Specific cultivation-independent enumeration of viable cells in probiotic products using a combination of fluorescence in situ hybridization and flow cytometry

This study introduces an optimized integration of flow cytometry and fluorescence in situ hybridization (Flow-FISH) as an approach for the specific enumeration of gram-positive bacteria in probiotic products, overcoming the limitations of conventional methods. The enhanced Flow-FISH technique synergizes the rapid and automated capabilities of flow cytometry with the high specificity of FISH, facilitating the differentiation of viable cells at the species level within probiotic blends. By analyzing lyophilized samples of Lacticaseibacillus rhamnosus, Lactiplantibacillus plantarum, and Bifidobacterium animalis subsp. lactis, and a commercial product, the study highlights the optimized Flow-FISH protocol's advantages, including reduced hybridization times to 1.5 h and elimination of centrifugation steps. Comparative evaluations with the widely accepted enumeration methods plate count and Live/Dead (L/D) staining were conducted. The study revealed that Flow-FISH produces higher viable cell counts than plate count, thereby challenging the traditional "gold standard" by highlighting its predisposition to underestimate actual viable cell numbers. Against L/D staining, Flow-FISH achieved comparable results, which, despite the different foundational premises of each technique, confirms the accuracy and reliability of our method. In conclusion, the optimized Flow-FISH protocol represents a significant leap forward in probiotic research and quality control. This method provides a rapid, robust, and highly specific alternative for the enumeration of probiotic bacteria, surpassing traditional methodologies. Its ability to enable a more detailed and reliable analysis of probiotic products paves the way for precise quality control and research insights, underscoring its potential to improve the field significantly.

Oxalobacter formigenes: A new hope as a live biotherapeutic agent in the management of calcium oxalate renal stones

Recent advances in understanding the association of gut microbiota with the host have shown evidence of certain bacterial therapeutic potentiality in preventing and treating metabolic diseases. Hyperoxaluria is a severe challenge in nephrology and has led to the novel gut eubiosis as current therapy. The human gut commensal, obligate anaerobic, and intestinal oxalate-degrading strains of Oxalobacter formigenes have drawn a promising significant interest for the next-generation probiotics (NGPs). This nonpathogenic, potential probiotic, and specialist oxalotrophic properties of O. formigenes give a new hope as a live biotherapeutic agent for calcium oxalate renal therapy. Numerous satisfactory outcomes of in vitro and in vivo studies were achieved on evaluating O. formigenes functionality, but the commercial production of this bacterium is yet to be achieved. This bacterium finds diverse application in dietary and endogenous oxalate degradation and the improvement of gut health, on which we concentrated our attention in this review. The relationship between good anaerobic gut bacterial dysbiosis and renal complications is comprehensively discussed to address the need for the development probiotic formulation. However, the commercial production of this bacteria on a broad scale is complex, with numerous obstacles, mainly because they are oxygen-sensitive and difficult to culture. This review will coherently present the current and available methodologies in producing, stabilizing, and delivering these NGPs to treat calcium stones. Moreover, the study presents the extensive work and key milestones achieved in the research on O. formigenes from tale to the truth.

Influence of Lactobacillus kefiri on Intestinal Microbiota and Fecal IgA Content of Healthy Dogs

The increasing incidence of gastrointestinal tract pathologies in dogs and the worrisome topic of antibiotic resistance have raised the need to look for new therapeutic frontiers. Of these, the use of probiotics represents a potential therapeutic alternative. Lactobacillus kefiri (Lk) is a species of Lactobacillus isolated from kefir. Previous studies have demonstrated that its administration in mice downregulates the expression of proinflammatory mediators and increases anti-inflammatory molecules in the gut immune system. It also regulates intestinal homeostasis, incrementing immunoglobulin A (IgA) secretion. Since Lk has never been studied as a single probiotic in dogs, the aim of this study was to evaluate the safety of Lk in dogs, and its effect on IgA secretion and on intestinal microbiota composition. Ten healthy dogs without a history of gastrointestinal diseases were included. The dogs received Lk at a dose of 10⁷ live microorganisms orally, once daily for 30 days. The fecal samples were tested before administration, in the middle, at the end, and 30 days after discontinuation. The IgA secretion concentration and the microbiota composition were evaluated on the fecal samples. The results in this study suggested that Lk did not influence the concentration of IgA, nor significant changes of the intestinal microbiota were observed during and after the treatment. Therefore, additional studies are needed to investigate if a higher daily dosage of Lk can influence the intestinal homeostasis of dogs.

How to Assess in vitro Probiotic Viability and the Correct Use of Neutralizing Agents

Probiotic viability is generally determined by quantifying its resistance to simulated gastric juice or to simulated intestinal fluid in in vitro tests, which measure microbial survival after given periods of contact. The use of a neutralizing agent is needed to avoid a carry-over of gastric or intestinal juice into the culture media of the subsequent analysis and to avoid any antimicrobial effect extended over the defined period of contact of the test. Neutralization of gastric juice and intestinal juice are of the utmost importance to present data accurately. Failing to do so determines a carry-over of bactericidal activity to the plates used for the enumeration, which further reduces the number of surviving cells. Examples of such incorrect adaptation of the test are available in literature. The purpose of this perspective stems from the discovery that many studies do not adhere to internationally recognized standards, e.g., EN 1040:2005 (European Committee for Standardization [ECS], 2005), to evaluate the basic, bactericidal activity of compounds, especially for the neutralization step.

Identification of Bacillus species: Implication on the quality of probiotic formulations

Spores of several Bacillus species have long history of consumption and safe use as probiotics and a variety of formulations containing these organisms are available in the global market. Considering the difficulties in the identification of Bacillus species and the poor microbiological quality of many probiotic formulations, we used three up-to-date methodological approaches for analyzing the content of ten formulations marketed in Italy and labeled to contain Bacillus spores. We compared the performance of biochemical tests based on the BCL Vitek2 card and MALDI-TOF mass spectrometry, using 16S rDNA sequencing as the reference technique. The BCL card performed well in identifying all Bacillus probiotic strains as well as the Bruker’s MALDI Biotyper. Nevertheless, the MALDI score values were sometimes lower than those indicated by the manufacturer for correct species identification. Contaminant bacteria (Lysinibacillus fusiformis, Acinetobacter baumannii, Bacillus cereus, Brevibacillus choshinensis, Bacillus licheniformis, Bacillus badius) were detected in some formulations. Characterization of the B. cereus contaminant showed the potential pathogenicity of this strain. Microbial enumeration performed by the plate count method revealed that the number of viable cells contained in many of the analyzed products differed from the labeled amount. Overall, our data show that only two of the ten analyzed formulations qualitatively and quantitatively respect what is on the label. Since probiotic properties are most often strain specific, molecular typing of isolates of the two most common Bacillus species, B. clausii and B. coagulans, was also performed. In conclusion, the majority of the analyzed products do not comply with quality requirements, most likely leading to reduced/absent efficacy of the preparation and representing a potential infective risk for consumers.

Consensus and contentious statements on the use of probiotics in clinical practice: A south east Asian gastro-neuro motility association working team report

The concept of consuming microorganisms in the treatment of a medical condition and in health maintenance has gained much attraction, giving rise to an abundance of medical claims and of health supplements. This study identified relevant clinical questions on the therapeutic use of probiotics and reviewed the literature in irritable bowel syndrome, inflammatory bowel disease, impaired intestinal immunity, liver disease, intestinal infections, and common childhood digestive disorders. Statements were developed to address these clinical questions. A panel of experienced clinicians was tasked to critically evaluate and debate the available data. Both consensus and contentious statements are presented to provide to clinicians a perspective on the potential of probiotics and importantly their limitations.

Compositional Quality and Potential Gastrointestinal Behavior of Probiotic Products Commercialized in Italy

Recent guidelines indicate that oral probiotics, living microorganisms able to confer a health benefit on the host, should be safe for human consumption, when administered in a sufficient amount, and resist acid and bile to exert their beneficial effects (e.g., metabolic, immunomodulatory, anti-inflammatory, competitive). This study evaluated quantitative and qualitative aspects and the viability in simulated gastric and intestinal juices of commercial probiotic formulations available in Italy. Plate counting and MALDI-TOF mass spectrometry were used to enumerate and identify the contained organisms. In vitro studies with two artificial gastric juices and pancreatin-bile salt solution were performed to gain information on the gastric tolerance and bile resistance of the probiotic formulations. Most preparations satisfied the requirements for probiotics and no contaminants were found. Acid resistance and viability in bile were extremely variable depending on the composition of the formulations in terms of contained species and strains. In conclusion, this study indicates good microbiological quality but striking differences in the behavior in the presence of acids and bile for probiotic formulations marketed in Italy.

Labeling quality and molecular characterization studies of products containing Lactobacillus spp. strains

The objective of the study was to characterize at species level by phenotypic and different molecular methods the strains of Lactobacillus spp. used as constituents of five oral and four vaginal products. Susceptibilities to representative antibiotics were evaluated. In addition, total viable counts at mid and 3 months to deadline of shelf life, in the different formulations and the presence of eventual contaminant microorganisms were investigated.In all oral products the molecular characterization at species level of the strains of Lactobacillus spp. confirmed the strains stated on the label, except for one strain cited on the label as Lactobacillus casei, that our study characterized as Lactobacillus paracasei. In oral products total viable cell content complied with content claimed on the label. In three out four vaginal products (one product claimed "bacillo di Döderlein"), molecular characterization complied with the bacterial name stated on the label. Two vaginal products reported viable counts on the label that were confirmed by our study. The other vaginal products, which did not report bacterial counts on the label, showed a similar decrease of viable counts at different dates to deadline compared to the others. From all the tested products, contaminant microorganisms and acquired resistance to representative antibiotics by the probiotic strains were not detected.

National survey outcomes on commercial probiotic food supplements in Italy

To assess whether the probiotic food supplements, produced and distributed on the Italian market during 2005-2006, complied with the Italian Guidelines on Prebiotics and Probiotics, 72 samples from 29 processing plants were analyzed. The survey included 41 samples from processing plants and 31 samples of the same brand from retailers collected at timed intervals (3, 8 and 13 months). A polyphasic approach based on a suitable analytical collection method (genotypic identification of total bacteria - differential presumptive enumeration - genotypic identification of viable bacteria) was adopted to identify and quantify the microorganisms labelled and recovered from the probiotic supplements examined. Most supplements analyzed (87%) did not conform to the Italian guidelines and the differences were both quantitative and qualitative (number determination, purity, types and viability of microorganisms). Even though most labelled supplements (25 samples) indicated the presence of Bifidobacterium bifidum, this organism was only detected sporadically and always as dead cells. Unexpected results were obtained during our survey due to the absence of viability of Bacillus coagulans spores in some labelled supplements. Besides this, some of these supplements also contained other spore-forming species, identified as B. cereus that are toxin producing. We have also documented a widespread use of misclassified microbial species or species with fictitious names. The main factors involved in the absence of compliance were examined and the poor quality control applied by manufacturers was emphasized.

The human microbiome and probiotics: implications for pediatrics

The “human super-organism” refers to the human body and the massive numbers of microbes which dwell within us and on the skin surface. Despite the large numbers of microbes co-existing within the human body, humans including infants and children achieve a physiologic state of equilibrium known as health in the context of this microbial world. These key concepts suggest that many individual members of the human microbiome, including bacterial and fungal species, confer different benefits on the human host. Probiotics, or beneficial microbes, may modulate immune responses, provide key nutrients, or suppress the proliferation and virulence of infectious agents. The human microbiome is in fact dynamic and often in flux, which may be indicative of the continuous interplay among commensal microbes, pathogens, and the human host. In this article we review the state-of-the-art regarding probiotics applications to prevent or treat diseases of the pediatric gastrointestinal and genitourinary systems. Additionally, probiotics may regulate local and systemic immunity, thereby reducing allergic disease severity and susceptibilities of infants and children to allergies and atopic diseases. In summary, beneficial microbes offer promising alternatives for new strategies in therapeutic microbiology with implications for different subspecialties within pediatrics. Instead of simply trying to counteract microbes with vaccines and antibiotics, a new field of medical microbiology is emerging that strives to translate human microbiome research into new probiotics strategies for promotion of health and prevention of disease in children.

New methods for selecting and evaluating probiotics

Recent studies have increased our understanding on the mechanistic basis of the proposed probiotic health effects. Well designed human studies have demonstrated that specific probiotic strains have health benefits in the human population. These have led to a wide acceptation of the probiotic concept. However, current probiotics have not been selected for specific purposes. Novel methods to select and characterise target-specific probiotic strains are thus needed. In addition to the traditional selection procedures, in recent years, knowledge on intestinal microbiota, nutrition, immunity and mechanisms of action has increased dramatically and can now be combined with genomic data to allow the isolation and characterization of new target- or site-specific probiotics. We should expect to see new, third generation probiotics emerging in the near future and also new selection criteria further defining the targets of future probiotics.