OBJECTIVE: To investigate the risk factors, clinical characteristics, and bacterial resistance of bloodstream infections caused by Streptococcus mitis in children with hematological disease, so as to provide a reference for infection control. METHODS: The clinical information and laboratory findings of pediatric patients complicated with blood cultures positive for Streptococcus mitis from January 2018 to December 2020 in the Institute of Hematology & Blood Diseases Hospital were searched and collected. The clinical characteristics, susceptibility factors, and antibiotic resistance of the children were retrospectively analyzed. RESULTS: Data analysis from 2018 to 2020 showed that the proportion of Streptococcus mitis isolated from bloodstream infections in children (≤14 years old) with hematological diseases was the highest (19.91%) and significantly higher than other bacteria, accounting for 38.64% of Gram-positive cocci, and presented as an increasing trend year by year. A total of 427 children tested positive blood cultures, including 85 children with bloodstream infections caused by Streptococcus mitis who tested after fever. Most children experienced a recurrent high fever in the early and middle stages (≤6 d) of neutropenia and persistent fever for more than 3 days. After adjusting the antibiotics according to the preliminary drug susceptibility results, the body temperature of most children (63.5%) returned to normal within 4 days. The 85 children were mainly diagnosed with acute myeloid leukemia (AML), accounting for 84.7%. The proportion of children in the neutropenia stage was 97.7%. The incidence of oral mucosal damage, lung infection, and gastrointestinal injury symptoms was 40%, 31.8%, and 27.1%, respectively. The ratio of elevated C-reactive protein (CRP) and procalcitonin was 65.9% and 9.4%, respectively. All isolated strains of Streptococcus mitis were not resistant to vancomycin and linezolid, and the resistance rate to penicillin, cefotaxime, levofloxacin, and quinupristin-dalfopristin was 10.6%, 8.2%, 9.4%, and 14.1%, respectively. None of children died due to bloodstream infection caused by Streptococcus mitis. CONCLUSION The infection rate of Streptococcus mitis is increasing year by year in children with hematological diseases, especially in children with AML. Among them, neutropenia and oral mucosal damage after chemotherapy are high-risk infection factors. The common clinical symptoms include persistent high fever, oral mucosal damage, and elevated CRP. Penicillin and cephalosporins have good sensitivity. Linezolid, as a highly sensitive antibiotic, can effectively control infection and shorten the course of disease.
Humans ; Child ; Streptococcal Infections/microbiology* ; Retrospective Studies ; Hematologic Diseases/complications* ; Streptococcus mitis ; Drug Resistance, Bacterial ; Risk Factors ; Microbial Sensitivity Tests ; Anti-Bacterial Agents ; Female ; Male ; Bacteremia/microbiology* ; Child, Preschool ; Adolescent

OBJECTIVES: This study aims to investigate the impact of glutathione S-transferase (GST) on the environmental adaptability of Streptococcus mutans (S. mutans). METHODS: A GST knockout strain ΔgsT was constructed. Transcriptomic sequencing was performed to analyze the gene expression differences between the wild-type S. mutans UA159 and its GST knockout strain ΔgsT. Comprehensive functional assessments, including acid tolerance assays, hydrogen peroxide challenge assays, nutrient limitation growth assays, and fluorescence in situ hybridization, were conducted to evaluate the acid tolerance, antioxidant stress resistance, growth kinetics, and interspecies competitive ability of ΔgsT within plaque biofilms. RESULTS: Compared with the wild-type S. mutans, 198 genes in ΔgsT were significantly differentially expressed and enriched in pathways related to metabolism, stress response, and energy homeostasis. The survival rate of ΔgsT in acid tolerance assays was markedly reduced (P<0.01). After 15 min of hydrogen peroxide challenge, the survival rate of ΔgsT decreased to 38.12% (wild type, 71.75%). Under nutrient-limiting conditions, ΔgsT exhibited a significantly lower final OD₆₀₀ value than the wild-type strain (P<0.05). In the biofilm competition assays, the proportion of S. mutans ΔgsT in the mixed biofilm (8.50%) was significantly lower than that of the wild type (16.89%) (P<0.05). CONCLUSIONS GST enhances the acid resistance, oxidative stress tolerance, and nutrient adaptation of S. mutans by regulating metabolism-related and stress response-related genes.
Streptococcus mutans/enzymology* ; Biofilms ; Glutathione Transferase/physiology* ; Adaptation, Physiological ; Hydrogen Peroxide/pharmacology* ; Gene Expression Regulation, Bacterial ; Oxidative Stress ; Metabolic Reprogramming

To explore the effects of plasma jet (PJ) and plasma activated water (PAW) on the sterilization of Streptococcus mutans ( S. mutans) and compare the advantages and disadvantages of the two methods, so as to provide a basis for plasma treatment of dental caries and to enrich the treatment means of dental caries, an atmospheric pressure plasma excitation system was built, and the effects of PJ and PAW on the sterilization rate of S. mutans and the changes of temperature and pH during treatment were studied under different excitation voltage ( U _e ) and different excitation time ( t _e ). The results showed that in the PJ treatment, the difference in the survival rate of S. mutans between the treatment group and the control group was statistically significant ( P = 0.007, d=2.66) when U _e = 7 kV and t _e = 60 s, and complete sterilization was achieved at U _e = 8 kV and t _e = 120 s in the PJ treatment. In contrast, in the PAW treatment, the difference in the survival rate of S. mutans between the treatment group and the control group was statistically significant ( P = 0.029, d = 1.71) when U _e = 7 kV and t _e = 30 s, and complete sterilization was achieved with PAW treatment when U _e = 9 kV and t _e = 60 s. Results of the monitoring of temperature and pH showed that the maximum temperature rise during PJ and PAW treatment did not exceed 4.3 °C, while the pH value after PAW treatment would drop to a minimum of 3.02. In summary, the optimal sterilization parameters for PJ were U _e =8 kV and 90 s < t _e ≤ 120 s, while the optimal sterilization parameters for PAW were U _e = 9 kV and 30 s< t _e ≤ 60 s. Both treatment methods achieved non-thermal sterilization of S. mutans, where PJ required only a smaller U _e to achieve complete sterilization, while at pH < 4.7, PAW only required a shorter t _e to achieve complete sterilization, but its acidic environment could cause some chemical damage to the teeth. This study can provide some reference value for plasma treatment of dental caries.
Humans ; Streptococcus mutans ; Dental Caries/therapy* ; Sterilization ; Temperature ; Water

Background: Antibacterial drugs are used for suppressing harmful bacteria. However, some are reported to have side effects which led researchers to investigate plants with antimicrobial properties as potential alternatives. One such indigenous plant is the Vitex parviflora A. juss, “molave” or “mulawin” tree. Objective: This study determined and compared the antibacterial efficacy of 50 mg/ml and 100 mg/ml concentrations of fresh local molave leaves methanolic extract with 0.12% chlorhexidine, distilled water, and 95% methanol on growth inhibition of S. mutans. Methodology: Five hundred grams of fresh molave leaves were collected and subjected to methanolic extraction. In vitro antimicrobial susceptibility test by disk diffusion of 50 mg/ml and 100 mg/ml molave extract concentrations, 0.12% chlorhexidine, distilled water, and 95% methanol on 18 Mueller-Hinton agar (MHA) plates inoculated with S. mutans was done. For cost-efficiency, the total sample size of 80 plates was reduced by placing 5 test groups in one plate divided into five portions done in 18 replicates. After 48 hours of incubation in anaerobic conditions, resulting zones of inhibition were measured. Data were analyzed through one-way ANOVA and Bonferroni tests. Results: The mean diameter of inhibition zones produced by 100 mg/ml and 50 mg/ml concentrations of molave methanolic leaves extract and 0.12% chlorhexidine was 15.78 mm, 11.63 mm, and 21.44 mm, respectively. Distilled water and 95% methanol did not inhibit bacterial growth. The 100 mg/ml concentration has stronger antibacterial properties than the 50 mg/ml. Conclusion The Vitex parviflora A. Juss methanolic leaves extract has the ability to inhibit the growth of S. mutans in vitro. Both concentrations were relatively weaker compared to chlorhexidine.
Streptococcus mutans

Objective: To explore the effect of csn2 gene deficiency on starvation tolerance and extracellular polysaccharides (EPS) synthesis in an oligotrophic environment of Streptococcus mutans (Sm). Methods: The csn2 gene deletion strains and complementary strains of Sm were cultivated and then an oligotrophic growth environment for Sm growth by setting different concentration gradient media were created. Cell growth in oligotrophic environment was detected by growth curve. Biofilm volume was measured by crystalline violet staining. Scanning electron microscopy (SEM) and laser confocal microscope were performed to observe the biofilm structure of Sm. The synthesis of EPS was measured by the anthrone-sulfuric acid method. The expression of genes related to EPS synthesis was evaluated by quantitative real-time PCR (qRT-PCR). Results: The growth curve results showed that the deletion of csn2 gene inhibited the growth of Sm under starvation stress. Furthermore, the results of laser confocal microscope showed that the biofilm EPS/bacteria ratios produced by the wild-type strain, csn2 gene-deficient strain and complement strains under nutrient sufficient culture conditions were 0.44±0.07, 1.05±0.13 and 0.57±0.08 respectively, while the ratios of EPS/bacteria in an oligotrophic environment were 0.93±0.24, 3.05±0.21 and 1.32±0.46 respectively, indicating that the deletion of csn2 gene enhanced the ability of extracellular polysaccharide synthesis of Sm in the oligotrophic environment. The expression levels of EPS synthesis-related genes gtfB and gtfC were up-regulated by 2.5 fold and 1.8 fold respectively and the expression level of gtfD was down-regulated by two-thirds. Conclusions: The csn2 gene deficiency showed multiple effects on the physiological functions and virulence characteristics of Sm, including starvation tolerance and EPS synthesis. These changes might be related to the shift of the complex regulative network caused by csn2 gene deletion.
Biofilms ; Microscopy, Electron, Scanning ; Polysaccharides ; Streptococcus mutans/genetics*

Background: Streptococcus mutans is the leading cause of dental caries. One of many medicinal plants, purple leaf [Graptophyllum pictum (L.) Griff], which contains flavonoids, alkaloids, tannins, steroids, and saponins, is a potential antibacterial agent. Objective: This study aimed to determine the antibacterial activity of purple leaf extract (Graptophyllum pictum L. Griff) against Streptococcus mutans. Methods: Streptococcus mutans were suspended in several Graptophyllum pictum (L.) Griff extract concentrations in a BHIB medium using the dilution method so that the concentration of 100%, 50%, 25%, 12.5%, 6.25%, 3.12%, 1.56%, 0.78% were obtained. Each tube was incubated for 24 hours, then subcultured in a Tryptone Yeast Extract Cystine medium in a petri dish using a spreader. Each petri dish was set for 24 hours; the growth of the colony, using CFU/mL unit, was manually calculated. The samples were then subjected to microbiological analysis. The Tukey's Honest Significant Difference test was performed to determine if the relationship between the sets of data in the treatment group is statistically significant (p<0.05). Results: Purple leaf extract contains bioactive compounds such as flavonoid, alkaloid, tannin, triterpenoid/ steroid, and saponin. The Minimum Inhibitory Concentration (MIC) of Graptophyllum pictum (L.) Griff against Streptococcus mutans was in concentration 3.125%, and the Minimum Bactericidal Concentration (MBC) was in concentration 6.25%. Conclusion Purple Leaf Extract [Graptophyllum pictum (L.) Griff] has antibacterial activity against Streptococcus mutans.
Medicine ; Phytochemicals ; Streptococcus mutans

Streptococcus mutans (S. mutans) is generally regarded as a major contributor to dental caries because of its ability to synthesize extracellular polysaccharides (EPS) that aid in the formation of plaque biofilm. The VicRKX system of S. mutans plays an important role in biofilm formation. The aim of this study was to investigate the effects of vicK gene on specific characteristics of EPS in S. mutans biofilm. We constructed single-species biofilms formed by different mutants of vicK gene. Production and distribution of EPS were detected through atomic force microscopy, scanning electron microscopy and confocal laser scanning microscopy. Microcosmic structures of EPS were analyzed by gel permeation chromatography and gas chromatography-mass spectrometry. Cariogenicity of the vicK mutant was assessed in a specific pathogen-free rat model. Transcriptional levels of cariogenicity-associated genes were confirmed by quantitative real-time polymerase chain reaction. The results showed that deletion of vicK gene suppressed biofilm formation as well as EPS production, and EPS were synthesized mostly around the cells. Molecular weight and monosaccharide components underwent evident alterations. Biofilms formed in vivo were sparse and contributed a decreased degree of caries. Moreover, expressional levels of genes related to EPS synthesis were down-regulated, except for gtfB. Our report demonstrates that vicK gene enhances biofilm formation and subsequent caries development. And this may due to its regulations on EPS metabolism, like synthesis or microcosmic features of EPS. This study suggests that vicK gene and EPS can be considered as promising targets to modulate dental caries.
Animals ; Biofilms ; Dental Caries ; Dental Plaque ; Rats ; Streptococcus mutans/genetics*

Glucosyltransferases (Gtfs) play critical roles in the etiology and pathogenesis of Streptococcus mutans (S. mutans)- mediated dental caries including early childhood caries. Gtfs enhance the biofilm formation and promotes colonization of cariogenic bacteria by generating biofilm extracellular polysaccharides (EPSs), the key virulence property in the cariogenic process. Therefore, Gtfs have become an appealing target for effective therapeutic interventions that inhibit cariogenic biofilms. Importantly, targeting Gtfs selectively impairs the S. mutans virulence without affecting S. mutans existence or the existence of other species in the oral cavity. Over the past decade, numerous Gtfs inhibitory molecules have been identified, mainly including natural and synthetic compounds and their derivatives, antibodies, and metal ions. These therapeutic agents exert their inhibitory role in inhibiting the expression gtf genes and the activities and secretion of Gtfs enzymes with a wide range of sensitivity and effectiveness. Understanding molecular mechanisms of inhibiting Gtfs will contribute to instructing drug combination strategies, which is more effective for inhibiting Gtfs than one drug or class of drugs. This review highlights our current understanding of Gtfs activities and their potential utility, and discusses challenges and opportunities for future exploration of Gtfs as a therapeutic target.
Biofilms ; Dental Caries/prevention & control* ; Glucosyltransferases/antagonists & inhibitors* ; Humans ; Streptococcus mutans/enzymology*

OBJECTIVES: To evaluate the effects of antimicrobial peptide GH12 designed METHODS: The cariogenic three-species biofilm consis-ted of the cariogenic RESULTS: The biomass and density of the cariogenic three-species biofilm treated with GH12 decreased compared with those of the control. The number of CONCLUSIONS GH12 can reduce the number of
Biofilms ; Dental Caries ; Humans ; In Situ Hybridization, Fluorescence ; Pore Forming Cytotoxic Proteins ; Streptococcus mutans

PURPOSE: The aim of this study is to evaluate the effectiveness of MnO₂-diatom microbubbler (DM) on the surface of prosthetic materials as a mouthwash by comparing the biofilm removal effect with those previously used as a mouthwash in dental clinic.MATERIALS AND METHODS: DM was fabricated by doping manganese dioxide nanosheets to the diatom cylinder surface. Scanning electron microscopy (SEM) was used to observe the morphology of DM and to analyze the composition of doped MnO₂. Stereomicroscope was used to observe the reaction of DM in 3% hydrogen peroxide. Non-precious metal alloys, zirconia and resin specimens were prepared to evaluate the effect of biofilm removal on the surface of prosthetic materials. And then Streptococcus mutans and Porphyromonas gingivalis biofilms were formed on the specimens. When 3% hydrogen peroxide solution and DM were treated on the biofilms, the decontamination effect was compared with chlorhexidine gluconate and 3% hydrogen peroxide solution by crystal violet staining.RESULTS: Manganese dioxide was found on the surface of the diatom cylinder, and it was found to produce bubble of oxygen gas when added to 3% hydrogen peroxide. For all materials used in the experiments, biofilms of the DM-treated groups got effectively removed compared to the groups used with chlorhexidine gluconate or 3% hydrogen peroxide alone.CONCLUSION: MnO₂-diatom microbubbler can remove bacterial membranes on the surface of prosthetic materials more effectively than conventional mouthwashes.
Alloys ; Biofilms ; Chlorhexidine ; Decontamination ; Dental Clinics ; Dental Plaque ; Diatoms ; Gentian Violet ; Hydrogen Peroxide ; In Vitro Techniques ; Manganese ; Membranes ; Microscopy, Electron, Scanning ; Mouthwashes ; Oral Hygiene ; Oxygen ; Porphyromonas gingivalis ; Streptococcus mutans