Chitosan capping of CuO nanoparticles: Facile chemical preparation, biological analysis, and applications in dentistry

This investigation is vital contribution to the healthcare system utilizing techniques of nanobiotechnology. It interestingly applies chitosan capped CuO nanoparticles in the field of medicine and restorative dentistry. The CuO nanoparticles and CuO-Chitosan nanoparticles are prepared by co-precipitation, and their characterization is performed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray (EDX). The average crystallite size of these nanoparticles has been found to be in the dimensions of <40 nm and <35 nm, respectively. CuO-Chitosan nanoparticles show significant enhancement in in vitro antibacterial, antioxidant, cytotoxic, and antidiabetic activity as compared to CuO nanoparticles. In addition, the successful amalgamation of CuO nanoparticles and CuO-Chitosan nanoparticles into dentine bonding agents results in providing efficient remedy against secondary caries. CuO-Chitosan nanoparticles reinforced dental adhesive discs cause significant upsurge in reduction of Lactobacillus acidophillus and Streptococcus mutans. Also, the augmentation of mechanical properties, water sorption and solubility plus slow and sustained release profile and slight variation of shear bond strength is attained. Taken together, the chemically synthesized CuO nanoparticles and CuO-Chitosan nanoparticles have proven to be promising candidates having enormous potential to be utilized in drug delivery and nanotheranostics.

Evaluation of pyroligneous acid as a therapeutic agent against Salmonella in a simulated gastrointestinal tract of poultry

Pyroligneous acid (PA) was evaluated as a potential alternative to therapeutic antibiotics in poultry. Antimicrobial activity of PA was studied at acidic pH (2.0) and neutral pH (7.0) of the liquid against Salmonella enterica and Lactobacillus acidophilus. Acidic PA gave a MIC value of 0.8% (v/v) and 1.6% (v/v), and neutralized PA gave a MIC value of 1.6% (v/v) and 3.2% (v/v) against S. enterica and L. acidophilus respectively. Acidic PA was evaluated at different concentrations in a simulated poultry digestive tract and cecal fermentation to study its effect on the cecal microflora and fermentation profile. PA at a concentration of 1.6% (v/v) completely inhibited S. enterica and was also found to have a similar effect on lactobacilli count as compared with the control (p = 0.17). Additionally, PA at this concentration was found not to have a significant effect on acetic acid production after 24 h of cecal fermentation (p = 0.20). Graphical abstract.

Linoleic acid inhibits Lactobacillus activity by destroying cell membrane and affecting normal metabolism

BACKGROUND

The reason why dietary polyunsaturated fatty acids (PUFAs) affect the activity of Lactobacillus remains unclear. In this study, linoleic acid was used to study the mechanism underlying its inhibition function against Lactobacillus activity.

RESULTS

The growth curve of Lactobacillus rhamnosus LGG and the metabolite content in bacterial liquid were determined at varying linoleic acid concentration. The degree of cell membrane damage of L. rhamnosus LGG was determined by flow cytometry and fluorescence microscopy, and the cell structure was observed by scanning electron microscopy and transmission electron microscopy. The effect of linoleic acid on Lactobacillus activity was assessed in a simulated gut environment. Results showed that L. rhamnosus LGG grew slowly, cell metabolites leaked into the liquid, cell membrane was damaged, and the cell structure changed at a linoleic acid concentration of 50 μg mL^-1 .

CONCLUSION

The mechanism of action of linoleic acid on Lactobacillus showed that that linoleic acid destroyed the cell membrane of bacteria, thereby affecting the normal metabolism of the bacteria and ultimately leading to their death. © 2019 Society of Chemical Industry.

Impact of oral probiotic Lactobacillus acidophilus vaccine strains on the immune response and gut microbiome of mice

The potential role of probiotic bacteria as adjuvants in vaccine trials led to their use as nonparenteral live mucosal vaccine vectors. Yet, interactions between these vectors, the host and the microbiome are poorly understood. This study evaluates impact of three probiotic, Lactobacillus acidophilus, vector strains, and their interactions with the host's immune response, on the gut microbiome. One strain expressed the membrane proximal external region from HIV-1 (MPER). The other two expressed MPER and either secreted interleukin-1ß (IL-1ß) or expressed the surface flagellin subunit C (FliC) as adjuvants. We also used MPER with rice bran as prebiotic supplement. We observed a strain dependent, differential effect suggesting that MPER and IL-1β induced a shift of the microbiome while FliC had minimal impact. Joint probiotic and prebiotic use resulted in a compound effect, highlighting a potential synbiotic approach to impact efficacy of vaccination. Careful consideration of constitutive adjuvants and use of prebiotics is needed depending on whether or not to target microbiome modulation to improve vaccine efficacy. No clear associations were observed between total or MPER-specific IgA and the microbiome suggesting a role for other immune mechanisms or a need to focus on IgA-bound, resident microbiota, most affected by an immune response.

Antimicrobial properties of acrylic resins doped with Undaria pinnatifida exposed to light-emitting diode: In silico and in vitro assessments on multispecies biofilm-producing microbiota

BACKGROUND

This study sought to evaluates the efficiency of anti-microbial activity of acrylic resins doped with different concentrations of Undaria pinnatifida after activation with light-emitting diode (LED) at producing photodynamic damage to multispecies biofilm-producing microbiome.

MATERIAL AND METHODS

In this study, bioinformatics tools and computer simulation molecular modeling were used to evaluate the capacity of ferredoxin (FDX), an electron acceptor in metabolic pathways of U. pinnatifida, which can discharge electrons produced from photo-excited chlorophyll-a (Chl-a) by LED irradiation. Acrylic resin discs containing different concentration of U. pinnatifida (0, 0.5, 1, and 2%) were fabricated and were subjected to LED irradiation immediately before each experiment. After continuously rinsed (up to 30 days), the antimicrobial activity of acrylic resins doped with U. pinnatifida following photo-activation was determined by disc agar diffusion, biofilm formation inhibition, and eluted component assays versus bacterial species linked to caries that constitute a mixed biofilm including Streptococcus mutans, S. sanguinis, and Lactobacillus acidophilus, as well as Candida albicans as main etiology of candidal stomatitis.

RESULTS

Modeling and a virtual screening analysis of FDX indicated that it is a stable protein with an iron-sulfur center that can discharge electrons produced from photo-excited Chl-a and transfers them to FDX-NADP+ reductase for NADP+ reduction in photosystem I, which is essential in the Calvin cycle for carbon assimilation. FDX acts as an electron transfer agent in the redox reactions. The results showed that growth inhibition zones were not seen around acrylic resin discs in any group. In biofilm test, the colony counts of all test microorganisms significantly decreased (36%-87%) by an increase in the percentage of U. pinnatifida in acrylic resins after photo-activation (P < 0.05). Acrylic resins doped with 2% wt. U. pinnatifida following photo-activation using LED was inhibited biofilm formation by the test microorganisms, up to 30 days of rinsing.

CONCLUSION

Based on the results presented here, an acrylic resin containing U. pinnatifida, even at the lowest concentration, following photo-activation using LED have antimicrobial properties against planktonic and biofilm forms of the cariogenic microorganisms as well as C. albicans.

The impact of tomato fruits containing multi-walled carbon nanotube residues on human intestinal epithelial cell barrier function and intestinal microbiome composition

Carbon nanomaterials (CNMs) can positively regulate seed germination and enhance plant growth. However, clarification of the impact of plant organs containing absorbed CNMs on animal and human health is a critical step of risk assessment for new nano-agro-technology. In this study, we have taken a comprehensive approach to studying the effect tomato fruits derived from plants exposed to multi-walled carbon nanotubes (CNTs) have on gastrointestinal epithelial barrier integrity and their impact on the human commensal intestinal microbiota using an in vitro cell culture and batch human fecal suspension models. The effects of CNTs on selected pure cultures of Salmonella enterica Typhimurium and Lactobacillus acidophilus were also evaluated. This study demonstrated that CNT-containing fruits or the corresponding residual level of pure CNTs (0.001 μg ml-1) was not sufficient to initiate a significant change in transepithelial resistance and on gene expression of the model T-84 human intestinal epithelial cells. However, at 10 μg ml-1 concentration CNTs were able to penetrate the cell membrane and change the gene expression profile of exposed cells. Moreover, extracts from CNT-containing fruits had minimal to no effect on human intestinal microbiota as revealed by culture-based analysis and 16S rRNA sequencing.

Adaptation of Lactobacillus acidophilus to Thermal Stress Yields a Thermotolerant Variant Which Also Exhibits Improved Survival at pH 2

Loss in probiotic viability upon exposure to stressful storage and transport conditions has plagued the probiotic market worldwide. Lactobacillus acidophilus is an important probiotic that is added to various functional foods. It is known to be fairly labile and susceptible to temperature variations that it encounters during processing and storage which increases production cost. It has been repeatedly demonstrated that pre-exposure to sub-lethal doses of stress, particularly, temperature and pH, leads to improved survival of various probiotics when they subsequently encounter the same stress of a much greater magnitude. Attempts to adapt L. acidophilus to temperatures as high as 65 °C to arrive at a thermotolerant variant have not been reported previously. To improve viability at elevated temperatures, we gradually adapted the L. acidophilus NCFM strain to survival at 65 °C for 40 min. Following adaptation, the variant showed a 2-log greater survival compared to wild-type at 65 °C. Interestingly, this thermotolerant variant also demonstrated a 2-log greater stability compared to wild-type at pH 2.0. The improved pH and temperature stress tolerance exhibited by this variant remained unaltered even when the strain was lyophilized. Moreover, the thermotolerant variant demonstrated improved stability compared to wild-type when stored for up to a week at 37 and 42 °C. Probiotic properties of the variant such as adherence to epithelial cells and antibacterial activity remained unaltered. This strain can potentially help address the issue of significant loss in viable cell counts of L. acidophilus which is typically encountered during probiotic manufacture and storage.

Antimicrobial photodynamic therapy of Lactobacillus acidophilus by indocyanine green and 810-nm diode laser

This study investigated the efficacy of photodynamic therapy (PDT) using EmunDo as a photosensitizer against Lactobacillus acidophilus. A gallium aluminum arsenide diode laser was used in this experiment (810 nm, CW). Standard suspensions of Lactobacillus acidophilus were divided into six groups by treatment: 1) EmunDo, 2) diode laser (100 mW, 90 s), 3) diode laser (300 mW, 30 s); 4) EmunDo + diode laser (100 mW, 90 s), 5) EmunDo + diode laser (300 mW, 30 s), 6) control (no treatment). Bacterial suspensions from each group were subcultured onto the surface of MRS agar plates immediately and 24 h after treatment, and the viable microorganisms of Lactobacillus acidophilus were counted. The data were analyzed by ANOVA and student's t-test at p < 0.05. There was a significant between-group difference in the number of Lactobacillus acidophilus colonies in cell cultures obtained at 24 h after treatment (p < 0.001). The viable counts were significantly lower in EmunDo and both PDT groups, as compared to the other groups (p < 0.05). In the control and laser-irradiated groups, the number of colonies increased significantly at 24 h compared to the immediately after treatment (p < 0.05), whereas in both PDT groups, the number of colonies showed a significant reduction after 24 h of therapy (p < 0.05). Under the conditions used in this study, L. acidophilus colonies were susceptible to PDT after sensitization with EmunDo and exposure to diode laser. These findings imply that PDT is capable to reduce cariogenic bacteria, potentially leading to more conservative cavity preparation.

Antimicrobial effects of terpinen-4-ol against oral pathogens and its capacity for the modulation of gene expression

This study evaluated the antibacterial activity of terpinen-4-ol against Streptococcus mutans and Lactobacillus acidophilus and its influence on gbpA (S. mutans) and slpA (L. acidophilus) gene expression. As measured by XTT assay, the concentrations of terpinen-4-ol that effectively inhibited the biofilm were 0.24% and 0.95% for S. mutans and L. acidophilus, respectively. Confocal microscopy revealed the presence of a biofilm attached to the enamel and dentin block surfaces with significant terpinen-4-ol effects against these microorganisms. The expression of the gbpA and slpA genes involved in adherence and biofilm formation was investigated using RT-PCR. Expression of these genes decreased after 15 min with 0.24% and 0.95% terpinen-4-ol in S. mutans and L. acidophilus, respectively. These findings demonstrate the antimicrobial activity of terpinen-4-ol and its ability to modulate the expression of gbpA and slpA genes, emphasizing the therapeutic capacity of terpinen-4-ol as an alternative to inhibit adherence in biofilm.

Antibacterial Effect of Silver Diammine Fluoride on Cariogenic Organisms

AIM

To screen the possible antimicrobial activity of a range of clinically used, silver-based compounds on cariogenic organisms: silver diammine fluoride (SDF), silver fluoride, and silver nitrate.

MATERIALS AND METHODS

Preliminary screening disk-diffusion susceptibility tests were conducted on Mueller-Hinton agar plates inoculated with Streptococcus mutans, Lactobacillus acidophilus, and Actinomyces naeslundii, organisms known to be cariogenic. In order to identify which component of the silver compounds was responsible for any antibacterial (AB) effect, and to provide controls, the following were also investigated at high and low concentrations: sodium fluoride, ammonium fluoride, ammonium chloride, sodium fluoride, sodium chloride, and sodium nitrate, as well as deionized water as control. A volume of 10 pL of a test solution was dispensed onto a paper disk resting on the inoculated agar surface, and the plate incubated anaerobically at 37°C for 48 hours. The zones of inhibition were then measured.

RESULTS

Silver diammine fluoride, silver fluoride, silver nitrate, and ammonium fluoride had significant AB effect (p < 0.05) on all three test organisms, although ammonium fluoride had no effect at low concentration; the remaining other compounds had no effect.

CONCLUSION

Silver ions appear to be the principal AB agent at both high and low concentration; fluoride ions only have an AB effect at high concentration, while ammonium, nitrate, chloride and sodium ions have none. The anticaries effect of topical silver solutions appears restricted to that of the silver ions.

CLINICAL SIGNIFICANCE

Silver compounds, such as SDF, silver fluoride, and silver nitrate have AB effect against cariogenic organisms and these may have clinical impact in arresting or preventing dental decay. Sodium fluoride did not have AB effect under the conditions tested.

Cellulase-Assisted Extraction of Polysaccharides from White Hyacinth Bean: Characterization of Antioxidant Activity and Promotion for Probiotics Proliferation

Food-derived polysaccharides have advantages over synthetical compounds and have attracted interest globally for decades. In this study, we optimized the cellulase-assisted extraction of polysaccharides from white hyacinth bean (PWBs) with the aid of response surface methodology (RSM). The optimum extraction parameters were a pH of 7.79, a cellulase of 2.73%, and a ratio of water to material of 61.39, producing a high polysaccharide yield (3.32 ± 0.03)%. The scavenging ability of PWBs varied on three radicals (hydroxyl > 2,2-diphenyl-1-picrylhydrazyl (DPPH) > superoxide). Furthermore, PWBs contributed to the proliferation of three probiotic bacteria (Lactobacillus acidophilus LA5, Bifidobacterium bifidum BB01, and Lactobacillus bulgaricus LB6). These investigations of PWBs provide a novel bioresource for the exploitation of antioxidant and probiotic bacterial proliferation.

Comparing the impact of ultrafine particles from petrodiesel and biodiesel combustion to bacterial metabolism by targeted HPLC-MS/MS metabolic profiling

Alterations of gut bacterial metabolism play an important role in their host metabolism, and can result in diseases such as obesity and diabetes. While many factors were discovered influencing the gut bacterial metabolism, exposure to ultrafine particles (UFPs) from engine combustions were recently proposed to be a potential risk factor for the perturbation of gut bacterial metabolism, and consequentially to obesity and diabetes development. This study focused on evaluation of how UFPs from diesel engine combustions impact gut bacterial metabolism. We hypothesize that UFPs from different type of diesel (petrodiesel vs. biodiesel) will both impact bacterial metabolism, and the degree of impact is also diesel type-dependent. Targeted metabolic profiling of 221 metabolites were applied to three model gut bacteria in vitro, Streptococcus salivarius, Lactobacillus acidophilus and Lactobacillus fermentum. UFPs from two types of fuels, petrodiesel (B0) and a biodiesel blend (B20: 20% soy biodiesel/80% B0 by volume), were exposed to the bacteria and their metabolic changes were compared. For each bacterial strain, metabolites with significantly changed abundance were observed in both perturbations, and all three strains have increased number of altered metabolites detected from B20 UFPs perturbation in comparison to B0 UFPs. Multivariate statistical analysis further confirmed that the metabolic profiles were clearly different between testing groups. Metabolic pathway analyses also demonstrated several important metabolic pathways, including pathways involves amino acids biosynthesis and sugar metabolism, were significantly impacted by UFPs exposure.

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.

Comparative Evaluation of Antibacterial Effect of Dental Luting Cements on Streptococcus mutans and Lactobacillus acidophilus: An In vitro Study

INTRODUCTION

This study aimed at evaluating and comparing the antibacterial activity of six types of dental luting cements on Streptococcus mutans and Lactobacillus acidophilus using the agar diffusion test (ADT) and the direct-contact test (DCT). The antibacterial activity in ADT was measured based on the diameter of the zone of inhibition formed, whereas in DCT the density of the bacterial suspension was measured. The lower the density of the suspension, the more antibacterial activity the cement possesses.

MATERIALS AND METHODS

Agar diffusion test was carried out on the bacteria. After an incubation period of 24 hours, the plates were checked for the presence of zone of inhibition. In DCT the cement was mixed and applied. Once the cement was set, bacterial suspension and brain-heart infusion medium was poured and incubated for 24 hours. After 24 hours, the plate was placed in the enzyme-linked immunosorbent assay plate reader, which measured the optical density of the fluid. The first set of data was recorded approximately 1 hour after incubation. Overall, three sets of data were recorded. Additional experiments were performed on set test materials that were allowed to age for 24 hours, 1 week, 1, 3, and 6 months.

RESULTS

When using ADT only two cements zinc oxide eugenol (ZOE) and zinc polycarboxylate (ZPC) cement showed antibacterial activity against the test organisms. When using DCT, all cements showed some amount of antibacterial activity. Zinc oxide eugenol and ZPC cement showed highest amount of antibacterial activity against S. mutans and L. acidophilus respectively.

CONCLUSION

Within the limitations of study, ZOE cement and ZPC cement were most effective against the tested microorganisms followed by the newer resin cement. The glass ionomer cement was the weakest of all.

CLINICAL SIGNIFICANCE

Patients with high caries index can be treated more effectively using the abovementioned cements.

Antibacterial Activity of Two Chemomechanical Caries Removal Gels on Carious Dentin of Primary Teeth: An in vitro Study

INTRODUCTION

Chemomechanical caries removal (CMCR) is an effective method of caries removal especially for primary teeth as they cause less discomfort when compared with conventional caries removal. The most significant thing about caries removal is the elimination of cariogenic bacteria. This study compares the antibacterial activity of two CMCR gels.

MATERIALS AND METHODS

A total of 40 primary molar teeth with carious dentin were split along the long axis in a laboratory. Total viable count (TVC) was taken for the teeth before splitting as a measure of colony-forming units per milliliter (CFU/mL). Each half was treated with either Carisolv or Carie-Care CMCR gels. Clean dentin samples were evaluated for Streptococcus mutans (SM) and Lactobacillus acidophilus (LB) after removal of carious tissue using the caries removal gels using serial dilutions and incubating on specific agar plates.

RESULTS

The results showed significant reduction in mean TVC after use of both the CMCR gels. Both gels reduced the CFU/mL of SM and LB to a significant level (p < 0.05). However, there was no significant difference between the antibacterial activities of the two CMCR gels.

CONCLUSION

The CMCR gels (Carisolv and Carie-Care) significantly reduced the residual TVC as well as SM and LB in carious primary dentin. Both CMCR gels had a similar antibacterial activity on the carious dentin of primary teeth.

CLINICAL SIGNIFICANCE

The CMCR gels tested have a significant antibacterial activity and can be effectively used for elimination of caries-causing bacteria in primary teeth.

Characterization of Extracellular Yeast Peptide Factors and Their Stress-Protective Effect on Probiotic Lactic Acid Bacteria

Protective effect of the extracellular peptide fraction (reactivating factors, RF) produced by yeasts of various taxonomic groups (Saccharomyces cerevisiae, Kluyveromyces lactis, Candida utilis, and Yarrowia li- polytica) on probiotic lactic acid bacteria (LAB) Lactobacillus casei, L. acidophilus,'and L. reuteri under bile salt (BS)-induced stress was shown. RF of all yeasts were shown to be of peptide nature; the active component of the S. cerevisiae RF was identified as a combination of low-molecular polypeptides with molecular masses of 0.6 to 1.5 kDa. The protective and reactivating effects of the yeast factors were not species-specific and were similar to those of the Luteococcusjaponicus subsp. casei R. In BS-treated cells of the tester bacteria, a pro- tective effect was observed after 10-min preincubation of the LAB cell suspension with yeast RE: the number of surviving cells (CFU) was 2 to 4.5 times higher than in the control. The reactivating effect was observed when RF was added to LAB cell suspensions not later than 15 min after stress treatment. It was less pro- nounced than the protector effect, with the CFU number I to 3 times that of the control. Both the protector and the reactivating effects were most pronounced in the S. cerevisiae and decreased in the row: C. utilis > K. lactis > Y lipolytica. The efficiency of protective action of yeast RF was found to depend on the properties of recepient LAB cells, with the L. casei strain being most sensitive to BS treatment. In both variants, the highest protective effect of RF (increase in the CFU number) was observed for L. acidophilus, while the least pronounced one, for L. casei. The reasons for application of the LAB strains combining high stress resistance and high response to stress-protecting metabolites, including RF factors, as probiotics, is discussed.

In Situ Electron Microscopy of Lactomicroselenium Particles in Probiotic Bacteria

Electron microscopy was used to test whether or not (a) in statu nascendi synthesized, and in situ measured, nanoparticle size does not differ significantly from the size of nanoparticles after their purification; and (b) the generation of selenium is detrimental to the bacterial strains that produce them. Elemental nano-sized selenium produced by probiotic latic acid bacteria was used as a lactomicroselenium (lactomicroSel) inhibitor of cell growth in the presence of lactomicroSel, and was followed by time-lapse microscopy. The size of lactomicroSel produced by probiotic bacteria was measured in situ and after isolation and purification. For these measurements the TESLA BS 540 transmission electron microscope was converted from analog (aTEM) to digital processing (dTEM), and further to remote-access internet electron microscopy (iTEM). Lactobacillus acidophilus produced fewer, but larger, lactomicroSel nanoparticles (200-350 nm) than Lactobacillus casei (L. casei), which generated many, smaller lactomicroSel particles (85-200 nm) and grains as a cloudy, less electrodense material. Streptococcus thermophilus cells generated selenoparticles (60-280 nm) in a suicidic manner. The size determined in situ in lactic acid bacteria was significantly lower than those measured by scanning electron microscopy after the isolation of lactomicroSel particles obtained from lactobacilli (100-500 nm), but higher relative to those isolated from Streptococcus thermopilus (50-100 nm). These differences indicate that smaller lactomicroSel particles could be more toxic to the producing bacteria themselves and discrepancies in size could have implications with respect to the applications of selenium nanoparticles as prebiotics.

Antimicrobial potential of commercial silver nanoparticles and the characterization of their physical properties toward probiotic bacteria isolated from fermented milk products

The application of nanotechnology in the agriculture and food sector is relatively recent compared to its usage in drug delivery or pharmaceuticals. Therefore, this paper presents a study of the effect of silver nanoparticles on probiotic bacteria based on the example of Lactobacillus acidophilus LA-5, Bifidobacterium animalis subsp. lactis BB-12 and Streptococcus thermophilus ST-Y31 isolated from fermented milk products. Probiotic bacteria are one of the most crucial groups of bacteria for the food industry, because of their claimed health-promoting properties. Studies have shown that the type and concentration of silver nanoparticle solutions have a significant impact on the tested probiotic bacteria which are profitable for the digestive system. In the presence of all tested silver nanoparticles, St. thermophilus ST-Y31 growth was inhibited significantly by the dilution method as opposed to the disk-diffusion method. Both the disk-diffusion and the dilution methods showed no significant differences between L. acidophilus LA-5 and B. animalis subsp. lactis BB-12. The concentrations 2 μg mL(-1) and 0.25 μg mL(-1) had the highest antibacterial activity and statistically significant impacts on the tested probiotic strains. To our knowledge, this is the first report on potential antimicrobial effect of nanosilver against the health-promoting probiotic bacteria L. acidophilus LA-5, B. animalis subsp. lactis BB-12 and St. thermophilus ST-Y31 isolated from fermented milk products.

Antimicrobial Effect of Jasminum grandiflorum L. and Hibiscus rosa-sinensis L. Extracts Against Pathogenic Oral Microorganisms--An In Vitro Comparative Study

PURPOSE

To assess and compare the antimicrobial potential and determine the minimum inhibitory concentration (MIC) of Jasminum grandiflorum and Hibiscus rosa-sinensis extracts as potential anti-pathogenic agents in dental caries.

MATERIALS AND METHODS

Aqueous and ethanol (cold and hot) extracts prepared from leaves of Jasminum grandiflorum and Hibiscus rosa-sinensis were screened for in vitro antimicrobial activity against Streptococcus mutans and Lactobacillus acidophilus using the agar well diffusion method. The lowest concentration of every extract considered as the minimum inhibitory concentration (MIC) was determined for both test organisms. Statistical analysis was performed with one-way analysis of variance (ANOVA).

RESULTS

At lower concentrations, hot ethanol Jasminum grandiflorum (10 μg/ml) and Hibiscus rosa-sinensis (25 μg/ml) extracts were found to have statistically significant (P≤0.05) antimicrobial activity against S. mutans and L. acidophilus with MIC values of 6.25 μg/ml and 25 μg/ml, respectively. A proportional increase in their antimicrobial activity (zone of inhibition) was observed.

CONCLUSION

Both extracts were found to be antimicrobially active and contain compounds with therapeutic potential. Nevertheless, clinical trials on the effect of these plants are essential before advocating large-scale therapy.

Lactobacillus acidophilus-Rutin Interplay Investigated by Proteomics

Dietary polyphenols are bioactive molecules that beneficially affect human health, due to their anti-oxidant, anti-inflammatory, cardio-protective and chemopreventive properties. They are absorbed in a very low percentage in the small intestine and reach intact the colon, where they are metabolized by the gut microbiota. Although it is well documented a key role of microbial metabolism in the absorption of polyphenols and modulation of their biological activity, molecular mechanisms at the basis of the bacteria-polyphenols interplay are still poorly understood. In this context, differential proteomics was applied to reveal adaptive response mechanisms that enabled a potential probiotic Lactobacillus acidophilus strain to survive in the presence of the dietary polyphenol rutin. The response to rutin mainly modulated the expression level of proteins involved in general stress response mechanisms and, in particular, induced the activation of protein quality control systems, and affected carbohydrate and amino acid metabolism, protein synthesis and cell wall integrity. Moreover, rutin triggered the expression of proteins involved in oxidation-reduction processes.This study provides a first general view of the impact of dietary polyphenols on metabolic and biological processes of L. acidophilus.

[Effect of Lactobacillus acidophilus on metabolizing lactic acid in formula milk: a quantitative analysis of the effect of erythritol]

OBJECTIVE

To evaluate the lactic acid productivity of Lactobacillus acidophilus (La) exposed to formula milk containing different concentration of erythritol.

METHODS

La was cultured under anaerobic condition (80% N(2), 10% CO(2), 10% H(2)) at 37 °C in five experimental groups (formula milk mixed with different concentrations of erythritol). The five experimental groups contained 1%, 2%, 4%, 6%, and 8% erythritol, respectively (groups 1% E-M, 2% E-M, 4% E-M, 6% E-M, 8% E-M). Formula milk served as control group (group M). The lactic acid was analyzed by high performance liquid chromatography (HPLC) at 4 h intervals during 24 h. The peak-area of lactic acid was recorded and used to calculate the concentration of lactic acid through the equation of a standard curve (y = 590 244x + 67 507). ANOVA and Tukey HDS analysis were used to analyze the data.

RESULTS

The concentration of lactic acid at 24 h was group M [(4.693 ± 0.105) g/L], group 1% E-M[(4.114 ± 0.186) g/L], group 2% E-M[(3.720 ± 0.158) g/L], group 4% E-M[(3.045 ± 0.152) g/L], group 6% E-M[(2.971 ± 0.086) g/L], group 8% E-M[(2.789 ± 0.142) g/L]. Statistically significant differences in lactic acid concentrations were found between different time points (P < 0.05) and between different groups (F = 187.448, P < 0.05). Moreover, the concentrations of lactic acid in each experimental group was lower than that in control group (P < 0.05). The difference among groups 4% E-M, 6% E-M, and 8% E-M were not statistically significant (P > 0.05).

CONCLUSIONS

Erythritol showed the inhibition potential against La in metabolizing lactic acid in formula milk. The effect of erythritol was concentration depended. The higher concentration of erythritol contained in the milk, the better the inhibition potential against La in metabolizing lactic acid.

Interference of Antimicrobial Activity of Combinations of Oral Antiseptics Against Streptococcus mutans, Streptococcus sanguinis, and Lactobacillus acidophilus

PURPOSE

The purpose of this study was to compare the effects of combinations of sodium fluoride and antiseptic compounds on the growth of Streptococcus mutans, Streptococcus sanguinis, and Lactobacillus acidophilus.

METHODS

The agar diffusion assay was used to determine bacterial growth inhibition.

RESULTS

Of the combinations tested, 0.1 percent sodium fluoride and five percent povidone iodine produced synergistic antibacterial effects against S. mutans and S. sanguinis. The combination of 10 percent povidone iodine and 0.5 percent sodium hypochlorite produced additive antibacterial effects against L. acidophilus. Interference was seen in some combinations such as 0.01 percent chlorhexidine and 0.25 percent sodium lauryl sulphate, 0.5 percent sodium hypochlorite and 10 percent povidone iodine, and 0.01 percent cetyl pyridium chloride and 0.1 percent sodium fluoride. However, 0.1 percent sodium fluoride combined with 0.01 percent chlorhexidine did not interfere with the antibacterial effects of chlorhexidine against S. mutans or S. sanguinis.

CONCLUSIONS

Combinations of common antiseptics and fluoride compounds can produce interference, synergistic, or additive effects. The combination of 0.1 percent sodium fluoride and five percent povidone iodine had the greatest potential for suppression of S. mutans.

Cost effectiveness of cryoprotective agents and modified De-man Rogosa Sharpe medium on growth of Lactobacillus acidophilus

The effect of cryoprotective agents (namely, sodium chloride, sucrose, dextran, sorbitol, monosodium glutamate, glycerol, skim milk and skim milk with malt extract) and modified De-Man Rogosa Sharpe (MRS) medium, on the viability and stability of L. acidophilus ATCC 4962, was investigated. The modified MRS medium was not only economical, but it gave a relatively higher yield of L. acidophilus ATCC 4962 than the commercial MRS. Monosodium glutamate, skim milk and skim milk with malt extract provided significantly higher viable counts, with optimum concentration at 0.3%. Nevertheless, at concentration above 0.5%, there was a reduction in cell viability, which could be attributed to cell shrinkage associated with osmotic pressure changes inside the cells. It was also found that L. acidophilus ATCC 4962 was stable at 28 degrees C for eight weeks. Skim milk demonstrated a significant growth of probiotics. Skim milk was the preferred cryoprotective agent, as it is of low cost, easily available and demonstrated a significant growth of probiotics. In conclusion, modified MRS medium with skim milk is suggested for the remarkable growth and yield of L. acidophilus.

Plasma deactivation of oral bacteria seeded on hydroxyapatite disks as tooth enamel analogue

PURPOSE

To study the plasma treatment effects on deactivation of oral bacteria seeded on a tooth enamel analogue.

METHODS

A non-thermal atmospheric pressure argon plasma brush was used to treat two different Gram-positive oral bacteria including Lactobacillus acidophilus (L. acidophilus) and Streptococcus mutans (S. mutans). The bacteria were seeded on hydroxyapatite (HA) disks used as tooth enamel analogue with three initial bacterial seeding concentrations: a low inoculum concentration between 2.1 x 10(8) and 2.4 x 10(8) cfu/mL, a medium inoculum concentration between 9.8x10(8) and 2.4 x 10(9) cfu/mL, and a high inoculum concentration between 1.7 x 10(10) and 3.5 x 10(10) cfu/mL. The bacterial survivability upon plasma exposure was examined in terms of plasma exposure time and oxygen addition into the plasmas. SEM was performed to examine bacterial morphological changes after plasma exposure.

RESULTS

The experimental data indicated that a 13-second plasma exposure time completely killed all the bacteria when initial bacterial seeding density on HA surfaces was less than 6.9 x 10(6) cfu/cm2 for L. acidophilus and 1.7 x 10(7) cfu/cm2 for S. mutans, which resulted from low initial seeding inoculum concentration between 2.1 x 10(8) and 2.4 x 10(8) cfu/mL. Plasma exposure of the bacteria at higher initial bacterial seeding density obtained with high initial seeding inoculum concentration, however, only resulted in approximately 1.5 to 2 log reduction and approximately 2 to 2.5 log reduction for L. acidophilus and S. mutans, respectively. It was also noted that oxygen addition into the argon plasma brush did not affect the plasma deactivation effectiveness. SEM images showed that plasma deactivation mainly occurred with the top layer bacteria, while shadowing effects from the resulting bacterial debris reduced the plasma deactivation of the underlying bacteria.

Secreted aspartic peptidases of Candida albicans liberate bactericidal hemocidins from human hemoglobin

Secreted aspartic peptidases (Saps) are a group of ten acidic hydrolases considered as key virulence factors of Candida albicans. These enzymes supply the fungus with nutrient amino acids as well as are able to degrade the selected host's proteins involved in the immune defense. Our previous studies showed that the human menstrual discharge is exceptionally rich in bactericidal hemoglobin (Hb) fragments - hemocidins. However, to date, the genesis of such peptides is unclear. The presented study demonstrates that the action of C. albicans isozymes Sap1-Sap6, Sap8 and Sap9, but not Sap7 and Sap10, toward human hemoglobin leads to limited proteolysis of this protein and generates a variety of antimicrobial hemocidins. We have identified these peptides and checked their activity against selected microorganisms representative for human vagina. We have also demonstrated that the process of Hb hydrolysis is most effective at pH 4.0, characteristic for vagina, and the liberated peptides showed pronounced killing activity toward Lactobacillus acidophilus, and to a lower degree, Escherichia coli. However, only a very weak activity toward Staphylococcus aureus and C. albicans was noticed. These findings provide interesting new insights into pathophysiology of human vaginal candidiasis and suggest that C. albicans may be able to compete with the other microorganisms of the same physiological niche using the microbicidal peptides generated from the host protein.

[Identification and biological properties of intestinal lactic acid bacteria isolated from aged women]

The strains of lactic acid bacteria have been isolated from the intestine of older women. These strains were identified and their biological activity was studied. It has been established that Lactobacillus acidophilus, L. plantarum, L. salivarius var. salivarius and Enterococcus faecium had the highest antagonistic activity against opportunistic microorganisms. It has been revealed, that the adhesive properties and antibiotic resistance of the tested cultures had strain specificity. Most of the isolates were highly adhesive and did not produce hemolysins.

Broad-spectrum antibacterial activity of carbon nanotubes to human gut bacteria

Carbon nanotubes (CNTs) hold promise in manufacturing, environmental, and biomedical applications, as well as food and agricultural industries. Previous observations have shown that CNTs have antimicrobial activity; however, the impact of CNTs to human gut microbes has not been investigated. Here, the antibacterial activity of CNTs against the microbes commonly encountered in the human digestion system--L. acidophilus, B. adolescentis, E. coli, E. faecalis, and S. aureus--are evaluated. The bacteria studied include pathogenic and non-pathogenic, gram-positive and negative, and both sphere and rod strains. In this study, CNTs, including single-walled CNTs (SWCNTs, 1-3 μm), short and long multi-walled CNTs (s-MWCNTs: 0.5-2 μm; l-MWCNTs: >50 μm), and functionalized multi-walled CNTs (hydroxyl- and carboxyl-modification, 0.5-2 μm), all have broad-spectrum antibacterial effects. Notably, CNTs may selectively lyse the walls and membranes of human gut microbes, depending on not only the length and surface functional groups of CNTs, but also the shapes of the bacteria. The mechanism of antibacterial activity is associated with their diameter-dependent piercing and length-dependent wrapping on the lysis of microbial walls and membranes, inducing release of intracellular components DNA and RNA and allowing a loss of bacterial membrane potential, demonstrating complete destruction of bacteria. Thin and rigid SWCNT show more effective wall/membrane piercing on spherical bacteria than MWCNTs. Long MWCNT may wrap around gut bacteria, increasing the area making contact with the bacterial wall. This work suggests that CNTs may be broad-spectrum and efficient antibacterial agents in the gut, and selective application of CNTs could reduce the potential hazard to probiotic bacteria.

Antimicrobial activity of fractions and subfractions of Elaeagia utilis against microorganisms of importance in dental caries

Dental caries is a multifactorial infectious disease that leads to the destruction of dental hard tissue. The main goal of research into medicinal plants is to seek compounds with antimicrobial activity for subsequent use in prevention strategies and control of infectious diseases. The aim of this study was to evaluate the antimicrobial activity of fractions and subfractions obtained from Elaeagia utilis against Streptococcus mutans, Streptococcus sobrinus and Lactobacillus acidophilus. The plant material was collected in the town of Alban (Cundinamarca, Colombia), which is located at an altitude of 2245 meters above sea level. Two extracts were obtained by cold maceration of E. utilis leaves in (a) petroleum ether extract and (b) ethanol extract. Fractions were obtained from the petroleum ether extract by column vacuum chromatography, and from the ethanol extract by continuous liquid/liquid partitioning. The antimicrobial activity of fractions and subfractions was evaluated by the well diffusion method. At a concentration of 10 mg/well, several fractions from both extracts showed antimicrobial activity against S. mutans, S. sobrinus and L. acidophilus. Among the ethanol extract fractions, the dichloromethane fraction had notably greater antimicrobial activity. It was sub-partitioned, yielding three subfractions with inhibitory activity, of which the most active was MeOH: H2O (Bp) with minimum inhibitory concentration 0.1 mg/well on the 3 study bacteria. Terpenes, sesquiterpenlactones and simple phenolic compounds were identified in it. In conclusion, this study shows the antimicrobial potential of fractions and subfractions obtained from extracts of E. utilis leaves against bacteria that are important in dental caries.

Lactobacillus acidophilus La5 and Bifidobacterium lactis Bb12 cell surface hydrophobicity and survival of the cells under adverse environmental conditions

Changes in the cell surface hydrophobicity (CSH) of probiotic bacteria Lactobacillus acidophilus La5 and Bifidobacterium lactis Bb12 and the survival of these cells were examined in response to varied cultivation conditions and adverse environmental conditions. An inverse linear relationship (P < 0.01) was detected between the CSH of intact L. acidophilus La5 and B. lactis Bb12 and survival of cells subjected to subsequent freezing/thawing, long-term storage or exposure to mineral and bile acids. The observed relationships were supported by significant correlations between the CSH and changes in composition of the cell envelopes (proteins, lipids and carbohydrates) of L. acidophilus La5 and B. lactis Bb12 examined using FT-IR spectroscopy and conventional biochemical analysis methods. The results also suggest that the estimates of hydrophobicity, being a generalized characteristic of cell surfaces, are important parameters to predict the ability of intact probiotic bacteria to endure extreme environments and therefore should be monitored during cultivation. A defined balance of cell components, which can be characterized by the reduced CSH values, apparently helps to ensure the resistance, improved viability and hence the overall probiotic properties of bacteria.

Transcriptional analysis of prebiotic uptake and catabolism by Lactobacillus acidophilus NCFM

The human gastrointestinal tract can be positively modulated by dietary supplementation of probiotic bacteria in combination with prebiotic carbohydrates. Here differential transcriptomics and functional genomics were used to identify genes in Lactobacillus acidophilus NCFM involved in the uptake and catabolism of 11 potential prebiotic compounds consisting of α- and β- linked galactosides and glucosides. These oligosaccharides induced genes encoding phosphoenolpyruvate-dependent sugar phosphotransferase systems (PTS), galactoside pentose hexuronide (GPH) permease, and ATP-binding cassette (ABC) transporters. PTS systems were upregulated primarily by di- and tri-saccharides such as cellobiose, isomaltose, isomaltulose, panose and gentiobiose, while ABC transporters were upregulated by raffinose, Polydextrose, and stachyose. A single GPH transporter was induced by lactitol and galactooligosaccharides (GOS). The various transporters were associated with a number of glycoside hydrolases from families 1, 2, 4, 13, 32, 36, 42, and 65, involved in the catabolism of various α- and β-linked glucosides and galactosides. Further subfamily specialization was also observed for different PTS-associated GH1 6-phospho-β-glucosidases implicated in the catabolism of gentiobiose and cellobiose. These findings highlight the broad oligosaccharide metabolic repertoire of L. acidophilus NCFM and establish a platform for selection and screening of both probiotic bacteria and prebiotic compounds that may positively influence the gastrointestinal microbiota.

[Interaction of Bifidobacterium bifidum with members of normal microflora in human intestine microsymbiocenosis]

AIM

Study the influence of exometabolites of B. bifidum on biological properties of bacteria that are the members of normoflora and their ability to interact with associative microsymbionts.

MATERIALS AND METHODS

Bacterial strains that are members of the normal microflora of human intestine: B. bifidum, Lactobacillus acidophilus, Enterococcusfaecium and Escherichia coli lactose positive non-hemolytic (lac "+"/hly "-") were used. As opportunistic microorganisms cultures of E. coli lactose negative hemolytic (lac "-"/hly "+"), Klebsiella pneumoniae and Staphylococcus aureus were used. Isolation and identification of microorganisms was performed by generally accepted methods according to guidances. In the first series of experiments influence of B. bifidum metabolites on biological properties of microorganisms that are members ofnormoflora was studied. In the second series--the influence of bifidobacteria supernatants on interrelations of B. bifidum, L. acidophilus and E. coli lac "+"/hly "-" with opportunistic associants. Growth properties (GP), biofilm formation (BFF) and anti-lysozyme activity (ALA) of microorganisms was studied photometrically. Optical density measurement were performed on ELx808 (BioTek, U.S.A.) photometer. The data obtained were treated by nonparametric method using Mann-Whitney criteria.

RESULTS

B. bifidum supernatant was established to stimulate in 33.3-66.7% of cases or did not alter growth/reproduction, BFF and ALA of microorganisms that are characteristic for eubiosis of intestine including bacteria of the same species that could have implications for realization by bifidobacteria ofbiotope colonization resistance. Features of interaction ofexometabolites of bifidobacteria with microorganisms that are characteristic for eubiosis of human intestine consisting in enchantment or changes of effects of the influence of normoflora members on BFF of associants were revealed. The maximum enchantment of inhibitory effect of indigenous strains under the influence ofbifidobacteria was noted in associations E. coli lac "+"/hly "-" E. coli lac "-"/hly "+" as well as E. faecium--S. aureus.

CONCLUSION

Thus, the data obtained may be used for detection of mechanisms of functioning of normal microsymbiocenosis in human associative symbiosis.

[Influence of corynebacteria metabolites on antagonistic activity of H2O2 producing lactobacilli]

AIM

Study combined influence of Corynebacterium genus bacteria metabolites and H2O2 producing lactobacilli on survival rate of Staphylococcus aureus, Escherichia coli and Lactobacillus acidophilus.

MATERIALS AND METHODS

The ability to inhibit catalase of the test strains used and to reduce bactericidal effect of hydroxyl radical were determined in corynebacteria. H2O2 containing metabolites were obtained by cultivating lactobacilli in mineral medium, the amount of H2O2 was determined by oxidation of TMB by peroxidase. Bactericidal effect of lactobacilli metabolites for test strains treated by corynebacteria metabolites was evaluated by seeding results. Results. Inhibitio by corynebacteria metabolites of S. aureus catalase activity by 30-40% and E. coli catalase activ ity by 40-70% was shown. A reduction of bactericidal effect of hydroxyl radicals by corynebacteria metabolites by 30-35% for S. aureus, 38-42% for E. coli and 70-73% for L. acidophilus was noted. The enchantment of bactericidal effect of lactobacilli after treatment of the test strain by corynebacteria metabolites against S. aureus and E. coli manifested by reduction of the numbe of viable cells by 2-3 lg CFU. For L. acidophilus the bactericidal effect oflactobacilli metabolite in the same conditions reduced, and that led to the increase ofviability by 2-4 lg PFU.

CONCLUSION

A conclusion on the possibility of regulation by associative bacteria the manifestations of antagonistic activity of H2O2 producing dominant microorganisms is made based on the data obtained.

Bacteriocin production and resistance to drugs are advantageous features for Lactobacillus acidophilus La-14, a potential probiotic strain

L. acidophilus La-14 produces bacteriocin active against L. monocytogenes ScottA (1600 AU/ml) in MRS broth at 30°C or 37°C. The bacteriocin proved inhibitory to different serological types of Listeria spp. Antimicrobial activity was completely lost after treatment of the cell-free supernatant with proteolytic enzymes. Addition of bacteriocin produced by L. acidophilus La-14 to a 3 h-old culture of L. monocytogenes ScottA repressed cell growth in the following 8h. Treatment of stationary phase cells of L. monocytogenes ScottA (107-108 CFU/ml) by the bacteriocin resulted in growth inhibition. Growth of L. acidophilus La-14 was not inhibited by commercial drugs from different generic groups, including nonsteroidal anti-inflammatory drugs (NSAID) containing diclofenac potassium or ibuprofen arginine. Only one non-antibiotic drug tested, Atlansil (an antiarrhythmic agent), had an inhibitory effect on L. acidophilus La-14 with MIC of 2.5 mg/ml. L. acidophilus La-14 was not affected by drugs containing sodium or potassium diclofenac. L. acidophilus La-14 shows a good resistance to several drugs and may be applied in combination for therapeutic use.

Evaluation of safety margins of Chenopodium album seed decoction: 14-day subacute toxicity and microbicidal activity studies

BACKGROUND

Sperm immobilizing activity and plausible mechanism of action of Chenopodium album seed decoction (CAD) have been elucidated in our earlier studies. The present study has been carried out to explore the safety standards of CAD along with microbicidal properties as prerequisite for its use as a topically applicable vaginal contraceptive.

METHODS

The safety standards of CAD were assessed by a) Hemolytic index determination using rabbit erythrocytes, to set the doses of the other experiments, b) Dermal irritancy test using refined version of Draize scoring system on rabbits, c) Possible effect on local tissues and reproductive performance in female rats after fourteen daily single dose application, d) PCNA staining- to evaluate the effect of CAD on vaginal tissue proliferation, e) TUNEL assay- to examine its ability to induce in situ apoptosis in the vaginal tissue sections of the treated animals, and f) Microbicidal activity- to explore the effect of CAD on the growth of Lactobacillus acidophilus and Candida albicans.

RESULTS

In vitro irritation studies on rabbit erythrocytes revealed the hemolytic index of CAD to be 8.2 mg/ml. The dermal irritation test showed it to be a non-irritant even at higher doses. Intra vaginal application of CAD in rat vagina for 14 consecutive days caused slight reversible inflammation on vaginal epithelial cells at doses as high as 82 mg/ml. However, at this dose level it neither had any adverse effect on vaginal tissue proliferation nor did it cause in situ apoptosis as evident from PCNA staining and TUNEL assay. Fertility and fecundity were restored 4-15 days after withdrawal of CAD application. At dose level 10 times that of its spermicidal MEC (minimum effective concentration), CAD did not block the growth of Lactobacillus, although the size of individual colony was marginally reduced. However, growth of the pathogenic fungus Candida albicans was completely inhibited with 20 mg/ml of CAD.

CONCLUSION

The overall result evolved from the study strengthens the candidature of CAD as a safe microbicidal spermicide. It is almost non-irritant to rabbit skin and rat vaginal tissues at doses 10 fold higher than its hemolytic index. The effect of CAD on Lactobacillus culture was not highly encouraging but it prevented the growth of the fungal pathogen Candida albicans at 20 mg/ml of CAD.

[PH and oxidation-reduction potential change of environment during a growth of lactic acid bacteria: effects of oxidizers and reducers]

Decrease of pH and dropping of oxidation-reduction potential have been observed during growing Lactobacillus salivarius 1588 and 3823, Lactobacillus acidophilus 101E, and Lactococcus lactis 3690 in anaerobic conditions in medium with glucose acidification. These parameters and membrane proton permeability of bacteria (C(M)(H+)) changed in the mediums with different pH. Oxidizer ferrycianide and reducer DL-dithiothreitol affected the bacterial growth and their changed H+ extrusion from the cells and K+ uptake by the cells in experiment conditions. Application of oxidizers and reducers are suggested for regulation of growth related with H+ ion transport in lactic acid bacteria.

The in vitro antimicrobial activity of natural infant fluoride-free toothpastes on oral micro-organisms

PURPOSE

The objective of this study was to evaluate the antimicrobial activity of six toothpastes for infants: 3 fluoride-free experimental toothpastes--cashew-based, mango-based and without plant extract and fluoride compared with 2 commercially fluoride-free toothpastes and 1 fluoridated toothpastes.

METHODS

Six toothpastes for infants were evaluated in this study: (1) experimental cashew-based toothpaste; (2) experimental mango-based toothpaste; (3) experimental toothpaste without plant extract and fluoride (negative control); (4) First Teeth brand toothpaste; (5) Weleda brand toothpaste; and (6) Tandy brand toothpaste (positive control). The antimicrobial activity was recorded against Streptococcus mutans, Streptococcus sobrinus, Lactobacillus acidophilus, and Candida albicans using the agar plate diffusion test.

RESULTS

First Teeth, Weleda, mango-based toothpaste, and toothpaste without plant extract presented no antimicrobial effect against any of the tested micro-organisms. Cashew toothpaste had antimicrobial activity against S mutans, S sobrinus, and L acidophilus, but it showed no antimicrobial activity against C albicans. There was no statistical difference between the inhibition halo of cashew and Tandy toothpastes against S mutans and L acidophilus.

CONCLUSIONS

Cashew fluoride-free toothpaste had inhibitory activity against Streptococcus mutans and Lactobacillus acidophilus, and these results were similar to those obtained for fluoridated toothpaste.

Oral bacterial deactivation using a low-temperature atmospheric argon plasma brush

OBJECTIVE

To study the plasma treatment effects on deactivation effectiveness of oral bacteria.

METHODS

A low temperature atmospheric argon plasma brush were used to study the oral bacterial deactivation effects in terms of plasma conditions, plasma exposure time, and bacterial supporting media. Oral bacteria of Streptococcus mutans and Lactobacillus acidophilus with an initial bacterial population density between 1.0×10(8) and 5.0×10(8)cfu/ml were seeded on various media and their survivability with plasma exposure was examined. Scanning electron microscopy was used to examine the morphological changes of the plasma treated bacteria. Optical absorption was used to determine the leakage of intracellular proteins and DNAs of the plasma treated bacteria.

RESULTS

The experimental data indicated that the argon atmospheric plasma brush was very effective in deactivating oral bacteria. The plasma exposure time for a 99.9999% cell reduction was less than 15s for S. mutans and within 5 min for L. acidophilus. It was found that the plasma deactivation efficiency was also dependent on the bacterial supporting media. With plasma exposure, significant damages to bacterial cell structures were observed with both bacterium species. Leakage of intracellular proteins and DNAs after plasma exposure was observed through monitoring the absorbance peaks at wavelengths of 280 nm and 260 nm, respectively.

CONCLUSION

The experimental results from this study indicated that low temperature atmospheric plasma treatment was very effective in deactivation of oral bacteria and could be a promising technique in various dental clinical applications such as bacterial disinfection and caries early prevention.

Nisin inhibits dental caries-associated microorganism in vitro

Nisin, produced by Lactococcus lactis, is an antibiotic peptide to effectively antagonize a broad spectrum of Gram-positive bacteria, and is widely used as a safe food antimicrobial agent. In the present study, we investigated whether nisin could be used as an effective antibiotic peptide against the nine common cariogenic microorganisms, and its antimicrobial activity could be affected by the ingredients of saliva in oral cavity. In the minimal inhibitory concentration (MIC) and minimal bactericide concentration (MBC) and spot-on-lawn assay, nisin displayed different MIC, MBC and antimicrobial activity against the nine tested strains. There was statistical difference between the inhibitory zone diameters of nisin against the different tested bacteria (p<0.05), but no statistical difference between the inhibitory zone diameters of nisin dissolved in PBS and saliva (p>0.05). Furthermore, morphology and membranes of Streptococcus sanguinis, Streptococcus mutans, Lactobacillus fermenti and Lactobacillus acidophilus with nisin treatment were observed and showed different degrees of variation by a Field Emission Scanning Electron Microscope (FE-SEM). Our findings suggested that nisin has considerable potential for prevention and treatment of dental caries.

[Genetic improvement of technological characteristics of starters for fermented milk products]

Possibility for improvement of technological characteristics of lactobacilli using mutations of resistance to rifampicin (rif(r)) and streptomycin (str(r)) was studied. Using starter model of Narine Lactobacillus acidophilus INMIA-9602 Armenian diet milk product, it was showed that a possibility for selecting strains with increased rate of milk fermentation and acid production is higher in Rif(r) and Str(r) mutants induced by nitrosoguanidine than in cultures sensitive to antibiotics. The milk products obtained using Rif(r) and Str(r) strains had high viscosity, improved texture, increased amount of alive cells and good organoleptic features.

Assessment of bile salt effects on s-layer production, slp gene expression and some physicochemical properties of Lactobacillus acidophilus ATCC 4356

In many conditions, bacterial surface properties are changed as a result of variation in growth medium and conditions. This study examined the influence of bile salt concentrations (0-0.1%) on colony morphotype, hydrophobicity, H2O2 concentration, S-layer protein production and slpA gene expression in Lactobacillus acidophilus ATCC 4356. It was observed that two types of colonies (R and S) were in the control group and the stress condition. When the bile level increased in the medium, the amount of S type was more than the R. A stepwise increment in the bile concentration resulted in a stepwise decline in the maximum growth rate. The results showed that hydrophobicity was increased in 0.01%-0.02% bile but it was decreased in 0.1% bile. Treatment by bile (0.01%- 0.1%) profoundly decreased H2O2 formation. S-layer protein and slpA gene expression was also altered by stress condition. S-protein expression was increased in stress condition. slpA gene expression increased in 0.01%-0.05% bile and it decreased in 0.1% bile. However, we found that different of bile salt concentrations influence on morphology and some surface properties of L. acidophilus ATCC 4356. These changes were very different in the 0.1% bile. It appears that the bacteria respond abruptly to 0.1% bile.

The effect of nonylphenol on the growth of Lactobacillus acidophilus and Bifidobacterium bifidum

BACKGROUND AND PURPOSE

Nonylphenol (NP) is a well-known environmental hormone recognized as detrimental to the reproductive systems of aquatic animals and humans. The effect of NP on probiotics in the human gastrointestinal tract remains unclear. This study investigated the effect of NP on the growth of Lactobacillus acidophilus and Bifidobacterium bifidum.

METHODS

L. acidophilus and B. bifidum were grown in anaerobic cultures. Both strains were incubated with and without NP. The dose effects of NP on the growth of both probiotics were compared, and the effects of NP on the growth of L. acidophilus and B. bifidum in different concentrations were evaluated.

RESULTS

NP 5 to 10 microg/mL inhibited the growth of L. acidophilus (p < 0.05), but was ineffective at 2.5 microg/mL (p > 0.05). NP significantly inhibited the growth of B. bifidum in a dose-dependent manner (p < 0.05). NP inhibited the growth of different concentrations of L. acidophilus (6.25 x 10(4); to 2.5 x 10(5); colony-forming units [CFU]/mL) and B. bifidum (1.25 x 10(9); to 5.0 x 10(9); CFU/mL) [p < 0.05].

CONCLUSIONS

Growth of L. acidophilus and B. bifidum was inhibited by NP. This finding suggests that NP may interfere with normal gastrointestinal microbiota. This may alter immunomodulation in the intestinal mucosa and may be correlated with an increase in the incidence of allergic diseases or other gastrointestinal disorders.

Can different chlorhexidine agents be used as cavity disinfectants?

This study used the agar well method to compare the antimicrobial effect of cavity disinfectants containing chlorhexidine with other chlorhexidine agents (such as mouthrinses and antiseptics) and to determine whether there was a difference in composite bond strength when these chlorhexidine agents were applied to the dentin surface. All tested solutions showed antimicrobial effect against Streptococcus mutans, Lactobacillus acidophilus, and Candida albicans (p < 0.05). However, Savlex was found to be the most effective antibacterial agent against all microorganisms (p < 0.05). There were no significant differences between the bond strengths obtained from the cavity disinfectants and those of the control group (p > 0.05). However, the mouthrinse and the antiseptic decreased the shear bond strength compared with the control group (p < 0.05).

Screening of Lactobacilli derived from chicken feces and partial characterization of Lactobacillus acidophilus A12 as an animal probiotics

This study was performed to screen and select Lactobacillus strains from chicken feces for probiotic use in animals. Of these strains, strain A12 had the highest immunostimulatory effect. Therefore, strain A12 was characterized as a potential probiotic. Strain A12 was tentatively identified as Lactobacillus acidophilus A12, using the API 50 CHL kit based on a 99.9% homology. L. acidophilus A12 was highly resistant to artificial gastric juice (pH 2.5) and bile acid (oxgall). Based on results from the API ZYM kit, leucine arylamidase, crystine arylamidase, acid phosphatase, naphthol-AS-BI-phosphohydrolase, alpha-galactosidase, beta- galactosidase, alpha-glucosidase, beta-glucosidase, and N-acetyl-beta- glucosamidase were produced by strain A12. L. acidophilus A12 showed resistance to several antibiotics (nisin, gentamycin, and erythromycin). The amount of interleukin (IL)-1alpha in 20x concentrated supernatant from L. acidophilus A12 was approximately 156 pg/ml. With regard to antioxidant activity, L. acidophilus A12 supernatant showed 60.6% DPPH radical scavenging activity. These results demonstrate the potential use of L. acidophilus A12 as a health-promoting probiotics.

Antibacterial activity of four glass ionomer cements used in atraumatic restorative treatment

The in vitro antibacterial activity of four glass ionomer cements (Fuji IX, Ketac Molar, Vidrion R and Vitromolar) indicated for Atraumatic Restorative Treatment (ART) was studied against strains of bacteria involved in the development of oral diseases, Streptococcus mutans, Streptococcus sobrinus, Lactobacillus acidophilus and Actinomyces viscosus. The agar plate diffusion test was used for the cultures, which included chlorhexidine as a positive control. The results demonstrated that all the cements evaluated presented antibacterial activity. Based on the results of this study, it can be concluded that Fuji IX and Ketac Molar presented the most effective antibacterial activity considering the ART approach.

Characterization of a novel bile-inducible operon encoding a two-component regulatory system in Lactobacillus acidophilus

Lactobacillus acidophilus NCFM is an industrially important strain used extensively as a probiotic culture. Tolerance of the presence of bile is an attribute important to microbial survival in the intestinal tract. A whole-genome microarray was employed to examine the effects of bile on the global transcriptional profile of this strain, with the intention of elucidating genes contributing to bile tolerance. Genes involved in carbohydrate metabolism were generally induced, while genes involved in other aspects of cellular growth were mostly repressed. A 7-kb eight-gene operon encoding a two-component regulatory system (2CRS), a transporter, an oxidoreductase, and four hypothetical proteins was significantly upregulated in the presence of bile. Deletion mutations were constructed in six genes of the operon. Transcriptional analysis of the 2CRS mutants showed that mutation of the histidine protein kinase (HPK) had no effect on the induction of the operon, whereas the mutated response regulator (RR) showed enhanced induction when the cells were exposed to bile. These results indicate that the 2CRS plays a role in bile tolerance and that the operon it resides in is negatively controlled by the RR. Mutations in the transporter, the HPK, the RR, and a hypothetical protein each resulted in loss of tolerance of bile. Mutations in genes encoding another hypothetical protein and a putative oxidoreductase resulted in significant increases in bile tolerance. This functional analysis showed that the operon encoded proteins involved in both bile tolerance and bile sensitivity.

Tetracycline susceptibility of the ingested Lactobacillus acidophilus LaCH-5 and Bifidobacterium animalis subsp. lactis Bb-12 strains during antibiotic/probiotic intervention

We investigated the effects of oral therapy with doxycycline, a tetracycline group antibiotic, on the gastrointestinal (GI) survival and tetracycline susceptibility of probiotic strains Lactobacillus acidophilus LaCH-5 and Bifidobacterium animalis subsp. lactis Bb-12. In addition, the influence of doxycycline therapy on the diversity of the predominant faecal microbiota was evaluated by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Faecal samples from the antibiotic group (receiving antibiotics and probiotics) and the control group (receiving probiotics only) were analysed for anaerobically and aerobically growing bacteria, bifidobacteria and lactic acid bacteria as well as for the dominant microbiota. Although doxycycline consumption did not have a large impact on GI survival of the probiotics, it had a detrimental effect on the bifidobacteria and on the diversity of the dominant faecal microbiota. A higher proportion of tetracycline-resistant anaerobically growing bacteria and bifidobacteria was detected in the antibiotic group than in the control group. Several antibiotic group subjects had faecal B. animalis subsp. lactis Bb-12-like isolates with reduced tetracycline susceptibility. This was unlikely to be due to the acquisition of novel tetracycline resistance determinants, since only tet(W), which is also present in the ingested B. animalis subsp. lactis Bb-12, was found in the resistant isolates. Thus, concomitant ingestion of probiotic L. acidophilus LaCH-5 and B. animalis subsp. lactis Bb-12 with the antibiotic did not generate a safety risk regarding the possible GI transfer of tetracycline resistance genes to the ingested strains.

Photocatalytic antibacterial effect of TiO2 film formed on Ti and TiAg exposed toLactobacillus acidophilus

When irradiated under near-ultraviolet (UV) light, TiO(2) exhibits strong bactericidal activity. The TiO(2) photocatalyst would be effective on orthodontic appliances after its antibacterial effect on the carcinogenic microorganism Lactobacillus acidophilus is evaluated. To compare the antibacterial effect of two crystalline forms of TiO(2), rutile and anatase, thermal oxidation and anodic oxidation were employed to form each structure, respectively. The antibacterial effect of TiO(2) film on TiAg was also compared with that on Ti. Bacterial solutions were pipetted onto the TiO(2)-coated specimen and illuminated with UVA (2 x 15 W, black light, 356 nm) up to 100 min and the reaction solutions were incubated to count the colony-forming units. The antibacterial activity of the coated specimens was similar to that of the uncoated group. The antibacterial activity of the coated specimens of TiAg was not different from that of Ti. TiO(2) coatings formed on both Ti and TiAg specimens did not exhibit cytotoxicity on the L-929 cells of mice.

Effect of ginseng polysaccharide on the stability of lactic acid bacteria during freeze-drying process and storage

Lactic acid bacteria (LAB) quickly attenuate or are killed during the freeze-drying process and storage. The effect of some natural polysaccharides, which are known as potent antitumor and immunomodulating substances, on the viability of the LAB, Lactobacillus acidophilus and Bifidobacterium breve, on freeze-drying and storage were investigated. Among the polysaccharides tested, red ginseng polysaccharide (RGP) and chitosan significantly inhibited the cell death of the LAB during freeze-drying, and fucoidan and RGP most potently protected the cell death of the LAB during storage. The stabilities of the LAB on the addition of RGP and fucoidan were comparable to that of skimmed milk. However, white ginseng polysaccharide (WGP) did not promote storage stability. When 5% skimmed milk/5% RGP treated LAB were freeze-dried and stored, their viabilities were found to be significantly higher those treated with 5% or 10% RGP. The stabilizing effect of 5% RGP/5% skimmed milk during LAB freeze-drying and storage stability was comparable to that of treatment with 10% skimmed milk. Based on these findings, we believe that RGP beneficially improves the stability of LAB during the freeze-dry process and storage.

Antimicrobial effect of acidified nitrate and nitrite on six common oral pathogens in vitro

BACKGROUND

Salivary nitrate is positively correlated with plasma nitrate and its level is 9 times the plasma level after nitrate loading. Nitrate in saliva is known to be reduced to nitrite by oral bacteria. Nitrate and nitrite levels in saliva are 3 - 5 times those in serum in physiological conditions respectively in our previous study. The biological functions of high salivary nitrate and nitrite are still not well understood. The aim of this in vitro study was to investigate the antimicrobial effects of nitrate and nitrite on main oral pathogens under acidic conditions.

METHODS

Six common oral pathogens including Streptococcus mutans NCTC 10449, Lactobacillus acidophilus ATCC 4646, Porphyromonas gingivalis ATCC 33277, Capnocytophaga gingivalis ATCC 33624, Fusobacterium nucleatum ATCC 10953, and Candida albicans ATCC 10231 were cultured in liquid medium. Sodium nitrate or sodium nitrite was added to the medium to final concentrations of 0, 0.5, 1, 2, and 10 mmol/L. All of the microorganisms were incubated for 24 to 48 hours. The optical densities (OD) of cell suspensions were determined and the cultures were transferred to solid nutrient broth medium to observe the minimum inhibitory concentration and minimum bactericidal/fungicidal concentration for the six tested pathogens.

RESULTS

Nitrite at concentrations of 0.5 to 10 mmol/L had an inhibitory effect on all tested organisms at low pH values. The antimicrobial effect of nitrite increased with the acidity of the medium. Streptococcus mutans NCTC 10449 was highly sensitive to nitrite at low pH values. Lactobacillus acidophilus ATCC 4646 and Candida albicans ATCC 10231 were relatively resistant to acidified nitrite. Nitrate at the given concentrations and under acidic conditions had no inhibitory effect on the growth of any of the tested pathogens.

CONCLUSION

Nitrite, at a concentration equal to that in human saliva, is both cytocidal and cytostatic to six principal oral pathogens in vitro, whereas nitrate at a similar concentration has no antimicrobial effect on these organisms.

Novel disulphide esters of carbothioic acid as potent, non-detergent spermicides with low toxicity to Lactobacillus and HeLa cells in vitro

BACKGROUND

The design, synthesis, characterization and evaluation of a novel series of non-detergent spermicides has led to the discovery of two unique molecules (DSE-36 and DSE-37) that were approximately 25 times more potent spermicides than nonoxynol-9 (N-9).

METHODS

Normal human spermatozoa were used to assess the spermicidal activity (Sander-Cramer Assay), the effect on sperm-membrane integrity [hypo-osmotic swelling test (HOST)], supravital staining and scanning electron microscopy (SEM) and the induction of apoptosis [fluorescein isothiocyanate (FITC) Annexin-V and JC-1 labelling using flow cytometry] by the new class of compounds. HeLa and Lactobacillus cultures were used to assess the cytotoxicity of compounds and their compatibility to normal vaginal flora, respectively.

RESULTS

Compounds DSE-36 and DSE-37 exhibited a strong spermicidal activity [minimum effective concentration (MEC) = 0.002%], which was approximately 25 times more potent than that of N-9 and Sapindus saponins (MEC = 0.05%). As compared with surfactants, DSE-36 and DSE-37 were found to be safer at MEC towards the growth and survival of Lactobacilli and HeLa cells in vitro and to have a milder effect on sperm plasma membrane. At EC(50) both induced apoptosis in sperm cells as characterized by increased labelling with Annexin-V and decreased polarization of sperm mitochondria.

CONCLUSION

Preliminary studies have revealed that in sharp contrast to the non-specific surfactant action of N-9, DSE-36 and DSE-37 have a highly potent, mechanism-based, detrimental action on human sperm. The unique ability of these non-detergent molecules to selectively kill sperm and spare Lactobacilli and HeLa cells at MEC values much lower than that required for N-9 indicates their potential as superior ingredients for formulation into microbicidal contraceptives.