Probiotic Potential of Lactobacillus Strains Isolated from Sorghum-Based Traditional Fermented Food

Antimicrobial and Probiotic Potential of Lactobacilli Associated with Traditional Fermented Beverages

Fermented foods have been recognized as a source of probiotic bacteria which can have a positive effect when administered to humans and animals. Discovering new probiotics in fermented food products poses a global economic and health importance. In this study, we investigated the antimicrobial and probiotic potential of lactobacilli isolated from fermented beverages produced traditionally by ethnic groups in Northeast India. Out of thirty Lactobacilli, fifteen exhibited strong antimicrobial activity against Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter aerogenes with significant anti-biofilm and anti-quorum sensing activity. These isolates also showed characteristics associated with probiotic properties, such as tolerance to low pH and bile salts, survival in the gastric tract, auto-aggregation, and hydrophobicity without exhibiting hemolysis formation or resistance to certain antibiotics. The isolates were identified using gram staining, biochemical tests, and 16S rDNA sequencing. They exhibited probiotic potential, broad-spectrum of antibacterial activity, promising anti-biofilm, anti-quorum sensing activity, non-hemolytic, and tolerance to acidic pH and bile salts. Overall, four specific Lactobacillus isolates, Lactiplantibacillus plantarum BRD3A and Lacticaseibacillus paracasei RB10OW from fermented rice-based beverage, and Lactiplantibacillus plantarum RB30Y and Lacticaseibacillus paracasei MP11A from traditional local curd demonstrated potent antimicrobial and probiotic properties. These findings suggest that these lactobacilli isolates from fermented beverages have the potential to be used as probiotics with therapeutic benefits, highlighting the importance of traditional fermented foods for promoting gut health and infectious disease management.

Bacterial diversity of stingless bee honey in Yunnan, China: isolation and genome sequencing of a novel acid-resistant Lactobacillus pentosus (SYBC-MI) with probiotic and L. tryptophan producing potential via millet fermentation

Stingless bee (Hymenoptera, Apidae, and Trigona) honey is a remarkable "miracle liquid" with a wide range of medical benefits for conditions including gastroenteritis, cataracts, and wound healing. Our study aimed to isolate, identify, and characterize acid-resistant Lactobacillus spp. from sour honey distributed in Yunnan, China. To assess the safety of an entirely novel Lactobacillus pentosus strain, S4 (OM618128), based on probiotic property evaluation and whole-genome sequencing analysis. A 16S rRNA gene high-throughput sequencing analysis showed that Lactobacillus was abundant at the genus level in sour honey. Seven Lactobacillus strains (viz. S1-7) were isolated from sour honey using a multiple-anaerobic culture enrichment method. One potential acid-resistant isolate, Lactobacillus sp. S4, was obtained after screening the seven Lactobacillus isolates, and it had the highest lactic acid production (17.62 g/L), followed by Lactobacillus sp. S3 (17.07 g/L). Phylogenetic and comparative analyses of conserved sequence regions have shown that all seven strains are phylogenetically located in the Lactobacillus pentosus sub-cluster. In L. pentosus SYBC-MI, there is a circular chromosome (3288615 bps) and 11,466 bps plasmids. GC content is 44.03%. The number of predicted genes is 3,129, with 16 rRNAs and 74 tRNAs present. During the fermentation of foxtail millet by seven Lactobacillus pentosus (S1-7) strains isolated from sour honey, a potential tryptophan accumulating isolate, Lactobacillus pentosus S4, was obtained, which could reach a maximum tryptophan content of 238.43 mgL-1 that is 1.80 times the initial tryptophan content in the fermentation broth. This strain has strong acid tolerance, salt tolerance, and fermentation acid production abilities. This strain degrades nitrite at a rate of over 99%, and it has high probiotic potential as well. This project has established a solid foundation for further exploring the excellent lactic acid bacteria in sour honey. It is also investigating the key taxa and their role in the environment. According to the results of our studies, these LAB isolates provide a lot of potential for use in the future, as a source of probiotics for human, animals, and starter cultures for food applications.

Probiotic Lactobacillus and the potential risk of spreading antibiotic resistance: a systematic review

Background and purpose

Lactobacillus, the most popular probiotic, has recently gained more attention because it is a potential reservoir of antibiotic resistance. This review summarized and discussed the phenotypic-genotypic characteristics of antibiotic resistance.

Experimental approach

Google Scholar, PubMed, Web of Science, and Scopus were searched up to February 2022. The inclusion criteria were all studies testing antibiotic resistance of probiotic Lactobacillus strains present in human food supplementation and all human/animal model studies in which transferring antibiotic-resistant genes from Lactobacillus strains to another bacterium were investigated.

Findings/Results

Phenotypic and genotypic characterization of Lactobacillus probiotics showed that the most antibiotic resistance was against protein synthesis inhibitors (fourteen studies, 87.5%) and cell wall synthesis inhibitors (ten studies, 62.5%). Nine of these studies reported the transfer of antibiotic resistance from Lactobacillus probiotic as donor species to pathogenic bacteria and mostly used in vitro methods for resistance gene transfer.

Conclusion and implications

The transferability of resistance genes such as tet and erm in Lactobacillus increases the risk of spreading antibiotic resistance. Further studies need to be conducted to evaluate the potential spread of antibiotic resistance traits via probiotics, especially in elderly people and newborns.

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.

ESKAPEE Pathogen Biofilm Control on Surfaces with Probiotic Lactobacillaceae and Bacillus species

Combatting the rapidly growing threat of antimicrobial resistance and reducing prevalence and transmission of ESKAPEE pathogens in healthcare settings requires innovative strategies, one of which is displacing these pathogens using beneficial microorganisms. Our review comprehensively examines the evidence of probiotic bacteria displacing ESKAPEE pathogens, with a focus on inanimate surfaces. A systematic search was conducted using the PubMed and Web of Science databases on 21 December 2021, and 143 studies were identified examining the effects of Lactobacillaceae and Bacillus spp. cells and products on the growth, colonization, and survival of ESKAPEE pathogens. While the diversity of study methods limits evidence analysis, results presented by narrative synthesis demonstrate that several species have the potential as cells or their products or supernatants to displace nosocomial infection-causing organisms in a variety of in vitro and in vivo settings. Our review aims to aid the development of new promising approaches to control pathogen biofilms in medical settings by informing researchers and policymakers about the potential of probiotics to combat nosocomial infections. More targeted studies are needed to assess safety and efficacy of different probiotic formulations, followed by large-scale studies to assess utility in infection control and medical practice.

Oral microbial shift induced by probiotic Bacillus coagualans along with its clinical perspectives

When used in adequate amounts, Probiotics are considered to beneficially affect host health in many respects. Bacillus coagulans, with its probiotic characteristics, has recently attracted the attention of many researchers and food manufacturers due to its high tolerance in extreme environments because of its spore-forming nature. Several beneficial effects of B. coagulans have been estimated as it exhibits properties of both the genera Bacillus as well as Lactobacillus. Recent literature has proven that B. coagulans has therapeutic effects on intestinal diseases including acute diarrhea, irritable bowel syndrome, antibiotic-related diarrhea, constipation, and colitis via modulation of the microbial composition, host immunity, and general metabolism. Due to the evidence supporting various probiotic effects of B. coagulans, the administration of many B. coagulans strains has been studied in the prevention and management of several oral diseases and conditions. The current review summarizes the probiotic characteristics and clinical, microbiological changes associated with the application of B. coagulans in oral health and diseases along with its future perspectives.

Antibacterial and antibiofilm activity of Lactobacillus strains secretome and extraction against Escherichia coli isolated from urinary tract infection

The purpose of this study was to antibacterial, and antibiofilm activity of two Lactobacillus strains secretome and extraction against E. coli isolated from women with urinary tract infection (UTI). We isolated 100 E. coli samples from women with UTI. Lactobacillus acidophilus and Lactobacillus casei characteristics were evaluated, and their secretome and extraction were prepared. The antibacterial and antibiofilm activity of secretome and extraction of both Lactobacillus strains were evaluated against isolated E. coli samples. L. acidophilus and L. casei were able to tolerate pH 3, bile salts, and pancreatic enzymes. Both probiotics were not resistant to antibiotics and demonstrated an appropriate ability to adhere to the intestinal epithelial cells. Secretome and extraction of L. acidophilus and L. casei strains showed a good antibacterial and antibiofilm against E. coli isolates. Generally, present study suggested that the secretome and extraction of L. acidophilus and L. casei strains exhibits a good antimicrobial activity.

The Impacts of Lactiplantibacillus plantarum on the Functional Properties of Fermented Foods: A Review of Current Knowledge

One of the most varied species of lactic acid bacteria is Lactiplantibacillus plantarum (Lb. plantarum), formerly known as Lactobacillus plantarum. It is one of the most common species of bacteria found in foods, probiotics, dairy products, and beverages. Studies related to genomic mapping and gene locations of Lb. plantarum have shown the novel findings of its new strains along with their non-pathogenic or non-antibiotic resistance genes. Safe strains obtained with new technologies are a pioneer in the development of new probiotics and starter cultures for the food industry. However, the safety of Lb. plantarum strains and their bacteriocins should also be confirmed with in vivo studies before being employed as food additives. Many of the Lb. plantarum strains and their bacteriocins are generally safe in terms of antibiotic resistance genes. Thus, they provide a great opportunity for improving the nutritional composition, shelf life, antioxidant activity, flavour properties and antimicrobial activities in the food industry. Moreover, since some Lb. plantarum strains have the ability to reduce undesirable compounds such as aflatoxins, they have potential use in maintaining food safety and preventing food spoilage. This review emphasizes the impacts of Lb. plantarum strains on fermented foods, along with novel approaches to their genomic mapping and safety aspects.

Fermented Food in Asthma and Respiratory Allergies—Chance or Failure?

In the last few decades, a dramatic increase in the global prevalence of allergic diseases and asthma was observed. It was hypothesized that diet may be an important immunomodulatory factor influencing susceptibility to allergic diseases. Fermented food, a natural source of living microorganisms and bioactive compounds, has been demonstrated to possess health-promoting potentials and seems to be a promising strategy to reduce the risk of various immune-related diseases, such as allergic diseases and asthma. The exact mechanisms by which allergic diseases and asthma can be alleviated or prevented by fermented food are not well understood; however, its potential to exert an effect through modulating the immune response and influencing the gut microbiota has been recently studied. In this review, we provide the current knowledge on the role of diet, including fermented foods, in preventing or treating allergic diseases and asthma.

Isolation, characterization and comparative genomics of potentially probiotic Lactiplantibacillus plantarum strains from Indian foods

Lactiplantibacillus plantarum is one of the most diverse species of lactic acid bacteria found in various habitats. The aim of this work was to perform preliminary phenotypic and genomic characterization of two novel and potentially probiotic L. plantarum strains isolated from Indian foods, viz., dhokla batter and jaggery. Both the strains were bile and acid tolerant, utilized various sugars, adhered to intestinal epithelial cells, produced exopolysaccharides and folate, were susceptible for tetracycline, erythromycin, and chloramphenicol, did not cause hemolysis, and exhibited antimicrobial and plant phenolics metabolizing activities. The genetic determinants of bile tolerance, cell-adhesion, bacteriocins production, riboflavin and folate biosynthesis, plant polyphenols utilization, and exopolysaccharide production were found in both the strains. One of the strains contained a large number of unique genes while the other had a simultaneous presence of glucansucrase and fructansucrase genes which is a rare trait in L. plantarum. Comparative genome analysis of 149 L. plantarum strains highlighted high variation in the cell-adhesion and sugar metabolism genes while the genomic regions for some other properties were relatively conserved. This work highlights the unique properties of our strains along with the probiotic and technically important genomic features of a large number of L. plantarum strains.

Characterization of Streptococcus salivarius as New Probiotics Derived From Human Breast Milk and Their Potential on Proliferative Inhibition of Liver and Breast Cancer Cells and Antioxidant Activity

Breast milk is well known as the abundant source of beneficial bacteria. A new alternative source of human probiotic origin from breast milk is in demand and currently of interest for both the functional food industry and biopharmaceuticals. The aim in this study was to investigate the anticancer and antioxidant efficacies of the new potential probiotics isolated from human breast milk. Three strains of lactic acid bacteria (LAB) have shown their potential probiotic criteria including antimicrobial activity, non-hemolytic property, and survival in acid and bile salt conditions. These strains showed high abilities on cell surface hydrophobicity, auto-aggregation, and co-aggregation. The genera identification by 16S rRNA sequencing and comparison revealed that they were Streptococcus salivarius BP8, S. salivarius BP156, and S. salivarius BP160. The inhibition of liver cancer cells (HepG2) and breast cancer cells (MCF-7) proliferation by these probiotic strains using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was 44.83–59.65 and 29.85–37.16%, respectively. The probiotic action mode was inducted via apoptotic mechanisms since they stimulate the liver and breast cancer cell death through DNA fragmentation and positive morphological changes by acridine orange (AO) and propidium iodide (PI) staining. The antioxidant activity of these probiotics in the form of intact cells, cell free supernatant (CFS), and heat-killed cells was evaluated by a 2,2–diphenyl–1–picrylhydrazyl (DPPH) assay, resulting in the scavenging activity rates of 16.93–25.43, 15.47–28.03, and 13.67–23.0%, respectively. These S. salivarius probiotic strains protected the L929 mouse fibroblasts against oxidative stress with very high survival rates at 94.04–97.77%, which was significantly higher (P < 0.05) than L-ascorbic acid at 75.89–78.67% in the control groups. The results indicated that S. salivarius BP8 and S. salivarius BP160 probiotic strains could be applied as functional foods or new alternative bioprophylactics for treating liver and breast cancers.

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.

Probiotic Properties of New Lactobacillus Strains Intended to Be Used as Feed Additives for Monogastric Animals

The study aimed to evaluate the safety and probiotic properties of selected Lactobacillus strains, which are intended to be fed to monogastric animals. The Lactobacillus spp. appeared to be safe since they did not degrade mucus and did not exhibit β-haemolysis. Moreover, the survival of Caco-2 cells in the presence of metabolites of the selected strains was high, which also indicated their safety. The analysed strains showed moderate or strong antagonistic activity against Salmonella spp., Listeria monocytogenes, Campylobacter jejuni and Campylobacter coli, which was tested with the usage of the agar slab method. Furthermore, the strains showed high survivability in an acidic environment and the presence of bile salts (~90%). High resistivity or moderate susceptibility to antibiotics was also observed, as a result of the disc diffusion method. The strains were mostly moderately hydrophilic (hydrophobicity: 10.43–41.14%); nevertheless, their auto-aggregation capability exceeded 50% and their co-aggregation with pathogens varied between 12.12 and 85.45%. The ability of the selected strains to adhere to Caco-2 cells was also analysed; they were found to be moderately adhesive (85.09–95.05%) and able to hinder pathogens attaching to the cells (up to 62.58%). The analysed strains exhibit probiotic properties, such as high survivability and adherence to epithelial cells; therefore, they are suitable for administration to monogastric animals. Since the overuse of antibiotic growth promoters in livestock leads to the spread of antibiotic-resistant pathogens and accumulation of chemotherapeutic residues in food of animal origin, it is of vital importance to introduce alternative feed additives.

Assessment of some metabolic activities and potential probiotic properties of eight Enterococcus bacteria isolated from white cheese microbiota

In the present study, eight strains of Enterococcus spp. were isolated from Turkish and Iranian white cheese test pieces. Enterococcus spp. strains were identified as Enterococcus faecium (6 strains) and E. faecalis (2) with 16S rDNA sequence analysis. All Enterococcus spp. strains showed susceptibility to the most of antibiotics tested in this investigation. The amount of produced acid (0.59-1.17%), hydrogen peroxide (0.65-3.91 µg/ml), and exopolysaccharide (252-362 mg/L) of these strains were determined. These strains possess the ability to inhibit Escherichia coli ATCC 35,218, Salmonella enteritidis ATCC 13,076, and Salmonella typhimurium MU 80. E. faecium RI53 and RI 42 strains were determined as the most resistant to acid (1.86 and 1.56 OD, respectively) and also exhibited high percentage of aggregation (54.1 and 51.7%, respectively). E. faecium RI 42 exhibited a higher growth viability in gastric and intestinal juice. E. faecium RI 53 and RI 42 are determined as optimal potential probiotic candidates for utilization in cheese preparations.

The Use of Probiotics to Fight Biofilms in Medical Devices: A Systematic Review and Meta-Analysis

Medical device-associated infections (MDAI) are a critical problem due to the increasing usage of medical devices in the aging population. The inhibition of biofilm formation through the use of probiotics has received attention from the medical field in the last years. However, this sparse knowledge has not been properly reviewed, so that successful strategies for biofilm management can be developed. This study aims to summarize the relevant literature about the effect of probiotics and their metabolites on biofilm formation in medical devices using a PRISMA-oriented (Preferred Reporting Items for Systematic reviews and Meta-Analyses) systematic search and meta-analysis. This approach revealed that the use of probiotics and their products is a promising strategy to hinder biofilm growth by a broad spectrum of pathogenic microorganisms. The meta-analysis showed a pooled effect estimate for the proportion of biofilm reduction of 70% for biosurfactants, 76% for cell-free supernatants (CFS), 77% for probiotic cells and 88% for exopolysaccharides (EPS). This review also highlights the need to properly analyze and report data, as well as the importance of standardizing the in vitro culture conditions to facilitate the comparison between studies. This is essential to increase the predictive value of the studies and translate their findings into clinical applications.

High-throughput Sequencing-based Analysis of Microbial Diversity in Rice Wine Koji from Different Areas

Rice wine, a traditional fermented alcoholic beverage in China, is produced with grains such as rice, which are fermented with saccharifying starter-koji. Its flavor quality is closely associated to the starter culture-koji, which is made by mixing botanical materials with high-class glutinous rice in certain ecological context. However, there are few reports on the microbial community structure of rice wine koji. In this paper, bacterial community structures of rice wine koji were analyzed using 16S rRNA gene sequencing based on Illumina MiSeq high-throughput technology in 20 samples collected from Xiaogan area, Hubei province and Dazhu area, Sichuan province (10 from each area). We found rice wine koji flora mainly consisted of Weissella, Lactobacillus, Lactococcus, Bacillus, Enterococcus, and Cronobacter, with relative abundances of 29.49%, 10.93%, 8.85%, 4.75%, 1.16% and 1.15%, respectively, as well as an accumulative average relative abundance of 58.71%. They all belonged to Firmicutes and Proteobacteria-the two known dominant genus. Genus-level PCA (Principal component analysis) and OTU-level PCoA (Principal coordinates analysis) based on unweighted UniFrac distances showed that the bacterial community structure differed significantly between the samples from the 2 areas. 7 OTUs were detected in all samples, accounting for 4.4% of the total qualified assembly. Among the 7 OTUs, 3 OTUs were identified as Enterococcus, 2 OTUs were identified as Cronobacter, 1 OTU was identified as Bacillus and 1 OTU was identified as Alkaliphilus. Fifty-eight lactic acid bacteria (LAB) strains were isolated from the 20 koji samples with traditional microbial methods. Among them, Enterococcus faecium and Pediococcus pentosaceus were the dominant LAB isolates, with relative abundances of 51.72% and 31.03%. Despite the differences, a large number of shared bacteria were detected in samples from the two areas.

Probiotic Properties of Lactic Acid Bacteria Isolated From Neera: A Naturally Fermenting Coconut Palm Nectar

Probiotic bacteria were isolated from different traditional fermented foods as there are several such foods that are not well explored for their probiotic activities. Hence, the present study was conducted to find the potential of lactic acid bacteria (LAB) as probiotics that were isolated from the sap extract of the coconut palm inflorescence - Neera, which is a naturally fermented drink consumed in various regions of India. A total of 75 isolates were selected from the Neera samples collected aseptically in the early morning (before sunrise). These isolates were initially screened for cultural, microscopic, and biochemical characteristics. The initial screening yielded 40 Gram-positive, catalase-negative isolates that were further subjected to acid - bile tolerance with resistance to phenol. Among 40 isolates, 16 survived screening using analysis of cell surface hydrophobicity, auto aggregation with adhesion to epithelial cells, and gastric-pancreatic digestion for gastrointestinal colonization. The isolates were also assessed for antimicrobial, antibiotic sensitivity, and anti-oxidative potential. The safety of these isolates was evaluated by their hemolytic and deoxyribonuclease (DNase) activities. Based on these results, seven isolates with the best probiotic attributes were selected and presented in this study. These LAB isolates, with 51.91-70.34% survival at low pH, proved their resistance to gastric conditions. The cell surface hydrophobicity of 50.32-77.8% and auto aggregation of 51.02-78.95% represented the adhesion properties of these isolates. All the seven isolates exhibited good antibacterial and antifungal activity, showing hydroxyl-scavenging activity of 32.86-77.87%. The results proved that LAB isolated from Neera exhibited promising probiotic properties and seem favorable for use in functional fermented foods as preservatives.

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

BACKGROUND/AIMS

Cronobacter sakazakii, an emergent pathogen is considered as a major concern to infants and neonates fed on reconstituted powdered infant milk formula. In conjunction with many other factors, biofilm forming capacity adds to its pathogenic potential. In view of the facts that infants are at highest risk to C. sakazakii infections, and emerging antibiotic resistance among pathogens, it is imperative to evaluate probiotic cultures for their efficacy against C. sakazakii. Therefore, pure probiotic strains were isolated from commercial probiotic products and tested for their antimicrobial and anti-biofilm activities against C. sakazakii.

METHODS

A total of 6 probiotic strains were tested for their antibiotic susceptibility followed by antimicrobial activity using cell-free supernatant (CFS) against C. sakazakii. The inhibitory activity of CFS against biofilm formation by C. sakazakii was determined using standard crystal violet assay and microscopic observations.

RESULTS

All the probiotic strains were sensitive to ampicillin, tetracycline, vancomycin and carbenicillin whereas most of the strains were resistant to erythromycin and novobiocin. Four of the 6 probiotic derived CFS possessed antimicrobial activity against C. sakazakii at a level of 40 μL. A higher biofilm inhibitory activity (>80%) was observed at initial stages of biofilm formation with weaker activity during longer incubation upto 48 hours (50%-60%).

CONCLUSIONS

The study indicated the efficacy of isolated commercial probiotics strains as potential inhibitor of biofilm formation by C. sakazakii and could be further explored for novel bioactive molecules to limit the emerging infections of C. sakazakii.

Lower respiratory tract microbial composition was diversified in Pseudomonas aeruginosa ventilator-associated pneumonia patients

Background

Probiotics could prevent Pseudomonas aeruginosa colonization in lower respiratory tract (LRT) and reduced P. aeruginosa ventilator-associated pneumonia (VAP) rate. Recent studies also suggested that probiotics could improve lung inflammation in mice infected with P. aeruginosa. It seems that microbiota regulation may be a potential therapy for P. aeruginosa VAP patients. However, we know less about the LRT microbial composition and its correlation with prognosis in P. aeruginosa VAP patients. This study aimed to characterize LRT microbiota in P. aeruginosa VAP patients and explore the relationship between microbiota and patient prognosis.

Methods

Deep endotracheal secretions were sampled from subjects via intubation. Communities were identified by 16S ribosomal RNA gene sequencing. The relationship between microbiota and the prognosis of P. aeruginosa VAP patients were evaluated. Clinical pulmonary infection score and the survival of intensive care unit were both the indicators of patient prognosis.

Results

In this study, the LRT microbial composition of P. aeruginosa VAP patients was significantly different from non-infected intubation patients, and showed significant individual differences, forming two clusters. According to the predominant phylum of each cluster, these two clusters were named Pro cluster and Fir-Bac cluster respectively. Patients from Pro cluster were dominated by Proteobacteria (adj.P < 0.001), while those from Fir-Bac cluster were dominated by Firmicutes, and Bacteroidetes (both adj.P < 0.001). These two varied clusters (Pro and Fir-Bac cluster) were associated with the patients’ primary disease (χ²-test, P < 0.0001). The primary disease of the Pro cluster mainly included gastrointestinal disease (63%), and the Fir-Bac cluster was predominantly respiratory disease (89%). During the two-week dynamic observation period, despite the use of antibiotics, the dominant genera and Shannon diversity of the LRT microbiota did not change significantly in patients with P. aeruginosa VAP. In prognostic analysis, we found a significant negative correlation between Lactobacillus and clinical pulmonary infection score on the day of diagnosis (P = 0.014); but we found no significant difference of microbial composition between survivors and non-survivors.

Conclusions

LRT microbial composition was diversified among P. aeruginosa VAP patients, forming two clusters which were associated with the primary diseases of the patients.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0847-3) contains supplementary material, which is available to authorized users.

Effect of the environment microbiota on the flavour of light-flavour Baijiu during spontaneous fermentation

Light-flavour Baijiu is a type of Chinese liquor with a pure and mild flavour produced by traditional spontaneous solid-state fermentation. The flavour of this liquor has been found to vary in the different periods of annual production. To explore the factors affecting flavour, the microbiota of the surrounding environment, starter and fermentation process in different periods were investigated. Results showed that the ester content and acidity of light-flavour Baijiu were significantly lower when annual production was resumed after a summer break. HCA plot of volatile flavour profile and bacterial PCoA results indicated that the differences occurred at later stages, mainly due to different structures of Lactobacillus. Correlation analysis by O2PLS indicated that Lactobacillus positively correlated with esters. Species-level analysis showed that the lack of L. acetotolerans on the surface of the jar might cause a lag in fermentation and lower ester content. Thereafter, L. acetotolerans was revived during fermentation and enriched on the surface of the jar, which promoted ester formation. As important sources of L. acetotolerans, the air and fermentation jars played a critical role during fermentation. Therefore, this systematic study on environmental microbial ecology is valuable for quality control and to explore environmental microbiota functions during spontaneous fermentation.

Bacillus As Potential Probiotics: Status, Concerns, and Future Perspectives

Spore-forming bacilli are being explored for the production and preservation of food for many centuries. The inherent ability of production of large number of secretory proteins, enzymes, antimicrobial compounds, vitamins, and carotenoids specifies the importance of bacilli in food chain. Additionally, Bacillus spp. are gaining interest in human health related functional food research coupled with their enhanced tolerance and survivability under hostile environment of gastrointestinal tract. Besides, bacilli are more stable during processing and storage of food and pharmaceutical preparations, making them more suitable candidate for health promoting formulations. Further, Bacillus strains also possess biotherapeutic potential which is connected with their ability to interact with the internal milieu of the host by producing variety of antimicrobial peptides and small extracellular effector molecules. Nonetheless, with proposed scientific evidences, commercial probiotic supplements, and functional foods comprising of Bacillus spp. had not gained much credential in general population, since the debate over probiotic vs pathogen tag of Bacillus in the research and production terrains is confusing consumers. Hence, it’s important to clearly understand the phenotypic and genotypic characteristics of selective beneficial Bacillus spp. and their substantiation with those having GRAS status, to reach a consensus over the same. This review highlights the probiotic candidature of spore forming Bacillus spp. and presents an overview of the proposed health benefits, including application in food and pharmaceutical industry. Moreover, the growing need to evaluate the safety of individual Bacillus strains as well as species on a case by case basis and necessity of more profound analysis for the selection and identification of Bacillus probiotic candidates are also taken into consideration.

The complete genome sequence of the yogurt isolate Streptococcus thermophilus ACA-DC 2

Streptococcus thermophilus ACA-DC 2 is a newly sequenced strain isolated from traditional Greek yogurt. Among the 14 fully sequenced strains of S. thermophilus currently deposited in the NCBI database, the ACA-DC 2 strain has the smallest chromosome, containing 1,731,838 bp. The annotation of its genome revealed the presence of 1,850 genes, including 1,556 protein-coding genes, 70 RNA genes and 224 potential pseudogenes. A large number of pseudogenes were identified. This was also accompanied by the absence of pathogenic features suggesting evolution of strain ACA-DC 2 through genome decay processes, most probably due to adaptation to the milk ecosystem. Analysis revealed the existence of one complete lactose-galactose operon, several proteolytic enzymes, one exopolysaccharide cluster, stress response genes and four putative antimicrobial peptides. Interestingly, one CRISPR-cas system and one orphan CRISPR, both carrying only one spacer, were predicted indicating low activity or inactivation of the cas proteins. Nevertheless, four putative restriction-modification systems were determined that may compensate any deficiencies of the CRISPR-cas system. Furthermore, whole genome phylogeny indicated three distinct clades within S. thermophilus. Comparative analysis among selected strains representative for each clade, including strain ACA-DC 2, revealed a high degree of conservation at the genomic scale, but also strain specific regions. Unique genes and genomic islands of strain ACA-DC 2 contained a number of genes potentially acquired through horizontal gene transfer events, that could be related to important technological properties for dairy starters. Our study suggests genomic traits in strain ACA-DC 2 compatible to the production of dairy fermented foods.

Prevalence, Virulence Potential, and Antibiotic Susceptibility Profile of Listeria monocytogenes Isolated From Bovine Raw Milk Samples Obtained From Rajasthan, India

Listeriosis is a serious foodborne disease of a global concern, and can effectively be controlled by a continuous surveillance of the virulent and multidrug-resistant strains of Listeria monocytogenes. This study was planned to investigate prevalence of L. monocytogenes in bovine raw milk samples. A total of 457 raw milk samples collected from 15 major cities in Rajasthan, India, were analyzed for the presence of L. monocytogenes by using standard microbiological and molecular methods. Five of the 457 samples screen tested positive for L. monocytogenes. Multiplex serotyping showed that 3/5 strains belonged to serotype 4b followed by one strain each to 1/2a and to 1/2c. Further virulence potential assessment indicated that all strains possessed inlA and inlC internalins, and, in addition, two strains also possessed the gene for inlB. All strains were positive for Listeriolysin O (LLO) and showed phosphatidylinositol-specific phospholipase C (PI-PLC) activity on an in vitro agar medium with variations in production levels among the strains. A good correlation between the in vitro pathogenicity test and the chick embryo test was observed, as the strains showing higher LLO and PI-PLC activity were found to be lethal to fertilized chick embryos. All strains were resistant to the majority of antibiotics and were designated as multidrug-resistant strains. However, these strains were susceptible to 9 of the 22 tested antibiotics. The maximum zone of inhibition (mm) and acceptable minimum inhibitory concentration were observed with azithromycin, and thus it could be the first choice of a treatment. Overall, the presence of multidrug-resistant L. monocytogenes strains in the raw milk of Rajasthan region is an indicator of public health hazard and highlighting the need of consumer awareness in place and implementation of stricter food safety regulations at all levels of milk production.

Antifungal Attributes of Lactobacillus plantarum MYS6 against Fumonisin Producing Fusarium proliferatum Associated with Poultry Feeds

Fumonisins, being common in occurrence in maize-based feeds, pose a great threat to animal and human health. The present study is aimed at determining the antifungal activity of Lactobacillus plantarum MYS6 against a fumonisin producing fungus, Fusarium proliferatum MYS9. The isolate was subjected to standard tests for determining its probiotic attributes and antifungal properties. L. plantarum MYS6 thrived well at pH 3.0 and 6.0, and exhibited strong resistance up to 3% bile. The isolate showed a high degree of cell surface hydrophobicity corresponding to its strong adhesion to chicken crop epithelial cells. Co-inoculation with the fungus on modified de Man Rogosa Sharpe medium revealed the inhibitory effect of L. plantarum MYS6 on fungal growth and biomass. Observation using scanning electron microscopy showed distortion of hyphal structures, swollen tips and disrupted conidia. Conidia germination inhibition assay restrained germination and showed deformed hyphae. The bioprotective feature of the isolate was evident by the inhibition of fungal development in maize-kernel treated with the cell free supernatant of L. plantarum MYS6. Both the isolate and its extracellular metabolites lowered fumonisin content in feed model up to 0.505 mg/Kg of feed and 0.3125 mg/Kg of feed respectively when compared to the level of 0.870 mg/Kg of feed in control. The major antifungal compounds produced by the isolate were 10-Octadecenoic acid, methyl ester; palmitic acid, methyl ester; heptadecanoic acid, 16-methyl ester; stearic acid and lauric acid. L. plantarum MYS6 reduced 61.7% of fumonisin possibly by a binding mechanism. These findings suggest the application of L. plantarum MYS6 as an efficient probiotic additive and biocontrol agent in feed used in poultry industry. Additionally, the antifungal metabolites pose a conspicuous inhibition of Fusarium growth and fumonisin production.