dietary intervention with novel wild-type strains, isolated from various sources, on high-fat diet (HFD)-induced insulin resistance. Initially, the strains were evaluated in vitro for their ability to survive in simulated gastrointestinal (GI) conditions, for adhesion to Caco-2 cells, for bile salt hydrolase secretion, for cholesterol-lowering and cellular cholesterol-binding ability, and for growth inhibition of food-borne pathogens. In addition, safety criteria were assessed, including hemolytic activity and susceptibility to antibiotics. The in vivo test on insulin resistance showed that mice receiving the HFD supplemented with Pediococcus acidilactici SK (isolated from human feces) or P. acidilactici OLS3-1 strain (isolated from olive fruit) exhibited significantly improved insulin resistance compared to HFD-fed mice or to the normal diet (ND)-fed group.

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.

Probiotic potentials of lactic acid bacteria isolated from Egyptian fermented food

Lactic acid bacteria (LAB) are of major concern due to their health benefits. Fermented food products comprise variable LAB demonstrating probiotic properties. Discovering and evaluating new probiotics in fermented food products poses a global economic and health importance. Therefore, the present work aimed to investigate and evaluate the probiotic potentials of LAB strains isolated from Egyptian fermented food. In this study, we isolated and functionally characterized 100 bacterial strains isolated from different Egyptian fermented food sources as probiotics. Only four LAB strains amongst the isolated LAB showed probiotic attributes and are considered to be safe for their implementation as feed or dietary supplements. Additionally, they were shown to exert antimicrobial activities against pathogenic bacteria and anticancer effects against the colon cancer cell line Caco-2. The Enterococcus massiliensis IS06 strain was exclusively reported in this study as a probiotic strain with high antimicrobial, antioxidant, and anti-colon cancer activity. Hitherto, few studies have focused on elucidating the impact of probiotic supplementation in vivo. Therefore, in the current study, the safety of the four strains was tested in vivo through the supplementation of rats with potential probiotic strains for 21 days. The results revealed that probiotic bacterial supplementation in rats did not adversely affect the general health of rats. The Lactiplantibacillus plantarum IS07 strain significantly increased the growth performance of rats. Furthermore, the four strains exhibited increased levels of antioxidants such as superoxide dismutase and glutathione in vivo. Consistently, all strains also showed high antioxidant activity of the superoxide dismutase enzyme in vitro. Overall, these findings demonstrated that these isolated potential probiotics harbor desirable characteristics and can be applied widely as feed additives for animals or as dietary supplements for humans to exert their health benefits and combat serious diseases.

Diversity of the bacteriocins, their classification and potential applications in combat of antibiotic resistant and clinically relevant pathogens

There is almost a century since discovery of penicillin by Alexander Fleming, a century of enthusiasm, abuse, facing development of antibiotic-resistance and clear conclusion that the modern medicine needs a new type of antimicrobials. Bacteriocins produced by Gram-positive and Gram-negative bacteria, Archaea and Eukaryotes were widely explored as potential antimicrobials with several applications in food industry. In last two decades bacteriocins showed their potential as promising alternative therapeutic for the treatment of antibiotic-resistant pathogens. Bacteriocins can be characterised as highly selective antimicrobials and therapeutics with low cytotoxicity. Most probably in order to solve the problems associated with the increasing number of antibiotic-resistant bacteria, the application of natural or bioengineered bacteriocins in addition to synergistically acting preparations of bacteriocins and conventional antibiotics, can be the next step in combat versus drug-resistant pathogens. In this overview we focussed on diversity of specific lactic acid bacteria and their bacteriocins. Moreover, some additional examples of bacteriocins from non-lactic acid, Gram-positive and Gram-negative bacteria, Archaea and eukaryotic organisms are presented and discussed. Therapeutic properties of bacteriocins, their bioengineering and combined applications, together with conventional antibiotics, were evaluated with the scope of application in human and veterinary medicine for combating (multi-)drug-resistant pathogens.

Cytotoxic effect of potential probiotic Lactiplantibacillus plantarum KUMS-Y8 isolated from traditional dairy samples on the KB and OSCC human cancer cell lines

Oral cancer is one of the leading causes of death worldwide, and its prevalence is especially high in developing countries. As an oral cancer treatment, traditional therapies are commonly used. Nonetheless, these treatments frequently result in a variety of side effects. As a consequence, there is an urgent need to enhance oral cancer therapies. Probiotics have recently demonstrated intriguing properties as therapeutic options for cancer treatment. Thus, the purpose of this study was to investigate the anticancer effect of probiotic Lactobacillus strains on the mouth epidermal carcinoma cells (KB) and oral squamous cell carcinoma (OSCC) cell lines. In this study, we looked at 21 Lactobacillus strains isolated from traditional dairy products in the Kermanshah province of western Iran to see if they had any inhibitory effects on oral cancer cell lines in vitro. We isolated and characterized Lactobacillus strains before assessing and comparing their probiotic potential and safety. Using the MTT assay, the bacterial extract was then prepared and used as an anti-proliferative agent on oral cancer (KB and OSCC) and normal (fibroblast and human umbilical vein endothelial cells (HUVEK) cell lines. Finally, acridine orange/ethidium bromide staining was used to determine whether cell death was caused by apoptosis. Four Lactobacillus isolates (C14, M22, M42, and Y8) were shown to have beneficial probiotic qualities. Lactobacillus extracts (of a protein nature) decreased the survival and proliferation of the KB and OSCC cancer cell lines (dose- and time-dependent) by inducing apoptosis, with no basic damaging effects on normal cells. The staining with acridine orange/ethidium bromide revealed that the cell death was caused by apoptosis. Furthermore, of the four Lactobacillus strains examined, isolate Y8 (Lactiplantibacillus plantarum) showed the strongest probiotic potential for suppressing KB and OSCC cell proliferation when compared to anticancer medicines (doxorubicin and paclitaxel). The current research found that Lactobacillus extract might reduce the growth and viability of the KB and OSCC cancer cell lines by inducing apoptosis, increasing the survival rate of oral cancer patients.

Bifidobacterium breve CBT BR3 is effective at relieving intestinal inflammation by augmenting goblet cell regeneration

BACKGROUND AND AIM

Bifidobacterium breve was the first bacteria isolated in the feces of healthy infants and is a dominant species in the guts of breast-fed infants. Some strains of B. breve have been shown to be effective at relieving intestinal inflammation, but the modes of action have yet to be elucidated. In this study, we investigated the mechanisms of action of B. breve CBT BR3 isolated from South Korean infant feces in relieving colitis in vitro and in vivo.

METHODS

Colitis was induced in mice with dextran sodium sulfate (DSS) and dinitrobenzene sulfonic acid (DNBS). Quantitative reverse-transcription polymerase chain reaction, in vitro FITC-dextran flux permeability assay, and aryl hydrocarbon receptor (AhR) luciferase assay are performed using Caco-2 cells and HT29-Lucia™ AhR cells.

RESULTS

B. breve CBT BR3 was orally administered. B. breve CBT BR3 improved colitis symptoms in both DSS- and DNBS-induced colitis models. B. breve CBT BR3 increased the number of goblet cells per crypt. B. breve increased the mRNA expressions of Notch, Spdef, Muc5, and Il22. The mRNA expressions of Occludin, which encodes a membrane tight-junction protein, and Foxo3, which encodes a protein related to butyrate metabolism, were also increased in the DSS- and DNBS-induced colitis models. B. breve CBT BR3 protected inflammation-induced epithelial cell permeability and improved goblet cell function by inducing aryl hydrocarbon receptor in vitro.

CONCLUSIONS

These results indicate that B. breve CBT BR3 is effective at relieving intestinal inflammation by augmenting goblet cell regeneration.

A systematic review on selection characterization and implementation of probiotics in human health

Probiotics are live bacteria found in food that assist the body's defence mechanisms against pathogens by reconciling the gut microbiota. Probiotics are believed to aid with gut health, the immune system, and brain function, among other factors. They've furthermore been shown to help with constipation, high blood pressure, and skin issues. The global probiotics market has been incrementally growing in recent years, as consumers' demand for healthy diets and wellness has continued to increase. This has prompted the food industry to develop new probiotic-containing food products, as well as researchers to explore their specific characteristics and impacts on human health. Although most probiotics are fastidious microorganisms that are nutritionally demanding and sensitive to environmental conditions, they become less viable as they are processed and stored. In this review we studied the current literature on the fundamental idea of probiotic bacteria, their medical benefits, and their selection, characterization, and implementations.

Graphical Abstract

Effects of Bifidobacteria Fermentation on Physico-Chemical, Thermal and Structural Properties of Wheat Starch

Lactic acid bacteria have been considered to be a very important species during sourdough fermentation. In order to explore the effects of bifidobacteria fermentation on thermal, physico-chemical and structural properties of wheat starch during dough fermentation, starch granules were separated from the fermented dough at different fermentation times, including 0 h, 2 h, 6 h, 9 h and 12 h. The results showed that the morphology of starch granules was destroyed gradually as the fermentation time increased, which appeared as erosion and rupture. With the increase in fermentation time, the solubility showed a significant increase, which changed from 8.51% (0 h) to 9.80% (12 h), and the swelling power was also increased from 9.31% (0 h) to 10.54% (12 h). As for the gelatinization property, the enthalpy was increased from 6.77 J/g (0 h) to 7.56 J/g (12 h), indicating a more stable thermal property of fermented starch, especially for the longer fermentation. The setback value was decreased with short fermentation time, indicating that the starch with a longer fermentation time was difficult to retrograde. The hardness of the gel texture was decreased significantly from 50.11 g to 38.66 g after fermentation for 12 h. The results show that bifidobacteria fermentation is an effective biological modification method of wheat starch for further applications.

Modulation of Lactobacillus rhamnosus GG on the gut microbiota and metabolism in mice with Clostridioides difficile infection

Clostridioides difficile infection (CDI) is a common nosocomial infection and is an urgent threat to public health. Vancomycin is the preferred antibiotic treatment for CDI but is associated with recurrence. Lactobacillus rhamnosus GG is an adjunctive treatment for gastroenteritis and diarrhea and exerts its effects by modulating the immune responses and repairing the intestinal barrier. This study explored the effect of LGG on restoring the intestinal microbiota in mouse models. Primary and recurrent CDI models were constructed, and LGG was administered to C57BL/6 mice. Structural changes in the mouse gut microbiota were determined using 16S rRNA gene analysis based on Illumina sequencing. In the CDI model, 6 days after infection, 33.3% mortality, significant weight loss and colonic injury were observed. LGG can ameliorate these events. In the R-CDI mouse model, vancomycin combined with LGG prevented weight loss, improved the histopathological scores, and effectively reduced the mortality. LGG + vancomycin administration promoted the recovery of the intestinal flora by inhibiting Enterococcus and counteracting the side effects of vancomycin treatment. In both the preventive and therapeutic CDI mouse models, the oral LGG strain showed the ability to protect against primary and recurrent infections, indicating that probiotics have potential for treating intestinal diseases. Overall, these observations suggest that LGG can be applied as a preventive treatment for CDI or in combination with antibiotics to reduce recurrence.

Probiotics Exhibit Strain-Specific Protective Effects in T84 Cells Challenged With Clostridioides difficile-Infected Fecal Water

Clostridioides difficile infection (CDI) is frequently associated with intestinal injury and mucosal barrier dysfunction, leading to an inflammatory response involving neutrophil localization and upregulation of pro-inflammatory cytokines. The severity of clinical manifestations is associated with the extent of the immune response, which requires mitigation for better clinical management. Probiotics could play a protective role in this disorder due to their immunomodulatory ability in gastrointestinal disorders. We assessed five single-strain and three multi-strain probiotics for their ability to modulate CDI fecal water (FW)-induced effects on T84 cells. The CDI-FW significantly (p < 0.05) decreased T84 cell viability. The CDI-FW-exposed cells also exhibited increased pro-inflammatory cytokine production as characterized by interleukin (IL)-8, C-X-C motif chemokine 5, macrophage inhibitory factor (MIF), IL-32, and tumor necrosis factor (TNF) ligand superfamily member 8. Probiotics were associated with strain-specific attenuation of the CDI-FW mediated effects, whereby Saccharomyces boulardii CNCM I-1079 and Lacticaseibacillus rhamnosus R0011 were most effective in reducing pro-inflammatory cytokine production and in increasing T84 cell viability. ProtecFlor™, Lactobacillus helveticus R0052, and Bifidobacterium longum R0175 showed moderate effectiveness, and L. rhamnosus GG R0343 along with the two other multi-strain combinations were the least effective. Overall, the findings showed that probiotic strains possess the capability to modulate the CDI-mediated inflammatory response in the gut lumen.

Progress in Alternative Strategies to Combat Antimicrobial Resistance: Focus on Antibiotics

Antibiotic resistance, and, in a broader perspective, antimicrobial resistance (AMR), continues to evolve and spread beyond all boundaries. As a result, infectious diseases have become more challenging or even impossible to treat, leading to an increase in morbidity and mortality. Despite the failure of conventional, traditional antimicrobial therapy, in the past two decades, no novel class of antibiotics has been introduced. Consequently, several novel alternative strategies to combat these (multi-) drug-resistant infectious microorganisms have been identified. The purpose of this review is to gather and consider the strategies that are being applied or proposed as potential alternatives to traditional antibiotics. These strategies include combination therapy, techniques that target the enzymes or proteins responsible for antimicrobial resistance, resistant bacteria, drug delivery systems, physicochemical methods, and unconventional techniques, including the CRISPR-Cas system. These alternative strategies may have the potential to change the treatment of multi-drug-resistant pathogens in human clinical settings.

In Vitro and In Vivo Anti-Clostridioides difficile Effect of a Probiotic Bacillus amyloliquefaciens Strain

Clostridioides difficile infection (CDI) is a significant cause of hospital-acquired and antibiotic-mediated intestinal diseases and is a growing global public health concern. Overuse of antibiotics and their effect on normal intestinal flora has increased the incidence and severity of infections. Thus, the development of new, effective, and safe treatment options is a high priority. Here, we report a new probiotic strain, Bacillus amyloliquefaciens (BA PMC-80), and its in vitro/in vivo anti-C. difficile effect as a prospective novel candidate for replacing conventional antibiotics. BA PMC-80 showed a significant anti-C. difficile effect in coculture assay, and its cell-free supernatant (CFS) also exhibited a considerable anti-C. difficile effect with an 89.06 μg/ml 50% minimal inhibitory concentration (MIC) in broth microdilution assay. The CFS was stable and equally functional under different pHs, heat, and proteinase treatments. It also exhibited a high sensitivity against current antibiotics and no toxicity in subchronic toxicity testing in hamsters. Finally, BA PMC-80 showed a moderate effect in a hamster CDI model with reduced infection severity and delayed death. However, further studies are required to optimize the treatment condition of the hamster CDI model for better efficacy and identify the antimicrobial compound produced by BA PMC-80.

Probiotic Activity of Enterococcus faecium and Lactococcus lactis Isolated from Thai Fermented Sausages and Their Protective Effect Against Clostridium difficile

Lactic acid bacteria, Enterococcus faecium and Lactococcus lactis, previously isolated from Thai fermented sausages were elucidated their probiotic properties especially in the control of Clostridium difficile 630. Both isolates survived in simulated gastric solution at pH 3 followed in simulated intestinal solution at pH 8. The presence of skimmed milk also helped the bacteria to survive through acidic and alkaline in gastrointestinal conditions. The adhesion properties of both isolates were tested using a human colon adenocarcinoma cell line. The result showed that both isolates exhibited desirable probiotic properties which adhered to Caco-2 cells. The neutralized cell-free supernatant of both isolates demonstrated that no cytotoxicity toward Caco-2 cells vice versa cell-free supernatant of C. difficile 630 toward Caco-2 cell demonstrated high toxicity. The immunomodulation effect in response to bacterial neutralized cell-free supernatant and cell-free supernatant was also studied. The expression level of pro-inflammatory cytokine of Caco-2 cell which are tumor necrosis factor-α and interleukin-8 was evaluated using quantitative reverse transcriptase PCR. Both isolates were able to diminish the expression level of TNF-α and IL-8 induced by the cell-free supernatant of C. difficile 630. Hence, these isolates would be able to improve the gut health through counteracting the C. difficile-associated intestinal inflammation in human cell lines. These results may contribute to the development of the isolates using as probiotics.

Antimicrobial Activity of Bacillus subtilis KATMIRA1933 and Bacillus amyloliquefaciens B-1895 Against Staphylococcus aureus Biofilms Isolated from Wound Infection

Staphylococcal wound infections range from mild to severe with life-threatening complications. The challenge of controlling such infections is related to bacterial biofilm formation, which is a major factor contributing to antibiotic resistance and infection recurrence. In this study, four clinical isolates of staphylococci species; two isolates of methicillin-resistant Staphylococcus aureus (MRSA) and two methicillin-sensitive Staphylococcus aureus (MSSA) isolates. The identification of bacterial species based on cell morphology, initial biochemical tests, and the VITEK2 system were used to confirm the clinical microbiological diagnosis. Antibiotic sensitivity testing showed that the isolated staphylococci were highly resistant to the following antibiotics, amoxicillin, penicillin G, cefotaxime, and methicillin. Combinations of cefotaxime with the cell-free supernatants (CFS) of Bacillus subtilis KATMIRA1933 and Bacillus amyloliquefaciens B-1895, each one separately showed complementary activity against the tested staphylococci. The co-aggregation capability of the tested bacilli as beneficial bacteria against isolated staphylococci was also evaluated. The data showed a strong co-aggregation with scores (+ 3, + 4) which were reported between the bacilli strains and the isolated staphylococci. Furthermore, the CFS of bacilli strains showed an inhibitory effect against biofilm-associated MRSA and MSSA. These findings confirmed the ability of beneficial bacteria to compete with the pathogens at the site of colonization or for the source of nutrients and, eventually, lead to inhibition of the pathogens' capability of causing a wound infection. Such beneficial bacteria could play an important role in future pharmaceutical and industrial applications.

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.

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.

Growing consumption of antibiotics and epidemiology of Clostridioides difficile infections in Poland: A need to develop new solutions

Clostridioides (formerly Clostridium) difficile infections (CDIs) are becoming more common and more serious. C. difficile is the etiologic agent of antibiotic-associated diarrhea, pseudomembranous enterocolitis, and toxic megacolon while CDIs recur in 7.9% of patients. About 42.9 CDI cases/10,000 patient-days are diagnosed each day in Europe, whereas in Poland 5.6 CDI cases/10,000 patient-days are reported; however, the median for European countries is 2.9 CDI cases/10,000 patient-days. Epidemiology of CDIs has changed in recent years and risk of developing the disease has doubled in the past decade that is largely determined by use of antibiotics. Studies show that rate of antibiotic consumption in the non-hospital sector in Poland is much higher than the European average (27 vs. 21.8 DDD/1,000 patient-days), and this value has increased in recent years. Antibiotic consumption has also increased in the hospital sector, especially in the intensive care units - 1,520 DDD/1,000 patient-days (ranging from 620 to 3,960 DDD/1,000 patient-days) - and was significantly higher than in Germany 1,305 (ranging from 463 to 2,216 DDD/1,000 patient-days) or in Sweden 1,147 (ranging from 605 to 2,134 DDD/1,000 patient-days). The recent rise in CDI incidence has prompted a search for alternative treatments. Great hope is placed in probiotics, bacteriocins, monoclonal antibodies, bacteriophages, and developing new vaccines.

Bacteria producing antimicrobials against Clostridium difficile isolated from human stool

Clostridium difficile infection (CDI) is a common cause of morbidity and mortality in hospitalized patients worldwide. The major problem facing current treatment is multiple recurrences, prompting the need for alternative therapies. In this study we isolated bacterial species, from Egyptian individuals' stool, with antimicrobial activity against clinical isolates of C. difficile and tried to examine the nature of the produced antimicrobials. In vitro antibacterial activity against C. difficile was initially screened in 123 fecal samples cultures using an agar overlay method. The isolates with antimicrobial activity against C. difficile in addition to Clostridium isolates were identified using partial 16S rDNA gene sequencing analysis. The isolates acting against C. difficile belonged to Lactobacillus, Enterococcus and Clostridium genera. The concentrated cell-free supernatants (CFSs) from these bacterial isolates were examined for antimicrobial activity against C. difficile growth by broth dilution method. 10 x concentrated CFSs of five isolates showed inhibition for C. difficile growth which was significantly different (p < 0.001) from control. Lactobacillus agilis T99A and Clostridium butyricum T58A isolates were selected for further evaluation of the produced antimicrobials. The antimicrobial activity of 10x CFSs of the two isolates was stable after enzymatic treatment with proteinase K or heating treatments up to 90 °C or neutralizing pH. The spectrum of activity of the two isolates was evaluated using different gram-positive and gram-negative bacterial species and did not show antimicrobial activity against these species. Our results showed two unconventional bacterial isolates: L. agilis T99A and C. butyricum T58A producing extracellular thermo stable antimicrobial agents against C. difficile clinical isolates.

Encapsulating Viability of Multi-strain Lactobacilli as Potential Probiotic in Pigs

Important aspects of the selection of probiotics to be used for mixing in animal feed include host species specificity and probiotic cell survival during production and storage of their products. The research was to screen and investigate some probiotic properties of lactic acid bacteria (LAB) isolated from pig fecal samples. One hundred and thirty-eight representative LAB isolates, which were isolated from 51 pig fecal samples, were tested for acid and bile tolerance, antimicrobial susceptibility, antibacterial activity, potential adhesion to the cell surface, and survival rates when stored in varied microencapsulation forms: freeze-dried, spray-dried, and micro-beads. The antibacterial activity results of the ten LAB isolates, which were acid- (pH 2, 3 h) and bile- (50% (v/v) fresh pig bile, 8 h) tolerant and suitable for resisting the five antibiotics commonly used for treating pig infections with pathogenic indicator strains, showed that three isolates (L21, L80, L103) had strong inhibition to Escherichia coli, Salmonella group B, and Salmonella group D using co-culturing and agar spot assays. The three isolates had high hydrophobicity (65-73%) and did not show antagonistic growth against each other. All three selected isolates had greater than 80% survival in freeze-dried and micro-bead forms at 25-30 °C after 2 days of storage (80.4-86.75%, 7.31-7.89 log CFU/ml). Sequence analysis of the 16S rRNA genes demonstrated that the three isolates belong to Lactobacillus plantarum (strain L21 and strain L80) and L. paraplantarum (strain L103). The single and multiple strains of these bacteria may have potential use as probiotics in pig diets.

Characterization of Lactic Acid Bacteria Isolated From the Gastrointestinal Tract of a Wild Boar as Potential Probiotics

Lactic acid bacteria (LAB) are major microorganisms used for probiotic purposes and prime parts of the human and mammalian gut microbiota, which exert important health-promoting effects on the host. The present study aimed to evaluate and compare the probiotic potential and safety of LAB strains isolated from the gastrointestinal tract of a wild boar from the Greater Khingan Mountains, China. Amongst all of the isolated LAB strains, five isolates identified as Lactobacillus mucosae, Lactobacillus salivarius, Enterococcus hirae, Enterococcus durans, and Enterococcus faecium, were remarkably resistant to acid and bile salt. The probiotic characteristics (including adhesion capability, antimicrobial activities, autoaggregation, and coaggregation abilities), and safety properties (including hemolytic activity, antibiotic resistance, absence/presence of virulence factors, and in vivo safety) were evaluated. The results showed that all five isolates exhibited high adhesive potential, remarkable aggregation capacity, and antibacterial activities. Upon assessment of the safety, these strains were negative for hemolytic activity and all tested virulence genes. In vivo safety assessment showed no adverse effects of isolated strains supplementation on the body weight gain and organ indices of the treated mice. This study revealed that these LAB isolates, especially L. salivarius M2-71, possess desirable probiotic properties and have great potentials for the development of feed additives for animals to promote health.

Effect of probiotics on obesity-related markers per enterotype: a double-blind, placebo-controlled, randomized clinical trial

Background

Prevention and improvement of disease symptoms are important issues, and probiotics are suggested as a good treatment for controlling the obesity. Human gut microbiota has different community structures. Because gut microbial composition is assumed to be linked to probiotic function, this study evaluated the efficacy of probiotics on obesity-related clinical markers according to gut microbial enterotype.

Methods

Fifty subjects with body mass index over 25 kg/m² were randomly assigned to either the probiotic or placebo group. Each group received either unlabeled placebo or probiotic capsules for 12 weeks. Body weight, waist circumference, and body composition were measured every 3 weeks. Using computed tomography, total abdominal fat area and visceral fat area were measured. Blood and fecal samples were collected before and after the intervention for biochemical parameters and gut microbial compositions analysis.

Results

Gut microbial compositions of all the subjects were classified into two enterotypes according to Prevotella/Bacteroides ratio. The fat percentage, blood glucose, and insulin significantly increased in the Prevotella-rich enterotype of the placebo group. The obesity-related markers, such as waist circumference, total fat area, visceral fat, and ratio of visceral to subcutaneous fat area, were significantly reduced in the probiotic group. The decrease of obesity-related markers was greater in the Prevotella-rich enterotype than in the Bacteroides-rich enterotype.

Conclusion

Administration of probiotics improved obesity-related markers in obese people, and the efficacy of probiotics differed per gut microbial enterotype and greater responses were observed in the Prevotella-dominant enterotype.

Therapeutic effects of probiotics on neurotoxicity induced by clindamycin and propionic acid in juvenile hamsters

The present study investigated the therapeutic effects of probiotics on brain intoxication induced by clindamycin and propionic acid (PPA) in hamsters. Fifty golden Syrian hamsters were randomly divided into five experimental groups of ten animals each: (A) control group receiving phosphate buffered saline; (B) oral buffered PPA-treated group being administered with a neurotoxic dose of 250 mg/kg PPA during three days; (C) oral clindamycin-treated group receiving a single dose of 30 mg clindamycin/kg; and (D, E) the two therapeutic groups being administered the same doses of clindamycin and PPA followed by probiotics for three weeks at a daily dose of 0.2 g/kg. Biochemical parameters of energy metabolism and oxidative stress were examined in brain homogenates from all hamsters. The development of pathogenic bacteria was monitored on stool samples from all hamsters. Descriptive changes in fecal microbiota and overgrowth of Clostridium species in clindamycin and PPA treated hamsters were recorded. Interestingly, probiotics were shown effective to restore normal gut microbiota. Clindamycin and PPA treatments caused an elevation in lipid peroxidation and catalase activity, as oxidative stress markers, together with a reduction in GST activity and GSH level. Energy metabolism impairment was ascertained via the activation of creatine kinase and a decrease of lactate dehydrogenase. These findings suggest that bacteria overgrowth caused by PPA and clindamycin was efficient to illustrate signs of neuronal toxicity. The present study indicates that probiotic treatment can improve poor detoxification, oxidative stress, and altered gut microbiota as mechanisms implicated in the etiology of many neurological disorders.

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.

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

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.

Use of Lactobacillus plantarum Strains as a Bio-Control Strategy against Food-Borne Pathogenic Microorganisms

Lactobacillus plantarum is one of the most versatile species extensively used in the food industry both as microbial starters and probiotic microorganisms. Several L. plantarum strains have been shown to produce different antimicrobial compounds such as organic acids, hydrogen peroxide, diacetyl, and also bacteriocins and antimicrobial peptides, both denoted by a variable spectrum of action. In recent decades, the selection of microbial molecules and/or bacterial strains able to produce antagonistic molecules to be used as antimicrobials and preservatives has been attracting scientific interest, in order to eliminate or reduce chemical additives, because of the growing attention of consumers for healthy and natural food products. The aim of this work was to investigate the antimicrobial activity of several food-isolated L. plantarum strains, analyzed against the pathogenic bacteria Listeria monocytogenes, Salmonella Enteritidis, Escherichia coli O157:H7 and Staphylococcus aureus. Antagonistic activity was assayed by agar spot test and revealed that strain L. plantarum 105 had the strongest ability to contrast the growth of L. monocytogenes, while strains L. plantarum 106 and 107 were the most active microorganisms against E. coli O157:H7. The antimicrobial ability was also screened by well diffusion assay and broth micro-dilution method using cell-free supernatants (CFS) from each Lactobacillus strain. Moreover, the chemical nature of the molecules released in the CFS, and possibly underlying the antagonistic activity, was preliminary characterized by exposure to different constraints such as pH neutralization, heating, catalase, and proteinase treatments. Our data suggest that the ability of L. plantarum cultures to contrast pathogens growth in vitro depends, at least in part, on a pH-lowering effect of supernatants and/or on the presence of organic acids. Cluster analysis was performed in order to group L. plantarum strains according to their antimicrobial effect. This study emphasizes the tempting use of the tested L. plantarum strains and/or their CFS as antimicrobial agents against food-borne pathogens.

Microorganisms with claimed probiotic properties: an overview of recent literature

Probiotics are defined as live microorganisms, which when administered in adequate amounts, confer a health benefit on the host. Health benefits have mainly been demonstrated for specific probiotic strains of the following genera: Lactobacillus, Bifidobacterium, Saccharomyces, Enterococcus, Streptococcus, Pediococcus, Leuconostoc, Bacillus, Escherichia coli. The human microbiota is getting a lot of attention today and research has already demonstrated that alteration of this microbiota may have far-reaching consequences. One of the possible routes for correcting dysbiosis is by consuming probiotics. The credibility of specific health claims of probiotics and their safety must be established through science-based clinical studies. This overview summarizes the most commonly used probiotic microorganisms and their demonstrated health claims. As probiotic properties have been shown to be strain specific, accurate identification of particular strains is also very important. On the other hand, it is also demonstrated that the use of various probiotics for immunocompromised patients or patients with a leaky gut has also yielded infections, sepsis, fungemia, bacteraemia. Although the vast majority of probiotics that are used today are generally regarded as safe and beneficial for healthy individuals, caution in selecting and monitoring of probiotics for patients is needed and complete consideration of risk-benefit ratio before prescribing is recommended.

A Probiotic Preparation Duolac-Gold Ameliorates Dextran Sulphate Sodium-induced Mouse Colitis by Downregulating the Expression of IL-6

Probiotics are live microorganisms that confer a health benefit on the host. Duolac-Gold is a mixture of six probiotic bacteria containing three species of Bifidobacteria, two species of Lactobacillus, and Streptococcus thermophilus [corrected]. The aim of this study was to assess the anti-inflammatory effects of Duolac-Gold in an inflammatory bowel disease (IBD) mouse model. IBD was induced by administering 1.5% dextran sulfate sodium (DSS) for 10 days. After induction of DSS-induced colitis, Duolac-Gold was orally administered at three different concentrations. Interestingly, Duolac-Gold treatment accelerated IBD healing, and anti-inflammatory activity was assessed by weight loss, length of the colon, and a microscopic damage score by histology. The expression of inflammatory related cytokines was measured in colon tissues and serum. Of these cytokines, the expression of interleukin-6 decreased remarkably after Duolac-Gold treatment. Taken together, these results suggest that Duolac-Gold treatment is effective in IBD healing by regulating IL-6.