Influence of nutrient availability on in vitro growth of major bovine mastitis pathogens.

The aim of the present study was to investigate the effects of milk composition changes on the in vitro growth of bovine mastitis pathogens. Nutritional requirements of three major bovine mastitis pathogens Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Streptococcus uberis (S. uberis) were investigated in vitro. We used ultra-high temperature (UHT) treated milk with different contents of fat, protein, and carbohydrates to test the influence of the availability of various milk constituents on pathogen growth characteristics. Additionally, the bacterial growth was investigated under experimentally modified nutrient availability by dilution and subsequent supplementation with individual nutrients (carbohydrates, different nitrogen sources, minerals, and different types of B vitamins) either to milk or to a conventional medium (thioglycolate broth, TB). Varying contents of fat, protein or lactose did not affect bacterial growth with the exception of growth of S. uberis being promoted in protein-enriched milk. The addition of nutrients to diluted whole milk and TB partly revealed different effects, indicating that there are media-specific growth limiting factors after dilution. Supplementation of minerals to diluted milk did not affect growth rates of all studied bacteria. Bacterial growth in diluted whole milk was decreased by the addition of high concentrations of amino acids in S. aureus, and by urea and additional B vitamins in E. coli and S. aureus. The growth rate of S. uberis was increased by the addition of B vitamins to diluted whole milk. The present results demonstrate that growth-limiting nutrients differ among pathogen types. Because reduced bacterial growth was only shown in diluted milk or TB, it is unlikely that alterations in nutrient availability occurring as a consequence of physiological changes of milk composition in the cow's udder would directly affect the susceptibility or course of bovine mastitis.

Inhibition of streptococcal biofilm formation by Aronia by extracellular RNA degradation.

BACKGROUND: The accumulation of oral bacterial biofilms is one of the primary etiological factors for oral diseases. Aronia melanocarpa extracts display general health benefits, including antimicrobial activities. This study evaluates the inhibitory effect of Aronia juice on oral streptococcal biofilm formation. RESULTS: Exposure to 1/10-diluted Aronia juice for 1 min significantly decreased in vitro streptococcal biofilm formation (P < 0.001). No remarkable difference was noted in streptococcal growth by Aronia under the same conditions. Interestingly, 1 week of oral rinse with diluted Aronia juice led to significantly fewer salivary streptococcal colony-forming units (CFUs) relative to oral rinsing with tap water (P < 0.05). Furthermore, Aronia exerted an extracellular RNA-degrading effect, and RNase inhibitor alleviated Aronia-dependent streptococcal biofilm inhibition. CONCLUSION: Aronia might inhibit initial biofilm formation by decomposing extracellular RNA, which plays an important role in bacterial biofilm formation. Our data suggest that oral rinsing with Aronia juice will aid in treating oral biofilm-dependent diseases easily and efficiently. © 2019 Society of Chemical Industry.

Iranian propolis efficiently inhibits growth of oral streptococci and cancer cell lines.

BACKGROUND: Propolis is a natural bee product with a wide range of biological activities that are related to its chemical composition. The present study investigated the quantification of quercetin (Q) in Ardabil ethanol extract of propolis (AEEP), and then compared its anti-bacterial, anti- biofilm and cytotoxic effects on cancer and normal cell lines. METHOD: In the present study, the chemical composition of AEEP was determined through the high-performance liquid chromatography (HPLC). The AEEP and its main component, quercetin (Q), were evaluated in vitro against 57 oral streptococci by a broth micro-dilution method. The biofilm formation was assessed through the crystal violet staining and MTT assays. The impact of AEEP and Q anti-proliferative effect were evaluated on the fibroblast as normal and cancer cell lines (KB and A431). RESULTS: The Q concentration in the composition of AEEP was 6.9% of all its components. The findings indicated that the AEEP and Q were efficient against the cariogenic bacteria and were able to inhibit the S.mutans biofilm adherence at a sub-MIC concentration. Moreover, electron micrographs indicated the inhibition of biofilms compared to control biofilms. In addition, the AEEP and Q indicated a dose-dependent cytotoxic effect on A431 and KB cell lines. On the contrary, they had no cytotoxic effect on fibroblast cells. CONCLUSION: The results indicated that the synergistic impact of main components of AEEP was related to the inhibition of the cancer cell proliferation, cariogenic bacteria and oral biofilm formation. It may play a promising role in the complementary medicine and, it is suggested to be used as food additives.

Effect of Photodynamic Therapy on Microorganisms Responsible for Dental Caries: A Systematic Review and Meta-Analysis.

The aim of this study was to perform a systematic review of the literature followed by a meta-analysis about the efficacy of photodynamic therapy (PDT) on the microorganisms responsible for dental caries. The research question and the keywords were constructed according to the PICO strategy. The article search was done in Embase, Lilacs, Scielo, Medline, Scopus, Cochrane Library, Web of Science, Science Direct, and Pubmed databases. Randomized clinical trials and in vitro studies were selected in the review. The study was conducted according the PRISMA guideline for systematic review. A total of 34 articles were included in the qualitative analysis and four articles were divided into two subgroups to perform the meta-analysis. Few studies have achieved an effective microbial reduction in microorganisms associated with the pathogenesis of dental caries. The results highlight that there is no consensus about the study protocols for PDT against cariogenic microorganisms, although the results showed the PDT could be a good alternative for the treatment of dental caries.

Altered mucosa-associated microbiota in the ileum and colon of neonatal calves in response to delayed first colostrum feeding.

The present study investigated whether delaying the first feeding of colostrum affected ileum and colon mucosa-associated microbiota in calves. Twenty-seven male Holstein calves were randomly assigned to 1 of 3 groups, fed colostrum at 45 min, 6 h, and 12 h after birth, respectively. Ileum and colon mucosa were collected at 51 h after birth, and their associated microbial profiles were assessed using amplicon sequencing. Both ileum and colon mucosa-associated microbiota were predominated by genus Escherichia-Shigella. The negative correlation between the molar proportion of short-chain fatty acids (SCFA) and ileum mucosa-associated opportunistic pathogens, and the positive correlation between the molar proportion of SCFA and colon mucosa-associated beneficial bacteria, suggest that SCFA might play an important role in maintaining the gut health of 2-d-old calves. A higher relative abundance of ileum mucosa-associated Enterococcus and Streptococcus was detected when the first colostrum feeding was delayed for 12 h. The relative abundance of colon mucosa-associated Lactobacillus tended to be lower in calves fed colostrum 12 h than those under the other 2 treatments, whereas that of Faecalibacterium tended to be lower in calves fed colostrum immediately after birth than those fed colostrum 6 and 12 h after birth, respectively. Our findings suggest that delayed first colostrum feeding affects the establishment of ileum and colon mucosa-associated bacteria, which may have long-term effects on gut health of calves.

Selection of an appropriate empiric antibiotic regimen in hematogenous vertebral osteomyelitis.

BACKGROUND: Empiric antibiotic therapy for suspected hematogenous vertebral osteomyelitis (HVO) should be initiated immediately in seriously ill patients and may be required in those with negative microbiological results. The aim of this study was to inform the appropriate selection of empiric antibiotic regimens for the treatment of suspected HVO by analyzing antimicrobial susceptibility of isolated bacteria from microbiologically proven HVO. METHOD: We conducted a retrospective chart review of adult patients with microbiologically proven HVO in five tertiary-care hospitals over a 7-year period. The appropriateness of empiric antibiotic regimens was assessed based on the antibiotic susceptibility profiles of isolated bacteria. RESULTS: In total, 358 cases of microbiologically proven HVO were identified. The main causative pathogens identified were methicillin-susceptible Staphylococcus aureus (33.5%), followed by methicillin-resistant S. aureus (MRSA) (24.9%), Enterobacteriaceae (19.3%), and Streptococcus species (11.7%). Extended spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae and anaerobes accounted for only 1.7% and 1.4%, respectively, of the causative pathogens. Overall, 73.5% of isolated pathogens were susceptible to levofloxacin plus rifampicin, 71.2% to levofloxacin plus clindamycin, and 64.5% to amoxicillin-clavulanate plus ciprofloxacin. The susceptibility to these oral combinations was lower in cases of healthcare-associated HVO (52.6%, 49.6%, and 37.6%, respectively) than in cases of community-acquired HVO (85.8%, 84.0%, and 80.4%, respectively). Vancomycin combined with ciprofloxacin, ceftriaxone, ceftazidime, or cefepime was similarly appropriate (susceptibility rates of 93.0%, 94.1%, 95.8%, and 95.8%, respectively). CONCLUSIONS: Based on our susceptibility data, vancomycin combined with a broad-spectrum cephalosporin or fluoroquinolone may be appropriate for empiric treatment of HVO. Fluoroquinolone-based oral combinations may be not appropriate due to frequent resistance to these agents, especially in cases of healthcare-associated HVO.

New Polyhydroxylated Steroidal Saponins from Solanum paniculatum L. Leaf Alcohol Tincture with Antibacterial Activity against Oral Pathogens.

Solanum paniculatum L. is widely used in Brazilian folk medicine for the treatment of liver and gastrointestinal disorders as well as for culinary purposes and beverage production. Fractionation of hydroalcoholic [ethanol (EtOH) 70%] tincture from S. paniculatum leaves led to the isolation of six new spirostanic saponins which included 6- O-α-l-rhamnopyranosyl-(1''→3')-ß-d-quinovopyranosyl-(22 S,23 R,25 S)-3ß,6α,23-trihydroxy-5α-spirostane (1), 6- O-ß-d-xylopyranosyl-(1''→3')-ß-d-quinovopyranosyl-(22 S,23 R,25 R)-3ß,6α,23-trihydroxy-5α-spirostane (4), 3- O-α-l-rhamnopyranosyl-(1''→3')-ß-d-quinovopyranosyl-(22 S,23 S,25 R)-3ß,6α,23-trihydroxy-5α-spirostane (5), 3- O-ß-d-xylopyranosyl-(1''→3')-ß-d-quinovopyranosyl-(22 S,23 S,25 R)-3ß,6α,23-trihydroxy-5α-spirostane (6), 6- O-α-l-rhamnopyranosyl-(1''→3')-ß-d-quinovopyranosyl-(22 S,25 S)-1ß,3ß,6α-trihydroxy-5α-spirostane (7), and 6- O-ß-d-xylopyranosyl-(1''→3')-ß-d-quinovopyranosyl-(22 S,25 S)-3ß,4ß,6α-trihydroxy-5α-spirostane (8) together with two known spirostanic saponins (2, 3). The structures of these compounds were determined by one-dimensional (1D) and two-dimensional (2D) NMR experiments in addition to high-resolution electrospray ionization mass spectrometry (HRESIMS) analyses. The 70% alcohol tincture, used as phytomedicine, exhibited promising activities against oral pathogens, including, Steptococcus sanguinis, St. oralis, St. mutans, St. mitis, and Lactobacillus casei with minimal inhibitory concentration (MIC) values ranging from 6.25 to 50 µg/mL. The saponin fraction, nonetheless, showed lower activity against all the strains tested (from 100 to >400 µg/mL).

Activity of Salvia dolomitica and Salvia somalensis Essential Oils against Bacteria, Molds and Yeasts.

Essential oils (EOs) from Salvia dolomitica and Salvia somalensis, widely employed in the cosmetic and perfume industry, were analyzed for composition and tested against bacterial and fungal pathogens isolated from clinical and environmental specimens. The analyses were carried out against Staphylococcus aureus, Staphylococcus pseudointermedius, Pseudomonas aeruginosa, Escherichia coli, Streptococcus canis, Streptococcus pyogenes, Klebsiella pneumoniae, Proteus mirabilis, Microsporum canis, Microsporum gypseum, Trichophyton mentagrophytes, Aspergillus niger, Aspergillus flavus, Candida albicans, Candida krusei, Mucor sp. and Trichothecium roseum. Both EOs showed similar percentages of total monoterpenes and sesquiterpene hydrocarbons. The main constituents were 1,8-cineole and ß-caryophyllene in S. dolomitica and bornyl acetate and camphor in S. somalensis. The selected EOs have no relevant antifungal or antibacterial activities if compared to conventional drugs.

Passion fruit by-product and fructooligosaccharides stimulate the growth and folate production by starter and probiotic cultures in fermented soymilk.

Two starter cultures (Streptococcus (St.) thermophilus ST-M6 and TA-40) and five probiotic strains (St. thermophilus TH-4, Lactobacillus (Lb.) acidophilus LA-5, Lb. rhamnosus LGG, Lb. fermentum PCC, and Lb. reuteri RC-14) were used to ferment different soymilk formulations supplemented with passion fruit by-product and/or fructo-oligosaccharides (FOS) with the aim of increasing folate concentrations. Growth and folate production of individual strains were evaluated and the results used to select co-cultures. Both St. thermophilus ST-M6 and TH-4 were the best folate producers and were able to increase the folate content of all soymilk formulations when used alone or in co-culture with lactobacilli strains, especially in the presence of both passion fruit by-product and FOS. Thus, passion fruit by-product and FOS could be used as dietary ingredients to stimulate the folate production by selected bacterial strains during the fermentation of soymilk. It was also shown that vitamin production by microorganisms is strain-dependent and may also be influenced by nutritional and environmental conditions.

To add or not to add probiotics to infant formulae? An updated systematic review.

We updated evidence on the effects of the administration of probiotic-supplemented infant formulae (IF) compared with unsupplemented IF. Five databases were searched up to September 2016 for randomised controlled trials. Twenty publications were identified, including five new RCTs. Supplementation of IF with Bifidobacterium lactis Bb12, either alone or with Streptococcus thermophilus, had no effect on growth, respiratory illness, antibiotic use, stool frequency or consistency. However, there was a significant reduction in the number of episodes of gastrointestinal infections (Bb12) and a lower frequency of colic or irritability (when both strains were used). Lactobacillus johnsonii La1 had no effect on growth, gastrointestinal infections, or respiratory illness episodes. There were no effects of supplementation of IF with Bifidobacterium longum BL999, alone or with Lactobacillus rhamnosus LPR. L. rhamnosus GG was associated with better growth; it had no effect on colic/crying, or irritability, and it was associated with greater indexes of loose stools and a higher defecation frequency. Lactobacillus reuteri ATCC 55730 had no effect on growth, colic, crying, irritability, respiratory illness, antibiotic use, stool frequency, or stool consistency; however, it reduced the number of episodes of diarrhoea. L. reuteri DSM 17938 had no effect on growth, night-time sleeping, or flatulence, but it reduced the number of spitting episodes. Lactobacillus salivarius CEC5713 had no effect on growth, colic, crying, or irritability; however, it resulted in a significant reduction in the rate of diarrhoea and the number of episodes of respiratory symptoms. In conclusion, the administration of probiotic-supplemented formulae to healthy infants does not raise safety concerns with regard to growth and adverse effects. Some beneficial clinical effects are possible; however, there is no existing robust evidence to recommend their routine use. The latter conclusion may reflect the small amount of data on a specific probiotic strain(s) and outcomes, rather than a genuine lack of an effect.

Nasopharyngeal glial heterotopia with delayed postoperative meningitis.

A male infant, who underwent radical resection of a large glial heterotopia at the nasopharynx at 8 days, developed delayed postoperative bacterial meningitis at 9 months. Neuroradiological examination clearly demonstrated that meningitis had occurred because of the intracranial and extracranial connections, which were scarcely seen in the perioperative period. A transsphenoidal extension of hypothalamic hamartoma is possible because the connection started from the right optic nerve, running through the transsphenoidal canal in the sphenoid bone and terminating at the recurrent mass in the nasopharyngeal region.

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.

Supplementation with fruit and okara soybean by-products and amaranth flour increases the folate production by starter and probiotic cultures.

The ability of two starter cultures (Streptococcus (S.) thermophilus ST-M6 and St. thermophilus TA-40) and eleven probiotic cultures (St. thermophilus TH-4, Lactobacillus (Lb.) acidophilus LA-5, Lb. fermentum PCC, Lb. reuteri RC-14, Lb. paracasei subsp. paracasei, Lb. casei 431, Lb. paracasei subsp. paracasei F19, Lb. rhamnosus GR-1, and Lb. rhamnosus LGG, Bifidobacterium (B.) animalis subsp. lactis BB-12, B. longum subsp. longum BB-46, and B. longum subsp. infantis BB-02) to produce folate in a modified MRS broth (mMRS) supplemented with different fruit (passion fruit, acerola, orange, and mango) and okara soybean by-products and amaranth flour was investigated. Initially, the folate content of each vegetable substrate was determined: passion fruit by-product showed the lowest folate content (8±2ng/mL) and okara the highest (457±22ng/mL). When the orange by-product and amaranth flour were added to mMRS, all strains were able to increase folate production after 24h of fermentation. B. longum subsp infantis BB-02 produced the highest concentrations (1223±116ng/mL) in amaranth flour. Okara was the substrate that had the lowest impact on the folate production by all strains evaluated. Lb. acidophilus LA-5 (297±36ng/mL) and B. animalis subsp. lactis BB-12 (237±23ng/mL) were also able to produce folate after growth in mMRS containing acerola and orange by-products, respectively. The results of this study demonstrate that folate production is not only strain-dependent but also influenced by the addition of different substrates in the growth media.

Effects of extremely low frequency magnetic field on production of mannatide by α-hemolytic Streptococcus.

The effect of the extremely low frequency magnetic field (ELF-MF) on biomass and mannatide production by α-hemolytic Streptococcus in liquid-state fermentation culture medium was studied during shake flask culture. Magnetic field (MF) inductions, exposure times, and exposure periods varied in a range of 0-1.5 mT, 0-16 h, and six periods of incubation time, respectively. Results showed both biomass and mannatide production increased significantly at MF induction 0.4, 0.6, and 0.9 mT and decreased at both 1.2 and 1.5 mT. Biomass increased by exposure for initial and middle stages of fermentation. Mannatide production increased significantly at 4-8, 8-12, and 17-21 h. Peak yield of biomass and mannatide production increased by 10.7% and 14.0% at 25 and 27 h of incubation at 0.6 mT MF induction and exposure to 8-12 h of incubation time, compared with the control experiment, respectively. ELF-MF could also enhance the growth rate and mannatide production rate of α-hemolytic Streptococcus. However, ELF-MF did not alter α-hemolytic Streptococcus cell growth and mannatide metabolizing regulation or fermentation pattern. Mannatide production was not associated with cellular growth but rather only partially associated. Bioelectromagnetics. 37:331-337, 2016. © 2016 Wiley Periodicals, Inc.

Streptococcus salivarius 24SMB administered by nasal spray for the prevention of acute otitis media in otitis-prone children.

This paper reports the results of the first study in which Streptococcus salivarius 24SMB, a safe α-haemolytic strain capable of producing bacteriocin-like substances with significant activity against acute otitis media (AOM) pathogens, was intranasally administered in an attempt to reduce the risk of new episodes of AOM in otitis-prone children. In this prospective, randomized, double-blind, placebo-controlled study, 100 children aged 1-5 years with histories of recurrent AOM were randomized 1:1 to receive an intranasal S. salivarius 24SMB or placebo twice daily for 5 days each month for 3 consecutive months. Fifty treated children and 47 who received placebo who were compliant with study protocol were followed monthly for 6 months. The number of children who did not experience any AOM was higher among the children treated with the S. salivarius 24SMB preparation than among those in the placebo group (30.0 vs 14.9%; p = 0.076). Moreover, the number of children who received antibiotics during the study period was lower among the children treated with S. salivarius 24 SMB than among those who received placebo (70 vs 83.0%; p = 0.13). Compared with the children who were not colonized by S. salivarius 24SMB after treatment, the number of colonized children who experienced any AOM was significantly lower (42.8 vs 13.6%; p = 0.03). Similar results were observed when the children treated with antibiotics for AOM were analysed (67.8 vs 95.5%; p = 0.029). This study revealed the ability of intranasally administered S. salivarius 24SMB to reduce the risk of AOM in otitis-prone children.

Inhibition of Oral Streptococci Growth Induced by the Complementary Action of Berberine Chloride and Antibacterial Compounds.

Synergistic interactions between natural bioactive compounds from medicinal plants and antibiotics may exhibit therapeutic benefits, acting against oral cariogenic and opportunistic pathogens. The aim of the presented work was to assess the antibacterial activity of berberine chloride (BECl) in light of the effect exerted by common antibiotics on selected reference strains of oral streptococci (OST), and to evaluate the magnitude of interactions. Three representative oral microorganisms were investigated: Streptococcus mutans ATCC 25175 (SM), S. sanguinis ATCC 10556 (SS), S. oralis ATCC 9811 (SO) and microdilution tests, along with disc diffusion assays were applied. Here, we report that growth (viability) of all oral streptococci was reduced by exposure to BECl and was dependent primarily on exposure/ incubation time. A minimum inhibitory concentrations (MIC) of BECl against OST ranged from 512 µg/mL (SS) to 1024 µg/mL (SM, SO). The most noticeable antibacterial effects were observed for S. sanguinis (MIC 512 µg/mL) and the most significant synergistic action was found for the combinations BECl-penicillin, BECl-clindamycin and BECl-erythromycin. The S. oralis reflects the highest MBC value as assessed by the AlamarBlue assay (2058 µg/mL). The synergy between berberine and common antibiotics demonstrates its potential use as a novel antibacterial tool for opportunistic infections and also provides a rational basis for the use of berberine as an oral hygiene measure.

Mechanistic analysis of PLGA/HPMC-based in-situ forming implants for periodontitis treatment.

In-situ forming implant formulations based on poly(lactic-co-glycolic acid) (PLGA), acetyltributyl citrate (ATBC), minocycline HCl, N-methyl pyrrolidone (NMP) and optionally hydroxypropyl methylcellulose (HPMC) were prepared and thoroughly characterized in vitro. This includes electron paramagnetic resonance (EPR), nuclear magnetic resonance ((1)H NMR), mass change and drug release measurements under different conditions, optical microscopy, size exclusion chromatography (SEC) as well as antibacterial activity tests using gingival crevicular fluid samples from periodontal pockets of periodontitis patients. Based on these results, deeper insight into the physico-chemical phenomena involved in implant formation and the control of drug release could be gained. For instance, the effects of adding HPMC to the formulations, resulting in improved implant adherence and reduced swelling, could be explained. Importantly, the in-situ formed implants effectively hindered the growth of bacteria present in the patients' periodontal pockets. Interestingly, the systems were more effectively hindering the growth of pathogenic bacterial strains (e.g., Fusobacterium nucleatum) than that of strains with a lower pathogenic potential (e.g., Streptococcus salivarius). In vivo, such a preferential action against the pathogenic bacteria can be expected to give a chance to the healthy flora to re-colonize the periodontal pockets.

Stability and resilience of oral microcosms toward acidification and Candida outgrowth by arginine supplementation.

Dysbiosis induced by low pH in the oral ecosystem can lead to caries, a prevalent bacterial disease in humans. The amino acid arginine is one of the pH-elevating agents in the oral cavity. To obtain insights into the effect of arginine on oral microbial ecology, a multi-plaque "artificial mouth" (MAM) biofilm model was inoculated with saliva from a healthy volunteer and microcosms were grown for 4 weeks with 1.6 % (w/v) arginine supplement (Arginine) or without (Control), samples were taken at several time-points. A cariogenic environment was mimicked by sucrose pulsing. The bacterial composition was determined by 16S rRNA gene amplicon sequencing, the presence and amount of Candida and arginine deiminase system genes arcA and sagP by qPCR. Additionally, ammonium and short-chain fatty acid concentrations were determined. The Arginine microcosms were dominated by Streptococcus, Veillonella, and Neisseria and remained stable in time, while the composition of the Control microcosms diverged significantly in time, partially due to the presence of Megasphaera. The percentage of Candida increased 100-fold in the Control microcosms compared to the Arginine microcosms. The pH-raising effect of arginine was confirmed by the pH and ammonium results. The abundances of sagP and arcA were highest in the Arginine microcosms, while the concentration of butyrate was higher in the Control microcosms. We demonstrate that supplementation with arginine serves a health-promoting function; it enhances microcosm resilience toward acidification and suppresses outgrowth of the opportunistic pathogen Candida. Arginine facilitates stability of oral microbial communities and prevents them from becoming cariogenic.

In-office bleaching gel with 35% hydrogen peroxide enhanced biofilm formation of early colonizing streptococci on human enamel.

OBJECTIVES: To compare the effects of 25% and 35% hydrogen peroxide in-office bleaching systems on surface roughness and streptococcal biofilm formation on human enamel. METHODS: Enamel specimens (3mm×3mm×2mm, n=162) from human permanent teeth were randomly divided into 3 treatment groups (n=54 each): (1) control, (2) bleached with 25% hydrogen peroxide (Zoom2™), and (3) bleached with 35% hydrogen peroxide (Beyond™). The enamel surface roughness was measured by a profilometer before and after treatments. Subsequently, the treated enamel specimens were randomly placed into 3 subgroups (n=18 each) and incubated with: (1) trypticase soy broth control, (2) Streptococcus mutans culture and (3) Streptococcus sanguinis culture for 24h. Biofilm formation was quantified by crystal violet staining. The biofilm structure on three specimens from each group was visualized by scanning electron microscopy. Data were analyzed by Kruskal-Wallis and Mann-Whitney U tests with Bonferroni corrections. Significance level was set at p<0.05. RESULTS: Both bleaching systems significantly reduced enamel surface roughness comparing to the control group (p<0.001), but there was no difference between the two treatment groups. Remarkably, S. sanguinis biofilm formation was significantly higher on enamel specimens bleached with 35% hydrogen peroxide than other treatments (p<0.001), but was lower on those bleached with 25% hydrogen peroxide (p<0.001). In contrast, no difference in S. mutans biofilm formation was observed among the three treatment groups. CONCLUSION: Both 25% and 35% hydrogen peroxide caused similar degrees of reduction in enamel surface roughness. Nevertheless, bleaching with 35% hydrogen peroxide appeared to markedly promote S. sanguinis biofilm formation. CLINICAL SIGNIFICANCE: The increase of early colonizer biofilm raised concerns over adverse effects of in-office bleaching on plaque formation. This should be further investigated in vivo and efficient plaque control should be emphasized after bleaching with high concentrations of hydrogen peroxide.

Characterization of Streptococcus tigurinus small-colony variants causing prosthetic joint infection by comparative whole-genome analyses.

Small-colony variants (SCVs) of bacteria are associated with recurrent and persistent infections. We describe for the first time SCVs of Streptococcus tigurinus in a patient with a prosthetic joint infection. S. tigurinus is a novel pathogen of the Streptococcus mitis group and causes invasive infections. We sought to characterize S. tigurinus SCVs using experimental methods and find possible genetic explanations for their phenotypes. The S. tigurinus SCVs were compared with the wild-type (WT) isolate using phenotypic methods, including growth under different conditions, autolysis, and visualization of the cell ultrastructure by use of transmission electron microscopy (TEM). Furthermore, comparative genome analyses were performed. The S. tigurinus SCVs displayed reduced growth compared to the WT and showed either a very stable or a fluctuating SCV phenotype. TEM analyses revealed major alterations in cell separation and morphological abnormalities, which were partially explained by impaired autolytic behavior. Intriguingly, the SCVs were more resistant to induced autolysis. Whole-genome sequencing revealed mutations in the genes involved in general cell metabolism, cell division, stringent response, and virulence. Clinically, the patient recovered after a 2-stage exchange of the prosthesis. Comparative whole-genome sequencing in clinical strains is a useful tool for identifying novel genetic signatures leading to the most persistent bacterial forms. The detection of viridans streptococcal SCVs is challenging in a clinical laboratory due to the small colony size. Thus, it is of major clinical importance for microbiologists and clinicians to be aware of viridans streptococcal SCVs, such as those of S. tigurinus, which lead to difficult-to-treat infections.