Evaluation of commercial probiotic lactic cultures against biofilm formation by Cronobacter sakazakii

Exploring Technological, Safety and Probiotic Properties of Enterococcus Strains: Impact on Rheological Parameters in Fermented Milk

Enterococci, known for their resilience, are commonly found in food, the environment, and the gastrointestinal tracts of humans and animals. In recent research, six strains of enterococcus were isolated from bat guano. These include Enterococcus mundtii SRBG1, Enterococcus gallinarum SRBG3, Enterococcus faecium SRBG2, Enterococcus casseliflavus EC1, and Enterococcus devriesei CAU 1344. Identification was done using 16S DNA analysis. Each strain underwent evaluation for its technological properties (such as tolerances to various NaCl concentrations and temperatures, as well as amylolytic, β-galactosidase, lipolytic, and proteolytic activities, and EPS production) and selected probiotic properties (including safety profile, resistance to 0.3 percent bile salts and gastric juice with a pH of 2.5, lysozyme tolerance, and antibacterial and antibiofilm activities against four foodborne pathogens). The results were analyzed using Principal Component Analysis. This analysis revealed that E. mundtii SRBG1 and E. gallinarum SRBG3, followed by E. faecium SRBG2, were most closely associated with a broad range of technological characteristics and were subsequently used for fermenting skimmed milk. The rheological properties of the samples indicated a shear-thinning or non-Newtonian behavior. Furthermore, during storage of the fermented milk at 4 °C over periods of 1, 7, 14, and 21 days, there were no significant changes in bacterial count (at around 7 log10 CFU/mL) and pH when fermented with the three evaluated strains.

Antifungal activity of probiotic strain Lactiplantibacillus plantarum MYSN7 against Trichophyton tonsurans

The primary objective of this study was to assess the probiotic attributes and antifungal activity of lactic acid bacteria (LAB) against the fungus, Trichophyton tonsurans. Among the 20 isolates screened for their antifungal attributes, isolate MYSN7 showed strong antifungal activity and was selected for further analysis. The isolate MYSN7 exhibited potential probiotic characteristics, having 75 and 70% survival percentages in pH3 and pH2, respectively, 68.73% tolerance to bile, a moderate cell surface hydrophobicity of 48.87%, and an auto-aggregation percentage of 80.62%. The cell-free supernatant (CFS) of MYSN7 also showed effective antibacterial activity against common pathogens. Furthermore, the isolate MYSN7 was identified as Lactiplantibacillus plantarum by 16S rRNA sequencing. Both L. plantarum MYSN7 and its CFS exhibited significant anti-Trichophyton activity in which the biomass of the fungal pathogen was negligible after 14 days of incubation with the active cells of probiotic culture (10⁶ CFU/ml) and at 6% concentration of the CFS. In addition, the CFS inhibited the germination of conidia even after 72 h of incubation. The minimum inhibitory concentration of the lyophilized crude extract of the CFS was observed to be 8 mg/ml. Preliminary characterization of the CFS showed that the active component would be organic acids in nature responsible for antifungal activity. Organic acid profiling of the CFS using LC-MS revealed that it was a mixture of 11 different acids, and among these, succinic acid (9,793.60 μg/ml) and lactic acid (2,077.86 μg/ml) were predominant. Additionally, a scanning electron microscopic study revealed that CFS disrupted fungal hyphal structure significantly, which showed scanty branching and bulged terminus. The study indicates the potential of L. plantarum MYSN7 and its CFS to control the growth of T. tonsurans. Furthermore, in vivo studies need to be conducted to explore its possible applications on skin infections.

Multivariate analysis of structural and functional properties of fibres from apple pomace using different extraction methods

In recent years, diets rich in fibres have become more popular due to their well-documented beneficial health effects. This has driven exploration of novel dietary fibres from various bioresources. Apple pomace, an industrial waste rich in fibres was used in this study to extract the insoluble dietary fibres. The effect of various extraction methods (hot water, acid, and alkali) on the physico-chemical, structural and functional properties, and prebiotic activity of dietary fibres was evaluated. Hot water extraction resulted in highest yield of dietary fibres in comparison to other methods (p < 0.05). All the fractions resulted in different organization of fibrous components as depicted by scanning electron micrographs, Fourier Transform Infrared spectroscopy (FTIR), X-Ray Diffraction (XRD) pattern and Thermo Gravimetric Analysis (TGA). The acid extracted fibre fraction was observed to be amorphous with loose and porous structure whereas the alkali extracted fraction was more thermal stable based on TGA profile. Among the functional properties, acid extracted dietary fibres fraction possessed highest water and oil holding capacity (p < 0.05). The hot water extracted dietary fraction resulted in maximum increase in viable cell count of standard probiotic strains Lactobacillus sporogenes and Streptococcus faecalis. The Principal Component Analysis revealed that acid extracted fraction possessed better functional activity which also correlates with the structural properties whereas for prebiotic activities, the fibre obtained from hot water extraction method served the best method. These results indicate that dietary fibres extracted through hot water can be employed as a potential prebiotic substrate for the probiotic cultures and could be further explored in foods to improve textural, functional, and bioactive properties of foods.

Graphical Abstract

Selection of a Potential Synbiotic against Cronobacter sakazakii

ABSTRACT

Cronobacter sakazakii is an opportunistic foodborne pathogen that can be fatal to infants; it is commonly associated with powdered infant formula due to contamination during manufacturing processes or during preparation in hospitals or homes. This project aimed to select a potential synbiotic, a combination of probiotic strains with a prebiotic product, to inhibit the growth of C. sakazakii in an in vitro dynamic infant gut model (Simulator of the Human Intestinal Microbial Ecosystem). A total of 16 lactic acid bacteria (LAB) were tested for their inhibitory properties against four different C. sakazakii strains by a zone of inhibition test. Lactobacillus and Pediococcus species were able to inhibit the growth (>15-mm inhibition zones) of all C. sakazakii strains tested, and only one strain from the two genera exhibited atypical resistance to tetracycline. All C. sakazakii strains and the selected LAB strains, which inhibited C. sakazakii and did not exhibit atypical antibiotic resistance, were grown in Luria-Bertani or de Man Rogosa Sharpe broth, respectively, containing 1% dextrose or 1% commercial prebiotic (w/v) to compare their ability to metabolize the prebiotic product. Overall, based on the growth inhibition of C. sakazakii, antibiotic susceptibility, and prebiotic metabolism, 6 of the 16 LAB were chosen to be part of a potential synbiotic. This study has provided valuable information that will help with the development of a synbiotic that can be used in powdered infant formula to reduce the potential for C. sakazakii-related illnesses in infants.

HIGHLIGHTS

Antibacterial and Antibiofilm Effect of Cell-Free Supernatant of Lactobacillus brevis KCCM 202399 Isolated from Korean Fermented Food against Streptococcus mutans KCTC 5458

This study aims to determine the antibiofilm effect of cell-free supernatant (CFS) of Lactobacillus brevis strains against Streptococcus mutans strains. To study the antibiofilm mechanism against S. mutans strains, antibacterial effects, cell surface properties (auto-aggregation and cell surface hydrophobicity), exopolysaccharide (EPS) production, and morphological changes were examined. The antibiofilm effect of L. brevis KCCM 202399 CFS as morphological changes were evaluated by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM), compared with the control treatment. Among the L. brevis strains, L. brevis KCCM 202399 showed the highest antibiofilm effect on S. mutans KCTC 5458. The antibacterial effect of L. brevis KCCM 202399 against S. mutans KCTC 5458 was investigated using the deferred method (16.00 mm). The minimum inhibitory concentration of L. brevis KCCM 202399 against S. mutans KCTC 5458 was 25.00%. Compared with the control treatment, L. brevis KCCM 202399 CFS inhibited the bacterial adhesion of S. mutans KCTC 5458 by decreasing auto-aggregation, cell surface hydrophobicity, and EPS production (45.91%, 40.51%, and 67.44%, respectively). L. brevis KCCM 202399 CFS inhibited and eradicated the S. mutans KCTC 5458 biofilm. Therefore, these results suggest that L. brevis KCCM 202399 CFS may be used to develop oral health in the probiotic industry.

Probiotic properties of Lactobacillus casei - MYSRD 108 and Lactobacillus plantarum-MYSRD 71 with potential antimicrobial activity against Salmonella paratyphi

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This study reports the anti-salmonella activity by cell free supernatant of potential probiotics strains.

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Lactobacillus casei MYSRD 108 and Lactobacillus plantarum MYSRD 71 strains exhibited strong survival and antagonistic activities for probiotic application in the gastrointestinal tract against S. paratyphi biofilm.

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The CFS were characterized by various constraints and represented antagonistic activity against Salmonella due to the presence of organic acids that lowered the pH.

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The strains may be used to produce antimicrobial compounds which can be a substitute for chemical preservatives in food industry.

A total of 130 isolates were screened, twelve isolates were characterized for probiotic attributes and two isolates with best probiotic features were evaluated in the study. Isolates MYSRD108 and MYSRD71 survived gastric conditions and were susceptible to tested antibiotics. Isolates showed more vital cell surface traits such as autoaggregation of 89.2 and 88.5% and cell surface hydrophobicity of 61 and 64%. PCR amplification followed by 16sRNA sequencing results confirmed that the isolates as Lactobacillus casei (MYSRD 108) and Lactobacillus plantarum (MYSRD 71). During this study, the Cells and their Cell Free Supernatant (CFS) were examined for antimicrobial activity. Both the isolates inhibited different bacterial pathogens in which the growth of S. paratyphi was significantly reduced. Further, their CFS also showed inhibitory effects against S. paratyphi with agar well diffusion and Minimum Inhibitory Concentration using Broth micro dilution method. The antimicrobial compounds in the CFS was characterized to different constraints such as pH neutralization, heat treatment, Hydrogen peroxide test and storage stability at -20> °C and represented that the antagonistic acitivity against Salmonella is due to the presence of organic acids in the supernatants that lowered the pH. These strains were further examined for the inhibition of S. paratyphi biofilm. The results indicated that CFS reduced S. paratyphi biofilm by more than 75% and the number of Salmonella biofilm was effectively reduced using 15% concentration of CFS. These strains may be used to produce antimicrobial compounds which can be a substitute for chemical preservatives in food industry.

Intestinal microbiota and inflammatory bowel diseases

Background: The prevalence of inflammatory bowel diseases (IBD) has been rapidly increasing over the past several decades in Korea. IBD appears to be resulted from inappropriate and chronic activation of the mucosal immune system driven by stimuli such as intestinal microbiota and various environmental factors in genetically susceptible individuals.Current Concepts: Recent advances in next-generation sequencing technology have identified alterations in the composition and function of the intestinal microbiota in individuals with IBD. Dysbiosis in patients with IBD is characterized by decreased bacterial diversity combined with an expansion of putative aggressive species and a reduction in protective species. Altered microbial composition and function in IBD correlates with increased immune stimulation, epithelial dysfunction, or enhanced mucosal permeability. Thus, dysbiosis may play an essential role in the pathogenesis of IBD.Discussion and Conclusion: Although it is currently unclear whether dysbiosis is a cause or consequence of intestinal inflammation in IBD, several microbial-based and microbial-targeted therapies have yielded promising early results.

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.

Postbiotics against Pathogens Commonly Involved in Pediatric Infectious Diseases

The Sustainable Development goals for 2020 included reducing all causes associated with infant and perinatal mortality in their priorities. The use of compounds with bioactive properties has been proposed as a therapeutic strategy due to their stimulating effect on the host's immune system. Additionally, biotherapeutic products such as postbiotics, tentatively defined as compounds produced during a fermentation process that support health and well-being, promote intestinal barrier integrity without posing considerable risks to children's health. Although this is a concept in development, there are increasing studies in the field of nutrition, chemistry, and health that aim to understand how postbiotics can help prevent different types of infections in priority populations such as minors under the age of five. The present review aims to describe the main mechanisms of action of postbiotics. In addition, it presents the available current evidence regarding the effects of postbiotics against pathogens commonly involved in pediatric infections. Postbiotics may constitute a safe alternative capable of modulating the cellular response and stimulating the host's humoral response.

The Battle of Probiotics and Their Derivatives Against Biofilms

Biofilm-related infections have been a major clinical problem and include chronic infections, device-related infections and malfunction of medical devices. Since biofilms are not fully available for the human immune system and antibiotics, they are difficult to eradicate and control; therefore, imposing a global threat to human health. There have been avenues to tackle biofilms largely based on the disruption of their adhesion and maturation. Nowadays, the use of probiotics and their derivatives has gained a growing interest in battling against pathogenic biofilms. In the present review, we have a close look at probiotics with the ultimate objective of inhibiting biofilm formation and maturation. Overall, insights into the mechanisms by which probiotics and their derivatives can be used in the management of biofilm infections would be warranted.

Impairment of Cronobacter sakazakii and Listeria monocytogenes biofilms by cell-free preparations of lactobacilli of goat milk origin

Biofilm-associated bacterial infections represent one of the major threats to modern medical treatments. Bacteria encased in biofilm matrix are more resistant towards antimicrobials and thus the capability of microbes to persist and nurture in a biofilm seems to be the foremost aspect of pathogenesis and therapeutic failure. Therefore, there is a pressing demand for new drugs active against microbial biofilms. In the current study, anti-biofilm potential of Lactobacillus spp. cell-free supernatants (CFSs) against Cronobacter sakazakii and Listeria monocytogenes was characterized using crystal violet staining and MTT assay. CFSs of goat milk origin lactobacilli not only prevented biofilm formation but also disrupted preformed biofilms. Neutralized and heat-treated preparations of Lactobacillus CFSs also inhibited biofilm formation by test pathogens. The results were quantitatively confirmed by light and fluorescent microscopy observations. Biofilms developed under static conditions displayed typical compact microcolonies with uniform distribution over the surface, while upon CFS challenge, biofilms were disrupted with presence of dead cells. These findings highlight the anti-biofilm potency of Lactobacillus spp. strains of goat milk origin and their potential application in food industries.