Lactobacillus acidophilus VB1 co-aggregates and inhibits biofilm formation of chronic otitis media-associated pathogens.

This study aims to evaluate the antibacterial activity of Lactobacillus acidophilus, alone and in combination with ciprofloxacin, against otitis media-associated bacteria. L. acidophilus cells were isolated from Vitalactic B (VB), a commercially available probiotic product containing two lactobacilli species, L. acidophilus and Lactiplantibacillus (formerly Lactobacillus) plantarum. The pathogenic bacterial samples were provided by Al-Shams Medical Laboratory (Baqubah, Iraq). Bacterial identification and antibiotic susceptibility testing for 16 antibiotics were performed using the VITEK2 system. The minimum inhibitory concentration of ciprofloxacin was also determined. The antimicrobial activity of L. acidophilus VB1 cell-free supernatant (La-CFS) was evaluated alone and in combination with ciprofloxacin using a checkerboard assay. Our data showed significant differences in the synergistic activity when La-CFS was combined with ciprofloxacin, in comparison to the use of each compound alone, against Pseudomonas aeruginosa SM17 and Proteus mirabilis SM42. However, an antagonistic effect was observed for the combination against Staphylococcus aureus SM23 and Klebsiella pneumoniae SM9. L. acidophilus VB1 was shown to significantly co-aggregate with the pathogenic bacteria, and the highest co-aggregation percentage was observed after 24 h of incubation. The anti-biofilm activities of CFS and biosurfactant (BS) of L. acidophilus VB1 were evaluated, and we found that the minimum biofilm inhibitory concentration that inhibits 50% of bacterial biofilm (MBIC50) of La-CFS was significantly lower than MBIC50 of La-BS against the tested pathogenic bacterial species. Lactobacillus acidophilus, isolated from Vitane Vitalactic B capsules, demonstrated promising antibacterial and anti-biofilm activities against otitis media pathogens, highlighting its potential as an effective complementary/alternative therapeutic strategy to control bacterial ear infections.

Antibiofilm effects of Thymus vulgaris and Hyptis spicigera essential oils on cariogenic bacteria.

Aim: The inhibitory and antibiofilm effects of Thymus vulgaris (EOTv) and Hyptis spicigera essential oils (EOHs) on cariogenic microorganisms were evaluated. Materials & methods: The chemical characterization of EOTv was performed by gas chromatography/mass spectrometry. Streptococcus mutans, Streptococcus gordonii, Streptococcus sanguinis, Streptococcus mitis, Streptococcus sobrinus, Lactobacillus acidophilus and Actinomyces naeslundii were used for agar diffusion assays and determination of minimal inhibitory and minimal bactericide concentrations. In addition, 20 streptococci and lactobacilli clinical isolates were also tested. The effects of essential oil on microbial initial biofilm formation and on preformed microcosm biofilm formed from human saliva were studied. Results & conclusion: Both essential oils had inhibitory effects on the cariogenic species and reduced the bacterial adherence to dental enamel. Essential oils were able to disrupt preformed microcosm biofilms. Thymus vulgaris and Hyptis spicigera essential oils have potential to be used in the development of formulations to the control of cariogenic biofilms.

Protective effect of the probiotic Lactobacillus acidophilus ATCC 4356 in BALB/c mice infected with Toxocara canis.

Human toxocariasis consists of chronic tissue parasitosis that is difficult to treat and control. This study aimed to evaluate the action of the probiotic Lactobacillus acidophilus ATCC 4356 on larvae of Toxocara canis and the effect of IFN-γ cytokine on parasite-host in vivo (1.109 CFU) and in vitro (1.106, 1.107, 1.108, 1.109 CFU) interactions. Four groups of six BALB/c mice were formed: G1 - L. acidophilus supplementation and T. canis infection; G2 - T. canis infection; G3 - L. acidophilus supplementation; and G4 - PBS administration. Mice were intragastrically suplemented with probiotics for 15 days before inoculation and 48 h after inoculation with 100 T. canis eggs. The inoculation of T. canis was also perfomed intragastrically. The recovery of larvae took place through digestion of liver and lung tissues; the evaluation of IFN-γ gene transcription in leukocytes was performed by qPCR. The in vitro test consisted of incubating the probiotic with T. canis larvae. The supplementation of probiotics produced a reduction of 57.7% (p = 0.025) in the intensity of infection of T. canis larvae in mice, whereas in the in vitro test, there was no larvicidal effect. In addition, a decrease in the IFN-γ gene transcription was observed in both, T. canis-infected and uninfected mice, regardless of whether or not they received supplementation. The probiotic L. acidophilus ATCC 4356 reduced T. canis infection intensity in mice, however, the probiotic did not have a direct effect on larvae, demonstrating the need of interaction with the host for the beneficial effect of the probiotic to occur. Yet, the proinflammatory cytokine IFN-γ did not apparently contributed to the observed beneficial effect of probiotics.

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.

Prebiotic activity of monofloral honeys produced by stingless bees in the semi-arid region of Brazilian Northeastern toward Lactobacillus acidophilus LA-05 and Bifidobacterium lactis BB-12.

This study assessed the in vitro prebiotic effects of honeys from Ziziphus joazeiro Mart. (juazeiro; J) and Mimosa arenosa Willd Poir (jurema branca; JB) produced by native stingless bees, namely Melipona subnitida Ducke (jandaíra; J) and M. scutellaris Latrelle (uruçu; U), in the Brazilian Northeastern semi-arid region toward the probiotics Lactobacillus acidophilus LA-05 and Bifidobacterium animalis subsp. lactis BB-12. Cells of the probiotic strains were enumerated over 48 h of cultivation in broths containing each honey (JJ, JU, JBJ or JBU) as a sole carbon source. The metabolic activities of probiotic strains in these media were assessed by measuring changes in pH values and sugars, organic acids and phenolics contents. All honeys (20 or 30 g/L) exerted growth promoting effects and displayed positive prebiotic activity scores (0.94-1.22) on tested probiotics. JJ showed the highest (p < 0.05) stimulatory effects on probiotics growth and prebiotic scores. At the end of the cultivation period, counts of L. acidophilus LA-05 and B. lactis BB-12 increased (p < 0.05) more than 2 log in broths regardless the monofloral honey added. The pH values and sugars contents decreased (p < 0.05), while the organic acids contents increased (p < 0.05) during cultivation of probiotics in broths containing JJ, JU, JBJ or JBU as carbon source. After 48 h of cultivation, contents of gallic, caftaric and caffeic acid, catechin and procyanidins (B1 and B2) decreased (p < 0.05) in media containing JJ, JU, JBJ or JBU despite of the inoculated probiotic. JJ honey presented overall the better stimulatory effects on the growth and metabolism of L. acidophilus LA-05 and B. lactis BB-12. These results showed for the first time the potential prebiotic properties of four monofloral honeys produced by stingless bees in the Brazilian Northeastern semi-arid region.

Survival of Lactobacillus acidophilus LA-5 and Escherichia coli O157:H7 in Minas Frescal cheese made with oregano and rosemary essential oils.

The effects of the incorporation of the essential oils from Origanum vulgare L. (OVEO; 0.07 µL/g) and Rosmarinus officinalis L. (ROEO; 2.65 µL/g) in combination in Minas Frescal cheese on the counts of the probiotic Lactobacillus acidophilus LA-5 and Escherichia coli O157:H7 were evaluated during refrigerated storage (7 ±â€¯0.5 °C). The terpenes of OVEO and ROEO, survival of the probiotic strain during in vitro digestion, as well as the physicochemical and sensory aspects were also monitored in Minas Frescal cheese. All terpenes decreased in cheese when the storage time increased. The incorporation of OVEO and ROEO delayed the increase in L. acidophilus LA-5 counts in cheese, but did not affect its ability to survive in cheese under simulated gastrointestinal conditions. The decreases in counts of E. coli O157:H7 observed in the first 15 days of refrigerated storage were strongly correlated (r ≥ 0.82) with the terpenes detected in cheese. Scores attributed for aroma, flavor, overall impression and purchase intention of cheese with OVEO and ROEO increased with the increase of the storage time. The incorporation of OVEO and ROEO in combination could be a strategy to control E. coli O157:H7 in probiotic Minas cheese during storage; however, the amounts of these substances should be cautiously selected considering possible negative sensory impacts in this product.

Effect of iodonium salt and chitosan on the physical and antibacterial properties of experimental infiltrants.

Resinous infiltrants are indicated in the treatment of incipient carious lesions, and further development of these materials may contribute to greater control of these lesions. The aim of this study was to analyze the physical and antibacterial properties of experimental infiltrants containing iodonium salt and chitosan. Nine experimental infiltrants were formulated by varying the concentration of the diphenyliodonium salt (DPI) at 0, 0.5 and 1 mol%; and chitosan at 0, 0.12 and 0.25 g%. The infiltrants contained the monomeric base of triethylene glycol dimethacrylate and bisphenol-A dimethacrylate ethoxylate in a 75 and 25% proportion by weight, respectively; 0.5 mol% camphorquinone and 1 mol% ethyl 4-dimethylaminobenzoate. The degree of conversion was evaluated using Fourier transformer infrared spectroscopy, and the flexural strength and elastic modulus using the three-point bending test. Sorption and solubility in water, and antibacterial analysis (minimum inhibitory concentration and minimum bactericidal concentration) were also analyzed. Data was analyzed statistically by two-way ANOVA and Tukey's test (p<0.05), with the exception of the antibacterial test, which was evaluated by visual inspection. In general, the infiltrant group containing 0.5% DPI and 0.12% chitosan showed high values of degree of conversion, higher values of elastic modulus and flexural strength, and lower sorption values in relation to the other groups. Antibacterial activity was observed in all the groups with DPI, regardless of the concentration of chitosan. The addition of DPI and chitosan to experimental infiltrants represents a valid option for producing infiltrants with desirable physical and antibacterial characteristics.

Effect of iodonium salt and chitosan on the physical and antibacterial properties of experimental infiltrants

Abstract Resinous infiltrants are indicated in the treatment of incipient carious lesions, and further development of these materials may contribute to greater control of these lesions. The aim of this study was to analyze the physical and antibacterial properties of experimental infiltrants containing iodonium salt and chitosan. Nine experimental infiltrants were formulated by varying the concentration of the diphenyliodonium salt (DPI) at 0, 0.5 and 1 mol%; and chitosan at 0, 0.12 and 0.25 g%. The infiltrants contained the monomeric base of triethylene glycol dimethacrylate and bisphenol-A dimethacrylate ethoxylate in a 75 and 25% proportion by weight, respectively; 0.5 mol% camphorquinone and 1 mol% ethyl 4-dimethylaminobenzoate. The degree of conversion was evaluated using Fourier transformer infrared spectroscopy, and the flexural strength and elastic modulus using the three-point bending test. Sorption and solubility in water, and antibacterial analysis (minimum inhibitory concentration and minimum bactericidal concentration) were also analyzed. Data was analyzed statistically by two-way ANOVA and Tukey's test (p<0.05), with the exception of the antibacterial test, which was evaluated by visual inspection. In general, the infiltrant group containing 0.5% DPI and 0.12% chitosan showed high values of degree of conversion, higher values of elastic modulus and flexural strength, and lower sorption values in relation to the other groups. Antibacterial activity was observed in all the groups with DPI, regardless of the concentration of chitosan. The addition of DPI and chitosan to experimental infiltrants represents a valid option for producing infiltrants with desirable physical and antibacterial characteristics.

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.

Cymbopogon citratus essential oil: effect on polymicrobial caries-related biofilm with low cytotoxicity.

The objective of this study was to evaluate the effects of Cymbopogon citratus essential oil and its main compound (citral) against primary dental colonizers and caries-related species. Chemical characterization of the essential oil was performed by gas chromatography/mass spectroscopy (GC/MS), and the main compound was determined. Antimicrobial activity was tested against Actinomyces naeslundii, Lactobacillus acidophilus, S. gordonii, S. mitis, S. mutans, S. sanguinis and S. sobrinus. Minimum inhibitory and bactericide concentrations were determined by broth microdilution assay for streptococci and lactobacilli reference, and for clinical strains. The effect of the essential oil on bacterial adhesion and biofilm formation/disruption was investigated. Negative (without treatment) and positive controls (chlorhexidine) were used. The effect of citral on preformed biofilm was also tested using the same methodology. Monospecies and microcosm biofilms were tested. ANOVA or Kruskal-Wallis tests were used (α=0.05). Cytotoxicity of the essential oil to human keratinocytes was performed by MTT assay. GC/MS demonstrated one major component (citral). The essential oil showed an inhibitory effect on all tested bacterial species, including S. mutans and L. acidophilus. Essential oil of C. citratus (10X MIC) reduced the number of viable cells of lactobacilli and streptococci biofilms (p < 0.05). The essential oil inhibited adhesion of caries-related polymicrobial biofilm to dental enamel (p < 0.01). Citral significantly reduced the number of viable cells of streptococci biofilm (p < 0.001). The essential oil showed low cytotoxicity to human keratinocytes. Based on these findings, this study can contribute to the development of new formulations for products like mouthwash, against dental biofilms.

In vitro and in vivo evaluations of glass-ionomer cement containing chlorhexidine for Atraumatic Restorative Treatment.

OBJECTIVES: Addition of chlorhexidine has enhanced the antimicrobial effect of glass ionomer cement (GIC) indicated to Atraumatic Restorative Treatment (ART); however, the impact of this mixture on the properties of these materials and on the longevity of restorations must be investigated. The aim of this study was to evaluate the effects of incorporating chlorhexidine (CHX) in the in vitro biological and chemical-mechanical properties of GIC and in vivo clinical/ microbiological follow-up of the ART with GIC containing or not CHX. MATERIAL AND METHODS: For in vitro studies, groups were divided into GIC, GIC with 1.25% CHX, and GIC with 2.5% CHX. Antimicrobial activity of GIC was analyzed using agar diffusion and anti-biofilm assays. Cytotoxic effects, compressive tensile strength, microhardness and fluoride (F) release were also evaluated. A randomized controlled trial was conducted on 36 children that received ART either with GIC or GIC with CHX. Saliva and biofilm were collected for mutans streptococci (MS) counts and the survival rate of restorations was checked after 7 days, 3 months and one year after ART. ANOVA/Tukey or Kruskal-Wallis/ Mann-Whitney tests were performed for in vitro tests and in vivo microbiological analysis. The Kaplan-Meier method and Log rank tests were applied to estimate survival percentages of restorations (p<0.05). RESULTS: Incorporation of 1.25% and 2.5% CHX improved the antimicrobial/anti-biofilm activity of GIC, without affecting F release and mechanical characteristics, but 2.5% CHX was cytotoxic. Survival rate of restorations using GIC with 1.25% CHX was similar to GIC. A significant reduction of MS levels was observed for KM+CHX group in children saliva and biofilm 7 days after treatment. CONCLUSIONS: The incorporation of 1.25% CHX increased the in vitro antimicrobial activity, without changing chemical-mechanical properties of GIC and odontoblast-like cell viability. This combination improved the in vivo short-term microbiological effect without affecting clinical performance of ART restorations.

In vitro and in vivo evaluations of glass-ionomer cement containing chlorhexidine for Atraumatic Restorative Treatment

Abstract Objectives: Addition of chlorhexidine has enhanced the antimicrobial effect of glass ionomer cement (GIC) indicated to Atraumatic Restorative Treatment (ART); however, the impact of this mixture on the properties of these materials and on the longevity of restorations must be investigated. The aim of this study was to evaluate the effects of incorporating chlorhexidine (CHX) in the in vitro biological and chemical-mechanical properties of GIC and in vivo clinical/ microbiological follow-up of the ART with GIC containing or not CHX. Material and Methods: For in vitro studies, groups were divided into GIC, GIC with 1.25% CHX, and GIC with 2.5% CHX. Antimicrobial activity of GIC was analyzed using agar diffusion and anti-biofilm assays. Cytotoxic effects, compressive tensile strength, microhardness and fluoride (F) release were also evaluated. A randomized controlled trial was conducted on 36 children that received ART either with GIC or GIC with CHX. Saliva and biofilm were collected for mutans streptococci (MS) counts and the survival rate of restorations was checked after 7 days, 3 months and one year after ART. ANOVA/Tukey or Kruskal-Wallis/ Mann-Whitney tests were performed for in vitro tests and in vivo microbiological analysis. The Kaplan-Meier method and Log rank tests were applied to estimate survival percentages of restorations (p<0.05). Results: Incorporation of 1.25% and 2.5% CHX improved the antimicrobial/anti-biofilm activity of GIC, without affecting F release and mechanical characteristics, but 2.5% CHX was cytotoxic. Survival rate of restorations using GIC with 1.25% CHX was similar to GIC. A significant reduction of MS levels was observed for KM+CHX group in children saliva and biofilm 7 days after treatment. Conclusions: The incorporation of 1.25% CHX increased the in vitro antimicrobial activity, without changing chemical-mechanical properties of GIC and odontoblast-like cell viability. This combination improved the in vivo short-term microbiological effect without affecting clinical performance of ART restorations.

Photodynamic Inactivation of Cariogenic Pathogens Using Curcumin as Photosensitizer.

OBJECTIVE: This investigation assessed the susceptibility of Streptococcus mutans and Lactobacillus acidophilus to Photodynamic Therapy (PDT) when grown simultaneously in dentine carious lesions. BACKGROUND DATA: PDT is a technique that utilizes light to activate photosensitizers in the presence of oxygen to produce reactive radicals. MATERIALS AND METHODS: A culture medium of 1% glucose, 2% sucrose, 1% young primary culture of L. acidophilus 108 CFU/mL, and S. mutans 108 CFU/mL was utilized to inoculate the bacterial induced caries on human dentine slabs. Different concentrations of the photosensitizer (0.75, 1.5, 3.0, 4.0, and 5.0 g/L) were activated through exposure to the light-emitting diode source with a central wavelength of 450 nm and a fluency of 5.7 J/cm2. Two light intensities (19 and 47.5 mW/cm2) were tested. Four different groups were analyzed: L-D- (control group), L-D+ (drug group), L+D+1 (PDT group 1, light intensity of 19 mW/cm2), and L+D+2 (PDT group 2, light intensity of 47.5 mW/cm2). ANOVA/Tukey tests were utilized to compare groups (α = 5%). RESULTS: Both light intensities required 5.0 g/L of curcumin for significant bacterial reduction (p < 0.05). No significant effect was found for L-D+, thus proving the absence of a potential inherent toxicity. CONCLUSIONS: Curcumin has a toxic effect on microorganisms at appreciable concentrations upon photoactivation. However, it was required to use the maximum concentration of the drug for a successful procedure.

Antimicrobial activity of ozone and NaF-chlorhexidine on early childhood caries.

An early childhood carie (ECC) is an extremely destructive form of tooth decay. The aim of this study was to investigate the action of ozone (O3), and the association of sodium fluoride (NaF) with chlorhexidine (CHX) on bacteria related to ECC. Overnight culture of the bacteria was performed. On exponential phase the suspension was adjusted (101-108 CFU/mL). A drop (10µL) of each concentration of bacteria was applied on sheep blood agar plates and treated with O3 (2, 20, 200, and 2,000 ppm); after 18 hours, recovery analysis of CFU verified the reduction of bacterial activity. For NaF-CHX, sterile 96-well plates were prepared and divided into groups: G1 (150 µL TSB); G2 (20 µL of bacteria + 25 µL CHX + 25 µL NaF); and G3 (150 µL TSB + 20 µL of bacteria + 50 µL water). The plates were verified by analysis of the optical density (0, 12, 14, 16, and 18 hours). The data from O3 test were submitted to ANOVA and Tukey's test (p < 0.05). For the data from NaF-CHX, the ANOVA 2-way and Bonferroni's test (p < 0.05) were used. The number of CFU/mL showed death > 3log10 (99.9%) for all bacteria (ozone ≥ 20ppm), while the combination of NaF-CHX was more effective (p < 0.001) compared to each substance tested alone and the control group. The antimicrobial agents tested were able to inhibit all bacteria tested; O3 seemed to be a good alternative for controlling progression of carious lesions, while the association of NaF-CHX showed to be a good antimicrobial with easy and inexpensive application.

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.

Cymbopogon citratus essential oil: effect on polymicrobial caries-related biofilm with low cytotoxicity

Abstract The objective of this study was to evaluate the effects of Cymbopogon citratus essential oil and its main compound (citral) against primary dental colonizers and caries-related species. Chemical characterization of the essential oil was performed by gas chromatography/mass spectroscopy (GC/MS), and the main compound was determined. Antimicrobial activity was tested against Actinomyces naeslundii, Lactobacillus acidophilus, S. gordonii, S. mitis, S. mutans, S. sanguinis and S. sobrinus. Minimum inhibitory and bactericide concentrations were determined by broth microdilution assay for streptococci and lactobacilli reference, and for clinical strains. The effect of the essential oil on bacterial adhesion and biofilm formation/disruption was investigated. Negative (without treatment) and positive controls (chlorhexidine) were used. The effect of citral on preformed biofilm was also tested using the same methodology. Monospecies and microcosm biofilms were tested. ANOVA or Kruskal-Wallis tests were used (α=0.05). Cytotoxicity of the essential oil to human keratinocytes was performed by MTT assay. GC/MS demonstrated one major component (citral). The essential oil showed an inhibitory effect on all tested bacterial species, including S. mutans and L. acidophilus. Essential oil of C. citratus (10X MIC) reduced the number of viable cells of lactobacilli and streptococci biofilms (p < 0.05). The essential oil inhibited adhesion of caries-related polymicrobial biofilm to dental enamel (p < 0.01). Citral significantly reduced the number of viable cells of streptococci biofilm (p < 0.001). The essential oil showed low cytotoxicity to human keratinocytes. Based on these findings, this study can contribute to the development of new formulations for products like mouthwash, against dental biofilms.

Antimicrobial activity of ozone and NaF-chlorhexidine on early childhood caries

Abstract An early childhood carie (ECC) is an extremely destructive form of tooth decay. The aim of this study was to investigate the action of ozone (O3), and the association of sodium fluoride (NaF) with chlorhexidine (CHX) on bacteria related to ECC. Overnight culture of the bacteria was performed. On exponential phase the suspension was adjusted (101-108 CFU/mL). A drop (10μL) of each concentration of bacteria was applied on sheep blood agar plates and treated with O3 (2, 20, 200, and 2,000 ppm); after 18 hours, recovery analysis of CFU verified the reduction of bacterial activity. For NaF-CHX, sterile 96-well plates were prepared and divided into groups: G1 (150 µL TSB); G2 (20 µL of bacteria + 25 µL CHX + 25 µL NaF); and G3 (150 µL TSB + 20 µL of bacteria + 50 µL water). The plates were verified by analysis of the optical density (0, 12, 14, 16, and 18 hours). The data from O3 test were submitted to ANOVA and Tukey’s test (p < 0.05). For the data from NaF-CHX, the ANOVA 2-way and Bonferroni’s test (p < 0.05) were used. The number of CFU/mL showed death > 3log10 (99.9%) for all bacteria (ozone ≥ 20ppm), while the combination of NaF-CHX was more effective (p < 0.001) compared to each substance tested alone and the control group. The antimicrobial agents tested were able to inhibit all bacteria tested; O3 seemed to be a good alternative for controlling progression of carious lesions, while the association of NaF-CHX showed to be a good antimicrobial with easy and inexpensive application.

Effect of metronidazole supplemented with hydroquinone on the adhesion of Lactobacillus acidophilus in ovine vaginal cells.

This work demonstrates that the addition of metronidazole together with a ubiquitous quinone compound reduces adherence of Lactobacillus acidophilus to ovine vaginal cells. Spectrophotometric and voltammetric studies have shown that neoformed compounds were observed in these systems; there were also changes in their electroactive composition, and the oxidant status had a significantly higher value compared to the control (p<0.05). Based on reduction potential (E; mV), the distribution of electroactive compound concentrations suggests that the compounds with low reduction potential induce this behavior, which would indicate that the addition of metronidazole with a ubiquitous quinone compound to the vaginal system might increase the reductive capacity of these systems. This work shows that the study of behavior and fluctuations of the redox compounds that compose the vaginal environment, in terms of concentration and species of redox molecules, must be hierarchized in order to better understand the early stages of colonization by microorganisms.

Influence of osmotic stress on the profile and gene expression of surface layer proteins in Lactobacillus acidophilus ATCC 4356.

In this work, we studied the role of surface layer (S-layer) proteins in the adaptation of Lactobacillus acidophilus ATCC 4356 to the osmotic stress generated by high salt. The amounts of the predominant and the auxiliary S-layer proteins SlpA and SlpX were strongly influenced by the growth phase and high-salt conditions (0.6 M NaCl). Changes in gene expression were also observed as the mRNAs of the slpA and slpX genes increased related to the growth phase and presence of high salt. A growth stage-dependent modification on the S-layer protein profile in response to NaCl was observed: while in control conditions, the auxiliary SlpX protein represented less than 10 % of the total S-layer protein, in high-salt conditions, it increased to almost 40 % in the stationary phase. The increase in S-layer protein synthesis in the stress condition could be a consequence of or a way to counteract the fragility of the cell wall, since a decrease in the cell wall thickness and envelope components (peptidoglycan layer and lipoteichoic acid content) was observed in L. acidophilus when compared to a non-S-layer-producing species such as Lactobacillus casei. Also, the stationary phase and growth in high-salt medium resulted in increased release of S-layer proteins to the supernatant medium. Overall, these findings suggest that pre-growth in high-salt conditions would result in an advantage for the probiotic nature of L. acidophilus ATCC 4356 as the increased amount and release of the S-layer might be appropriate for its antimicrobial capacity.

Addition of silver nanoparticles to composite resin: effect on physical and bactericidal properties in vitro.

The objectives of this study were to evaluate physical properties and antibacterial activity of a light-activated composite modified with silver nanoparticles. Discs were produced with unmodified resin (control group - CG) and modified resin with silver nanoparticles at two concentrations, 0.3% wt (MR03) and 0.6% wt (MR06). Streptococcus mutans and Lactobacillus acidophilus biofilms were induced in vitro by incubation of discs in a 20% sucrose medium, followed by sonication and counting of viable cells after 1, 4 and 7 days (n=9). The arithmetic roughness of all three groups was evaluated by atomic force microscopy (n=9). Compression assay was conducted in all groups to measure the compressive strength at failure and elasticity modulus (n=5). Data were subjected to ANOVA and Tukey's tests (α=0.05%). At all three time points the number of viable cells was statistically lower for MR03 and MR06 compared with CG, for both specimens. MR03 and MR06 showed no significant differences. Microscopic analysis demonstrated no significant differences for roughness among the three groups (p>0.05). The MR03 was stronger to compression than CG, and MR06 was statistically lower than CG and MR03. It was concluded that the MR03 were less conducive to biofilm growth, without compromising the strength in compression and surface roughness.