Kinetic analysis of microcalorimetric data derived from microbial growth: Basic theoretical, practical and industrial considerations

We report here a mathematical framework for the quantitative interpretation of exponential bacterial growth measured with isothermal microcalorimetry. The method allows determination of many parameters that define the exponential growth phase. To automate the analysis, we also wrote a coding program, so that the approach could be embedded in a commercial setting. As an exemplar, we apply the method to a commercial probiotic product. The outcome was that we could identify characteristic parameters of growth (including rate constant and doubling time), and hence authenticate product quality, within 15 h. This compares favourably with the current 7-10 days required for conventional microbiological assessment (to allow release of product for bottling and marketing) via plating methods. The method would lend itself to growth analysis of single and mixed bacterial cultures.

Intestinal Dysbiosis Correlates With Sirolimus-induced Metabolic Disorders in Mice

BACKGROUND

Long-time use of pharmacological immunosuppressive agents frequently leads to metabolic disorders. Most studies have focused on islet toxicity leading to posttransplantation diabetes mellitus. In contrast, the link between intestinal dysbiosis and immunosuppressive drug-induced metabolic disorders remains unclear.

METHODS

We established a mouse model of metabolic abnormality via sirolimus treatment. Fecal microbiota was examined using 16S rRNA gene MiSeq sequencing. Intestinal barrier function was assessed using fluorescein isothiocyanate-dextran assay and mucus immunostaining. Systemic inflammation was determined using a multiplexed fluorescent bead-based immunoassay.

RESULTS

Sirolimus induced dyslipidemia and glucose intolerance in mice in a dose-dependent manner. Interestingly, the clinical-mimicking dose of sirolimus altered the intestinal microbiota community, which was characterized by the enrichment of Proteobacteria, depletion of Akkermansia, and potential function shifts to those involved in lipid metabolism and the immune system. In addition, the clinical-mimicking dose of sirolimus reduced the thickness of the intestinal mucosal layer, increased the intestinal permeability, and enriched the circulating pro-inflammatory factors, including interleukin (IL)-12, IL-6, monocyte chemotactic protein 1, granulocyte-macrophage colony stimulating factor, and IL-1β. Our results showed a close association between intestinal dysbiosis, intestinal barrier failure, systemic inflammation, and metabolic disorders. Furthermore, we demonstrated that oral intervention in the gut microbiota by Lactobacillus rhamnosus HN001 protected against intestinal dysbiosis, especially by depleting the lipopolysaccharide-producing Proteobacteria, and attenuated the sirolimus-induced systemic inflammation, dyslipidemia, and insulin resistance.

CONCLUSIONS

Our study demonstrated a potentially causative role of intestinal dysbiosis in sirolimus-induced metabolic disorders, which will provide a novel therapeutic target for transplant recipients.

Lactobacillus rhamnosus AD3 as a Promising Alternative for Probiotic Products

Lactobacillus strains dominate the vaginal habitat and they are associated with a lower risk of genital infections. In addition, they contribute to the conservation of the vaginal microbiota by producing postbiotic agents. Previous studies have shown that their predominance involves antimicrobial activity against urogenital pathologies. In this context, probiotics may improve treatment outcomes. The aim of this study was to evaluate the probiotic properties of lactobacilli strains of vaginal origin using a multidisciplinary approach. For this purpose, safety criteria, ability to resist at low pH and bile salts, antimicrobial activity, ability to produce biofilm, capacity to produce hydrogen peroxide and more importantly, auto-aggregation, co-aggregation (with Candida spp.) and adhesion to human cells were evaluated. The strains belonged to the species of L. crispatus, L. gasseri, L. rhamnosus and L. delbruckii. Among these, a strain of L. rhamnosus named AD3 showed the best probiotic properties. As probiotics are already in use in many clinical practice and there are no major safety concerns, L. rhamnosus AD3 showed promise in becoming a prevention and complementary treatment option for urogenital diseases. Indeed, these results suggest that strain L. rhamnosus AD3 is non-pathogenic and likely to be safe for human consumption. This study revealed the great amensalistic properties of a new L. rhamnosus strain which can aim to be used as probiotic in pharmaceutical applications.

Restraining the TiO2 nanoparticles-induced intestinal inflammation mediated by gut microbiota in juvenile rats via ingestion of Lactobacillus rhamnosus GG

Human were given a lot of opportunities to ingest TiO₂ NPs in the environment. Children have low, sensitive intestinal tolerance, and they could be exposed to higher levels of TiO₂ NPs than adults. Few studies have been conducted on the interaction between TiO₂ NPs and juvenile intestine phase models. Thus, in this work, weaning rats were orally exposed to TiO₂ NPs for 7 and 14 days. Results indicate that Ti accumulated in the intestine, liver, and feces. Inflammatory infiltration damage was observed in the colonic epithelial tissue, and gut microbiota fluctuated with a decreased abundance of Lactobacilli in feces. Oral supplementation with Lactobacillus rhamnosus GG (LGG) lessened TiO₂ NPs-induced colonic inflammatory injury, which might due to downregulation of nuclear factor kappa-B (NF-κB). Meanwhile, LGG maintained normal intestinal microbiome homeostasis, thereby improving TiO₂ NPs-induced colon injury in juvenile rats. Moreover, fecal microbiota transplant (FMT) experiment indicated possible TiO₂ NPs-induced intestinal microbiota disorder led to colonic inflammation. Our works suggested the urgent need for additional studies on the risk safety assessment, mechanism, and prevention of juvenile health damage from exposure to TiO₂ NPs.

Short-Chain Cello-oligosaccharides: Intensification and Scale-up of Their Enzymatic Production and Selective Growth Promotion among Probiotic Bacteria

Short-chain cello-oligosaccharides (COS; degree of polymerization, DP ≤ 6) are promising water-soluble dietary fibers. An efficient approach to their bottom-up synthesis is from sucrose and glucose using glycoside phosphorylases. Here, we show the intensification and scale up (20 mL; gram scale) of COS production to 93 g/L product and in 82 mol % yield from sucrose (0.5 M). The COS were comprised of DP 3 (33 wt %), DP 4 (34 wt %), DP 5 (24 wt %), and DP 6 (9 wt %) and involved minimal loss (≤10 mol %) to insoluble fractions. After isolation (≥95% purity; ≥90% yield), the COS were examined for growth promotion of probiotic strains. Benchmarked against inulin, trans-galacto-oligosaccharides, and cellobiose, COS showed up to 4.1-fold stimulation of cell density for Clostridium butyricum, Lactococcus lactis subsp. lactis, Lactobacillus paracasei subsp. paracasei, and Lactobacillus rhamnosus but were less efficient with Bifidobacterium sp. This study shows the COS as selectively functional carbohydrates with prebiotic potential and demonstrates their efficient enzymatic production.

Effect of different biopolymer-based structured systems on the survival of probiotic strains during storage and in vitro digestion

BACKGROUND

This study aimed to evaluate the protective effect of different biopolymer systems on the viability of two probiotics (Lactobacillus rhamnosus and Streptococcus thermophilus) during storage and in vitro digestion. Methylcellulose (MC), sodium alginate (SA), and whey protein (WP)-based structures were designed and characterized in terms of pH, rheological properties, and visual appearance.

RESULTS

The results highlighted that the WP-system ensured probiotic protection during both storage and in vitro digestion. This result was attributed to a combined effect of the physical barrier offered by the protein gel network and whey proteins as a nutrient for microbes. On the other hand, surprisingly, the viscous methylcellulose-based system was able to guarantee good microbial viability during storage. However, this was not confirmed during in vitro digestion. The opposite results were obtained for sodium alginate beads.

CONCLUSION

The results suggest that the capacity of a polymeric structure to protect probiotic bacteria is a combination of structural organization and system formulation. © 2020 Society of Chemical Industry.

Milk Fat Globule Membrane Protects Lactobacillus rhamnosus GG from Bile Stress by Regulating Exopolysaccharide Production and Biofilm Formation

The milk fat globule membrane (MFGM) is a complex, highly conserved structure surrounding fat droplets secreted into mammalian milk. This study evaluated the impact of MFGM on Lactobacillus rhamnosus GG (LGG). MFGM-10 (2.5 g/L, 5 g/L, and 10 g/L) did not affect LGG growth in MRS medium but enhanced the ability of LGG to survive in the presence of 0.5% porcine bile. In the presence of MFGM-10 (5 g/L) and bile (0.5%), there were less complex polysaccharides in the media and less capsular polysaccharides associated with the LGG cells compared to the bile exposure alone (p < 0.05). The expression of four EPS genes was modulated by bile stress and MFGM. Biofilm thickness was increased (p < 0.05) during bile stress with MFGM compared to other treatments. Furthermore, MFGM increased LGG survival during transit in the murine GI tract. Future experiments will determine the impact of MFGM on LGG probiotic functionality.

Viability of Lactobacillus rhamnosus GG microencapsulated in alginate/chitosan hydrogel particles during storage and simulated gastrointestinal digestion: role of chitosan molecular weight

Sodium alginate hydrogel particles coated with cationic biopolymers have been shown to be one of the promising means for probiotic encapsulation and protection. In this study, we aimed to systematically explore the effect of molecular weight of chitosan coating on the functional performance of sodium alginate hydrogel particles for improving the viability of Lactobacillus rhamnosus GG (LGG). We first electrostatically deposited three different molecular weights of chitosan coatings, i.e., chitosan oligosaccharide (COS), low molecular weight chitosan (LMW-chitosan) and medium molecular weight chitosan (MMW-chitosan) on sodium alginate hydrogel particles. Both SEM and FTIR results indicated that chitosan was successfully deposited onto the surface of the hydrogel particles. We then evaluated the effect of chitosan MW on the viability of LGG encapsulated in the hydrogels during long-term storage and simulated gastrointestinal digestion. Among them, the hydrogel particles coated with COS prevented the viability loss of LLG during long-term storage at different temperatures (4, 25 and 37 °C). However, we did not find any improvement in the viability of the encapsulated LGG by all three chitosan coatings during simulated digestion.

Lung transcriptional unresponsiveness and loss of early influenza virus control in infected neonates is prevented by intranasal Lactobacillus rhamnosus GG

Respiratory viral infections contribute substantially to global infant losses and disproportionately affect preterm neonates. Using our previously established neonatal murine model of influenza infection, we demonstrate that three-day old mice are exceptionally sensitive to influenza virus infection and exhibit high mortality and viral load. Intranasal pre- and post-treatment of neonatal mice with Lactobacillus rhamnosus GG (LGG), an immune modulator in respiratory viral infection of adult mice and human preterm neonates, considerably improves neonatal mice survival after influenza virus infection. We determine that both live and heat-killed intranasal LGG are equally efficacious in protection of neonates. Early in influenza infection, neonatal transcriptional responses in the lung are delayed compared to adults. These responses increase by 24 hours post-infection, demonstrating a delay in the kinetics of the neonatal anti-viral response. LGG pretreatment improves immune gene transcriptional responses during early infection and specifically upregulates type I IFN pathways. This is critical for protection, as neonatal mice intranasally pre-treated with IFNβ before influenza virus infection are also protected. Using transgenic mice, we demonstrate that the protective effect of LGG is mediated through a MyD88-dependent mechanism, specifically via TLR4. LGG can improve both early control of virus and transcriptional responsiveness and could serve as a simple and safe intervention to protect neonates.

Characterization of the immunomodulatory and anti-Helicobacter pylori properties of the human gastric isolate Lactobacillus rhamnosus UCO-25A

The ability to form biofilms and the potential immunomodulatory properties of the human gastric isolate Lactobacillus rhamnosus UCO-25A were characterized in vitro. It was demonstrated that L. rhamnosus UCO-25A is able to form biofilms on abiotic and cell surfaces, and to modulate the inflammatory response triggered by Helicobacter pylori infection in gastric epithelial cells and THP-1 macrophages. L. rhamnosus UCO-25A exhibited a substantial anti-inflammatory effect in both cell lines and improved IL-10 levels produced by challenged macrophages. Additionally, UCO-25A protected AGS cells against H. pylori infection with a higher pathogen inhibition when a biofilm was formed. Given the importance of inflammation in H. pylori-mediated diseases, the differential modulation of the inflammatory response in the gastric mucosa by an autochthonous strain is an attractive alternative for improving H. pylori eradication and reducing the severity of the diseases that arise from the resulting chronic inflammation.

Septicemia from Lactobacillus rhamnosus GG, from a Probiotic Enriched Yogurt, in a Patient with Autologous Stem Cell Transplantation

Probiotic-rich foods are consumed without much restriction. We report here, a case of septic shock caused by yogurt derived Lactobacillus species in a 54-year-old male patient with acute promyelocytic leukemia, in second complete remission, and who was an autologous stem cell transplantation recipient. He received high dose chemotherapy and autologous peripheral blood stem cell transplantation. He ingested commercially available probiotic-enriched yogurt because of severe diarrhea. One week later, he developed septic shock, and the pathogen was determined by strain-specific PCR analysis as Lactobacillus rhamnosus GG (ATCC 53103), which was found to be identical with the strain in the yogurt he consumed. Thus, because even low virulent Lactobacilli in the probiotic products can be pathogenic in the compromised hosts, ingestion of such products should be considered with caution in neutropenic patients with severe diarrhea, such as stem cell transplantation recipients.

Adhesion and Colonization of the Probiotic Lactobacillus rhamnosus Labeled by Dsred2 in Mouse Gut

The health-promoting effects of the probiotic strain Lactobacillus rhamnosus are based on its adherence and colonization ability. However, little is known about its adhesion and colonization rates. Lactobacillus rhamnosus in mouse intestinal mucosa a mutant of the red fluorescence protein (RFP) DSred2 was used to tag L. rhamnosus to observe the adhesion and distribution of L. rhamnosus in mouse intestinal mucosa. A mutant of the red fluorescence protein (RFP) Dsred2 was used to tag L. rhamnosus to allow us to observe and distinguish it in the mouse intestine. Seven-week-old female BALB/c mice were fed once (at day 0) with an oral administration of the labeled L. rhamnosus, and the number of labeled bacteria was detected in different regions of the intestinal tract at 3 h and at day 1, 2, 3, 4, 5, 6, 7, and 15 after administration. The labeling process changed the morphology of L. rhamnosus, as it appeared after observation under the microscope, but did not change its basic probiotic properties in vitro. In vivo, labeled L. rhamnosus reached the colonization peak at the fourth day after gavage. From the distribution point of view, the number of colonization strains increased from the proximal to the distal small intestine (duodenum < jejunum < ileum) and the number of strains in the colon was less than the distal small intestine (ileum). The labeling protocol actually allowed the detection of the distribution and adhesion of this bacterium to the intestine, thus demonstrating that the health-promoting effects of this probiotic are satisfied. This study provides a scientific basis in the use of probiotics such as L. rhamnosus in functional foods.

Lactobacillus rhamnosus GG in the Primary Prevention of Eczema in Children: A Systematic Review and Meta-Analysis

Current guidelines recommend the use of probiotics to reduce the risk of eczema. It remains unclear which strain(s) to use. We systematically evaluated data on the efficacy of Lactobacillus rhamnosus GG (LGG) supplementation prenatally and/or postnatally for the primary prevention of eczema. The Cochrane Library, MEDLINE, and EMBASE databases were searched up to August 2018, with no language restrictions, for systematic reviews of randomized controlled trials (RCTs) and RCTs published afterwards. The primary outcome was eczema. For dichotomous outcomes, we calculated the risk ratio (RR) and 95% confidence interval (CI). A random-effects model was used to pool data. Heterogeneity was explored using the I² statistics. The GRADE criteria were used to assess the overall quality of evidence supporting the primary outcome. Seven publications reporting 5 RCTs (889 participants) were included. High to moderate certainty in the body of evidence suggests that LGG supplementation (regardless of the timing of administration) did not reduce the risk of eczema. There was also no consistent effect on other allergic outcomes. This meta-analysis shows that LGG was ineffective in reducing eczema. It does not support the general recommendation to use probiotics for preventing eczema, unless specific strains would be indicated.

Framework for laboratory harmonization of folate measurements in low- and middle-income countries and regions

The measurement of serum and red blood cell folate, two commonly used biomarkers of folate status in populations, is complicated by analytical and data interpretation challenges. Folate results show poor comparability across laboratories, even using the same analytical technique. The folate microbiologic assay produces accurate results and requires simple instrumentation. Thus, it could be set up and maintained in low- and middle-income country laboratories. However, the assay has to be harmonized through the use of common critical reagents (e.g., microorganism and folate calibrator) in order to produce comparable results across laboratories and over time, so that the same cutoff values can be applied across surveys. There is a limited need for blood folate measurements in a country owing to the periodic nature of surveys. Having a network of regional resource laboratories proficient in conducting the folate microbiologic assay and willing and able to perform service work for other countries will be the most efficient way to create an infrastructure wherein qualified laboratories produce reliable blood folate data. Continuous participation of these laboratories in a certification program can verify and document their proficiency. If the resource laboratories conduct the work on a fee-for-service basis, they could become self-sustaining in the long run.

Addition of grape pomace extract to probiotic fermented goat milk: the effect on phenolic content, probiotic viability and sensory acceptability

BACKGROUND

Grape pomace is a source of phenolic compounds, which are associated with health benefits in humans. Additionally, fermented dairy foods with probiotics can be good vehicles to deliver these bioactive compounds. The effects of the addition of grape pomace extract (GPE) on the total phenolic (TP) content, physico-chemical characteristics and viability of Lactobacillus acidophilus LA-5 or Lactobacillus rhamnosus HN001 in fermented goat milks prepared with grape juice were investigated.

RESULTS

The TP concentration increased significantly in fermented milks with the addition of GPE. A protective effect of GPE on the viability of L. acidophilus was observed. However, after 14 days of storage, the populations of L. acidophilus were significantly lower when compared with those of L. rhamnosus, and only the last probiotic maintained its viability above 7 log CFU mL^-1 throughout the period investigated. The sensory scores of flavor, color and overall acceptability of the fermented milk containing L. rhamnosus HN001 were significantly increased when GPE was added.

CONCLUSION

The use of GPE might increase the functionality of probiotic fermented goat milk processed with L. rhamnosus HN001 and grape juice because grape polyphenols are known for their antioxidant properties and positive effect on the modulation of gut microbiota. © 2016 Society of Chemical Industry.

Effect of Drying Methods on Protein and DNA Conformation Changes in Lactobacillus rhamnosus GG Cells by Fourier Transform Infrared Spectroscopy

Microencapsulation protects cells against environmental stress encountered during the production of probiotics, which are used as live microbial food ingredients. Freeze-drying and spray-drying are used in the preparation of powdered microencapsulated probiotics. This study examines the ability of Fourier transform infrared (FTIR) spectroscopy to detect differences in cells exposed to freeze-drying and spray-drying of encapsulated Lactobacillus rhamnosus GG cells. The FTIR analysis clearly demonstrated there were more significant molecular changes in lipid, fatty acid content, protein, and DNA conformation of nonencapsulated compared to encapsulated bacterial cells. The technique was also able to differentiate between spray-dried and freeze-dried cells. The results also revealed the extent of protection from a protein-carbohydrate-based encapsulant matrix on the cells depending on the type drying process. The extent of this protection to the dehydration stress was shown to be less in spray-dried cells than in freeze-dried cells. This suggests that FTIR could be used as a rapid, noninvasive, and real-time measurement technique to detect detrimental drying effects on cells.

Lactobacillus rhamnosus GR-1 Attenuates Induction of Hypertrophy in Cardiomyocytes but Not through Secreted Protein MSP-1 (p75)

Previous animal studies have shown that the administration of probiotic Lactobacillus rhamnosus can provide a protective effect against ischemia/reperfusion and necrotic injury to the intestine, liver, and heart, as well as a therapeutic effect to the outcome of ischemic injury to the heart, including cardiac hypertrophy and heart failure. We hypothesized that L. rhamnosus GR-1 major secreted protein 1 (MSP-1), also known as p75, plays a major role in this phenomenon. Experiments using neonatal rat ventricular cardiomyocytes showed that live and dead GR-1 bacteria, probiotic-conditioned media, and other probiotic species and strains inhibited the α1-adrenergic receptor agonist phenylephrine-induced hypertrophy as assessed by markers atrial natriuretic peptide and α-skeletal actin. However, using a mutant strain, we showed that this MSP-1 was not required for the inhibition. The ability of factors produced by lactobacilli to improve cardiac function warrants further study for the management of cardiac hypertrophy and heart failure.

Characterization of a New Cell Envelope Proteinase PrtP from Lactobacillus rhamnosus CGMCC11055

Cell envelope proteinases (CEPs) play essential roles in lactic acid bacteria growth in milk and health-promoting properties of fermented dairy products. The genome of Lactobacillus rhamnosus CGMCC11055 possesses two putative CEP genes prtP and prtR2, and the PrtP displays the distinctive domain organization from PrtR2 reported. The PrtP was purified and biochemically characterized. The results showed that the optimal activity occurred at 44 °C, pH 6.5. p-Amidinophenylmethylsulfonyl fluoride obviously inhibited enzymatic activity, suggesting PrtP was a member of serine proteinases. Under the optimal conditions, β-casein was a favorite substrate over αS1- and κ-casein, and 35 oligopeptides were identified in the β-casein hydrolysate, including the phosphoserine peptide and bioactive isoleucine-proline-proline. By analysis of the amino acid sequences of those oligopeptides, proline was the preferred residue at the breakdown site. Therefore, we speculated that PrtP was a new type of CEPs from Lb. rhamnosus.

Probiotics: Prevention of Severe Pneumonia and Endotracheal Colonization Trial-PROSPECT: a pilot trial

BACKGROUND

Probiotics are live microorganisms that may confer health benefits when ingested. Randomized trials suggest that probiotics significantly decrease the incidence of ventilator-associated pneumonia (VAP) and the overall incidence of infection in critically ill patients. However, these studies are small, largely single-center, and at risk of bias. The aim of the PROSPECT pilot trial was to determine the feasibility of conducting a larger trial of probiotics to prevent VAP in mechanically ventilated patients in the intensive care unit (ICU).

METHODS

In a randomized blinded trial, patients expected to be mechanically ventilated for ≥72 hours were allocated to receive either 1 × 10(10) colony-forming units of Lactobacillus rhamnosus GG or placebo, twice daily. Patients were excluded if they were at increased risk of L. rhamnosus GG infection or had contraindications to enteral medication. Feasibility objectives were: (1) timely recruitment; (2) maximal protocol adherence; (3) minimal contamination; and (4) estimated VAP rate ≥10 %. We also measured other infections, diarrhea, ICU and hospital length of stay, and mortality.

RESULTS

Overall, in 14 centers in Canada and the USA, all feasibility goals were met: (1) 150 patients were randomized in 1 year; (2) protocol adherence was 97 %; (3) no patients received open-label probiotics; and (4) the VAP rate was 19 %. Other infections included: bloodstream infection (19.3 %), urinary tract infections (12.7 %), and skin and soft tissue infections (4.0 %). Diarrhea, defined as Bristol type 6 or 7 stools, occurred in 133 (88.7 %) of patients, the median length of stay in ICU was 12 days (quartile 1 to quartile 3, 7-18 days), and in hospital was 26 days (quartile 1 to quartile 3, 14-44 days); 23 patients (15.3 %) died in the ICU.

CONCLUSIONS

The PROSPECT pilot trial supports the feasibility of a larger trial to investigate the effect of L. rhamnosus GG on VAP and other nosocomial infections in critically ill patients.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01782755 . Registered on 29 January 2013.

Microencapsulation of Lactobacillus rhamnosus GG by Transglutaminase Cross-Linked Soy Protein Isolate to Improve Survival in Simulated Gastrointestinal Conditions and Yoghurt

Microencapsulation is an effective way to improve the survival of probiotics in simulated gastrointestinal (GI) conditions and yoghurt. In this study, microencapsulation of Lactobacillus rhamnosus GG (LGG) was prepared by first cross-linking of soy protein isolate (SPI) using transglutaminase (TGase), followed by embedding the bacteria in cross-linked SPI, and then freeze-drying. The survival of microencapsulated LGG was evaluated in simulated GI conditions and yoghurt. The results showed that a high microencapsulation yield of 67.4% was obtained. The diameter of the microencapsulated LGG was in the range of 52.83 to 275.16 μm. Water activity did not differ between free and microencapsulated LGG after freeze-drying. The survival of microencapsulated LGG under simulated gastric juice (pH 2.5 and 3.6), intestinal juice (0.3% and 2% bile salt) and storage at 4 °C were significantly higher than that of free cells. The survival of LGG in TGase cross-linked SPI microcapsules was also improved to 14.5 ± 0.5% during storage in yoghurt. The microencapsulation of probiotics by TGase-treated SPI can be a suitable alternative to polysaccharide gelation technologies.

Effect of histatin-5 and lysozyme on the ability of Streptococcus mutans to form biofilms in in vitro conditions

INTRODUCTION

The mechanisms of adhesion to solid surfaces enable S. mutans to colonize oral cavities and form biofilms, which play an important role in caries development. Additional properties enabling the survival of S. mutans in the oral cavity include its ability to survive in acidic environments and specific interactions with other microorganisms inhabiting this ecosystem.

AIM OF THE STUDY

The aim of this study was to determine the antibacterial activity of saliva histatin-5 (peptide) and lysozyme (protein) against S. mutans and L. rhamnosus, as representatives of physiological flora.

MATERIALS AND METHODS

The study involved strains of physiological (L. rhamnosus) and cariogenic (S. mutans) flora isolated from one patient with diagnosed early caries of the deciduous teeth.

RESULTS

It was proved that the presence of probiotic L. rhamnosus bacteria in the environment had a negative impact on the ability of S. mutans to produce biofilm. Moreover, the antibacterial activity of histatin-5 was confirmed, and it inhibited S. mutans growth at concentrations of 27.2 μg/ml and 54.4 μg/ml, both individually and in a mixture with lysozyme (in a total concentration of 54.4 μg/ml).

CONCLUSIONS

The data obtained constitute a promising result due to their potential future application in the prevention and early diagnosis of caries.

Adhesion Potential of Intestinal Microbes Predicted by Physico-Chemical Characterization Methods

Bacterial adhesion to epithelial surfaces affects retention time in the human gastro-intestinal tract and therefore significantly contributes to interactions between bacteria and their hosts. Bacterial adhesion among other factors is strongly influenced by physico-chemical factors. The accurate quantification of these physico-chemical factors in adhesion is however limited by the available measuring techniques. We evaluated surface charge, interfacial rheology and tensiometry (interfacial tension) as novel approaches to quantify these interactions and evaluated their biological significance via an adhesion assay using intestinal epithelial surface molecules (IESM) for a set of model organisms present in the human gastrointestinal tract. Strain pairs of Lactobacillus plantarum WCFS1 with its sortase knockout mutant Lb. plantarum NZ7114 and Lb. rhamnosus GG with Lb. rhamnosus DSM 20021T were used with Enterococcus faecalis JH2-2 as control organism. Intra-species comparison revealed significantly higher abilities for Lb. plantarum WCSF1 and Lb. rhamnosus GG vs. Lb. plantarum NZ7114 and Lb. rhamnosus DSM 20021T to dynamically increase interfacial elasticity (10-2 vs. 10-3 Pa*m) and reduce interfacial tension (32 vs. 38 mN/m). This further correlated for Lb. plantarum WCSF1 and Lb. rhamnosus GG vs. Lb. plantarum NZ7114 and Lb. rhamnosus DSM 20021T with the decrease of relative hydrophobicity (80-85% vs. 57-63%), Zeta potential (-2.9 to -4.5 mV vs. -8.0 to -13.8 mV) and higher relative adhesion capacity to IESM (3.0-5.0 vs 1.5-2.2). Highest adhesion to the IESM collagen I and fibronectin was found for Lb. plantarum WCFS1 (5.0) and E. faecalis JH2-2 (4.2) whereas Lb. rhamnosus GG showed highest adhesion to type II mucus (3.8). Significantly reduced adhesion (2 fold) to the tested IESM was observed for Lb. plantarum NZ7114 and Lb. rhamnosus DSM 20021T corresponding with lower relative hydrophobicity, Zeta potential and abilities to modify interfacial elasticity and tension. Conclusively, the use of Zeta potential, interfacial elasticity and interfacial tension are proposed as suitable novel descriptive and predictive parameters to study the interactions of intestinal microbes with their hosts.

A systems biology approach investigating the effect of probiotics on the vaginal microbiome and host responses in a double blind, placebo-controlled clinical trial of post-menopausal women

A lactobacilli dominated microbiota in most pre and post-menopausal women is an indicator of vaginal health. The objective of this double blinded, placebo-controlled crossover study was to evaluate in 14 post-menopausal women with an intermediate Nugent score, the effect of 3 days of vaginal administration of probiotic L. rhamnosus GR-1 and L. reuteri RC-14 (2.5×10⁹ CFU each) on the microbiota and host response. The probiotic treatment did not result in an improved Nugent score when compared to when placebo. Analysis using 16S rRNA sequencing and metabolomics profiling revealed that the relative abundance of Lactobacillus was increased following probiotic administration as compared to placebo, which was weakly associated with an increase in lactate levels. A decrease in Atopobium was also observed. Analysis of host responses by microarray showed the probiotics had an immune-modulatory response including effects on pattern recognition receptors such as TLR2 while also affecting epithelial barrier function. This is the first study to use an interactomic approach for the study of vaginal probiotic administration in post-menopausal women. It shows that in some cases multifaceted approaches are required to detect the subtle molecular changes induced by the host to instillation of probiotic strains.

Trial Registration

ClinicalTrials.gov NCT02139839

Effect of buckwheat flour and oat bran on growth and cell viability of the probiotic strains Lactobacillus rhamnosus IMC 501®, Lactobacillus paracasei IMC 502® and their combination SYNBIO®, in synbiotic fermented milk

Fermented foods have a great significance since they provide and preserve large quantities of nutritious foods in a wide diversity of flavors, aromas and texture, which enrich the human diet. Originally fermented milks were developed as a means of preserving nutrients and are the most representatives of the category. The first aim of this study was to screen the effect of buckwheat flour and oat bran as prebiotics on the production of probiotic fiber-enriched fermented milks, by investigating the kinetics of acidification of buckwheat flour- and oat bran-supplemented milk fermented by Lactobacillus rhamnosus IMC 501®, Lactobacillus paracasei IMC 502® and their 1:1 combination named SYNBIO®. The probiotic strains viability, pH and sensory characteristics of the fermented fiber-enriched milk products, stored at 4 °C for 28 days were also monitored. The results showed that supplementation of whole milk with the tested probiotic strains and the two vegetable substrates results in a significant faster lowering of the pH. Also, the stability of L. rhamnosus IMC 501®, L. paracasei IMC 502® and SYNBIO® during storage at 4 °C for 28 days in buckwheat flour- and oat bran-supplemented samples was remarkably enhanced. The second aim of the study was to develop a new synbiotic product using the best combination of probiotics and prebiotics by promoting better growth and survival and be acceptable to the consumers with high concentration of probiotic strain. This new product was used to conduct a human feeding trial to validate the fermented milk as a carrier for transporting bacterial cells into the human gastrointestinal tract. The probiotic strains were recovered from fecal samples in 40 out of 40 volunteers fed for 4 weeks one portion per day of synbiotic fermented milk carrying about 10(9) viable cells.

Lactobacillus rhamnosus GG antagonizes Giardia intestinalis induced oxidative stress and intestinal disaccharidases: an experimental study

The present study describes the in vivo modulatory potential of Lactobacillus rhamnosus GG (LGG), an effective probiotic, in Giardia intestinalis-infected BALB/c mice. Experimentally, it was observed that oral administration of lactobacilli prior or simultaneous with Giardia trophozoites to mice, efficiently (p < 0.05) reduced both the severity and duration of giardiasis. More specifically, probiotics fed, Giardia-infected mice, showed a significant increase in the levels of antioxidants [reduced glutathione (GSH) and superoxide dismutase (SOD)] and intestinal disaccharidases [sucrase and lactase] and decreased levels of oxidants in the small intestine, in comparison with Giardia-infected mice. Histopathological findings also revealed almost normal cellular morphology of the small intestine in probiotic-fed Giardia-infected mice compared with fused enterocytes, villous atrophy and increased infiltration of lymphocytes in Giardia-infected mice. The results of the present study has shed new light on the anti-oxidative properties of LGG in Giardia mediated tissue injury, thereby suggesting that the effects of probiotic LGG are biologically plausible and could be used as an alternative microbial interference therapy.

Fermentation of sugars and sugar alcohols by plaque Lactobacillus strains

OBJECTIVE

The objective was to analyse the ability of Lactobacillus strains isolated from supragingival plaque of subjects with hyposalivation and from healthy controls to ferment sugars and sugar alcohols.

MATERIAL AND METHODS

Fifty strains isolated from interproximal plaque from subjects with radiation-induced hyposalivation (25 strains), subjects with primary Sjögren's syndrome (16 strains) and from subjects with normal salivary secretion rate (9 strains) were tested. Growth and pH were determined after 24 and 48 h of anaerobic incubation in vials containing basal media with 1 % of glucose, fructose, sucrose, mannitol, sorbitol or xylitol.

RESULTS

No differences between strains isolated from hyposalivated subjects and controls were detected. All strains lowered the pH to <5.0 from fructose and the majority of the strains from glucose and sucrose. A pH of <5.5 was seen for 52 % of the strains using mannitol, 50 % using sorbitol and 36 % using xylitol. The ability to produce acids from sugars and sugar alcohols was highest among strains of Lactobacillus rhamnosus, Lactobacillus casei and Lactobacillus paracasei and lowest among Lactobacillus fermentum strains.

CONCLUSION

A large number of Lactobacillus strains are able to ferment not only sugars but also the sugar substitutes mannitol, sorbitol and xylitol to pH levels critical for enamel demineralisation.

CLINICAL RELEVANCE

Our findings suggest that products containing mannitol, sorbitol and/or xylitol may contribute to the acidogenic potential of the dental plaque and especially in hyposalivated subjects with high numbers of lactobacilli.

Human gut-on-a-chip inhabited by microbial flora that experiences intestinal peristalsis-like motions and flow

Development of an in vitro living cell-based model of the intestine that mimics the mechanical, structural, absorptive, transport and pathophysiological properties of the human gut along with its crucial microbial symbionts could accelerate pharmaceutical development, and potentially replace animal testing. Here, we describe a biomimetic 'human gut-on-a-chip' microdevice composed of two microfluidic channels separated by a porous flexible membrane coated with extracellular matrix (ECM) and lined by human intestinal epithelial (Caco-2) cells that mimics the complex structure and physiology of living intestine. The gut microenvironment is recreated by flowing fluid at a low rate (30 μL h(-1)) producing low shear stress (0.02 dyne cm(-2)) over the microchannels, and by exerting cyclic strain (10%; 0.15 Hz) that mimics physiological peristaltic motions. Under these conditions, a columnar epithelium develops that polarizes rapidly, spontaneously grows into folds that recapitulate the structure of intestinal villi, and forms a high integrity barrier to small molecules that better mimics whole intestine than cells in cultured in static Transwell models. In addition, a normal intestinal microbe (Lactobacillus rhamnosus GG) can be successfully co-cultured for extended periods (>1 week) on the luminal surface of the cultured epithelium without compromising epithelial cell viability, and this actually improves barrier function as previously observed in humans. Thus, this gut-on-a-chip recapitulates multiple dynamic physical and functional features of human intestine that are critical for its function within a controlled microfluidic environment that is amenable for transport, absorption, and toxicity studies, and hence it should have great value for drug testing as well as development of novel intestinal disease models.

Effect of LGG yoghurt on Streptococcus mutans and Lactobacillus spp. salivary counts in children

The aim of this study was to establish effect of 14 day consumption of commercially available yoghurt containing Lactobacillus rhamnosus ATCC53103 - LGG (Bioaktiv LGG, Dukat, Croatia) on Streptococcus mutans and Lactobacillus spp. salivary counts in children. Twenty five patients, 6-10 yr old participated in the study. At the inclusion in the study caries risk for every patient was evaluated. The saliva samples were tested with chair side kits for saliva buffer capacity (CRT buffer, Vivadent, Schaan, Liechtenstein), S. Mutans and Lactobacillus counts (CRT bacteria test, Vivadent, Schaan, Liechtenstein). Seven, 14 and 30d after yoghurt consumption saliva samples were tested again with CRT buffer and CRT bacteria tests. Obtained data were analyzed using chi2 and Kruskal-Wallis tests. Results showed significant increase in saliva buffer capacity 30d after yoghurt consumption. S. Mutans salivary counts were significantly decreased after 30d. Significant differences in Lactobacillus counts were not observed. It could be concluded that daily consumption of yoghurt containing LGG have an inhibitory effect on oral pathogenic bacteria and may be beneficial in caries prevention.

Reversal of primary root caries lesions after daily intake of milk supplemented with fluoride and probiotic lactobacilli in older adults

OBJECTIVE

To evaluate the effect of milk supplemented with fluoride and/or probiotic bacteria on primary root caries lesions (PRCL) in older adults.

MATERIALS AND METHODS

After informed consent, 160 healthy subjects, 58-84 years of age, with at least two PRCL were recruited and randomly assigned to one of four parallel study groups drinking 200 ml milk once daily for 15 months. Group A consumed standard milk (placebo); Group B ingested milk supplemented with 5 ppm F and probiotic bacteria (Lactobacillus rhamnosus LB21, 10(7) CFU/mL); Group C drank milk with only probiotic bacteria and group D milk contained only fluoride. Primary endpoints were Root Caries Index (RCI) and electric resistance measurements (ECM) carried out by one blinded single examiner. Secondary endpoints were mutans streptococci and lactobacilli counts in saliva and plaque estimated with chair-side tests. Data were compared within and between groups with non-parametric tests.

RESULTS

The drop out rate was 38%. At baseline there were no statistical differences between the groups. Significantly higher numbers of RCI reversals were found in groups B, C and D compared with group A (p < 0.05). The mean ECM values increased significantly (p < 0.05) in all groups except for the placebo group A, indicating that remineralization occurred. The effect was most beneficial in the two groups that contained fluoride. No significant alterations were displayed regarding the microbial counts. No severe adverse effects were reported during intervention.

CONCLUSION

Daily intake of milk supplemented with fluoride and/or probiotic bacteria may reverse soft and leathery PRCL in older adults.

Development of a fermented goats' milk containing Lactobacillus rhamnosus: in vivo study of health benefits

BACKGROUND

Lactobacillus rhamnosus CRL1505, a strain of goats' milk origin, is able to stimulate mucosal immunity and protect immunocompetent mice from intestinal and respiratory infections.

RESULTS

In this work we developed and characterized a fermented goats' milk containing L. rhamnosus CRL1505, and we demonstrated in a model of immunosuppression in mice that the final dairy product preserves the immunomodulatory properties of the strain. L. rhamnosus CRL1505 survived the manufacturing process of fermented milk and maintained a viability of 10(6) cfu g(-1) during storage. The fermented goats' milk was accepted by 90.48% of the panelists and was considered as having an acid taste and pleasant aroma. We also demonstrated that the developed product, used as a supplement during the repletion of immunocompromised malnourished mice, was effective in accelerating the recovery of clinical parameters altered by malnutrition and to induce increased resistance against intestinal and respiratory infections.

CONCLUSION

Goats' milk fermented with L. rhamnosus CRL1505 could be manufactured as an alternative probiotic dairy product since this new food has the ability to stimulate the common mucosal immune system and to improve defenses against respiratory and intestinal infections.

The Plackett-Burman design in optimization of media components for biomass production of Lactobacillus rhamnosus OXY

The central composite design was developed to search for an optimal medium for the growth of Lactobacillus rhamnosus OXY. The effect of various media components, such as carbon sources, simple and complex nitrogen sources, mineral agents, and growth factors (vitamins B, amino acids) was examined. The first-order model based on Plackett-Burman design showed that glucose, sodium pyruvate, meat extract and mineral salts significantly influenced the growth of the examined bacteria. The second-order polynomial regression confirmed that maximum biomass production could be achieved by the combination of glucose (12.38 g/l), sodium pyruvate (3.15 g/l), meat extract (4.08 g/l), potassium phosphate (1.46 g/l), sodium acetate (3.65 g/l) and ammonium citrate (1.46 g/l). The validation of the predicted model carried out in bioreactor conditions confirmed the usefulness of the new medium for the culture of L. rhamnosus OXY in large scale. The optimal medium makes the culture of the probiotic bacterium L. rhamnosus OXY more cost effective.

Optimization of medium composition for enhancing growth of Lactobacillus rhamnosus PEN using response surface methodology

Response surface methodology was used to optimize media components such as carbon and nitrogen (simple and complex) sources, mineral agents and growth factors (B vitamins, amino acids) for enhancing the biomass production of Lactobacillus rhamnosus PEN. For screening experiment the following carbon sources were selected: glucose, glucose+pyruvate, glucose+citrate, glucose+lactate, galactose, fructose, lactose, sucrose, maltose, lactulose, fructooligosaccharides, maltodextrins DP 4-7 and DP 13-17. Nitrogen sources such as yeast extract, meat extract and peptone K were used in lower concentrations than in MRS medium which served as a control. All experiments were run at 37 degrees C for 24-48 h under stationary conditions. Constituents chosen after the first screening experiments were further screened by the Plackett-Burman design. Glucose and sodium pyruvate, meat extract, potassium phosphate, sodium acetate, and ammonium citrate were chosen as promising medium components for further optimization studies. By solving the regression equation and analyzing the response surface carton, optimal concentrations of the components were determined as: glucose (13.4 g/l), sodium pyruvate (3.4 g/l), meat extract (7.2 g/l), potassium phosphate (2.0 g/I), sodium acetate (5.0 g/1) and ammonium citrate (2.0 g/l). In comparison to MRS broth the optimal medium contained fewer ingredients and in modified amounts but Lb. ihamnosus PEN showed better growth activity. Biomass concentration (as dry cell weight) of bacteria cultivated in optimal medium at bioreactor conditions was 5.5 g/l after 16 h of incubation, being higher in comparison with bacterial growth in MRS medium (1.9 g/l) under the same conditions. Moreover, the new medium was less expensive.

Lactobacillus by-products inhibit the growth and virulence of uropathogenic Escherichia coli

Uropathogenic strains of Escherichia coli (UPEC) can colonize the vagina and cause infections within the entire urogenital tract, including those associated with urinary tract devices. Lactobacilli typically dominate the vaginal microbiota in healthy women, and studies have shown that they can inhibit UPEC growth and vaginal colonization. However, little is known regarding the mechanisms behind these effects. Using a luciferase-based reporter construct, gradients of lactic acid, hydrogen peroxide and spent culture supernatants (SCS) from urogenital probiotic strains Lactobacillus rhamnosus GR-1 and L. reuteri RC-14 were examined for their effects on growth and virulence factor expression in UPEC isolate C1212. In a dose- and pH- dependent manner, lactic acid, hydrogen peroxide and Lactobacillus SCS all strongly inhibited UPEC C1212 growth and increased the promoter activity of outer membrane proteins (OMPs) A and X, two porins normally upregulated in response to UPEC membrane stress. Lactic acid and the culture supernatants also downregulated the promoter activity of the major subunits of type 1 and P fimbriae, critical adherence factors within the urogenital tract. Our findings indicate that compounds secreted by lactobacilli likely protect the urogenital tract from UPEC colonization and infection by inhibiting growth, inducing stress and downregulating proteins critical for host attachment.

The feasibility of serving liquid yoghurt supplemented with probiotic bacteria, Lactobacillus rhamnosus LB 21, and Lactococcus lactis L1A--a pilot study among old people with dementia in a residential care facility

BACKGROUND

Constipation and body weight loss are prevalent among old people. Treatment with different species of lactic acid bacteria has been suggested for various forms of gastrointestinal disorders. OBJECTIVE, PARTICIPANTS AND INTERVENTION: This pilot study was performed to assess the feasibility of administering and consuming a drinkable yoghurt containing Lactobacillus rhamnosus LB 21 and Lactococcus L1A, and to evaluate the influence on bowel movements and body weight in 15 people with dementia, aged 65-95 years in residential care facility.

DESIGN

A drinkable yoghurt (Verum Drickyoghurt) with added bacteria was served daily for 6 months in conjunction with ordinary food intake. Body weight, bowel movement frequency and consistency, food and fluid intake and time spent in various activities were recorded for two weeks pre-intervention, and 3 times during the follow-up period.

RESULT

This study showed that the yoghurt was easy to serve, with few side effects for the participants and that the various recording forms and diaries were easy for the staff to complete. The extra intake of yoghurt did not have any detectable beneficial effect on bowel movements. The overnight fast was almost 15 hours per day. Body weight decreased by 0.65 kg/month (95% confidence interval. 0.27-0.97).

CONCLUSIONS

The present study design was feasible in this group of old people with dementia. The absence of any detectable effect of the supplement on constipation, but rather a considerable loss in body weight, indicate that further research is needed in a large randomised controlled trial, if associations between dementia, constipation and energy balance are to be understood.

Antibacterial action of selenium-enriched probiotics against pathogenic Escherichia coli

The purpose of this study was to evaluate the inhibitory activity of selenium-enriched probiotics against pathogenic Escherichia coli (E. coli) in vitro and in vivo. Escherichia coli was co-cultured in vitro with each probiotic strain individually, and a mixture of the four strains and its population was counted at various time points. We also collected a cell-free culture supernatant (CFCS) of each probiotic strain and the four-strain mix to examine their antibacterial activity, using the cylinder plate method. Results demonstrated that co-culture with probiotics significantly reduced the number of E. coli. The different sizes of the inhibition zones made by each CFCS proved that E. coli was inhibited by the metabolites of the probiotics. In vivo, Kunming mice were allocated to different groups supplemented with selenium-enriched and other probiotics. After 28 days, the mice were inoculated with pathogenic E. coli so that we could compare mortality rates and inspect other indexes of each treatment. The mortality of the group with selenium-enriched probiotics was the lowest. In addition, the organic antioxidant status improved, immunity was fortified, and the internal environment of the intestinal tract was enhanced with selenium-enriched probiotic supplementation. In conclusion, selenium-enriched probiotics can strongly antagonize pathogenic E. coli in vitro and in vivo.

The probiotic Lactobacillus GG may augment intestinal host defense by regulating apoptosis and promoting cytoprotective responses in the developing murine gut

Necrotizing enterocolitis (NEC) remains a leading cause of morbidity and mortality in preterm infants. Although its pathogenesis is poorly understood, inappropriate apoptosis of the mucosal epithelia has been implicated. Recent clinical trials have shown that probiotics may reduce the incidence of NEC, and probiotics have been shown to suppress intestinal epithelial apoptosis in cultured cells. However, little is known about their mechanism of action in the developing intestine in vivo. Here, we confirm that the probiotic Lactobacillus rhamnosus GG (LGG) reduces chemically induced intestinal epithelial apoptosis in vitro. Furthermore, we report for the first time that LGG administered orally to live animals can reduce chemically induced epithelial apoptosis ex vivo, as measured by staining for active caspase 3 and terminal deoxynucleotidyltransferase. Using cDNA microarray analysis from the intestine of live, orally inoculated mice, we show that LGG up-regulates a battery of genes with known and likely cytoprotective effects. These studies indicate that probiotics such as LGG may augment intestinal host defenses in the developing intestine by stimulating antiapoptotic and cytoprotective responses. Because apoptosis may be a precursor to NEC, understanding the mechanism behind probiotic modulation of apoptotic pathways may allow for development of more specifically targeted therapies or preventive strategies in the future.

The potential influence of fruit polyphenols on colonic microflora and human gut health

The effect of common dietary polyphenols on growth of human gut bacteria and their adhesion to enterocytes was investigated. The influence on the growth of a probiotic (Lactobacillus rhamnosus), a commensal (Escherichia coli) and two pathogenic bacteria (Staphylococcus aureus, Salmonella typhimurium) was determined, together with effects on adhesion of pathogenic and probiotic bacteria to cultured Caco-2 cells. All polyphenols, except rutin, were found to affect the viability of representative gut flora in vitro, at doses likely to be present in the gastrointestinal tract, but to differing degrees. Naringenin and quercetin were the most active with the lowest minimum inhibitory concentrations for all the four bacteria tested. The remaining polyphenols had the most marked effect on the Gram positive enteropathogen S. aureus. Naringenin and phloridzin were the most effective inhibitors of S. typhimurium adherence to Caco-2 enterocytes while phloridzin and rutin enhanced the adherence of the probiotic L. rhamnosus. Polyphenols appear to have potential to alter gut microecology and, by affecting the total number of beneficial microflora in the gut, may confer positive gut health benefits.

Preliminary characterization of wild lactic acid bacteria and their abilities to produce flavour compounds in ripened model cheese system

AIMS

The aim of this work was to preliminary characterize wild lactic acid bacteria (LAB), previously isolated during artisanal Pecorino Siciliano (PS) cheese-making for technological and flavour formation abilities in a model cheese system.

METHODS AND RESULTS

Twelve LAB were studied for the ability to grow at 10 and 45 degrees C, to coagulate and acidify both reconstituted skim milk and ewe's milk. Moreover, the capacity of the strains to generate aroma compounds was evaluated in a model cheese system at 30- and 60-day ripening. Flavour compounds were screened by sensory analysis and throughout gas chromatography (GC)-mass spectrometry (MS). Most of the strains were able to grow both at 10 and 45 degrees C and exhibited high ability to acidify and coagulate ewes' milk. Sensory evaluation revealed that the wild strains produced more significant flavour attributes than commercial strains in the 60-day-old model cheese system. GC-MS data confirmed the results of sensory evaluations and showed the ability of wild lactobacilli to generate key volatile compounds. Particularly, three wild lactobacilli strains, belonging to Lactobacillus casei, Lb. rhamnosus and Lb. plantarum species, generated both in 60- and 30-day-old model cheeses system, the 3-methyl butan(al)(ol) compound, which is associated with fruity taste.

CONCLUSIONS

The present work preliminarily demonstrated that the technological and flavour formation abilities of the wild strains are strain-specific and that wild lactobacilli, which produced key flavour compounds during ripening, could be used as tailor-made starters.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study reports the technological characterization and flavour formation ability of wild LAB strains isolated from artisanal Pecorino cheese and highlights that the catabolic activities were highly strain dependent. Hence, wild lactobacilli could be selected as tailor-made starter cultures for the PS cheese manufacture.

Media and process parameters affecting the growth, strain ratios and specific acidifying activities of a mixed lactic starter containing aroma-producing and probiotic strains

AIMS

The effects of medium-composition and fermentation parameters on the properties of mixed mesophilic starters were studied. The starter was composed of Lactococcus lactis ssp. lactis (L. lactis), Lactococcus lactis ssp. cremoris (L. cremoris), Lactobacillus rhamnosus (Lact. rhamnosus) and Leuconostoc mesenteroides ssp. cremoris (Leuc. cremoris).

METHODS AND RESULTS

The media used were reconstituted skim milk (RSM), and whey-based media with either citrate or phosphate buffers. The fermentation parameters were incubation temperature (22 degrees C or 32 degrees C), no pH control, and pH control in pH zones of either pH 6.0-5.8 or pH 6.0-5.2. The starter properties were strain ratio, specific acidifying activity (SAA), total population, residual carbohydrates and organic acids produced. The growth of L. lactis was favoured under pH control in whey-based media. High concentrations of Lact. rhamnosus were favoured in whey-based media prepared at 32 degrees C. The highest contents of Leuc. cremoris were obtained in starters prepared in RSM at 22 degrees C without pH control. Starters prepared under pH control gave the highest populations and made it possible for significantly lower inoculation rates (IR) to be used to carry out subsequent milk fermentations. However, the SAA of starters prepared under pH control were lower than the SAA of starters grown without any pH control.

CONCLUSIONS

None of the conditions enabled the strain ratio at inoculation to be maintained. The data show that it is possible to prepare a mesophilic starter that has a significant probiotic Lact. rhamnosus content; this starter could be used in the preparation of probiotic-containing cheeses or in Leuc. cremoris for aroma production in fermented milks.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides data on what should be expected with respect to strain ratios and IR if cheesemakers decide to shift their aroma-producing starter production method from the traditional 'milk-based without pH control' method to whey-based media used with pH-zone control strategies.

Probiotics for the treatment of women with bacterial vaginosis

This review considers whether probiotics are effective agents for the treatment and/or prevention of bacterial vaginosis (BV). There seems to be an association between the absence of, or low concentrations of, vaginal lactobacilli and the development of BV. Many studies have suggested that the presence of H2O2-producing vaginal lactobacilli may protect against BV, although some studies do not support this hypothesis. In-vitro studies have suggested that certain specific strains of lactobacilli are able to inhibit the adherence of Gardnerella vaginalis to the vaginal epithelium and/or produce H2O2, lactic acid and/or bacteriocins, which inhibit the growth of bacteria causing BV. Clinical trials showed that intra-vaginal administration of Lactobacillus acidophilus for 6-12 days, or oral administration of L. acidophilus or Lactobacillus rhamnosus GR-1 and Lactobacillus fermentum RC-14 for 2 months, resulted in the cure of BV (defined as a 0-1 positive score according to Amsel's criteria), and/or reduced the recurrences of BV, and/or caused an increase in vaginal lactobacilli and restoration of a normal vaginal microbiota, significantly more frequently than did a placebo, acetic acid or no treatment. However, several trials have found no significant difference in the cure rate of BV and in the number of vaginal lactobacilli after intra-vaginal instillation of lactobacilli when compared with the effect of a placebo or oestrogen. Thus, although the available results concerning the effectiveness of the administration of lactobacilli for the treatment of BV are mostly positive, it cannot yet be concluded definitively that probiotics are useful for this purpose.

Prevention of antibiotic-associated diarrhoea by a fermented probiotic milk drink

OBJECTIVE

To study the preventive effect of a milk drink fermented with multistrain probiotics on antibiotic associated diarrhoea (AAD).

DESIGN

Double-blind placebo controlled study.

SETTING

University Hospital of North Norway.

SUBJECTS AND METHODS

Of 853 patients treated with antibiotics, 87 met the inclusion criteria, and were randomized to ingestion of a fermented milk drink containing LGG, La-5 and Bb-12 (n=46) or placebo with heat-killed bacteria (n=41), during a period of 14 days. A diary was recorded, and stool samples were collected for microbiological analyses.

RESULTS

Sixty-three patients completed the study according to the protocol; two patients (5.9%) in the treatment group and eight (27.6%) in the placebo group developed AAD (P=0.035). The relative risk of developing AAD was 0.21 (95% confidence interval: 0.05-0.93) when given probiotic milk drink.

CONCLUSION

A fermented multistrain probiotic milk drink may prevent four of five cases of AAD in adult hospitalized patients.

SPONSORSHIP

TINE BA, Oslo, Norway.

Synergistic antidigestion effect of Lactobacillus rhamnosus and bovine colostrums in simulated gastrointestinal tract (in vitro)

Probiotics and bovine colostrums had been proven to be beneficial for human health. Lactobacillus rhamnosus ZDY114 and anti-Helicobacter pylori bovine colostrums were used for the preparation of microecological additives, and their synergistic antidigestion effect in the simulated gastrointestinal tract (in vitro) was investigated. Either L. rhamnosus or purified IgG from immune colostrums was very sensitive in simulated gastric environment and slightly sensitive in simulated intestinal tract. No viable counts were recovered from the solution of dissolved freeze-dried powder (7.14 log(10) CFU/ml) of L. rhamnosus when digested at pH 3.0 with pepsin for 30 min. Activity of purified IgGs from immune colostrums could not be detected when digested at pH 3.0 with pepsin for 30 min; 29% titer could be detected when digested at pH 8.0 with trypsin for 5 h. The IgGs in nonpurified immune colostrums presented stronger resistance against gastrointestinal digestion than purified IgGs. Moreover, the combination of L. rhamnosus ZDY114 and immune colostrums strengthened their antidigestion ability. Even under pH 3.0, 4.0 with pepsin, the titer of anti-HP IgG maintained above 123 and 83.3%, respectively. Similarly, that titer was above 93.3% when digested at pH 8.0 with trypsin for 4.5 h. In conclusion, L. rhamnosus and anti-Helicobacter pylori bovine colostrums had synergistic antidigestion effect in simulated gastrointestinal tract (in vitro).

Synergistic effects of Lactobacillus rhamnosus ZDY114 and bovine colostrums on the immunological function of mouse in vivo and in vitro

The synergistic effects of Lactobacillus rhamnosus and bovine colostrums on the immunity of mice in vivo and in vitro were investigated. Eight- to ten-week-old mice were used for two series experiments; one part of mice were immunocompromised by intraperitoneal injections of cyclophosphamide. In series I, immunocompromised mice were continuously fed with diet A (L. rhamnosus ZDY114 5 x 10(7) CFU/kg), B (bovine colostrums 0.5 g/kg), C (combination of diet A and B), and D (sterile saline) for 4 weeks and killed. Thereof, phagocytosis ratio and index of macrophage to chicken red blood cells in abdominal cavity and lymphocyte transformation rate were determined. In series II, both normal and immunocompromised mice were used to investigate the in vitro stimulation of lymphocyte proliferation by substances from the overnight culture of L. rhamnosus ZDY114 by the MTT colorimetric method. Compared with diet D, in the diet A, B, and C groups, the phagocytosis ratio of macrophages increased by 1.63, 1.54, and 2.3-fold, respectively, and the lymphocyte transformation ratio by 1.78, 2.08, and 2.35-fold, respectively. In vitro test with MTT showed that 3, 10, 50 kD substances from the overnight culture of L. rhamnosus ZDY114 significantly increased the growth of lymphocyte by 1.63, 1.53, and 1.34-fold, respectively. In conclusion, L. rhamnosus and bovine colostrums can enhance the functions of immune system supported by lymphocytes and peritoneal macrophages either in vivo or in vitro.

Effect of Lactobacillus challenge on Gardnerella vaginalis biofilms

Bacterial vaginosis (BV) is the most common infectious condition in women. It is caused primarily by anaerobic bacteria which rapidly form biofilms recalcitrant to antibiotic treatment, elevate vaginal pH, induce inflammatory processes and displace indigenous lactobacilli from the vault. Gardnerella vaginalis is commonly associated with these infections. Microscopy analysis showed that within 72 h, viable G. vaginalis covered a surface area of 567 microm(2), reached a depth of 16 microm and a density of approximately 104 microm(3). They maintained these levels for a further 3 days unless challenged with lactobacilli strains. Lactobacillus reuteri RC-14 produced the biggest displacement of Gardnerella. This was not due to pH, which remained between 4.7 and 5.1 for all experiments, nor by hydrogen peroxide which is produced in low amounts by strain L. reuteri RC-14, high amounts by L. crispatus 33820 and not at all by L. rhamnosus GR-1. Deconvolution microscopy showed changes in structure and viability of the biofilms, with loss of dense Gardnerella biofilm pods. For the first time, a strain of L. iners, the most commonly isolated vaginal Lactobacillus in healthy women, was tested for potential probiotic properties. It was found to disrupt Gardnerella biofilm surface area, density and depth, albeit to a lesser extent than L. reuteri RC-14. These studies help to provide insight into the clinical situation in which probiotic and indigenous vaginal lactobacilli can interfere with Gardnerella's presence and reduce the risk of bacterial vaginosis.

Colonisation of the gastrointestinal tract by probiotic L. rhamnosus strains in acute diarrhoea in children

Lactobacillus rhamnosus (573L/1-3) strains are considered effective in the treatment of rotaviral diarrhoea in children. The colonisation of the gastrointestinal (G.I.) tract by the Lactobacillus rhamnosus strains and the determining factors are discussed reporting data of a prospective, double-blinded, placebo-controlled randomized study in children between the 2nd month and 6th year of life with acute diarrhoea lasting not longer than 5 days. The examined strains were detected in 37/46 (80.43%) patients after 5 days and in 19/46 (41.3%) patients after 14 days since the start of the treatment. L. rhamnosus 573L/1 strain colonised the G.I. tract more persistently. L. rhamnosus strains are effective in colonising the G.I. tract during acute diarrhoea. Persistence of colonisation is dependent on the properties of administered probiotic strains.

In vitro studies of the digestion of caprine whey proteins by human gastric and duodenal juice and the effects on selected microorganisms

The in vitro digestion of caprine whey proteins was investigated by a two-step degradation assay, using human gastric juice (HGJ) at pH 2.5 and human duodenal juice (HDJ) at pH 7.5. Different protein and peptide profiles were observed after the first (HGJ) and second (HDJ) enzymatic degradation. The minor whey proteins serum albumin, lactoferrin and Ig were rapidly degraded by HGJ, while alpha-lactalbumin (alpha-LA) and beta-lactoglobulin (beta-LG) were more resistant and survived both 30 and 45 min of the enzymatic treatment. Further digestion with HDJ still showed intact beta-LG, and the main part of alpha-LA also remained unchanged. The protein degradation by HGJ and HDJ was also compared with treatment by commercial enzymes, by using pepsin at pH 2.5, and a mixture of trypsin and chymotrypsin at pH 7.5. The two methods resulted in different caprine protein and peptide profiles. The digests after treatment with HGJ and HDJ were screened for antibacterial effects on some selected microorganisms, Escherichia coli, Bacillus cereus, Lactobacillus rhamnosus GG and Streptococcus mutans. Active growing cells of E. coli were inhibited by the digestion products from caprine whey obtained after treatment with HGJ and HDJ. Cells of B. cereus were inhibited only by whey proteins obtained after reaction with HGJ, while the products after further degradation with HDJ demonstrated no significant effect. Screenings performed on cells of Lb. rhamnosus GG and S. mutans all showed no signs of inhibition.

Microentrapment of probiotic bacteria in a Ca(2+)-induced whey protein gel and effects on their viability in a dynamic gastro-intestinal model

Entrapping probiotic bacteria in gels with ionic cross-linking is typically achieved with polysaccharides (alginate, pectin, carraghenan). In this study, whey proteins were used for this purpose by carrying out the Ca(2+)-induced gelation of pre-heated whey protein isolate (WPI). A Lactobacillus rhamnosus cell suspension was added in a denatured WPI solution in a 30 : 70 volume ratio. Gelation was carried out by extrusion of the cell suspension in a CaCl(2) solution. Beads of approximately 3 mm diameter were formed. The population in the beads was 8.0 x 10(8) cells g(-1). Entrapment efficiency in gel beads was 96%, with a survival level of 23%. Scanning electron microscopy of beads before freeze-drying showed a tight protein network containing encapsulated Lb. rhamnosus cells homogeneously distributed throughout the matrix. The survival to freeze-drying of the bead-entrapped cells was 41%. Viability of microentrapped cells in a dynamic gastro-intestinal (GI) model was studied and the results were compared to free cells freeze-dried in a milk-based cryoprotective solution, as well as in a pre-denatured WPI solution. Results showed that protein gelation provided protection against acidic conditions in the stomach after 90 min, as well as against bile after 30, 60 and 90 min in the duodenum. Moreover, the milk-based cryoprotective solution was equally effective after 90 min in the duodenum. It is concluded that the gelation of whey proteins induced by Ca(2+) ions can protect the cells against adverse conditions of the GI system. However, certain stages in the entrapment process, particularly extrusion in the solution of CaCl(2), still need to be optimized in order to reduce the mortality of the cells during gelation.

Probiotic intervention in the first months of life: short-term effects on gastrointestinal symptoms and long-term effects on gut microbiota

OBJECTIVES

To determine whether probiotics administered for 6 months postnatally affect gastrointestinal symptoms, crying and the compositional development of the gut microbiota through infancy.

METHODS

The study comprised of 132 newborns whose mothers were randomized to receive placebo or Lactobacillus rhamnosus GG (ATCC 53103) before delivery. The treatments of mothers/infants continued for 6 months postnatally. A specific symptom chart was used to monitor gastrointestinal symptoms and infant's crying during the 7th and the 12th weeks of life. Fluorescent in situ hybridization was used to establish the Bifidobacterium, Lactobacillus/Enterococcus, Bacteroides and Clostridium counts in fecal samples at 6, 12, 18 and 24 months of age.

RESULTS

Numbers of different types of stools, vomits and crying time were comparable between the groups during the 7th and the 12th weeks of life. Dominant microbiota consisted of bifidobacteria throughout the study. At 6 months, there were less clostridia in faeces in the placebo compared with the probiotic group (P = 0.026), whereas after long-term follow-up at 2 years, there were less lactobacilli/enterococci and clostridia in faeces in the probiotic group than in the placebo group (P = 0.011 and P = 0.032, respectively), reflecting the impact of clostridia as a marker of microbiota succession in healthy infants.

CONCLUSIONS

Probiotic administration in the first months of life was well tolerated and did not significantly interfere with long-term composition or quantity of gut microbiota.

Improved production of live cells of Lactobacillus rhamnosus by continuous cultivation using glucose-yeast extract medium

In this study, the growth kinetics of Lactobacillus rhamnosus and lactic acid production in continuous culture were assessed at a range of dilution rates (0.05 h(-1) to 0.40 h(-1)) using a 2 L stirred tank fermenter with a working volume of 600 ml. Unstructured models, predicated on the Monod and Luedeking-Piret equations, were employed to simulate the growth of the bacterium, glucose consumption, and lactic acid production at different dilution rates in continuous cultures. The maximum specific growth rate of L. rhamnosus, mu-max, was estimated at 0.40 h(-1), and the Monod cell growth saturation constant, Ks, at approximately 0.25 g/L. Maximum cell viability (1.3 x 10(10) CFU/ml) was achieved in the dilution rate range of D = 0.28 h(-1) to 0.35 h(-1). Both maximum viable cell yield and productivity were achieved at D = 0.35 h(-1). The continuous cultivation of L. rhamnosus at D = 0.35 h(-1) resulted in substantial improvements in cell productivity, of 267% (viable cell count) that achieved via batch cultivation.

Strong antimicrobial activity of Lactobacillus rhamnosus GG against Salmonella typhimurium is due to accumulation of lactic acid

Spent culture supernatant (SCS) of the probiotic Lactobacillus rhamnosus GG had been reported to exert antibacterial activity against Salmonella typhimurium. However, the chemical identity of the antimicrobial compound(s) responsible remained unknown. A survey of the antimicrobial compounds produced by L. rhamnosus GG was performed. Lactobacillus rhamnosus GG produced a low-molecular weight, heat-stable, non-proteinaceous bactericidal substance, active at acidic pH against a wide range of bacterial species. SCS of L. rhamnosus GG grown in MRS medium contained five compounds that could meet the above description, if present at the appropriate concentration. Based on different experimental approaches, it could be concluded that under the growth conditions tested, the strong antimicrobial activity of L. rhamnosus GG against Salmonella was mediated by lactic acid.