Probiotics and Their Antimicrobial Effect

Evaluation of Single and Multi-Strain Probiotics with Gentamicin Against E. coli O157:H7: Insights from In Vitro and In Vivo Studies

The emergence of antibiotic-resistant food-borne pathogens, especially Escherichia coli O157:H7, highlights the urgent need for innovative treatment strategies, particularly in light of rising resistances and the ongoing controversy surrounding antibiotic use in response to E. coli O157:H7 infections. To address this issue, we explored the potential of single- and multi-strain probiotics, both independently and in combination with gentamicin, through a series of in vitro and in vivo experiments. In vitro, gentamicin alone produced a mean inhibition zone of 12.9 ± 2.27 mm against E. coli O157:H7. The combination of gentamicin with single-strain probiotics (P1) increased the inhibition zone to 16.5 ± 2.24 mm (p < 0.05), while the combination with multi-strain probiotics (P2) resulted in the largest inhibition zone of 19 ± 2.8 mm (p < 0.05). In vivo, mice infected with E. coli O157:H7 and treated with P2, gentamicin (G), or their combination (G+P2), achieved 100% survival, no pathological symptoms, and full weight recovery within seven days. Conversely, mice treated with P1 or G+P1 exhibited lower survival rates (71.4% and 85%, respectively) and slower weight recovery. Hematological parameters improved across all groups, but kidney function analysis showed significantly higher serum creatinine levels in the P1, G, G+P1, and G+P2 groups compared to the P2 group (P1: 0.63 ± 0.15 mg/dL; G: 0.34 ± 0.09 mg/dL; G+P1: 0.53 ± 0.19 mg/dL; G+P2: 0.5 ± 0.23 mg/dL vs. P2: 0.24 ± 0.2 mg/dL). Histological analysis showed better intestinal and kidney tissue recovery in the P2 group, while the P1 and G+P1 groups exhibited abnormal ileal structures and severe cortical bleeding. These findings highlight the promise of multi-strain probiotics, alone or in conjunction with antibiotics, as a therapeutic strategy for E. coli O157:H7 infections. However, the nephrotoxicity associated with gentamicin co-administration remains a limitation, warranting further studies to optimize this approach.

Antimicrobial Activity of Probiotic Bacteria Isolated from Plants: A Review

Lactic acid bacteria (LAB) constitute a heterogeneous group of bacteria isolated from fermented foods, animals, plants, and mammalian guts, with many health-promoting properties. Probiotics with antagonistic properties against human pathogens and foodborne bacteria have garnered significant attention from the scientific fraternity. A dedicated review focusing on plant-derived probiotic bacteria and their antagonistic properties has not been comprehensively reviewed. Thus, this review aimed at providing an overview of LAB isolates derived from several unconventional sources such as fruits, seeds, fruit pulp, leaves, roots, vegetables, grasses, and flowers and with their antibacterial, antifungal, and antiviral properties. This paper reviewed the antimicrobial properties of different genera, Lactobacillus, Leuconostoc, Weissella, Enterococcus, Pediococcus, Bacillus, and Fructobacillus, their postbiotics, and paraprobiotics. Several important mechanisms, including the secretion of bacteriocins, bacteriocin-like substances, reuterin, organic acids (lactic and acetic), peptides, exopolysaccharides, and hydrogen peroxide, have been attributed to their antimicrobial actions against pathogens. However, their precise mode of action is poorly understood; hence, further research should be conducted to reveal detailed mechanisms. Finally, the review discusses the summary and future implications. Given the significance, LAB and derived antimicrobial compounds can potentially be exploited in food preservation and safety or for medicinal applications after evaluating their safety.

Antimicrobial activity of Lactobacillus casei on Staphylococcus pseudintermedius isolates

BACKGROUND

Antimicrobial resistance is increasing each year. For example, in 2019 it was directly responsible for an estimated >1 million deaths. Additionally, the development of new drugs is much slower, generating enormous concerns about responses to infection in the future health scenario. Therefore, probiotics have emerged as an alternative to antibiotics.

OBJECTIVES

This study aimed to isolate and identify a Lactobacillus casei from healthy canine skin and investigate its antimicrobial effect on isolates of Staphylococcus pseudintermedius originating from dogs with pyoderma.

MATERIALS AND METHODS

L. casei was isolated from skin samples collected with a sterile cotton swab from the inner pinnae of healthy dogs. It was then cultured, identified using matrix-assisted laser desorption ionisation time-of-flight mass spectrometry, and tested against 30 different clinical isolates and one American Type Culture Collection strain of S. pseudintermedius using the spot-on-the-lawn technique. Its safety was assessed through a modified Kirby-Bauer disc diffusion susceptibility test.

RESULTS

L. casei inhibited the growth of all isolates of S. pseudintermedius. The mean value of the inhibition halo of all isolates was 11.3 mm. A significant positive correlation (Pearson's linear correlation = 0.444; p = 0.014) was noted between the inhibitory halos formed by L. casei on the S. pseudintermedius isolates and the halos produced by the tested antimicrobial discs on the same isolates. The L. casei strain demonstrated sensitivity to all tested antimicrobials.

CONCLUSIONS AND CLINICAL RELEVANCE

The study indicates that using commensal bacteria from canine skin, specifically L. casei, to control bacterial infections caused by S. pseudintermedius can be a promising complementary or alternative therapy to antibiotics relevant to animal and human health.

Immune Boosting Effect of Limosilactobacillus Reuteri in Immunocompetent C57BL/6J Mice

Probiotics are well-known to be directly or indirectly involved in the host immune system. In this study, we analyzed the immune-boosting effects of lactic acid bacteria, including Limosilactobacillus and Lactococcus, in immunocompetent C57BL/6J mice. Three different lactic acid bacteria strains were orally administered to C57BL/6J mice for 8 weeks. Then, liver, spleen, and whole blood were harvested after sacrificing the animals. There were no significant changes in whole-body weight, weight of organs, or complete blood cell count by oral administration of lactic acid bacteria. The frequencies of CD3+, CD4+, and CD8+ T cells were significantly increased in the Limosilactobacillus reuteri MG5462 group compared to control. The frequency of NK1.1+ cells was significantly increased in the Lactococcus lactis MG5474 group compared to control. On the other hand, splenocyte proliferations and natural killer cytotoxicity did not differ between groups. In addition, the MG5462 group had a significant increase in the production of TNF-α compared to the control, which is consistent with the upregulation of T cells in the MG5462 group. Therefore, Limosilactobacillus reuteri could be a functional food additive to boost immunity by positively affecting T cell populations.

Efficacy of the Probiotic L. brevis in Counteracting the Demineralizing Process of the Tooth Enamel Surface: Results from an In Vitro Study

BACKGROUND

Enamel plays an essential role in protecting the underlying layers of the human tooth; therefore, preserving it is vital. This experimental study aimed to evaluate the potential ability of L. brevis to counteract the action of a demineralizing agent on dental enamel morphology and mineral composition in vitro.

METHODS

The sample consisted of 12 healthy human posterior teeth. The coronal portion of each tooth was subdivided into two equal parts longitudinally. The specimens were randomly divided into four groups: artificial saliva, L. brevis suspension, demineralizing agent (DA), and DA plus L. brevis. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to evaluate the surface micromorphology and the mineral content, respectively. The statistical analysis was conducted using a one-way ANOVA, followed by Tukey's post hoc test.

RESULTS

SEM analysis did not highlight significant changes in the enamel microstructure of L. brevis-treated specimens compared to the control. DA-induced damage to the enamel structure was drastically reduced when the specimens were contextually exposed to the probiotic. The treatment with DA substantially reduced the weight % of crucial enamel minerals, i.e., Ca and P. Notably, the probiotic was able to reverse the demineralization process, bringing Ca and P weight % back to basal levels, including the Ca/P ratio.

CONCLUSIONS

The findings indicate that L. brevis is able to efficiently protect the dental enamel surface from the damage caused by DA and increase the enamel resistance to demineralization. Overall, L. brevis confirms its efficacy in preventing or counteracting the action of carious lesions through a novel mechanism that protects the tooth surface under a chemical challenge that mimics the caries process.

Antioxidant and Antibacterial Activities of Nano-probiotics Versus Free Probiotics Against Gastrointestinal Pathogenic Bacteria

Antibiotic-resistant pathogenic bacteria and the oxidative stress related to their infections are dangerous health problems. Finding new safe, effective antibacterial and antioxidant agents is an urgent global need. Probiotics are a strong candidate for possible antibacterial and antioxidant agents. The delivery of these probiotics without any effect on gastrointestinal digestion is the most important point for their application. The encapsulation of the probiotics on nanoparticles or other supports is a well-known method for the safe delivery of the probiotics. Little information is known about the effect of the probiotic encapsulation on its antibacterial and antioxidant activity. The present study tried to investigate the effect of probiotic encapsulation on nano-chitosan on its antioxidant activity and antibacterial activity against some pathogenic bacteria. We encapsulated some known probiotic species on nano-chitosan and investigated the antibacterial activity of the nano-probiotics and free probiotics against gastrointestinal pathogenic bacteria. The antioxidant characters of the free and encapsulated probiotics were investigated in terms of DPPH radicle scavenging activity, ferric ion chelating activity, hydroxyl radicle scavenging activity, superoxide anion radicle scavenging activity, and anti-lipid peroxidation activity. Results showed the superiority of the encapsulated probiotics as antibacterial and antioxidant agents over the free ones. The encapsulation improved the antibacterial activity of Sporolactobacillus laevolacticus against Bacteroides fragilis by 134% compared to the free one. Also, significantly, the encapsulation increased the hydroxyl radicle scavenging activity of Enterococcus faecium by about 180% compared to the free one. Nano-chitosan encapsulation synergistically increased the antioxidant and antibacterial activity of the studied probiotics. This can be promising for controlling pathogenic bacteria.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-023-01140-2.

A Novel Water-Soluble Polysaccharide from Daylily (Hemerocallis citrina Baroni): Isolation, Structure Analysis, and Probiotics Adhesion Promotion Effect

The daylily (Hemerocallis citrina Baroni) flower is a traditional raw food material that is rich in a variety of nutrients. In particular, the content of polysaccharides in daylily is abundant and has been widely used as a functional component in food, cosmetics, medicine, and other industries. However, studies on the structure-effective relationship of daylily flower polysaccharides are still lacking. In view of this, daylily flower polysaccharides were isolated and purified, and their physical and chemical properties, structure, antioxidant activity, and adhesion-promoting effect on probiotics were evaluated. The results showed that a novel water-soluble polysaccharide (DPW) with an average molecular weight (Mw) of 2.224 kDa could be successfully isolated using column chromatography. Monosaccharide composition analysis showed that DPW only comprised glucose and fructose, with a molar ratio of 0.242:0.758. Through methylation and nuclear magnetic resonance (NMR) analysis, it was inferred that DPW belonged to the fructans group with a structure of α-D-Glcp-1→2-β-D-Fruf-1→(2-β-D-Fruf-1)n→. Antioxidant analysis showed that DPW showed strong 2-Phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-Oxide (PTIO-scavenging activity with IC50 of 1.54 mg/mL. DPW of 1.25 to 5 mg/mL could significantly increase the adhesion rate of Lactobacillus acidophilu, Lactobacillus casei, Bifidobacterium adolescentis, and Lactobacillus plantarum on Caco-2 cells. Considering the above results, the present study provides a theoretical basis and practical support for the development and application of daylily polysaccharides as a functional active ingredient.

In vitro safety and functional characterization of the novel Bacillus coagulans strain CGI314

Introduction

Bacillus coagulans species have garnered much interest in health-related functional food research owing to their desirable probiotic properties, including pathogen exclusion, antioxidant, antimicrobial, immunomodulatory and food fermentation capabilities coupled with their tolerance of extreme environments (pH, temperature, gastric and bile acid resistance) and stability due to their endosporulation ability.

Methods

In this study, the novel strain Bacillus coagulans CGI314 was assessed for safety, and functional probiotic attributes including resistance to heat, gastric acid and bile salts, the ability to adhere to intestinal cells, aggregation properties, the ability to suppress the growth of human pathogens, enzymatic profile, antioxidant capacity using biochemical and cell-based methods, cholesterol assimilation, anti-inflammatory activity, and attenuation of hydrogen peroxide (H2O2)-induced disruption of the intestinal-epithelial barrier.

Results

B. coagulans CGI314 spores display resistance to high temperatures (40°C, 70°C, and 90°C), and gastric and bile acids [pH 3.0 and bile salt (0.3%)], demonstrating its ability to survive and remain viable under gastrointestinal conditions. Spores and the vegetative form of this strain were able to adhere to a mucous-producing intestinal cell line, demonstrated moderate auto-aggregation properties, and could co-aggregate with potentially pathogenic bacteria. Vegetative cells attenuated LPS-induced pro-inflammatory cytokine gene expression in HT-29 intestinal cell lines and demonstrated broad antagonistic activity toward numerous urinary tract, intestinal, oral, and skin pathogens. Metabolomic profiling demonstrated its ability to synthesize several amino acids, vitamins and short-chain fatty acids from the breakdown of complex molecules or by de novo synthesis. Additionally, B. coagulans CGI314's strong antioxidant capacity was demonstrated using enzyme-based methods and was further supported by its cytoprotective and antioxidant effects in HepG2 and HT-29 cell lines. Furthermore, B. coagulans CGI314 significantly increased the expression of tight junction proteins and partially ameliorated the detrimental effects of H2O2 induced intestinal-epithelial barrier integrity.

Discussion

Taken together these beneficial functional properties provide strong evidence for B. coagulans CGI314 as a promising potential probiotic candidate in food products.

Role of probiotics in managing various human diseases, from oral pathology to cancer and gastrointestinal diseases

The imbalance of microbial composition and diversity in favor of pathogenic microorganisms combined with a loss of beneficial gut microbiota taxa results from factors such as age, diet, antimicrobial administration for different infections, other underlying medical conditions, etc. Probiotics are known for their capacity to improve health by stimulating the indigenous gut microbiota, enhancing host immunity resistance to infection, helping digestion, and carrying out various other functions. Concurrently, the metabolites produced by these microorganisms, termed postbiotics, which include compounds like bacteriocins, lactic acid, and hydrogen peroxide, contribute to inhibiting a wide range of pathogenic bacteria. This review presents an update on using probiotics in managing and treating various human diseases, including complications that may emerge during or after a COVID-19 infection.

Genomic insights into antimicrobial potential and optimization of fermentation conditions of pig-derived Bacillus subtilis BS21

Bacillus spp. have been widely used as probiotic supplements in animal feed as alternatives to antibiotics. In the present study, we screened a Bacillus subtilis strain named BS21 from pig feces. Antimicrobial activities, whole genome mining and UHPLC-MS/MS analysis were used to explore its antimicrobial mechanism. Strain BS21 showed Significant growth inhibition against a variety of animal pathogens, including Escherichia coli, Salmonella enterica Pullorum, Salmonella enterica Typhimurium, Citrobacter rodentium, Shigella flexneri and Staphylococcus aureus. Seven gene clusters involved in antimicrobial biosynthesis of secondary metabolites were encoded by strain BS21 genome, including four non-ribosomal peptides (bacillibactin, fengycin, surfactin and zwittermicin A), one ribosomal peptide (subtilosin A), one dipeptide (bacilysin) and one polyketide (bacillaene). Among them, production of surfactin, fengycin, bacillibactin, bacilysin and bacillaene was detected in the supernatant of B. subtilis strain BS21. To develop the potential application of BS21 in animal production, medium components and fermentation parameters optimization was carried out using response surface methodology (RSM). Production of antimicrobial secondary metabolites of strain BS21 was increased by 43.4%, and the best medium formula after optimization was corn flour 2%, soybean meal 1.7% and NaCl 0.5% with optimum culture parameters of initial pH 7.0, temperature 30°C, rotating speed at 220 rpm for 26 h. Our results suggested that strain BS21 has the potential for large-scale production and application as a potential source of probiotics and alternative to antibiotics for animal production.

Probiotic Properties of Lactic Acid Bacteria Newly Isolated from Algerian Raw Cow's Milk

This study aims to screen new LAB from Algerian cow's milk to assess their probiotic properties. Molecular identification and MALDI-TOF mass spectrometry methods were used to identify the LAB isolates. The probiotic potential of isolates was determined with in vitro tests of survival to gastrointestinal conditions (pH 2, 0.3% pepsin, 0.5% bile salts, 0.1% trypsin, and 0.1% pancreatic amylase) and antimicrobial and antioxidant activities. Eight isolates were identified as Lactiplantibacillus plantarum (100%) and one isolate as Lacticaseibacillus rhamnosus (95.75%). The MALDI-TOF MS analysis of the isolates confirms that the strains belong to the group of lactobacilli bacteria, particularly Lactiplantibacillus plantarum. The high survival rate reflects a good strain tolerance to the in vitro host simulated gastrointestinal conditions. All bacteria exhibit an antibacterial activity strain with inhibition zone diameters ranging from 4.9 mm against Aspergillus niger ATCC 106404 to 17.47 mm against Candida albicans ATCC 10231. The antioxidant activity with the highest DPPH scavenging activity (92.15%) was obtained with the LbN09 strain. In light of these results, some of the strains isolated from raw milk of the local Algerian breed cows show promising probiotic properties, giving them a possible use in preserving food from microbial spoilage and oxidation during storage.

Genome Sequence and Evaluation of Safety and Probiotic Potential of Lactiplantibacillus plantarum LPJZ-658

This study aims to systematically evaluate the safety of a novel L. plantarum LPJZ-658 explored on whole-genome sequence analysis, safety, and probiotic properties assessment. Whole genome sequencing results demonstrated that L. plantarum LPJZ-658 consists of 3.26 Mbp with a GC content of 44.83%. A total of 3254 putative ORFs were identified. Of note, a putative bile saline hydrolase (BSH) (identity 70.4%) was found in its genome. In addition, the secondary metabolites were analyzed, and one secondary metabolite gene cluster was predicted to consist of 51 genes, which verified its safety and probiotic properties at the genome level. Additionally, L. plantarum LPJZ-658 exhibited non-toxic and non-hemolytic activity and was susceptible to various tested antibiotics, indicating that L. plantarum LPJZ-658 was safe for consumption. Moreover, the probiotic properties tests confirm that L. plantarum LPJZ-658 also exhibits tolerance to acid and bile salts, preferably hydrophobicity and auto-aggregation, and excellent antimicrobial activity against both Gram-positive and Gram-negative gastrointestinal pathogens. In conclusion, this study confirmed the safety and probiotic properties of L. plantarum LPJZ-658, suggesting it can be used as a potential probiotic candidate for human and animal applications.

Limosilactobacillus fermentum KAU0021 Abrogates Mono- and Polymicrobial Biofilms Formed by Candida albicans and Staphylococcus aureus

Candida albicans and Staphylococcus aureus, representing two different kingdoms, are the most frequently isolated pathogens from invasive infections. Their pathogenic attributes, combined with drug resistance, make them a major threat and a challenge to successful treatments, mainly when involved in polymicrobial biofilm-associated infections. In the present study, we investigated the antimicrobial potential of Lactobacillus metabolite extracts (LMEs) purified from cell-free supernatant of four Lactobacillus strains (KAU007, KAU0010, KAU0021, and Pro-65). Furthermore, LME obtained from the strain KAU0021 (LMEKAU0021), being the most effective, was analyzed for its anti-biofilm property against mono- and polymicrobial biofilms formed by C. albicans and S. aureus. The impact of LMEKAU0021 on membrane integrity in single and mixed culture conditions was also evaluated using propidium iodide. The MIC values recorded for LMEKAU0021 was 406 µg/mL, 203 µg/mL, and 406 µg/mL against planktonic cells of C. albicans SC5314, S. aureus and polymicrobial culture, respectively. The LMEKAU0021 at sub-MIC values potentially abrogates both biofilm formation as well as 24 h mature mono- and polymicrobial biofilms. These results were further validated using different microscopy and viability assays. For insight mechanism, LMEKAU0021 displayed a strong impact on cell membrane integrity of both pathogens in single and mixed conditions. A hemolytic assay using horse blood cells at different concentrations of LMEKAU0021 confirmed the safety of this extract. The results from this study correlate the antimicrobial and anti-biofilm properties of lactobacilli against bacterial and fungal pathogens in different conditions. Further in vitro and in vivo studies determining these effects will support the aim of discovering an alternative strategy for combating serious polymicrobial infections caused by C. albicans and S. aureus.