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Background: Helicobacter pylori changes from spiral to coccoid depending on the host state, environmental factors, and surrounding microbial communities. The coccoid form of H. pylori still maintains its complete cellular structure, retains virulence genes, and thus plays a role in pathogenicity. To understand the coccoid form, it is crucial to establish the in vitro generation of the coccoid H. pylori. Although some conditions have been studied for the generation of the coccoid form, few studies have compared these conditions for coccoid generation. Here, we generated coccoid forms via three methods and compared the differences in morphology, viability, culturability, and protein expression. Results: The coccoid H. pylori was generated in vitro via three methods: a starvation method, a method using amoxicillin, and a method using the culture supernatant of Streptococcus mitis. The morphology and viability of the cells were examined by fluorescence microscopy after staining with SYTO9 and propidium iodide. The culturability of H. pylori was examined by counting colony-forming units on chocolate agar plates. In the starvation group, no colonies formed after 7 days, but viable coccoids were continuously observed. In the amoxicillin-treated group, the culturability decreased rapidly after 12 h, and showed a viable but non culturable (VBNC) state after the third day. Most cells treated with S. mitis supernatant changed to coccoid forms after 7 days, but colonies were continuously formed, probably due to living spiral forms. We performed proteomics to analyse the differences in protein profiles between the spiral and coccoid forms and protein profiles among the coccoid forms generated by the three methods. Conclusion: Amoxicillin treatment changed H. pylori to VBNC cells faster than starvation. Treatment with the S. mitis supernatant prolonged the culturability of H. pylori, suggesting that the S. mitis supernatant may contain substances that support spiral form maintenance. Proteomic analysis revealed that the expression of proteins differed between the spiral form and coccoid form of H. pylori, and this variation was observed among the coccoid forms produced via three different methods. The proteins in the coccoid forms produced by the three methods differed from each other, but common proteins were also observed among them. [ABSTRACT FROM AUTHOR]

Abstract Background Helicobacter pylori changes from spiral to coccoid depending on the host state, environmental factors, and surrounding microbial communities. The coccoid form of H. pylori still maintains its complete cellular structure, retains virulence genes, and thus plays a role in pathogenicity. To understand the coccoid form, it is crucial to establish the in vitro generation of the coccoid H. pylori. Although some conditions have been studied for the generation of the coccoid form, few studies have compared these conditions for coccoid generation. Here, we generated coccoid forms via three methods and compared the differences in morphology, viability, culturability, and protein expression. Results The coccoid H. pylori was generated in vitro via three methods: a starvation method, a method using amoxicillin, and a method using the culture supernatant of Streptococcus mitis. The morphology and viability of the cells were examined by fluorescence microscopy after staining with SYTO9 and propidium iodide. The culturability of H. pylori was examined by counting colony-forming units on chocolate agar plates. In the starvation group, no colonies formed after 7 days, but viable coccoids were continuously observed. In the amoxicillin-treated group, the culturability decreased rapidly after 12 h, and showed a viable but non culturable (VBNC) state after the third day. Most cells treated with S. mitis supernatant changed to coccoid forms after 7 days, but colonies were continuously formed, probably due to living spiral forms. We performed proteomics to analyse the differences in protein profiles between the spiral and coccoid forms and protein profiles among the coccoid forms generated by the three methods. Conclusion Amoxicillin treatment changed H. pylori to VBNC cells faster than starvation. Treatment with the S. mitis supernatant prolonged the culturability of H. pylori, suggesting that the S. mitis supernatant may contain substances that support spiral form maintenance. Proteomic analysis revealed that the expression of proteins differed between the spiral form and coccoid form of H. pylori, and this variation was observed among the coccoid forms produced via three different methods. The proteins in the coccoid forms produced by the three methods differed from each other, but common proteins were also observed among them.

Burns are a significant problem with high associated morbidity and mortality worldwide. Bacteremia is a serious complication that is important in increasing the overall fatality rate in burn injury patients. In this study, we report a case of Streptococcus mitis and Klebsiella pneumoniae mixed infection in severe burns in a 40-year-old female. The patient was transferred from an outside hospital to the emergency unit after burn injuries in a gas explosion accident at home. The patient underwent surgical debridement and antibiotics treatment but died due to sepsis and multiorgan failure. Our case study will help to underscore the important role of Streptococcus mitis and Klebsiella pneumoniae as human opportunistic pathogens in severe burn injury patients.

Purpose: This study aimed to evaluate the surface properties and bacterial adhesion of computer-aided design-computer-aided manufacturing (CADCAM) restorative materials. Methods: Four CAD-CAM resin-based blocks (Vita Enamic, Shofu block HC, Cerasmart [CS] and Lava Ultimate [LU]) and a leucite-reinforced glass ceramic block (IPS Empress CAD) were used in the present study. Specimens prepared with dimensions of 10 × 10 × 1 mm were polished. Surface characteristics were assessed with hydrophobicity and surface free energy (SFE) analysis. Surface roughness was measured using a profilometer, and elemental and topographic evaluations were performed with SEM-EDX analysis. After being kept in artificial saliva for 1 h, Streptococcus mutans (S. mutans) and Streptococcus mitis (S. mitis) were incubated separately in 5% CO2 atmosphere at 37°C for 24 h. The adhered bacteria were counted as ×108 CFU/mL. Results: Surface roughness, contact angle and SFE measurement values were found to be in the range of 0.144-0.264 Ra, 28.362°-70.074° and 39.65-63.62 mN/m, respectively. The highest adhered amount of S. mutans was found in CS and the lowest in LU, while there was no significant difference between the amounts of adhered S. mitis. Conclusion: Despite differences in the surface properties of the materials used for the study, the materials exhibited identical properties with respect to bacterial adhesion. [ABSTRACT FROM AUTHOR]

Burns are a significant problem with high associated morbidity and mortality worldwide. Bacteremia is a serious complication that is important in increasing the overall fatality rate in burn injury patients. In this study, we report a case of Streptococcus mitis and Klebsiella pneumoniae mixed infection in severe burns in a 40-year-old female. The patient was transferred from an outside hospital to the emergency unit after burn injuries in a gas explosion accident at home. The patient underwent surgical debridement and antibiotics treatment but died due to sepsis and multiorgan failure. Our case study will help to underscore the important role of Streptococcus mitis and Klebsiella pneumoniae as human opportunistic pathogens in severe burn injury patients. [ABSTRACT FROM AUTHOR]

ABSTRACT Streptococcus mitis/oralis can cause invasive diseases, including bloodstream infections. However, existing research primarily focuses on specific populations, and limited studies have been conducted on the prevalence of bloodstream infection caused by S. mitis/oralis across the entire pediatric population. Therefore, clinical data of S. mitis/oralis isolated from blood samples at Children’s Hospital, Zhejiang University School of Medicine, during the period 2019–2023 were collected retrospectively to provide a comprehensive understanding of the clinical characteristics and drug resistance patterns associated with bloodstream infections caused by S. mitis/oralis in pediatric populations. There were 57 (43.5%) instances of contamination across various departments, indicating a relatively dispersed pattern. Bloodstream infections caused by S. mitis/oralis are notably prevalent among pediatric patients with hematological diseases and tumors. The susceptibility rates of the 74 S. mitis/oralis isolates to different antibiotics were as follows: penicillin (23%), ceftriaxone (74.3%), levofloxacin (86.5%), chloramphenicol (89.2%), erythromycin (27%), clindamycin (67.6%), linezolid (100%), and vancomycin (100%). Notably, 21.6% of the isolates exhibited multi-drug resistance (MDR). The predominant mode of MDR in S. mitis/oralis infections was identified as resistance to β-lactams, erythromycin, and clindamycin. The observed low susceptibility rate to penicillin, coupled with the emergence of MDR strains, underscores the imperative for continuous monitoring of the evolving antimicrobial resistance in S. mitis/oralis.IMPORTANCEExisting research primarily focuses on specific populations, such as those with hematopathy or tumors, who experience Streptococcus mitis/oralis bacteremia. Limited studies have been conducted on the prevalence of bloodstream infections caused by S. mitis/oralis across the entire pediatric population. It was found that the contamination rate of S. mitis/oralis isolated from blood cultures was notably high in our study. Therefore, this study evaluated the clinical characteristics and drug resistance patterns of bloodstream infections caused by S. mitis/oralis across the entire pediatric populations, explicitly excluding cases of blood culture contamination. The observed low susceptibility rate to penicillin, coupled with the emergence of multi-drug-resistant strains, underscores the imperative for continuous monitoring of the evolving antimicrobial resistance in S. mitis/oralis.

The Streptococcus mitis-oralis subgroup of the viridans group streptococci (VGS) are the most common cause of infective endocarditis (IE) in many parts of the world. These organisms are frequently resistant in vitro to standard β-lactams (e.g., penicillin; ceftriaxone [CRO]), and have the notable capacity for rapidly developing high-level and durable daptomycin resistance (DAP-R) during exposures in vitro, ex vivo, and in vivo. In this study, we used 2 prototypic DAP-susceptible (DAP-S) S. mitis-oralis strains (351; and SF100), which both evolved stable, high-level DAP-R in vitro within 1 to 3 days of DAP passage (5 to 20 μg/mL DAP). Of note, the combination of DAP + CRO prevented this rapid emergence of DAP-R in both strains during in vitro passage. The experimental rabbit IE model was then employed to quantify both the clearance of these strains from multiple target tissues, as well as the emergence of DAP-R in vivo under the following treatment conditions: (i) ascending DAP-alone dose-strategies encompassing human standard-dose and high-dose-regimens; and (ii) combinations of DAP + CRO on these same metrics. Ascending DAP-alone dose-regimens (4 to 18 mg/kg/d) were relatively ineffective at either reducing target organ bioburdens or preventing emergence of DAP-R in vivo. In contrast, the combination of DAP (4 or 8 mg/kg/d) + CRO was effective at clearing both strains from multiple target tissues (often with sterilization of bio-burdens in such organs), as well as preventing the emergence of DAP-R. In patients with serious S. mitis-oralis infections such as IE, especially caused by strains exhibiting intrinsic β-lactam resistance, initial therapy with combinations of DAP + CRO may be warranted.

Streptococcus mitis commonly causes bloodstream infections (BSIs) in neutropenic patients but infrequently results in infective endocarditis (IE) in this population. Among 210 patients with neutropenia and S. mitis BSI, 55% underwent cardiac imaging. None were diagnosed with S. mitis IE; 3 had recurrent S. mitis BSI within 12 weeks. [ABSTRACT FROM AUTHOR]

This case report highlights the rare association among a dental procedure, infective endocarditis, and an acute ischemic stroke. A 54-year-old woman who experienced an acute ischemic stroke 5 weeks after a tooth extraction is described. The initial symptoms of this patient included mild to moderate word-finding difficulty and right facial droop. Computed tomographic angiography revealed a left M1 segment middle cerebral artery occlusion (thrombolysis in cerebral infarction scale, 0) with reconstitution of the distal middle cerebral branches through arterial collaterals. After initial administration of tissue plasminogen activator, endovascular thrombectomy was successfully performed with thrombolysis in cerebral infarction scale 3 (complete) recanalization. After the procedure, the patient showed improvement in language and neurologic deficits. Imaging showed multifocal, bilateral, cortical, and deep brain hemorrhages. Blood cultures grew Streptococcus mitis , ultimately leading to the diagnosis of endocarditis. Echocardiographic imaging revealed moderate to severe aortic insufficiency, a mitral valve vegetation, and mild mitral valve regurgitation. After evaluation by the cardiothoracic surgery team, the patient was discharged with intravenous antibiotics and short-term outpatient follow-up with the cardiothoracic surgery team. Dental procedures, although generally safe, can introduce oral bacteria into the bloodstream, leading to bacterial seeding of cardiac valves and subsequent infective endocarditis. Recognizing infective endocarditis subsequent to a dental procedure, including a tooth extraction, as a potential cause of an acute ischemic stroke is vital so that prompt treatment can be initiated. [ABSTRACT FROM AUTHOR]

Abstract Background Among a cohort of patients who underwent chest wall resection and reconstruction by rigid prosthesis, 6% required removal of the prosthesis, and in 80% of these cases the indication for prosthesis removal was infection. Although artificial prosthesis removal is the primary approach in such cases of infection, the usefulness of vacuum-assisted closure (VAC) has also been reported. Case presentation A 64-year-old man with diabetes mellitus underwent right middle and lower lobectomy with chest wall (3rd to 5th rib) resection and lymph node dissection because of lung squamous cell carcinoma. The chest wall defect was reconstructed by an expanded polytetrafluoroethylene (PTFE) sheet. Three months after surgery, the patient developed an abscess in the chest wall around the PTFE sheet. We performed debridement and switched to VAC therapy 2 weeks after starting continuous drainage of the abscess in the chest wall. The space around the PTFE sheet gradually decreased, and formation of wound granulation progressed. We performed wound closure 6 weeks after starting VAC therapy, and the patient was discharged 67 days after hospitalization. Conclusions We experienced a case of chest wall reconstruction infection after surgery for non-small cell lung cancer that was successfully treated by VAC therapy without removal of the prosthesis. Although removal of an infectious artificial prosthesis can be avoided by application of VAC therapy, perioperative management to prevent surgical site infection is considered essential.

Background: Among a cohort of patients who underwent chest wall resection and reconstruction by rigid prosthesis, 6% required removal of the prosthesis, and in 80% of these cases the indication for prosthesis removal was infection. Although artificial prosthesis removal is the primary approach in such cases of infection, the usefulness of vacuum-assisted closure (VAC) has also been reported. Case presentation: A 64-year-old man with diabetes mellitus underwent right middle and lower lobectomy with chest wall (3rd to 5th rib) resection and lymph node dissection because of lung squamous cell carcinoma. The chest wall defect was reconstructed by an expanded polytetrafluoroethylene (PTFE) sheet. Three months after surgery, the patient developed an abscess in the chest wall around the PTFE sheet. We performed debridement and switched to VAC therapy 2 weeks after starting continuous drainage of the abscess in the chest wall. The space around the PTFE sheet gradually decreased, and formation of wound granulation progressed. We performed wound closure 6 weeks after starting VAC therapy, and the patient was discharged 67 days after hospitalization. Conclusions: We experienced a case of chest wall reconstruction infection after surgery for non-small cell lung cancer that was successfully treated by VAC therapy without removal of the prosthesis. Although removal of an infectious artificial prosthesis can be avoided by application of VAC therapy, perioperative management to prevent surgical site infection is considered essential. [ABSTRACT FROM AUTHOR]

Objective: To describe two different degrees of clinical commitment and results in the evolution of infectious endarteritis in patients without a previous diagnosis of aortic coarctation. Case description: Two male patients aged 13 and 9 years old were admitted. The first due to a fever for 2 months, which started after dental cleaning, and the second due to high blood pressure, both patients with asthenia and weight loss. In the first case, the transthoracic echocardiogram showed aortic coarctation, and the transesophageal echocardiogram showed the presence of vegetations in the post-coarctation area, without pseudoaneurysms, with blood culture positive for Streptococcus mitis. This patient was treated for six weeks with crystalline penicillin, resolving the infection without complications. The second case was assessed for high blood pressure with a history of fever, and was treated with antibiotics. When performing a transthoracic echocardiogram, aortic coarctation was observed with a saccular image classified as a pseudoaneurysm by angiography and tomography. Blood culture was negative, and the patient developed an episode of hematemesis whose initial etiology could not be determined. Before surgical repair, he had a second episode of copious hematemesis with hypovolemic shock and death. Comments: We need to have a high index of clinical suspicion to establish the diagnosis of aortic coarctation complicated by endarteritis and start the appropriate antibiotic treatment, always maintaining surveillance for the early detection of pseudoaneurysms. [ABSTRACT FROM AUTHOR]

ABSTRACT: Objectives: Viridans group streptococci (VGS) have been previously linked to infective endocarditis (IE) in patients with mitral valve prolapse (MVP). The species identification of VGS is now available in clinical laboratories; however, it has not been examined in MVP IE. Therefore, we detailed the clinical profile, species designations, and antibiotic susceptibility of VGS isolates from patients with MVP IE. Methods: We retrospectively queried all adults with MVP and a definite or possible IE diagnosis seen at medical centers of the Mayo Clinic Enterprise from January 2009 to December 2021. Data, including clinical characteristics, comorbidities, microbiology, and outcomes, were extracted from electronic health records. VGS isolates from patients with MVP and IE were subclassified into mutans, salivarius, anginosus, sanguinis, and mitis groups. Results: A total of 38 patients with MVP with IE due to streptococcal species were included. Overall, median age was 62.4 years and 32% of patients were females. The most prevalent comorbidities were diabetes mellitus (26%), hypertension (21%), heart failure (16%), and malignancy (16%). A total of (37%) patients presented with an embolic event at the time of their IE diagnosis, 27 (66%) required valve surgery, and no patient died within the hospital stay. The Streptococcus mitis group was the predominant (n = 17, 45%) species designation; S. anginosus and S. sanguinis were identified in three (8%) each; S. mutans in two (5%); and S. salivarius in one (3%). Non-VGS streptococcal pathogens included S. agalactiae in three patients (8%), S. equi in two (5%), and S. dysgalactiae and S. bovis in one each (3%). VGS were identified in five (13%) patients, but species designation was not done. No penicillin resistance was identified among the isolates. Conclusion: The S. mitis group was the predominant species in our investigation. Continued evaluation of VGS species should be considered to profile the IE risk based on species identification.

ABSTRACT Objective: To describe two different degrees of clinical commitment and results in the evolution of infectious endarteritis in patients without a previous diagnosis of aortic coarctation. Case description: Two male patients aged 13 and 9 years old were admitted. The first due to a fever for 2 months, which started after dental cleaning, and the second due to high blood pressure, both patients with asthenia and weight loss. In the first case, the transthoracic echocardiogram showed aortic coarctation, and the transesophageal echocardiogram showed the presence of vegetations in the post-coarctation area, without pseudoaneurysms, with blood culture positive for Streptococcus mitis. This patient was treated for six weeks with crystalline penicillin, resolving the infection without complications. The second case was assessed for high blood pressure with a history of fever, and was treated with antibiotics. When performing a transthoracic echocardiogram, aortic coarctation was observed with a saccular image classified as a pseudoaneurysm by angiography and tomography. Blood culture was negative, and the patient developed an episode of hematemesis whose initial etiology could not be determined. Before surgical repair, he had a second episode of copious hematemesis with hypovolemic shock and death. Comments: We need to have a high index of clinical suspicion to establish the diagnosis of aortic coarctation complicated by endarteritis and start the appropriate antibiotic treatment, always maintaining surveillance for the early detection of pseudoaneurysms.

Oral microbiome disruptions in periodontitis are related to the chronic inflammatory reactions that could in turn lead to the development of multiple oral diseases. The objective of the study was to assess the frequencies of Streptococcus mitis, Prevotella melaninogenica, and Prevotella intermedia in oral benign lesions, oral potentially malignant disorders (OPMDs), and oral squamous cell carcinomas (OSCCs) and investigate the impact of these bacteria on the expression patterns of the selected (potential) target genes (PI3CA/AKT2/mTOR, DUSP16/MAPK14, and COX2). After sample collection (25 benign lesions, 30 OPMDs, and 35 OSCCs) and DNA/RNA extraction, quantitative real-time polymerase chain reaction (qPCR) was performed to detect bacterial presence and assess relative gene expression levels in different lesion groups. Prevotella melaninogenica was the most prevalent of the three analyzed bacteria, with the frequency being 60% in benign lesions, 87% in OPMDs (p = 0.024), and 77% in OSCC. The OPMD tissues in which Prevotella melaninogenica was present exhibited a higher expression level of AKT2 (p = 0.042). Significantly lower expression of DUSP16 was observed in OSCC tissues containing Streptococcus mitis (p = 0.011). The obtained results indicate a substantial contribution of P. melaninogenica and Str. mitis in the pathogenesis of oral mucosal lesions, possibly via AKT2 upregulation and DUSP16 downregulation. [ABSTRACT FROM AUTHOR]

Expression of bacteriophage lysinSM1 by Streptococcus oralis strain SF100 is thought to be important for the pathogenesis of infective endocarditis, due to its ability to mediate bacterial binding to fibrinogen. To better define the lysinSM1 binding site on fibrinogen Aα, and to investigate the impact of binding on fibrinolysis, we examined the interaction of lysinSM1 with a series of recombinant fibrinogen Aα variants. These studies revealed that lysinSM1 binds the C-terminal region of fibrinogen Aα spanned by amino acid residues 534 to 610, with an affinity of equilibrium dissociation constant (KD) of 3.23 × 10-5 M. This binding site overlaps the known binding site for plasminogen, an inactive precursor of plasmin, which is a key protease responsible for degrading fibrin polymers. When tested in vitro, lysinSM1 competitively inhibited plasminogen binding to the αC region of fibrinogen Aα. It also inhibited plasminogen-mediated fibrinolysis, as measured by thromboelastography (TEG). These results indicate that lysinSM1 is a bi-functional virulence factor for streptococci, serving as both an adhesin and a plasminogen inhibitor. Thus, lysinSM1 may facilitate the attachment of bacteria to fibrinogen on the surface of damaged cardiac valves and may also inhibit plasminogen-mediated lysis of infected thrombi (vegetations) on valve surfaces. IMPORTANCE The interaction of streptococci with human fibrinogen and platelets on damaged endocardium is a central event in the pathogenesis of infective endocarditis. Streptococcus oralis can bind platelets via the interaction of bacteriophage lysinSM1 with fibrinogen on the platelet surface, and this process has been associated with increased virulence in an animal model of endocarditis. We now report that lysinSM1 binds to the αC region of the human fibrinogen Aα chain. This interaction blocks plasminogen binding to fibrinogen and inhibits fibrinolysis. In vivo, this inhibition could prevent the lysis of infected vegetations, thereby promoting bacterial persistence and virulence.

• Viridans group streptococci (VGS) are the most common pathogens of infective endocarditis in mitral valve prolapse. • Among VGS, Streptococcus mitis group isolates were the most frequent pathogens. • Penicillin resistance was not detected among S. mitis group isolates. • There were no in-hospital deaths due to VGS infective endocarditis. Viridans group streptococci (VGS) have been previously linked to infective endocarditis (IE) in patients with mitral valve prolapse (MVP). The species identification of VGS is now available in clinical laboratories; however, it has not been examined in MVP IE. Therefore, we detailed the clinical profile, species designations, and antibiotic susceptibility of VGS isolates from patients with MVP IE. We retrospectively queried all adults with MVP and a definite or possible IE diagnosis seen at medical centers of the Mayo Clinic Enterprise from January 2009 to December 2021. Data, including clinical characteristics, comorbidities, microbiology, and outcomes, were extracted from electronic health records. VGS isolates from patients with MVP and IE were subclassified into mutans, salivarius, anginosus, sanguinis, and mitis groups. A total of 38 patients with MVP with IE due to streptococcal species were included. Overall, median age was 62.4 years and 32% of patients were females. The most prevalent comorbidities were diabetes mellitus (26%), hypertension (21%), heart failure (16%), and malignancy (16%). A total of (37%) patients presented with an embolic event at the time of their IE diagnosis, 27 (66%) required valve surgery, and no patient died within the hospital stay. The Streptococcus mitis group was the predominant (n = 17, 45%) species designation; S. anginosus and S. sanguinis were identified in three (8%) each; S. mutans in two (5%); and S. salivarius in one (3%). Non-VGS streptococcal pathogens included S. agalactiae in three patients (8%) , S. equi in two (5%), and S. dysgalactiae and S. bovis in one each (3%). VGS were identified in five (13%) patients, but species designation was not done. No penicillin resistance was identified among the isolates. The S. mitis group was the predominant species in our investigation. Continued evaluation of VGS species should be considered to profile the IE risk based on species identification. [ABSTRACT FROM AUTHOR]

ABSTRACT Streptococcus mitis is a normal member of the human oral microbiota and a leading opportunistic pathogen causing infective endocarditis (IE). Despite the complex interactions between S. mitis and the human host, understanding of S. mitis physiology and its mechanisms of adaptation to host-associated environments is inadequate, especially compared with other IE bacterial pathogens. This study reports the growth-promoting effects of human serum on S. mitis and other pathogenic streptococci, including S. oralis, S. pneumoniae, and S. agalactiae. Using transcriptomic analyses, we identified that, with the addition of human serum, S. mitis downregulates uptake systems for metal ions and sugars, fatty acid biosynthetic genes, and genes involved in stress response and other processes related with growth and replication. S. mitis upregulates uptake systems for amino acids and short peptides in response to human serum. Zinc availability and environmental signals sensed by the induced short peptide binding proteins were not sufficient to confer the growth-promoting effects. More investigation is required to establish the mechanism for growth promotion. Overall, our study contributes to the fundamental understanding of S. mitis physiology under host-associated conditions. IMPORTANCE S. mitis is exposed to human serum components during commensalism in the human mouth and bloodstream pathogenesis. However, the physiological effects of serum components on this bacterium remain unclear. Using transcriptomic analyses, S. mitis biological processes that respond to the presence of human serum were revealed, improving the fundamental understanding of S. mitis physiology in human host conditions.

The viridans group streptococci (VGS) are a heterogeneous group of organisms which are important components of the normal human oral flora. Among the VGS, the Streptococcus mitis/oralis subgroup is one of the most common causes of infective endocarditis (IE). Daptomycin (DAP) is a potential alternative therapeutic option for invasive S. mitis infections, given high rates of β-lactam resistance and vancomycin tolerance in such strains. However, the ability of these strains to rapidly evolve high-level and durable DAP resistance (DAP-R) is problematic. Recent data suggest that combination DAP-β-lactam therapy circumvents this issue. Human-simulated dose-escalating DAP-alone dose regimens (6, 8, 10, or 12 mg/kg/day times 4 days) versus DAP (6 mg/kg/day) plus ceftriaxone (CRO) (2 g once daily times 4 days or 0.5 g, single dose) were assessed against two prototypical DAP-susceptible (DAP-S) S. mitis/oralis strains (SF100 and 351), as measured by a pharmacokinetic/pharmacodynamic (PK/PD) model of simulated endocardial vegetations (SEVs). No DAP-alone regimen was effective, with regrowth of high-level DAP-R isolates observed for both strains over 96-h exposures. Combinations of DAP-CRO with either single- or multidose regimens yielded significant reductions in log10 CFU/g amounts within SEVs for both strains (∼6 log10 CFU/g) within 24 h. In addition, no DAP-R strains were detected in either DAP-CRO combination regimens over the 96-h exposure. In contrast to prior in vitro studies, no perturbations in two key cardiolipin biosynthetic genes (cdsA and pgsA) were identified in DAP-R SEV isolates emerging from strain 351, despite defective phospholipid production. The combination of DAP-CRO warrants further investigation for treatment of IE due to S. mitis/oralis.

We investigated the ability of several recent clinical viridans group streptococci (VGS) bloodstream isolates (Streptococcus mitis/S. oralis subgroup) from daptomycin (DAP)-naive patients to develop DAP resistance in vitro All strains rapidly developed high-level and stable DAP resistance. Substitutions in two enzymes involved in the cardiolipin biosynthesis pathway were identified, i.e., CdsA (phosphatidate cytidylyltransferase) and PgsA (CDP-diacylglycerol-glycerol-3-phosphate-3-phosphatidyltransferase). These mutations were associated with complete disappearance of phosphatidylglycerol and cardiolipin from cell membranes. DAP interactions with the cell membrane differed in isolates with PgsA versus CdsA substitutions.

Aim: The aim of this in vitro study was to determine how different polishing kits affect the surface roughness of lithium disilicate glass-ceramic and to examine the effect of Streptococcus mitis and Streptococcus mutans on the adhesion of Streptococcus salivarius to the glass-ceramic. Methodology: A total of 96 lithium disilicate glass-ceramic specimens were prepared and divided into four groups: control, rough, D+Z polished, and OptraFine polished. A total of 16 subgroups were obtained based on four combinations of three bacteria. After adding artificial saliva to the surface, all specimens were incubated in suspensions prepared for bacterial combinations. Bacterial adhesion values in the colonies formed were obtained according to the colony-forming unit (CFU) system. Results: The highest Sa values were found for the rough group, followed by the OptraFine polished, D+Z polished, and control groups, but, except for the control group, the values were statistically similar (p > 0.05). The difference between S. salivarius and the triple bacteria combination was statistically significant for the S. salivarius CFU values in the control group. The difference between S. salivarius, S. salivarius + S. mutans, and the triple bacteria combination groups was significant for the rough group (p < 0.05). S. salivarius alone accumulated the most on all specimen surfaces. In the control group, a high level (r=0.6-0.8) of positive correlation was found between the S + Mit group and the S + Mit + Mut group. In the rough group, a high (r>0.8) positive correlation was found between the S + Mut and S + Mit + Mut groups in terms of S. salivarius adhesion. Conclusion: For lithium disilicate glass-ceramic material, polishing systems are not sufficiently efficient after the glaze layer has been removed. [ABSTRACT FROM AUTHOR]

Some strains of Streptococcus mitis exhibit β-hemolysis due to the β-hemolytic activity of cholesterol-dependent cytolysin (CDC). Recently, a gene encoding an atypical lectinolysin-related CDC was found in S. mitis strain Nm-76. However, the product of this gene remains uncharacterized. We aimed to characterize this atypical CDC and its molecular functions and contribution to the pathogenicity of S. mitis strain Nm-76. Phylogenetic analysis of the CDC gene was conducted based on the web-deposited information. The molecular characteristics of CDC were investigated using a gene-deletion mutant strain and recombinant proteins expressed in Escherichia coli. The gene encoding CDC found in Nm-76 and its homolog are distributed among many S. mitis strains. This CDC is phylogenetically different from other previously characterized CDCs, such as S. mitis-derived human platelet aggregation factor (Sm-hPAF)/lectinolysin and mitilysin. Because this CDC possesses an additional N-terminal domain, including a discoidin motif, it was termed discoidinolysin (DLY). In addition to the preferential lysis of human cells, DLY displayed N-terminal domain-dependent facilitation of human erythrocyte aggregation and intercellular associations between human cells. DLY functions as a hemolysin/cytolysin and erythrocyte aggregation/intercellular association molecule. This dual-function DLY could be an additional virulence factor in S. mitis. [ABSTRACT FROM AUTHOR]

It has been proposed that oral commensal bacteria are potential reservoirs of a wide variety of antimicrobial resistance genes (ARGs) and could be the source of pathogenic bacteria; however, there is scarce information regarding this. In this study, three common streptococci of the mitis group (S. oralis, S. sanguinis, and S. gordonii) isolated from dental plaque (DP) were screened to identify if they were frequent reservoirs of specific ARGs (blaTEM, cfxA, tetM, tetW, tetQ, ermA, ermB, and ermC). DP samples were collected from 80 adults; one part of the sample was cultured, and from the other part DNA was obtained for first screening of the three streptococci species and the ARGs of interest. Selected samples were plated and colonies were selected for molecular identification. Thirty identified species were screened for the presence of the ARGs. From those selected, all of the S. sanguinis and S. oralis carried at least three, while only 30% of S. gordonii strains carried three or more. The most prevalent were tetM in 73%, and blaTEM and tetW both in 66.6%. On the other hand, ermA and cfxA were not present. Oral streptococci from the mitis group could be considered frequent reservoirs of specifically tetM, blaTEM, and tetW. In contrast, these three species appear not to be reservoirs of ermA and cfxA.

Oral microbiome disruptions in periodontitis are related to the chronic inflammatory reactions that could in turn lead to the development of multiple oral diseases. The objective of the study was to assess the frequencies of Streptococcus mitis, Prevotella melaninogenica, and Prevotella intermedia in oral benign lesions, oral potentially malignant disorders (OPMDs), and oral squamous cell carcinomas (OSCCs) and investigate the impact of these bacteria on the expression patterns of the selected (potential) target genes (PI3CA/AKT2/mTOR, DUSP16/MAPK14, and COX2). After sample collection (25 benign lesions, 30 OPMDs, and 35 OSCCs) and DNA/RNA extraction, quantitative real-time polymerase chain reaction (qPCR) was performed to detect bacterial presence and assess relative gene expression levels in different lesion groups. Prevotella melaninogenica was the most prevalent of the three analyzed bacteria, with the frequency being 60% in benign lesions, 87% in OPMDs (p = 0.024), and 77% in OSCC. The OPMD tissues in which Prevotella melaninogenica was present exhibited a higher expression level of AKT2 (p = 0.042). Significantly lower expression of DUSP16 was observed in OSCC tissues containing Streptococcus mitis (p = 0.011). The obtained results indicate a substantial contribution of P. melaninogenica and Str. mitis in the pathogenesis of oral mucosal lesions, possibly via AKT2 upregulation and DUSP16 downregulation.

Background Some strains of Streptococcus mitis exhibit β-hemolysis due to the β-hemolytic activity of cholesterol-dependent cytolysin (CDC). Recently, a gene encoding an atypical lectinolysin-related CDC was found in S. mitis strain Nm-76. However, the product of this gene remains uncharacterized. We aimed to characterize this atypical CDC and its molecular functions and contribution to the pathogenicity of S. mitis strain Nm-76.Methods Phylogenetic analysis of the CDC gene was conducted based on the web-deposited information. The molecular characteristics of CDC were investigated using a gene-deletion mutant strain and recombinant proteins expressed in Escherichia coli.Results The gene encoding CDC found in Nm-76 and its homolog are distributed among many S. mitis strains. This CDC is phylogenetically different from other previously characterized CDCs, such as S. mitis-derived human platelet aggregation factor (Sm-hPAF)/lectinolysin and mitilysin. Because this CDC possesses an additional N-terminal domain, including a discoidin motif, it was termed discoidinolysin (DLY). In addition to the preferential lysis of human cells, DLY displayed N-terminal domain-dependent facilitation of human erythrocyte aggregation and intercellular associations between human cells.Conclusion DLY functions as a hemolysin/cytolysin and erythrocyte aggregation/intercellular association molecule. This dual-function DLY could be an additional virulence factor in S. mitis.

Due to the increased resistance to antibiotics and chemical biocides, the use of bacterial exopolysaccharides has been considered. The objective of the current study was to investigate the strength of the antibacterial and antibiofilm activity of EPS extracted from Lactobacillus reuteri and Streptococcus mitis because previous studies showed there were structural differences between EPS, during this study, EPS extracted from Lactobacillus reuteri and Streptococcus miti by ethanol precipitation method and estimated antibacterial and antibiofilm activity against several Oral Bacteria (Staphylococcus aureus, Staphylococcus hominis, Acinetobacter baumannii, Raoultella ornithinolytica, Streptococcus thoraltensis in different concentration as (100,150,200,250,300 mg/ml ), the results showed carbohydrates rate in extracted EPS from L. reuteri and S. mitis were recorded was 85, 80 % respectively.The concentration 100 and 150 mg/ml for EPS from L. reuteri and S. mitis, there was no inhibitory effect, except in S. aureus (1.1±0.10) and S. hominis (1.0±0.10) at 100 mg/ml, 3.1±2.01, 2.1±0.54 mg/ml respectively at 150 mg/ml concentration but no significant differences (P≤0.05). However, the antibacterial effect of that EPSs started at the concentration of 200 and upwards, where different results were recorded between the concentrations of both EPSs against all bacteria isolated (P≤0.05), On the other hand, the effect of EPS from L. reuteri and S. mitis was clear against the formation of biofilm compared with the control, worth mentioning that EPS from L. reuteri was more effective compared with EPS from S. mitis in all isolates (P≤0.05) except for S. thoraltensis where it was noted that the EPS from S. mitis is more effective than EPS from L. reuteri. Through the results obtained in this study, it was noted that the difference in the structural nature of EPS has an important role in its effectiveness as an antibacterial and anti biofilm formation and, as it was found that the EPS from L. reuteri showed more effectiveness than EPS from S. mitis and thus the mechanism of preventing and inhibiting bacteria depending of the structural nature of EPS. [ABSTRACT FROM AUTHOR]

Tissue engineering strategies include successful management of bone injuries with biomaterials to develop bone-like structures. The production of natural biomaterials for this purpose helps both to ensure tissue integrity and to present alternative products for clinical purposes. However, natural materials are mostly used together with synthetic or metallic materials due to their low stability and mechanical properties for bone tissue regeneration. There is a clinical need for material combinations that have both antimicrobial properties and the ability to increase osteogenic induction. This work aims to fabricate a nanofiber scaffold using polyurethane (PU) loaded with natural fish head powder (FHP) from Argyrosomus regius species and copper (II) chloride (CuCl2) using the electrospinning technique in order to respond to this clinical need. There has not been any material combination in the literature that contains these compounds, supports bone differentiation of stem cells, and prevents bacterial adhesion. To evaluate our composite materials morphology, chemical structure, wettability, and thermal analysis were studied with different techniques. Anti-adhesive properties of the Streptococcus mitis (S. mitis) on composite materials were tested with bacterial colonization, and osteogenic inductive properties by human bone marrow mesenchymal stem cells (hBMSCs) with and without osteogenic differentiation medium were performed with cell viability assay, Alizarin Red staining, Ca deposition and SEM analysis. According to FESEM-EDS and ATR_FTIR data, the additives were highly incorporated into the PU nanofibers. The produced materials had randomly oriented nanofiber with a porosity of ∼72 %. The FHP loaded nanofiber had an average diameter of ∼185 nm. The swelling behavior of FHP-loaded PU roughly decreased for 3, 5, and 7 days due to the hydrophobic character of the sample. An increasing percentage of FHP decreased the bacterial colonization of S. mitis. PUn-CuCl2-FHP nanofibers did not exhibit any cytotoxic effect on the hBMSCs. According to Alizarin Red Staining and Ca deposition analysis, stimulation with both the material and the osteogenic medium triggered the bone differentiation of the hBMSCs in a combined manner at days-14. Based on the results, it can be deduced that natural fish head is a promising additive material for fabricating bone-like biomaterials. [ABSTRACT FROM AUTHOR]

Streptococcus mitis/oralis can cause invasive diseases, including bloodstream infections. However, existing research primarily focuses on specific populations, and limited studies have been conducted on the prevalence of bloodstream infection caused by S. mitis/oralis across the entire pediatric population. Therefore, clinical data of S. mitis/oralis isolated from blood samples at Children's Hospital, Zhejiang University School of Medicine, during the period 2019-2023 were collected retrospectively to provide a comprehensive understanding of the clinical characteristics and drug resistance patterns associated with bloodstream infections caused by S. mitis/oralis in pediatric populations. There were 57 (43.5%) instances of contamination across various departments, indicating a relatively dispersed pattern. Bloodstream infections caused by S. mitis/oralis are notably prevalent among pediatric patients with hematological diseases and tumors. The susceptibility rates of the 74 S. mitis/oralis isolates to different antibiotics were as follows: penicillin (23%), ceftriaxone (74.3%), levofloxacin (86.5%), chloramphenicol (89.2%), erythromycin (27%), clindamycin (67.6%), linezolid (100%), and vancomycin (100%). Notably, 21.6% of the isolates exhibited multi-drug resistance (MDR). The predominant mode of MDR in S. mitis/oralis infections was identified as resistance to β-lactams, erythromycin, and clindamycin. The observed low susceptibility rate to penicillin, coupled with the emergence of MDR strains, underscores the imperative for continuous monitoring of the evolving antimicrobial resistance in S. mitis/oralis ., Importance: Existing research primarily focuses on specific populations, such as those with hematopathy or tumors, who experience Streptococcus mitis/oralis bacteremia. Limited studies have been conducted on the prevalence of bloodstream infections caused by S. mitis/oralis across the entire pediatric population. It was found that the contamination rate of S. mitis/oralis isolated from blood cultures was notably high in our study. Therefore, this study evaluated the clinical characteristics and drug resistance patterns of bloodstream infections caused by S. mitis/oralis across the entire pediatric populations, explicitly excluding cases of blood culture contamination. The observed low susceptibility rate to penicillin, coupled with the emergence of multi-drug-resistant strains, underscores the imperative for continuous monitoring of the evolving antimicrobial resistance in S. mitis/oralis ., Competing Interests: The authors declare no conflict of interest.

Purpose: Subdural hematoma (SDH) is a common pathology found in neurosurgery. Infected SDH, however, is less common, and reports have typically identified Escherichia coli as the causative organism., Case Report: We present here a case of an infected chronic SDH caused by Streptococcus mitis, likely for the first time, following a burn injury in a 40-year-old male patient., Conclusion: The workup for infected SDH should now include S. mitis as a possible culprit.

We present a 43‐year‐old woman, with a history of allergic bronchopulmonary aspergillosis and a chronic bronchocoele, who was admitted to hospital with an infection of the bronchocoele, progressing to a pulmonary abscess and polymicrobial empyema, following dental extraction and regular Lactobacillus probiotic ingestion. Interval chest imaging following this procedure demonstrated worsening right upper lobe opacities and a right‐sided pleural effusion. Bronchoscopies identified copious mucoid secretions and an infected bronchocoele with a right upper lobe airways impaction. Oral cavity organisms including Actinomyces odontolyticus were cultured on bronchial washings. Streptococcus mitis and Lactobacillus rhamnosus were cultured in pleural fluid. Treatment with endoscopic mucoid secretion suctioning; intercostal catheter insertion and therapeutic drainage; and antibiotic, glucocorticoid and anti‐IgE therapy resulted in clinical and radiological improvement. Our case illustrates the potential pulmonary complications from oral cavity organisms following tooth extraction and probiotic use in patients with chronic lung disease associated with mucoid lesions and airways obstruction. [ABSTRACT FROM AUTHOR]

Background and Aim: Antimicrobial-resistant Streptococcus species causes several diseases in humans with infection recurrence in some cases. Handling of food under unhygienic conditions resulted in transmission of pathogens to food leading to risks for consumers' health. This work studies the possible role of humans in transmission of human pathogens to food products. In this study, we focused on the presence of antimicrobial resistance Streptococcus pyogenes, Streptococcus mitis, and Streptococcus pneumoniae found in respiratory patients and in some meat products. We detected the risk factors for patient's infection and examined the antibacterial effect of oregano oil nanoemulsion (ONE) at different concentrations against the multi-drug resistance strains of streptococci. Materials and Methods: Microbiological culture and polymerase chain reaction were used to identify S. pyogenes, S. mitis, and S. pneumoniae in 120 throat swab samples and 200 meat products. The disk diffusion method was used for investigating the prevalence of resistance against 10 antimicrobials that are commonly used in the treatment of humans and animals. ONE at four concentrations (0.5%, 1.0%, 2.0%, and 3.0%) with an average particle size of 45.4 nm was identified using transmission electron microscopy. The effect of ONE on Streptococcus species isolates was examined using the well diffusion method. Risk factors for human infection were detected using statistical analysis. Results: S. pyogenes, S. mitis, and S. pneumoniae were detected in 14 (11.7%), 9 (7.5%), and 7 (5.8%), respectively, of 120 throat swabs of patients. These bacteria were also detected in 11 (5.5%), 8 (4%), and 6 (3%), respectively, of 200 meat products samples. Beef luncheon had the highest infection rate for the three species of streptococci. The majority of these isolates showed resistance to antimicrobials such as tetracycline and amoxicillin/clavulanic acid. ONE had an inhibitory effect on the growth of S. pyogenes, S. mitis, and S. pneumoniae, and its effect was significantly increased at a high concentration (3%), with a mean inhibition zone of 36.45±0.302 mm. Very young and old patients, those with chronic diseases, and those exposed to the infection several times were most susceptible to infection. Conclusion: ONE may be used as a therapeutic agent at safe and specific doses, and also in the food industry, to prevent the spoilage of food and protect human health.

ObjectivesAmong viridans group streptococcal infective endocarditis (IE), the Streptococcus mitis group is the most common aetiological organism. Treatment of IE caused by the S. mitis group is challenging due to the high frequency of β-lactam resistance, drug allergy and intolerability of mainstay antimicrobial agents such as vancomycin or gentamicin. Daptomycin has been suggested as an alternative therapeutic option in these scenarios based on its excellent susceptibility profile against S. mitis group strains . However, the propensity of many S. mitis group strains to rapidly evolve stable, high-level daptomycin resistance potentially limits this approach.MethodsWe evaluated the activity of 6 mg/kg/day daptomycin alone or in combination with gentamicin, ceftriaxone or ceftaroline against two daptomycin-susceptible S. mitis group strains over 96 h in a pharmacokinetic/pharmacodynamic model of simulated endocardial vegetations.ResultsDaptomycin alone was not bactericidal and high-level daptomycin resistance evolved at 96 h in both organisms. Combinations of daptomycin + ceftriaxone and daptomycin + ceftaroline demonstrated enhanced killing activity compared with each antibiotic alone and prevented emergence of daptomycin resistance at 96 h. Use of gentamicin as an adjunctive agent neither improved the efficacy of daptomycin nor prevented the development of daptomycin resistance.ConclusionsAddition of ceftriaxone or ceftaroline to daptomycin improves the bactericidal activity against S. mitis group strains and prevents daptomycin resistance emergence. Further investigation with combinations of daptomycin and β-lactams in a large number of strains is warranted to fully elucidate the clinical implications of such combinations for treatment of S. mitis group IE.

Among the viridans group streptococci, the Streptococcus mitis group is the most common cause of infective endocarditis. These bacteria have a propensity to be β-lactam resistant, as well as to rapidly develop high-level and durable resistance to daptomycin (DAP). We compared a parental, daptomycin-susceptible (DAPs) S. mitis/S. oralis strain and its daptomycin-resistant (DAPr) variant in a model of experimental endocarditis in terms of (i) their relative fitness in multiple target organs in this model (vegetations, kidneys, spleen) when animals were challenged individually and in a coinfection strategy and (ii) their survivability during therapy with daptomycin-gentamicin (an in vitro combination synergistic against the parental strain). The DAPr variant was initially isolated from the cardiac vegetations of animals with experimental endocarditis caused by the parental DAPs strain following treatment with daptomycin. The parental strain and the DAPr variant were comparably virulent when animals were individually challenged. In contrast, in the coinfection model without daptomycin therapy, at both the 106- and 107-CFU/ml challenge inocula, the parental strain outcompeted the DAPr variant in all target organs, especially the kidneys and spleen. When the animals in the coinfection model of endocarditis were treated with DAP-gentamicin, the DAPs strain was completely eliminated, while the DAPr variant persisted in all target tissues. These data underscore that the acquisition of DAPr in S. mitis/S. oralis does come at an intrinsic fitness cost, although this resistance phenotype is completely protective against therapy with a potentially synergistic DAP regimen.

Abstract We present a 43‐year‐old woman, with a history of allergic bronchopulmonary aspergillosis and a chronic bronchocoele, who was admitted to hospital with an infection of the bronchocoele, progressing to a pulmonary abscess and polymicrobial empyema, following dental extraction and regular Lactobacillus probiotic ingestion. Interval chest imaging following this procedure demonstrated worsening right upper lobe opacities and a right‐sided pleural effusion. Bronchoscopies identified copious mucoid secretions and an infected bronchocoele with a right upper lobe airways impaction. Oral cavity organisms including Actinomyces odontolyticus were cultured on bronchial washings. Streptococcus mitis and Lactobacillus rhamnosus were cultured in pleural fluid. Treatment with endoscopic mucoid secretion suctioning; intercostal catheter insertion and therapeutic drainage; and antibiotic, glucocorticoid and anti‐IgE therapy resulted in clinical and radiological improvement. Our case illustrates the potential pulmonary complications from oral cavity organisms following tooth extraction and probiotic use in patients with chronic lung disease associated with mucoid lesions and airways obstruction.

Infective endocarditis in native valves or in surgically replaced valves has been widely reported in the literature; however, it is still in a continuous process of investigation regarding infective endocarditis in transcatheter bioprosthetic valves. We present the case of a 66-year-old female patient with the diagnosis of early infective endocarditis (IE) of percutaneous prosthetic aortic valve SAPIEN 3 who had a favorable clinical evolution and outcome with conservative treatment with antibiotics despite that in-hospital mortality incidence due to IE-TAVR, represents > 40%. The report of new cases with their different characteristics, various treatments and results obtained, is considered of great importance to support the diagnosis and medical care for future patients. [ABSTRACT FROM AUTHOR]

The oral microbiome is a complex community of microorganisms that influences the health of the human host. A number of diseases are associated with dysbiotic oral microflora in infants and children, including dental and gastrointestinal diseases. A variety of factors can influence the composition of the oral microbial community in infants, including mode of delivery, feeding method, and diet. This study focuses on the effect of nutritional differences in infant formulae on the growth of a commensal species (Streptococcus mitis) and a pathogenic species (Streptococcus mutans) that are commonly found in the infant oral cavity. A culture-dependent model was utilized to test the effects of one infant formula (Nutramigen Enflora) supplemented with a probiotic (Lactobacillus rhamnosus) and a similar infant formula without probiotic supplementation (Enfamil NeuroPro) on the growth of each species. A Snyder's media test was used to assess acidogenic potential of each species. Bacterial growth in each formula was assessed by measuring colony forming units (CFUs) and by measuring the pH of the culture media over an 8 hour incubation. Results indicate that the probiotic formula may selectively inhibit the growth of the pathogen and aid in producing more favorable conditions for the commensal. These findings may make Nutramigen Enflora the preferred infant formula for overall health. The results of this study may assist parents in selecting alternatives to breastmilk that will support the proper development of the infant oral microbiome by favoring the growth of commensal bacteria. [ABSTRACT FROM AUTHOR]

Abstract Background Streptococcal toxic shock syndrome (STSS) is an acute, multisystem and toxin-mediated disease that usually causes shock and multiple organ failure in the early stages of its clinical course. It is associated with a substantial increase in mortality rate. The disease has been associated with invasive group A Streptococcus and is rarely caused by Streptococcus mitis (S. mitis). In healthy adults, S. mitis is closely related to endocarditis but rarely related to STSS. Case presentation We report a case of STSS caused by S. mitis in a healthy 45-year-old woman. She presented with fever 14 h after surgery and with hypotension 24 h later, and she subsequently suffered from septic shock, low albumin, dysfunction of coagulation, acute kidney dysfunction, respiratory alkalosis and metabolic acidosis, acute respiratory distress syndrome and cellulitis of the incision. The diagnosis was obtained through clinical manifestation and blood culture examination. The patient was treated with aggressive fluid resuscitation, adequate antibiotics for a total of 4 weeks, respiratory support, and surgical debridement and drainage of the incision. She was discharged after her vital signs returned to normal and the incision healed on day 40 after surgery. Conclusions The diagnosis of STSS is often delayed or missed, which leads to a high mortality rate. It is possible to cure patients if the disease can be identified early and treated with aggressive fluid resuscitation, adequate antibiotics and control of the source of infection. Clinicians should consider the disease in the differential diagnosis of septic shock to prevent death.

The opportunistic pathogen Streptococcus mitis possesses, like other members of the Mitis group of viridans streptococci, phosphorylcholine (P -Cho)-containing teichoic acids (TAs) in its cell wall. Bioinformatic analyses predicted the presence of TAs that are almost identical with those identified in the pathogen Streptococcus pneumoniae , but a detailed analysis of S. mitis lipoteichoic acid (LTA) was not performed to date. Here, we determined the structures of LTA from two S. mitis strains, the high-level beta-lactam and multiple antibiotic resistant strain B6 and the penicillin-sensitive strain NCTC10712. In agreement with bioinformatic predictions, we found that the structure of one LTA (type IV) was like pneumococcal LTA, except the exchange of a glucose moiety with a galactose within the repeating units. Further genome comparisons suggested that the majority of S. mitis strains should contain the same type IV LTA as S. pneumoniae , providing a more complete understanding of the biosynthesis of these P -Cho-containing TAs in members of the Mitis group of streptococci. Remarkably, we observed besides type IV LTA, an additional polymer belonging to LTA type I in both investigated S. mitis strains. This LTA consists of β-galactofuranosyl-(1,3)-diacylglycerol as glycolipid anchor and a poly-glycerol-phosphate chain at the O -6 position of the furanosidic galactose. Hence, these bacteria are capable of synthesizing two different LTA polymers, most likely produced by distinct biosynthesis pathways. Our bioinformatics analysis revealed the prevalence of the LTA synthase LtaS, most probably responsible for the second LTA version (type I), among S. mitis and Streptococcus pseudopneumoniae strains. [ABSTRACT FROM AUTHOR]

Objective(s): The present study aimed to investigate the antibacterial properties of a conventional epoxy-based dental sealer modified with synthesized bioactive glass (BG), hydroxyapatite (HA), and fluorine-substituted hydroxyapatite (FHA) nano-fillers. Materials and Methods: The synthesized nano-fillers were incorporated into the conventional epoxy-based dental seaer at the concentration of 10%. The antimicrobial properties of the unmodified sealers (controls) and modified seaers with BG, HA, and FHA nanoparticles (NPs) were evaluated based on biofilm formation and using the direct contact test (DCT) of Enterococcus faecalis and Streptococcus mitis. Data analysis was performed using one-way analysis of variance (ANOVA) and Tukey’s post-hoc test at the significance level of 5%. Results: A significant reduction was observed in the biofilm formation and DCT of the microbial strains in the three modified groups compared to the unmodified conventional epoxy sealer (PConclusion: According to the results of this preliminary study, nano-structured FHA, HA, and BG fillers incorporated into epoxy-based dental sealers could be potentially effective biomaterials for antibacterial approaches to root canal treatments.

Streptococcus pneumoniae and Streptococcus mitis are genetically closely related and both frequently colonise the naso-oropharynx, yet S. pneumoniae is a common cause of invasive infections whereas S. mitis is only weakly pathogenic. We hypothesise that sensitivity to innate immunity may underlie these differences in virulence phenotype. We compared the sensitivity of S. pneumoniae and S. mitis strains to complement-mediated immunity, demonstrating S. mitis strains were susceptible to complement-mediated opsonophagocytosis. S. pneumoniae resistance to complement is partially dependent on binding of the complement regulator Factor H by the surface protein PspC. However, S. mitis was unable to bind factor H. The S. pneumoniae TIGR4 strain pspC was expressed in the S. mitis SK142 strain to create a S. mitis pspC+ strain. Immunoblots demonstrated the S. mitis pspC+ strain expressed PspC, and flow cytometry confirmed this resulted in Factor H binding to S. mitis , reduced susceptibility to complement and improved survival in whole human blood compared to the wild-type S. mitis strain. However, in mouse models the S. mitis pspC+ strain remained unable to establish persistent infection. Unlike S. pneumoniae strains, culture in serum or blood did not support increased CFU of the S. mitis strains. These results suggest S. mitis is highly sensitive to opsonisation with complement partially due to an inability to bind Factor H, but even when complement sensitivity was reduced by expression of pspC , poor growth in physiological fluid limited the virulence of S. mitis in mice. [ABSTRACT FROM AUTHOR]

A group of phenotypically similar bacteria, collectively known as mutant streptococci, are considered as the main bacterial components responsible for the onset and development of cavities. The aim of our study is to identify the salivary bacteria (Lactobacillus spp., Streptococcus mutans, Streptococcus sobrinus, Streptococcus salivarius, and Streptococcus mitis) and analyze their interdependence with the dental status. The study included 71 children (26 female and 45 male) at the age of 12 years. According to their dental health status, they were divided into: control group - 31 examinees without caries, missing teeth (extractions) and dental fillings (DMF = 0); and experimental group - 40 examinees with caries, missing teeth (extractions) and dental fillings. In all examinees clinical and microbiological examinations were carried out. The lactobacilli in the saliva were determined with a diagnostic test CRT-bacteria (Vivadent, Schaan, Lihtenstein). Undivided sputum samples with sterile swabs were planted on Mitis Salivarius Agar (Fluka, a substrate with sucrose, glucose, trypan blue and crystal violet) which is recommended for the isolation of mixed cultures of streptococci, in particular: Streptococcus mitis, Streptococcus mutans, Streptococcus salivarius, Enterococcus faecalis, etc. Between the detected bacteria in the saliva - Streptococcus mutans, Streptococcus sobrinus, Streptococcus salivarius, Streptococcus mitis and the existence of dental caries there is a significant correlation (p < 0.001). Between the presences of Lactobacillus spp. in the saliva and the existence of dental caries there is a significant correlation (p < 0.01). The salivary bacterial parameters can be used as serious screening factors and can seriously participate as an instrument in the assessment of the dental caries risk. [ABSTRACT FROM AUTHOR]

Streptococcus pneumoniae and Streptococcus mitis are genetically closely related and both frequently colonise the naso-oropharynx, yet S. pneumoniae is a common cause of invasive infections whereas S. mitis is only weakly pathogenic. We hypothesise that sensitivity to innate immunity may underlie these differences in virulence phenotype. We compared the sensitivity of S. pneumoniae and S. mitis strains to complement-mediated immunity, demonstrating S. mitis strains were susceptible to complement-mediated opsonophagocytosis. S. pneumoniae resistance to complement is partially dependent on binding of the complement regulator Factor H by the surface protein PspC. However, S. mitis was unable to bind factor H. The S. pneumoniae TIGR4 strain pspC was expressed in the S. mitis SK142 strain to create a S. mitis pspC+ strain. Immunoblots demonstrated the S. mitis pspC+ strain expressed PspC, and flow cytometry confirmed this resulted in Factor H binding to S. mitis, reduced susceptibility to complement and improved survival in whole human blood compared to the wild-type S. mitis strain. However, in mouse models the S. mitis pspC+ strain remained unable to establish persistent infection. Unlike S. pneumoniae strains, culture in serum or blood did not support increased CFU of the S. mitis strains. These results suggest S. mitis is highly sensitive to opsonisation with complement partially due to an inability to bind Factor H, but even when complement sensitivity was reduced by expression of pspC, poor growth in physiological fluid limited the virulence of S. mitis in mice.