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Recently, it has been reported that eriC and crcB are involved in bacterial fluoride resistance. However, the fluoride-resistance mechanism in oral streptococci remains unclear. BLAST studies showed that two types of eriCs (eriC1 and eriC2) and two types of crcBs (crcB1 and crcB2) are present across 18 oral streptococci, which were identified in ≥ 10% of 166 orally healthy subjects with ≥ 0.01% of the mean relative abundance. They were divided into three groups based on the distribution of these four genes: group I, only eriC1; group II, eriC1 and eriC2; and group III, eriC2, crcB1, and crcB2. Group I consisted of Streptococcus mutans, in which one of the two eriC1s predominantly affected fluoride resistance. Group II consisted of eight species, and eriC1 was responsible for fluoride resistance, but eriC2 was not, in Streptococcus anginosus as a representative species. Group III consisted of nine species, and both crcB1 and crcB2 were crucial for fluoride resistance, but eriC2 was not, in Streptococcus sanguinis as a representative species. Based on these results, either EriC1 or CrcBs play a role in fluoride resistance in oral streptococci. Complementation between S. mutans EriC1 and S. sanguinis CrcB1/CrcB2 was confirmed in both S. mutans and S. sanguinis. However, neither transfer of S. sanguinis CrcB1/CrcB2 into wild-type S. mutans nor S. mutans EriC1 into wild-type S. sanguinis increased the fluoride resistance of the wild-type strain. Co-existence of different F- channels (EriC and CrcB) did not cause the additive effect on fluoride resistance in oral Streptococcus species.

The Centers for Disease Control and Prevention's Arctic Investigations Program evaluated whole-genome sequencing (WGS) workflows and bioinformatics pipelines developed by the Centers' Streptococcus Laboratory. We compared WGS-based antimicrobial drug resistance predictions with phenotypic testing for group B (n = 130) and group A (n = 217) Streptococcus and Streptococcus pneumoniae (n = 293). Isolates were collected in Alaska during January 2019-February 2021. We also included a historical phenotypically nonsusceptible subset. Concordances between phenotypic testing and WGS predictions were 99.9% (895/896) for group B Streptococcus, 100% (1,298/1,298) for group A Streptococcus, and 99.98% (3,516/3,517) for S. pneumoniae. Common resistance determinants were ermTR, ermB, and mef for macrolides, tetM for tetracyclines, and gyrA and parC for levofloxacin. S. pneumoniae trimethoprim/sulfamethoxazole nonsusceptibility was associated with folP gene insertions and folA mutations. In 2022, the Arctic Investigations Program transitioned Streptococcus spp. workflows to WGS, enabling more rapid monitoring and prevention of invasive disease.

Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide. Virulence-associated proteins common and conserved among all capsular types now represent the best strategy to combat pneumococcal infections. Our aim was to identify conserved targets in pneumococci that showed positive prediction for lipoprotein and extracellular subcellular location using bioinformatics programs and verify the distribution and the degree of conservation of these targets in pneumococci. These targets can be considered potential vaccine candidate to be evaluated in the future. A set of 13 targets were analyzed and confirmed the presence in all pneumococci tested. These 13 genes were highly conserved showing around >96 % of amino acid and nucleotide identity, but they were also present and show high identity in the closely related species Streptococcus mitis, Streptococcus oralis, and Streptococcus pseudopneumoniae. S. oralis clusters away from S. pneumoniae, while S. pseudopneumoniae and S. mitis cluster closer. The divergence between the selected targets was too small to be observed consistently in phylogenetic groups between the analyzed genomes of S. pneumoniae. The proteins analyzed fulfill two of the initial criteria of a vaccine candidate: targets are present in a variety of different pneumococci strains including different serotypes and are conserved among the samples evaluated.

The numerous species that make up the oral microbiome are now understood to play a key role in establishment and maintenance of oral health. The ability to taxonomically identify community members at the species level is important to elucidating its diversity and association to health and disease. We report the overall ecological effects of using a toothpaste containing enzymes and proteins compared to a control toothpaste on the plaque microbiome. The results reported here demonstrate that a toothpaste containing enzymes and proteins can augment natural salivary defences to promote an overall community shift resulting in an increase in bacteria associated with gum health and a concomitant decrease in those associated with periodontal disease. Statistical analysis shows significant increases in 12 taxa associated with gum health including Neisseria spp. and a significant decrease in 10 taxa associated with periodontal disease including Treponema spp. The results demonstrate that a toothpaste containing enzymes and proteins can significantly shift the ecology of the oral microbiome (at species level) resulting in a community with a stronger association to health.

This study proposes a bioprospection methodology regarding the antimicrobial potential of plant extracts against bacteria with cariogenic relevance. Sixty extracts were obtained from ten plants - (1) Jatropha weddelliana, (2) Attalea phalerata, (3) Buchenavia tomentosa, (4) Croton doctoris, (5) Mouriri elliptica, (6) Mascagnia benthamiana, (7) Senna aculeata, (8) Unonopsis guatterioides, (9) Allagoptera leucocalyx and (10) Bactris glaucescens - using different extraction methods - (A) 70° ethanol 72 h/25°C, (B) water 5 min/100°C, (C) water 1 h/55°C, (D) water 72 h/25°C, (E) hexane 72 h/25°C and (F) 90° ethanol 72 h/25°C. The plants were screened for antibacterial activity at 50 mg/ml using the agar well diffusion test against Actinomyces naeslundii ATCC 19039, Lactobacillus acidophilus ATCC 4356, Streptococcus gordonii ATCC 10558, Streptococcus mutans ATCC 35688, Streptococcus sanguinis ATCC 10556, Streptococcus sobrinus ATCC 33478 and Streptococcus mitis ATCC 9811. The active extracts were tested to determine their minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), cytotoxicity and chemical characterization. Forty-seven extracts (78%) were active against at least one microorganism. Extract 4A demonstrated the lowest MIC and MBC for all microorganisms except S. gordonii and the extract at MIC concentration was non-cytotoxic. The concentrated extracts were slightly cytotoxic. Electrospray ionization with tandem mass spectrometry analyses demonstrated that the extract constituents coincided with the mass of the terpenoids and phenolics. Overall, the best results were obtained for extraction methods A, B and C. The present work proved the antimicrobial activity of several plants. Particularly, extracts from C. doctoris were the most active against bacteria involved in dental caries disease.

In this study, the essential oils of Orthosiphon stamineus Benth and Ficus deltoidea Jack were evaluated for their antibacterial activity against invasive oral pathogens, namely Enterococcus faecalis, Streptococcus mutans, Streptococcus mitis, Streptococcus salivarius, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis and Fusobacterium nucleatum. Chemical composition of the oils was analyzed using gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The antibacterial activity of the oils and their major constituents were investigated using the broth microdilution method (minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC)). Susceptibility test, anti-adhesion, anti-biofilm, checkerboard and time-kill assays were also carried out. Physiological changes of the bacterial cells after exposure to the oils were observed under the field emission scanning electron microscope (FESEM). O. stamineus and F. deltoidea oils mainly consisted of sesquiterpenoids (44.6% and 60.9%, respectively), and β-caryophyllene was the most abundant compound in both oils (26.3% and 36.3%, respectively). Other compounds present in O. stamineus were α-humulene (5.1%) and eugenol (8.1%), while α-humulene (5.5%) and germacrene D (7.7%) were dominant in F. deltoidea. The oils of both plants showed moderate to strong inhibition against all tested bacteria with MIC and MBC values ranging 0.63–2.5 mg/mL. However, none showed any inhibition on monospecies biofilms. The time-kill assay showed that combination of both oils with amoxicillin at concentrations of 1× and 2× MIC values demonstrated additive antibacterial effect. The FESEM study showed that both oils produced significant alterations on the cells of Gram-negative bacteria as they became pleomorphic and lysed. In conclusion, the study indicated that the oils of O. stamineus and F. deltoidea possessed moderate to strong antibacterial properties against the seven strains pathogenic oral bacteria and may have caused disturbances of membrane structure or cell wall of the bacteria.

Abstract In the oral biofilm there are the presence of Streptococcus mutans, which is considered the main microorganism related to caries, and Streptococcus mitis and Streptococcus oralis that are considered commensal microorganisms. Mechanical disorganization of the biofilm associated with antimicrobial agents represents an effective method of injury prevention. Thus, the aim of this study was to evaluate the antibacterial effect of cinnamaldehyde-loaded microemulsion formulated in the presence (CEQ) and absence (CE) of chitosan. Single-species biofilms of S. mutans (UA159), S. mitis (ATCC 903) and S. oralis (ATCC 49456) were staggered (108 CFU/mL) and seeded in 96-well plates in BHI medium + 1% sucrose. The samples were incubated for 24 h and 48 h and then remained exposed for 24 h to CE and CEQ microemulsions. Microemulsions were produced by sonicator using cinnamaldehyde (1-10%). The concentration of chitosan included in the microemulsions was 0.1%. 0.12% chlorhexidine and BHI medium + 1% sucrose were used as positive and negative controls, respectively. Subsequently, an analysis of cellular metabolism was performed using the MTT test. Data were analyzed by Kruskal-Wallis test (α=5%). For S. oralis at 24 h, it was assumed that the 2.5% and 1% CE system showed activity similar to chlorhexidine (p>0.05). For the other biofilms, the effect of all concentrations of the CE and CEQ systems showed lower antimicrobial activity than chlorhexidine 0.12% (p<0.05). At 48 h, all microemulsion also showed lower activity than chlorhexidine (p<0.05). The antibacterial activity of cinnamaldehyde-loaded microemulsions was not dependent on concentration but varied according to the tested microorganism. The chitosan-based systems had low antimicrobial activity. Resumo O biofilme dentário é composto por espécies bacterianas pertencentes ao grupo dos Streptococcus. Destaca-se a presença de espécies como S. mutans, que é considerado o principal microrganismo relacionado à cárie, e Streptococcus mitis e Streptococcus oralis que são considerados microrganismos comensais. O objetivo deste estudo foi avaliar o efeito antibacteriano do cinamaldeído disperso em microemulsão formulada na presença (CEQ) e ausência (CE) de quitosana. Biofilmes uniespécies de S. mutans (UA159), S. mitis (ATCC 903) e S. oralis (ATCC 49456) foram padronizados (108 UFC/mL) e semeados em placas de 96 compartimentos, em meio BHI com 1% de sacarose. As amostras (n=12/grupo) foram cultivadas por 24 h e 48 h e em seguida, submetidas a exposição as microemulsões CE e CEQ, durante 24 h. As microemulsões foram produzidas por sonicação usando cinemaldeído (1-10%). CEQ contendo 10% de cinemaldeído foi formulada com quitosana a 0,1%. Clorexidina 0,12% e meio BHI com 1% de sacarose foram utilizados como controle positivo e negativo, respectivamente. Posteriormente foi realizada a análise do metabolismo celular por meio do teste de MTT. Os dados foram analisados pelo teste de Kruskal-Wallis (α=5%). As formulações otimizadas CE e CEQ apresentaram tamanho de gotículas de 125,1±1,7nm e 556,8±13,4nm com potencial zeta de -18,0±0,2mV e +14,7±0,2mV, respectivamente. Para o S. oralis no tempo de 24 h, verificou-se que as microemulsões CE 2,5% e 1% apresentaram atividade semelhante à clorexidina (p>0,05). Para os demais biofilmes, o efeito de todas as concentrações dos sistemas CE e CEQ apresentaram atividade antimicrobiana inferior a clorexidina 0,12% (p<0,05). No tempo de 48 h, todas as formulações também apresentaram atividade inferior à clorexidina (p<0.05). As microemulsões de cinamaldeído apresentaram atividade antibacteriana não dependente de concentração, mas dependente de microrganismo avaliado. As formulações contendo quitosana apresentaram baixa atividade antimicrobiana.

This study aimed to evaluate the antimicrobial effect of Thymoquinone (TQ) on four different oral microorganisms. Minimum Bactericidal Concentration (MBC), Minimum Inhibition Concentration (MIC), Broth microdilution, and Well diffusion tests were used to determine the optimum antimicrobial concentrations of TQ against Streptococcus salivarius, Streptococcus oralis, Streptococcus mutans, and Staphylococcus aureus over 1, 3, 6, 12 and 24 h. Chlorhexidine 0.12% was selected as a positive control. The inhibitory effect of TQ on bacterial growth was most noticeable with S. salivarius, while the least affected was S. aureus. TQ’s MBC and MIC for S. oralis and S. aureus were comparable 2 mg/mL and 3 mg/mL, respectively. S. salivarius was most resistant to TQ and displayed a value of 5 mg/mL and 4 mg/mL for MIC and MBC, respectively. The viable count of different strains after exposure to TQ’s MBC values was most noticeable with S. aureus followed by S. oralis and S. mutans, while S. salivarius was least affected. This study emphasized the promising antimicrobial effect of TQ against the four main oral microorganisms. It has a potential preventive effect against dental caries as well as other oral diseases.

Previous investigations showed that a high molecular mass, non-dialyzable material (NDM) from cranberries inhibits the adhesion of a number of bacterial species and prevents the co-aggregation of many oral bacterial pairs. In the present study we determined the effect of mouthwash supplemented with NDM on oral hygiene. Following 6 weeks of daily usage of cranberry-containing mouthwash by an experimental group ( n=29), we found that salivary mutans streptococci count as well as the total bacterial count were reduced significantly (ANOVA, P<0.01) compared with those of the control ( n=30) using placebo mouthwash. No change in the plaque and gingival indices was observed. In vitro, the cranberry constituent inhibited the adhesion of Streptococcus sobrinus to saliva-coated hydroxyapatite. The data suggest that the ability to reduce mutans streptococci counts in vivo is due to the anti-adhesion activity of the cranberry constituent.

Introduction: Propolis is a natural composite balsam. In the past decade, propolis has been extensively investigated as an adjuvant for the treatment of periodontitis. This study aimed to investigate antimicrobial activities of propolis solutions and plant essential oils against some oral cariogenic (Streptococcus mutans, Streptococcus mitis, Streptococcus sanguis, Lactobacillus acidophilus) and periodontopathic bacteria (Actinomyces odontolyticus, Eikenella corrodens, Fusobacterium nucleatum). Methodology: Determination of the minimum inhibitory concentration (MIC): The antimicrobial activity of propolis and essential oils was investigated by the agar dilution method. Serial dilutions of essential oils were prepared in plates, and the assay plates were estimated to contain 100, 50, 25 and 12.5 µg/mL of active essential oils. Dilutions for propolis were 50, 25, 12.5 and 6.3 µg/mL of active propolis solutions. Results: Propolis solutions dissolved in benzene, diethyl ether and methyl chloride, demonstrated equal effectiveness against all investigated oral bacteria (MIC=12.5 µg/mL). Propolis solution dissolved in acetone displayed MIC of 6.3 µg/mL only for Lactobacillus acidophilus. At the MIC of 12.5 µg/mL, essential oils of Salvia officinalis and Satureja kitaibelii were effective against Streptococcus mutans and Porphyromonas gingivalis, respectively. For the latter, the MIC value of Salvia officinalis was twice higher. Conclusions: The results indicate that propolis and plant essential oils appear to be a promising source of antimicrobial agents that may prevent dental caries and other oral infectious diseases.