Probiotic Viability Research Articles

Electrostatically reinforced and sealed nanocellulose-based macrosphere by alginate/chitosan multi-layer coatings for delivery of probiotics

Probiotic supplements have been widely employed to change gut microbiome compositions for the treatment of numerous human disorders since gut flora has a tight association with human health and disease. However, the viability of probiotics has been a major barrier to the application of probiotic products. Here, we developed an electrostatically reinforced and sealed nanocellulose-based macrosphere for probiotic encapsulation. The inside porous gel sphere provides abundant and relatively independent porous spaces for probiotics to live in. The introduction of chitosan hydrochloride (CHC) and alginate (ALG) strengthened the gel structure and contributed to the formulation of a multi-layered structure with pH-responsive properties. The mild strengthening and coating processes avoid severe damage to the sensitive probiotics in the processing process, and the synthesized multi-layer macrospheres could protect probiotics from gastric acid and bile salt conditions. In addition, the dissolvability of the outer shell and the stable inner porous skeleton in intestinal conditions allow the gradual release of the entrapped probiotics in targeted environments. Overall, this work suggests the electrostatically reinforced and sealed nanocellulose-based macrospheres are ideal materials for the probiotic delivery application.

Co-incorporation of probiotics into 3D printed custard cream with hydrophilic and hydrophobic bioactives

There is an emerging need for food with specific functionality and nutrition. This work investigated the feasibility of developing 3D printed custard cream co-enriched with probiotics, hydrophilic and hydrophobic bioactives. The effect of EGCG and resveratrol on survival of probiotics encapsulated in 3D printed custard cream during storage, heating, and simulated gastrointestinal conditions were investigated. The addition of bioactives and probiotic coacervates didn't exhibit great influence on the emulsion structure, gel-like rheological behavior and great printing properties of the resulting custard cream samples. The cell survival of encapsulated probiotics in the custard cream with bioactives was prominently increased during storage at 4 °C as well as under heating at 63 and 75 °C. The co-encapsulation of probiotics, EGCG and resveratrol in the custard cream improved the viability of probiotic in the gastrointestinal tract. There was only a 0.85 log and 1.52 log loss of probiotic viability in the custard cream after digestion in simulated gastric and small intestinal digestion conditions. Meanwhile, EGCG and resveratrol in this sample showed a maximum release after simulated digestion, which reached 68.10% and 71.69% release at the end of digestion. Therefore, the co-encapsulation of EGCG, resveratrol with probiotic in this 3D printable custard cream delivery system would be an efficient approach to simultaneous delivery bioactives and probiotic in the gastrointestinal tract with synergistic beneficial effects.

Alcoholic and non-alcoholic rosé wines made with Saccharomyces cerevisiae var. boulardii probiotic yeast

The production of alcoholic and non-alcoholic rosé winesusing Saccharomyces cerevisiae var. boulardii probiotic yeast is described in this study for the first time. Before and after fermentation and distillation, the volatile acidity, lactic, and malic acid levels were evaluated for S. cerevisiae var. boulardii. These contents were compared to those obtained with a standard S. cerevisiae EC-1118 yeast. We measured the levels of gluconic acid and free amino nitrogen in the musts. After fermentation and distillation, yeast viability was assessed as a function of time (0, 15days, 3months, and 6months), both at ambient temperature (25 ± 0.5 °C) and refrigerator temperature (4 ± 0.5 °C). The outcomes revealed that the rosé wine made with S. cerevisiae var. boulardii had the same values and preliminary sensory characteristics as other commercial wines made with S. cerevisiae EC-1118. The S. cerevisiae var. boulardii yeast successfully survived the high alcohol level produced during fermentation and vacuum distillation. The study also revealed that this unique rosé wine retains its probiotic viability for at least 6 months when stored at room temperature or in the refrigerator, making it a suitable candidate for large-scale production where long storage intervals are required by both producers and consumers.

Effect of microencapsulated Lactobacillus reuteri under simulated gastric conditions and its inhibition on Listeria monocytogenes

Food-borne diseases (FDB) are responsible for causing approximately 600 million illnesses and 420,000 deaths per year. Biologically related FBDs are typically associated with ubiquitous microorganisms, with bacteria such as Li. monocytogenes, Escherichia coli, Salmonella and Staphylococcus aureus being frequently implicated. The use of probiotics is limited by adverse conditions, that can impair the stability of La. reuteri and the evaluation of its probiotic properties and effects on pathogenic bacteria. Therefore, it is crucial to develop effective strategies to protect probiotics during their use. This study was conducted aiming to determine the effect of microencapsulation by spray drying technique on the probiotic viability of La. reuteri on Li. monocytogenes under simulated gastric conditions. The research involved reconstituting, planting, and inoculating La. reuteri and Li. monocytogenes; determining fermentation kinetics; conducting spray drying microencapsulation; studying and characterizing of microencapsulation; testing for exopolysaccharides production; conducting temperature tests; assessing exposure to gastric conditions; and conducting antibiotic susceptibility and inhibition tests. Such investigations allowed the establishment of the exponential phase in Probiotic (PRO) culture medium at 18 h and in De Man, Rogosa and Sharpe agar (MRS) medium at 12 h, exopolysaccharide production positive and growth at different temperatures (1.95x1013 CFU/ml and 2.16x1012 CFU/ml), survival against gastric conditions (greater than 108 CFU/ml) and inhibitory effect of La. reuteri on Li. monocytogenes (halos larger than 2 mm). The probiotic La. reuteri microencapsulated in a binary matrix composed of inulin and maltodextrin expresses probiotic properties against Li. monocytogenes, which is responsible for FBD and great stability after undergoing simulated gastric conditions.

The Survival of Psychobiotics in Fermented Food and the Gastrointestinal Tract: A Review.

In recent years, scientists have been particularly interested in the gut-brain axis, as well as the impact of probiotics on the nervous system. This has led to the creation of the concept of psychobiotics. The present review describes the mechanisms of action of psychobiotics, their use in food products, and their viability and survival during gastrointestinal passage. Fermented foods have a high potential of delivering probiotic strains, including psychobiotic ones. However, it is important that the micro-organisms remain viable in concentrations ranging from about 106 to 109 CFU/mL during processing, storage, and digestion. Reports indicate that a wide variety of dairy and plant-based products can be effective carriers for psychobiotics. Nonetheless, bacterial viability is closely related to the type of food matrix and the micro-organism strain. Studies conducted in laboratory conditions have shown promising results in terms of the therapeutic properties and viability of probiotics. Because human research in this field is still limited, it is necessary to broaden our understanding of the survival of probiotic strains in the human digestive tract, their resistance to gastric and pancreatic enzymes, and their ability to colonize the microbiota.

Process Development for the Spray-Drying of Probiotic Bacteria and Evaluation of the Product Quality

Probiotics and prebiotics are of great interest to the food and pharmaceutical industries due to their health benefits. Probiotics are live bacteria that can confer beneficial effects on human and animal wellbeing, while prebiotics are types of nutrients that feed the beneficial gut bacteria. Powder probiotics have gained popularity due to the ease and practicality of their ingestion and incorporation into the diet as a food supplement. However, the drying process interferes with cell viability since high temperatures inactivate probiotic bacteria. In this context, this study aimed to present all the steps involved in the production and physicochemical characterization of a spray-dried probiotic and evaluate the influence of the protectants (simulated skim milk and inulin:maltodextrin association) and drying temperatures in increasing the powder yield and cell viability. The results showed that the simulated skim milk promoted higher probiotic viability at 80 °C. With this protectant, the probiotic viability, moisture content, and water activity (Aw) reduce as long as the inlet temperature increases. The probiotics' viability decreases conversely with the drying temperature.At temperatures close to 120 °C, the dried probiotic showed viability around 90%, a moisture content of 4.6% w/w, and an Aw of 0.26; values adequate to guarantee product stability. In this context, spray-drying temperatures above 120 °C are required to ensure the microbial cells' viability and shelf-life in the powdered preparation and survival during food processing and storage.

Effects of fermenting with Lacticaseibacillus rhamnosus GG on quality attributes and storage stability of buffalo milk yogurt incorporated with bael (Aegle marmelos) fruit pulp

BackgroundProducing functional food by adding fruits or fruit pulps have attracted great attention. Simultaneously, buffalo milk is gaining an increasing demand as an alternative to cow milk. Thus, value addition and diversification of buffalo milk products have gained much commercial and research interest. Hence, we aimed to investigate the potentials of developing and characterizing probiotic enriched buffalo milk yogurts with bael fruit pulp using exopolysaccharides producing probiotic Lacticaseibacillus rhamnosus GG (LGG). MethodsFour types of buffalo milk yogurts were tested, e.g. fermenting with the yogurt starter culture only (e.g., control) and fermenting with the combination of yogurt starter culture and LGG with varying levels (w/v) of bael fruit pulp incorporations, i.e., 0%, 5% and 10%. Variation in pH, syneresis, hardness, probiotic viability and sensory attributes during 21 days of storage in 4 °C were assessed for all treatments. ResultsFermenting with LGG had a positive effect on post-acidification and syneresis rate compared to the control yogurt. Bael incorporation did not affect the post-acidification, but significantly decreased the level of syneresis at the end of storage. All probiotic formulations maintained LGG counts of >107 CFU/mL and the highest counts were observed in 5% (w/v) bael incorporated yogurt. ConclusionsResults confirmed the possibility of using buffalo milk yogurt as an ideal matrix to deliver LGG with promising probiotic capacity. The use of 5% bael incorporation provides an optimal combination for synbiotic product development.

Microencapsulation and Application of Probiotic Bacteria Lactiplantibacillus plantarum 299v Strain.

Microencapsulation is an up-and-coming technology for maintaining the viability of probiotics. However, the effect of core-to-wall ratios and ratios of polysaccharides on the protection of the Lactiplantibacillus plantarum 299v strain has not been deeply discussed. Lyophilization of the Lp. plantarum 299v strain was conducted, and different core-to-wall ratios and ratios of maltodextrin (MD) and resistant starch (RS) were applied. Results demonstrated that the content of MD and RS had an influence on the yield and bulk density in both core-to-wall ratios (1:1 and 1:1.5). In addition, samples coated with a core-to-wall ratio of 1:1.5 had significantly higher viability than those coated with a core-to-wall ratio of 1:1. Moreover, samples coated with core-to-wall ratios of 1:1 and MD:RS 1:1, as well as core-to-wall ratios of 1:1.5 and MD:RS 3:1, had the highest cell number after simulated gastric fluid and simulated intestinal fluid testing, respectively. Furthermore, the optimal formulation for the application of microencapsulated Lp. plantarum 299v in apple juice (serving as a functional beverage) is listed as follows: core-to-wall ratios of 1:1 and MD:RS 1:1, with the fortification method, and stored at 4 °C. After 11 weeks of storage, the cell count was 8.28 log (CFU/mL). This study provided a strategy for Lp. plantarum 299v to achieve high viability in long-term storage and provides an application in functional apple beverages.

Alginate encapsulation improves probiotics survival in carbonated sodas and beers.

Probiotic functionalization of non-dairy beverages has been garnering interest to provide dairy-sensitive populations with greater probiotic product varieties. The addition of probiotics into popularly consumed beverages-carbonated sodas and beers, presents an interesting challenge as the presence of acidic pH, hops-derived compounds, and ethanol have highly deleterious effects. Herein, alginate encapsulation was proposed to improve probiotics viability within sodas and beers. Three probiotics, namely Lacticaseibacillus rhamnosus GG, Escherichia coli Nissle 1917, and Bifidobacterium longum were encapsulated in alginate spheres and exposed to Coca-Cola, 7-Up, Tiger Beer, and Guinness under refrigerated, room temperature and simulated gastric fluid conditions. Results demonstrate that alginate encapsulation significantly improved the viabilities of all three probiotics in various beverages and conditions. Refrigerated storage better preserved probiotic viabilities and reduced the formation of the probiotic metabolic by-product, L-lactate, than at room temperature storage. Findings here could provide beverage manufacturers with a novel way to develop probiotic-sodas and probiotic-beers through encapsulation.

The influence of variations in starter concentration Lactobacillus plantarum AS4 indigenous from human breast milk to the characteristics of fermented milk

The fermentation of milk by Lactobacillus plantarum AS4 can be classified as a functional or nutraceutical food. Lactobacillus plantarum AS4 is a group of Lactic Acid Bacteria (LAB) isolated from human breast milk, which has the ability as a probiotic in vitro. This research aimed to determine the effect of Lactobacillus plantarum AS4 starter concentration on the characteristics of fermented milk produced. Variations concentration starter used were 0, 2, 4, 6, and 8% with an incubation temperature of 37 °C for 24 hours. Fermentation parameters collected were probiotic viability, total bacteria, titrable acidity, lactose, protein, and fat content. The results showed that variations in concentration starter Lactobacillus plantarum strain AS4 significantly affected the characteristics of fermented milk based on the parameters collected. The viability of fermented milk probiotics increased in milk treated with an 8% starter concentration variation (9.91 ±0.02 log CFU/mL) and total bacteria (8.84 ±0.07 log CFU/mL) in the fermented milk product. The levels of lactic acid (1.66 ±0.06%) and protein (4.32±0.03%) were also increased in fermented milk products with a starter variation of 8%. Significantly, fermented milk products with concentrations starter 8% decreased the pH value (4.10 ±0.01), lactose content (2.33±0.01%), and fat content (2.30±0.05%).

Development of synbiotic vegan beverages: probiotic viability, sensory profile, consumers' acceptance and functional stability

SummaryThe development of synbiotic vegan drinks expands the probiotic food options on the market as an alternative to dairy products and with no added sugars. This study aimed to investigate the impact of fermentation and inulin addition in mixed carrot‐orange juice with Lactiplantibacillus plantarum (LP) on the sensory profile, consumer acceptance and functional stability. The results demonstrated that all fermented juices had high antioxidant capacity (AOC) and were a rich source of bioactive compounds such as β‐carotene and phenolics. However, only the β‐carotene showed a high correlation with the AOC. Inulin could improve LP survival, remaining at high concentration during the 21 days of storage. Only fermented juices with 2% inulin showed a positive correlation with sweet taste and had the best impact on sensorial properties. Fermentation with LP and inulin addition could contribute to the improvement of orange flavour and taste. Penalty analysis showed that the control‐unfermented juices were the samples with a clear need for improvement with respect to the fermented ones. Therefore, carrot‐orange juices represent a promising vegan food matrix for probiotic delivery.

Novel gellan gum-based probiotic film with enhanced biological activity and probiotic viability: Application for fresh-cut apples and potatoes

A novel probiotic film based on gellan gum (GN), cranberry extract (CE), and Lactococcus lactis (LA) was developed in the present study. The fluorescence and SEM image results showed that GN/CE film containing LA was successfully fabricated. The incorporation of LA significantly enhanced the antibacterial activity of the film. The presence of CE strengthened the antioxidant activity and LA survivability in the film. The combination of LA (0–1.0 %) and CE (0.5–1.0 %) improved the mechanical property of the film through the formation of density structure. The best comprehensive properties were obtained with the film containing 2.0 %LA and 0.5 %CE. The GN/2.0 %LA/0.5 %CE film also showed the optimal preservation effect on fresh-cut potatoes and apples. Hence, GN/2.0 %LA/0.5 %CE probiotic film has proved to be suitable for fruit and vegetable preservation.

Lactobacillus rhamnosus GG alleviates colitis caused by chemotherapy via biofilm formation.

Severe colitis is a common side effect of chemotherapy in cancer patients. In this study, we attempted to enhance the viability of probiotics in a gastric acid environment and improve the colitis induced by dextran sulfate sodium (DSS) and docetaxel. We purified Lactobacillus from yogurt and estimated their growth at pH 6.8 and pH 2.0. In the further investigation, the bacterial biofilm formation was used to define the mechanism by which administration of Lactobacillus rhamnosus (LGG) via oral gavage alleviates the colitis and intestine permeability of the mice induced by DSS and docetaxel. The potential benefit of probiotics on the treatment of breast cancer metastasis has been assessed as well. Lactobacillus from yogurt growth was unexpectedly faster in the pH 2.0 than in the neutral pH medium during the first hour. LGG administered in the fasting state via oral gavage significantly improved the preventive effect in the colitis caused by DSS and docetaxel. LGG reduced the permeability of the intestine and decreased the expression of proinflammatory cytokines, TNF-α, IL-1β, and IL-6, in colitis by biofilm formation. Increasing the docetaxel dose may reduce breast tumor growth and metastasis in the lung but did not benefit survival due to severe colitis. However, the LGG supplement significantly improved the survival of tumor-bearing mice following a high dose of docetaxel treatment. Our findings provide new insights into the potential mechanism of probiotic protection of the intestine and provide a novel therapeutic strategy to augment the chemotherapeutic treatment of tumors.

Development of soy protein isolate/sodium carboxymethyl cellulose synbiotic microgels by double crosslinking with transglutaminase and aluminum chloride for delivery system of Lactobacillus acidophilus

This study was carried out to develop soy protein isolate (SPI)/sodium carboxymethyl cellulose (NaCMC) synbiotic microgels by applying a double-crosslinking technique using transglutaminase and different concentrations of AlCl3 (0 %, 6 %, 7 %, 8 %) and also by adding Lactobacillus acidophilus (L. acidophilus) and pectic oligosaccharide. Synbiotic microgels crosslinked using 8 % AlCl3 (SPI/NaCMC-Al3+8 microgels) showed the highest encapsulation efficiency (92 %). The double-crosslinked microgels exhibited a smooth surface as proved by SEM. FT-IR, XRD, and DSC analyses showed the possible interaction within matrices and demonstrated the higher thermal stability of synbiotic microgels prepared using a higher concentration of AlCl3. All in all, after exposure to simulated digestion fluid, heat treatment (72 °C, 15 s), and refrigerated storage, more cells in double-crosslinked microgels survived compared to single-crosslinked microgels. In particular, probiotic viability was highest in SPI/NaCMC-Al3+8 microgels. These results indicate that the SPI/NaCMC-Al3+8 microgels developed in this study can effectively protect L. acidophilus against the external environment.

A Novel Symbiotic Beverage Based on Sea Buckthorn, Soy Milk and Inulin: Production, Characterization, Probiotic Viability, and Sensory Acceptance.

Nowadays, vegan consumers demand that food products have more and more properties that contribute to the prevention of some diseases, such as lower fat content, increased mineral content (calcium, iron, magnesium, and phosphorus), pleasant flavor, and low calorie values. Therefore, the beverage industry has tried to offer consumers products that include probiotics, prebiotics, or symbiotics with improved flavor and appearance and beneficial effects on health. The possibility of producing beverages based on soy milk with sea buckthorn syrup or sea buckthorn powder supplemented with inulin and fermented with the Lactobacillus casei ssp. paracasei strain was examined. The aim of this study was to obtain a novel symbiotic product that exploits the bioactive potential of sea buckthorn fruits. Tests were carried out in the laboratory phase by fermenting soy milk, to which was added sea buckthorn syrup (20%) or sea buckthorn powder (3%) and inulin in proportions of 1% and 3%, with temperature variation of fermentation (30 and 37 °C). During the fermentation period, the survivability of prebiotic bacteria, pH, and titratable acidity were measured. The storage time of beverages at 4 °C ± 1 °C was 14 days, and the probiotic viability, pH, titratable acidity, and water holding capacity were determined. Novel symbiotic beverages based on sea buckthorn syrup or powder, inulin, and soy milk were successfully obtained using the Lactobacillus casei ssp. paracasei strain as a starter culture. Moreover, the inulin added to the novel symbiotic beverage offered microbiological safety and excellent sensory attributes as well.

Production, Formulation, and Application of Postbiotics in the Treatment of Skin Conditions

The skin microbiome is composed of a complex association of bacteria, fungi, and viruses. The maintenance of skin commensal microbes is essential for preventing the overgrowth of pathogenic microorganisms or already present opportunistic pathogens. Thus, the development of bioactive compounds capable of modulating skin microbiome has become an important topic for both researchers and the cosmetic industry. Increasingly, scientific evidence highlights that metabolites derived from probiotics have a great potential to prevent diseases affecting the skin. These compounds have recently been called postbiotics and are defined as a “preparation of inanimate microorganisms and/or their components that confers a health benefit on the host”. Postbiotics are obtained from fermentations performed almost exclusively by lactic acid bacteria and yeast. Short-chain fatty acids, bacteriocins, and organic acids are some examples of postbiotics. These compounds exhibit antimicrobial, immunomodulatory, antioxidant, and anti-inflammatory activities. In addition, postbiotic production possesses technological advantages, including high stability and increased safety, compared to viable probiotics. In this article, a model for the large-scale production of postbiotics and their uses in cosmetic formulations are reviewed. In addition, results obtained from in vivo tests for the treatment of alopecia, acne, atopic dermatitis, and wound healing are discussed. Finally, technological advances are shown based on a survey of the main patents filed in the area of postbiotics.

Improved infectious burn wound healing by applying lyophilized particles containing probiotics and prebiotics

Lactiplantibacillus plantarum cells were encapsulated in a mixture of cationic and anionic polymers, with the final composition stabilized through freeze-drying. A D-optimal design was used to examine the effects of different polymer concentrations as well as adding prebiotics on the probiotic viability and swelling behavior of the formulations. Scanning electron micrographs revealed stacked particles capable of rapidly absorbing significant amounts of water. These images corresponded to initial swelling percentages of around 2000% for the optimal formulation. The optimized formula had a viability percentage of more than 82%, with the stability studies suggesting that the powders should be stored at refrigerated temperatures. The physical characteristics of the optimized formula were examined to ensure compatibility with its application. According to antimicrobial evaluations, the difference in pathogen inhibition between formulated and fresh probiotics was less than a logarithm. The final formula was tested in vivo and showed improved wound healing indicators. The optimized formula resulted in a higher rate of wound closure and infection clearance. Furthermore, the molecular studies for oxidative stress indicated that the formula could modify wound inflammatory responses. In histological investigations, the probiotic-loaded particles functioned exactly as efficaciously as silver sulfadiazine ointment did.

Improvement of Probiotic Viability by Mixing with Ultrasound-Treated Yeast Cells and Spray Drying.

The objective of the study was to determine the efficacy of ultrasound-treatmentSaccharomyces cerevisiae and spray drying in preserving the viability of Lactiplantibacillus plantarum. The combination of ultrasound-treated S. cerevisiae and L. plantarum was evaluated. Next, the mixture was blended with maltodextrin and either Stevia rebaudiana-extracted fluid, prior to undergoing spray drying. The L. plantarum viability was assessed after the spray drying process, during storage, and in simulated digestive fluid (SDF) conditions. The results showed that the impact of ultrasound caused the crack and holes in the yeast cell wall. Besides, the moisture content values were not significantly different in all samples after spray drying. Although the amount of powder recovery in stevia-supplemented samples was not higher than that of the control sample, the L. plantarum viability was significantly improved after the spray drying process. The density of L. plantarum tended to be stable during the first 30days of storage and decreased more rapidly after that. The results reveal that there was no statistically significant difference in the trend of the samples before and after storage. In the SDF test, the L. plantarum viability mixing with ultrasound-treated yeast cells in the spray drying samples was significantly improved. Besides, the presence of Stevia showed positive efficiency on the L. plantarum viability. The L. plantarum viability mixing with ultrasound-treated yeast cells and stevia-extracted fluid by spray drying process showed potential application due to making powder form which helped to improve the L. plantarum stability during the storage time.

Co-encapsulation of Lactobacillus plantarum and bioactive compounds extracted from red beet stem (Beta vulgaris L.) by spray dryer

Probiotic bacteria and bioactive compounds obtained from plant origin stand out as ingredients with the potential to increase the healthiness of functional foods, as there is currently a recurrent search for them. Probiotics and bioactive compounds are sensitive to intrinsic and extrinsic factors in the processing and packaging of the finished product. In this sense, the present study aims to evaluate the co-encapsulation by spray dryer (inlet air temperature 120 °C, air flow 40 L / min, pressure of 0.6 MPa and 1.5 mm nozzle diameter) of probiotic bacteria (L.plantarum) and compounds extracted from red beet stems (betalains) in order to verify the interaction between both and achieve better viability and resistance of the encapsulated material. When studying the co-encapsulation of L.plantarum and betalains extracted from beet stems, an unexpected influence was observed with a decrease in probiotic viability in the highest concentration of extract (100 %), on the other hand, the concentration of 50 % was the best enabled and maintained the survival of L.plantarum in conditions of 25 °C (63.06 %), 8 °C (88.80 %) and −18 °C (89.28 %). The viability of the betalains and the probiotic was better preserved in storage at 8 and −18 °C, where the encapsulated stability for 120 days was successfully achieved. Thus, the polyfunctional formulation developed in this study proved to be promising, as it expands the possibilities of application and development of new foods.

In Vitro Evaluation of Commercial Probiotic Products Containing Streptococcus salivarius K12 by Assessment of Probiotic Viability and Inhibitory Potency against Respiratory Pathogens

Upper respiratory infections (URI) are the most frequent illnesses, especially in children. The majority of those infections are prescribed broad-spectrum antibiotics, which are associated with various side effects and with the increase in multi-drug-resistant strains. A promising alternative approach is the administration of the probiotic strain Streptococcus salivarius K12 (SSK12) that colonizes the upper respiratory tract (URT) and produces the salivaricins A2 and B, which strongly antagonize the growth of key respiratory pathogens. However, since for food supplements no quality controls of the active probiotic ingredient are mandatory, the efficacy of commercial products containing SSK12 may vary. This study aimed to investigate the in vitro efficacy of several commercial SSK12-containing probiotics, positioned for the prevention of respiratory infections. The parameters evaluated to determine the in vitro efficacy included the viability of the probiotic bacterial strain and the minimum inhibitory dilution (MID) of the probiotic, determined by the agar spot method, against the pathogenic/potential pathogenic bacterial strains Streptococcus pyogenes FF22 and Micrococcus luteus T18. All tests were carried out both 12 and 24 months after manufacturing (AM) for each commercial product. The viability ranged from 9 × 108 to 4.4 × 109 CFU/serving at 12 months AM and from 8.5 × 107 to 2.8 × 109 CFU/serving at 24 months AM. The MID was, in general, positively correlated with the probiotic bacterium viability and varied between the commercial products, ranging from 10−5 to 10−7 at 12 months AM and from 10−4 to 10−7 at 24 months AM. Moreover, the inhibition zones related to the two indicator strains were variable in diameter for different products. The high variation of the in vitro efficacy of commercial products containing SSK12 may explain the different results reported in the literature regarding the clinical benefits of these preparations, and the determination of this parameter may be useful to evaluate the quality of probiotic products containing this bacterial strain.