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Abstract Streptococcus mitis is a commensal bacterial species of the oral cavity, with the potential for opportunistic pathogenesis. For successful colonization, S. mitis must be able to adhere to surfaces of the oral cavity and survive and adapt to frequently changing environmental conditions. Cyclic‐di‐AMP (c‐di‐AMP) is a nucleotide second messenger, involved in the regulation of stress responses and biofilm formation in several bacterial species. Cyclic‐di‐AMP is produced by diadenylate cyclases and degraded by phosphodiesterases. We have previously shown that in S. mitis, one diadenylate cyclase (CdaA) and at least two phosphodiesterases (Pde1 and Pde2) regulate the intracellular concentration of c‐di‐AMP. In this study, we utilized S. mitis deletion mutants of cdaA, pde1, and pde2 to analyze the role of c‐di‐AMP signaling in various stress responses, biofilm formation, and adhesion to eukaryotic cells. Here, we demonstrate that the Δpde1 mutant displayed a tendency toward increased susceptibility to acetic acid at pH 4.0. Deletion of cdaA increases auto‐aggregation of S. mitis but reduces biofilm formation on an abiotic surface. These phenotypes are more pronounced under acidic extracellular conditions. Inactivation of pde1 or pde2 reduced the tolerance to ciprofloxacin, and UV radiation and the Δpde1 mutant was more susceptible to Triton X‐100, indicating a role for c‐di‐AMP signaling in responses to DNA damage and cell membrane perturbation. Finally, the Δpde2 mutant displayed a tendency toward a reduced ability to adhere to oral keratinocytes. Taken together, our results indicate an important role for c‐di‐AMP signaling in cellular processes important for colonization of the mouth.

Empyema is the collection of pus within the pleural space. The most common infective etiology of empyema is the Gram-positive organisms such as Streptococcus pneumonia and Staphylococcus aureus. Streptococcus mitis which is an oral commensal is known to cause serious infections in cancer patients receiving chemotherapy and in immunosuppressed individuals. However, there are very few case reports of S. mitis causing a complex empyema in a middle-aged woman with type 2 diabetes. Here, we discuss the case of a 58-year-old lady, a known case of type 2 diabetes mellitus under regular medication, who presented with complaints of loin pain on the right side for 1 week and breathlessness for 3 days. On evaluation, she had complex empyema on the right side with culture showing S. mitis.

Recent studies have identified a clinical isolate of the commensal Streptococcus mitis that expresses Streptococcus pneumoniae serotype 5 capsule (S. mitis serotype 5) and shows serospecificity toward pneumococcal serotype 5. However, it remains unknown whether S. mitis serotype 5 induces protective immunity against pneumococcal serotype 5. In this study, we evaluated the ability of S. mitis serotype 5 to generate protective immunity in a mouse model of lung infection with pneumococcal serotype 5. Upon challenge infection with S. pneumoniae serotype 5, mice intranasally immunized with S. mitis serotype 5 exhibited reduced pneumococcal loads in the lungs, nasal wash, and bronchoalveolar lavage fluid compared with those receiving PBS (control). The immunized mice displayed significantly higher levels of IgG and IgA antibodies reactive to S. mitis serotype 5, S. pneumoniae serotype 5 or S. pneumoniae serotype 4 than the antibody levels in control mice. In vaccinated mice, the IgG/IgA antibody levels reactive to S. mitis serotype 5 or S. pneumoniae serotype 5 were higher than the levels reactive to S. pneumoniae serotype 4. Furthermore, in-vitro restimulation of the lung-draining mediastinal lymph node cells and splenocytes from immunized mice with killed S. mitis serotype 5, S. pneumoniae serotype 5 or S. pneumoniae serotype 4 showed enhanced Th17, but not Th1 and Th2, responses. Overall, our findings show that mucosal immunization with S. mitis serotype 5 protects against S. pneumoniae serotype 5 infection and induces Th17 and predominant serotype-specific IgG/IgA antibody responses against pneumococcal infection.

Recent studies have identified a clinical isolate of the commensal Streptococcus mitis that expresses Streptococcus pneumoniae serotype 5 capsule (S. mitis serotype 5) and shows serospecificity toward pneumococcal serotype 5. However, it remains unknown whether S. mitis serotype 5 induces protective immunity against pneumococcal serotype 5. In this study, we evaluated the ability of S. mitis serotype 5 to generate protective immunity in a mouse model of lung infection with pneumococcal serotype 5. Upon challenge infection with S. pneumoniae serotype 5, mice intranasally immunized with S. mitis serotype 5 exhibited reduced pneumococcal loads in the lungs, nasal wash, and bronchoalveolar lavage fluid compared with those receiving PBS (control). The immunized mice displayed significantly higher levels of IgG and IgA antibodies reactive to S. mitis serotype 5, S. pneumoniae serotype 5 or S. pneumoniae serotype 4 than the antibody levels in control mice. In vaccinated mice, the IgG/IgA antibody levels reactive to S. mitis serotype 5 or S. pneumoniae serotype 5 were higher than the levels reactive to S. pneumoniae serotype 4. Furthermore, in-vitro restimulation of the lung-draining mediastinal lymph node cells and splenocytes from immunized mice with killed S. mitis serotype 5, S. pneumoniae serotype 5 or S. pneumoniae serotype 4 showed enhanced Th17, but not Th1 and Th2, responses. Overall, our findings show that mucosal immunization with S. mitis serotype 5 protects against S. pneumoniae serotype 5 infection and induces Th17 and predominant serotype-specific IgG/IgA antibody responses against pneumococcal infection. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Streptococcus pseudopneumoniae (SPpn) is a relatively new species closely related to S. pneumoniae (SPn) and S. mitis (SM) belonging to the Mitis group of the genus Streptococcus (MGS). Although genes encoding various pneumococcal virulence factors have been observed in the SPpn genome, the pathogenicity of SPpn against human, including the roles of virulence factor candidates, is still unclear. The present study focused on and characterized a candidate virulence factor previously reported in SPpn with deduced multiple functional domains, such as lipase domain, two lectin domains, and cholesterol‐dependent cytolysin‐related domain using various recombinant proteins. The gene was found not only in SPpn but also in the strains of SM and SPn. Moreover, the gene product was expressed in the gene‐positive strains as secreted and cell‐bound forms. The recombinant of gene product showed lipase activity and human cell‐binding activity depending on the function of lectin domain(s), but no hemolytic activity. Thus, based on the distribution of the gene within the MGS and its molecular function, the gene product was named mitilectin (MLC) and its contribution to the potential pathogenicity of the MLC‐producing strains was investigated. Consequently, the treatment with anti‐MLC antibody and the mlc gene‐knockout significantly reduced the human cell‐binding activity of MLC‐producing strains. Therefore, the multifunctional MLC was suggested to be important as an adhesion molecule in considering the potential pathogenicity of the MLC‐producing strains belonging to MGS, such as SPpn and SM. [ABSTRACT FROM AUTHOR]

Background: Viridans Group Streptococci (VGS) are a group of distinct species that can cause bacteraemia and other invasive infections. They are also among the common organisms causing infective endocarditis. Data on the epidemiology and clinical profile of VGS is limited, especially from India., Methods: We conducted an electronic medical record-based retrospective analysis of patients with VGS bacteraemia admitted to our hospital between January 2012 to December 2021. Blood cultures were incubated by BacT/ALERT system and bacterial identification and susceptibility testing were done by using the VITEK 2 microbial identification system. Susceptibility test reporting was as per Clinical and Laboratory Standards Institute (CLSI) guidelines. The incidence, clinical profile, source of bacteraemia, co-morbidities and antimicrobial resistance among VGS bacteraemia were analyzed., Results: VGS were isolated in 219 patients, accounting for 3.2% of positive blood cultures during the period studied. The median age of the patients was 58 years and 69% were males. Diabetes mellitus was the most common co-morbidity (55%) followed by chronic kidney disease and chronic liver disease. Patients with haematological malignancy and neutropenia were few. Intra-abdominal infections were the most common source of infection and was noted in 26%. Infective endocarditis was diagnosed in only 10% of the cases. Streptococcus mitis was the most common species isolated followed by S. gallolyticus and S. sanguinis . 9.58% of the isolates could not be identified up to the species level. Overall penicillin susceptibility was 71% and ceftriaxone susceptibility was 92%, with individual species variation. In-hospital mortality was 19%., Conclusions: VGS are an important cause of bacteraemia and was associated with 19% mortality in our study. High rates of penicillin and ceftriaxone resistance are a reason of concern. Molecular diagnostics like matrix assisted laser desorption ionization-time of flight (MALDI-TOF) identification must be increasingly applied for species identification considering that a substantial number of isolates were not identified to species level., Competing Interests: Conflict of interests: None to declare.

In the last decades, resistant microbial infection rate has dramatically increased, especially infections due to biofilm-producing strains that require increasingly complex treatments and are responsible for the increased mortality percentages compared with other infectious diseases. Considering that biofilms represent a key factor for a wide range of chronic infections with high drug tolerance, the treatment of biofilm-causing bacterial infections represents a great challenge for the future. Among new alternative strategies to conventional antimicrobial agents, the scientific interest has shifted to the study of biologically active compounds from plant-related extracts with known antimicrobial properties, in order to also evaluate their antibiofilm activity. In this regard, the aim of this study has been to assess the antibiofilm activity of polyphenolic extracts from myrtle leaf and pomegranate peel against oral pathogens of dental plaque, an excellent polymicrobial biofilm model. In particular, the in vitro antibiofilm properties of myrtle and pomegranate extracts, also in binary combination, were highlighted. In addition to inhibiting the biofilm formation, the tested polyphenolic extracts have been proven to destroy both preformed single-species and multispecies biofilms formed by Streptococcus mutans, Streptococcus oralis, Streptococcus mitis, and Rothia dentocariosa oral isolates, suggesting that the new natural sources are rich in promising compounds able to counteract biofilm-related infections.

We report a rare case of meningitis due to a combination of Streptococcus mitis and Neisseria subflava. An 80-year-old female had a 4-year history of type II diabetes mellitus (DM) and an 11-year history of rheumatoid arthritis, which was treated with prednisolone, tacrolimus, and methotrexate. One month after the removal of a dental implant, she complained of a disturbance of consciousness and suffered a convulsion. A cerebrospinal fluid culture was found to be positive for both S. mitis and N. subflava. After 14 days of antibiotic treatment with 4 g/day ceftriaxone, her stiff neck, somnolence, and laboratory data greatly improved, and she was successfully discharged at 27 days after admission. Although both S. mitis and N. subflava are generally considered to be benign bacteria, they can cause meningitis in patients with the following risk factors: older age, on immunosuppressive treatment, DM, or dental treatment.

Abstract Background In streptococci of the mitis group, competence for natural transformation is a transient physiological state triggered by competence stimulating peptides (CSPs). Although low transformation yields and the absence of a widespread functional competence system have been reported for Streptococcus mitis, recent studies revealed that, at least for some strains, high efficiencies can be achieved following optimization protocols. To gain a deeper insight into competence in this species, we used RNA-seq, to map the global CSP response of two transformable strains: the type strain NCTC12261T and SK321. Results All known genes induced by ComE in Streptococcus pneumoniae, including sigX, were upregulated in the two strains. Likewise, all sets of streptococcal SigX core genes involved in extracellular DNA uptake, recombination, and fratricide were upregulated. No significant differences in the set of induced genes were observed when the type strain was grown in rich or semi-defined media. Five upregulated operons unique to S. mitis with a SigX-box in the promoter region were identified, including two specific to SK321, and one specific to NCTC12261T. Two of the strain-specific operons coded for different bacteriocins. Deletion of the unique S. mitis sigX regulated genes had no effect on transformation. Conclusions Overall, comparison of the global transcriptome in response to CSP shows the conservation of the ComE and SigX-core regulons in competent S. mitis isolates, as well as species and strain-specific genes. Although some S. mitis exhibit truncations in key competence genes, this study shows that in transformable strains, competence seems to depend on the same core genes previously identified in S. pneumoniae.

In the last decades, resistant microbial infection rate has dramatically increased, especially infections due to biofilm-producing strains that require increasingly complex treatments and are responsible for the increased mortality percentages compared with other infectious diseases. Considering that biofilms represent a key factor for a wide range of chronic infections with high drug tolerance, the treatment of biofilm-causing bacterial infections represents a great challenge for the future. Among new alternative strategies to conventional antimicrobial agents, the scientific interest has shifted to the study of biologically active compounds from plant-related extracts with known antimicrobial properties, in order to also evaluate their antibiofilm activity. In this regard, the aim of this study has been to assess the antibiofilm activity of polyphenolic extracts from myrtle leaf and pomegranate peel against oral pathogens of dental plaque, an excellent polymicrobial biofilm model. In particular, the in vitro antibiofilm properties of myrtle and pomegranate extracts, also in binary combination, were highlighted. In addition to inhibiting the biofilm formation, the tested polyphenolic extracts have been proven to destroy both preformed single-species and multispecies biofilms formed by Streptococcus mutans , Streptococcus oralis , Streptococcus mitis , and Rothia dentocariosa oral isolates, suggesting that the new natural sources are rich in promising compounds able to counteract biofilm-related infections. [ABSTRACT FROM AUTHOR]

The biofilm formation by oral bacteria on the implant surface is one of the most remarkable factors of peri-implant infections, which may eventually lead to bone resorption and loss of the dental implant. Therefore, the elimination of biofilm is an essential step for the successful therapy of implant-related infections. In this work we created a basic in vitro model to evaluate the antibacterial effect of three widely used antiseptics. Commercially pure (CP4) titanium sample discs with sand blasted, acid etched, and polished surface were used. The discs were incubated with mono-cultures of Streptococcus mitis and Streptococcus salivarius. The adhered bacterial biofilms were treated with different antiseptics: chlorhexidine-digluconate (CHX), povidone-iodine (PI), and chlorine dioxide (CD) for 5 min and the control discs with ultrapure water. The antibacterial effect of the antiseptics was tested by colorimetric assay. According to the results, the PI and the CD were statistically the most effective in the elimination of the two test bacteria on both titanium surfaces after 5 min treatment time. The CD showed significant effect only against S. salivarius. Based on our results we conclude that PI and CD may be promising antibacterial agents to disinfecting the peri-implant site in the dental practice. [ABSTRACT FROM AUTHOR]

The use of nanoscale surface modifications offers a possibility to regulate the bacterial adherence behavior. The aim of this study was to evaluate the influence of nanoporous anodic aluminum oxide of different pore diameters on the bacterial species Streptococcus mitis and Streptococcus mutans. Nanoporous anodic aluminum oxide (AAO) surfaces with an average pore diameter of 15 and 40 nm, polished pure titanium and compact aluminum oxide (alumina) samples as reference material were investigated. S. mitis and mutans were evaluated for initial adhesion and viability after an incubation period of 30 and 120 min. After 30 min a significantly reduced growth of S. mitis and mutans on 15 nm samples compared to specimens with 40 nm pore diameter, alumina and titanium surfaces could be observed (p <.001). Even after 120 min incubation there was a significant difference between the surfaces with 15 nm pore diameter and the remaining samples (p <.001). AAO surfaces with a small pore diameter have an inhibitory effect on the initial adhesion of S. mitis and mutans. The use of such pore dimensions in the area of the implant shoulder represents a possibility to reduce the adhesion behavior of these bacterial species. [ABSTRACT FROM AUTHOR]

Objective(s): The present study aimed to investigate the antibacterial properties of a conventional epoxybased dental sealer modified with synthesized bioactive glass (BG), hydroxyapatite (HA), and fluorinesubstituted 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 sealers 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 (P<0.05). The addition of FHA NPs resulted in the most significant antibacterial effects against E. faecalis and S. mitis, as well as a statistically significant reduction compared to the unmodified and BG-modified groups (P=0.001). Conclusion: 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. [ABSTRACT FROM AUTHOR]

Infective endocarditis due to Streptococcus viridans is common, especially in immunocompromised patients, and patients with prosthetic heart valves. Bacteremia due to Streptococcus mitis is rare, but is associated with increased morbidity and mortality. A patient with infective endocarditis due to Streptococcus mitis is described, who presented with spondylodiskitis and endogenous endophthalmitis. [ABSTRACT FROM AUTHOR]

Background . Endophthalmitis post cataract surgery is rare, but the incidence and complications are higher in diabetics. Objectives . We present 3 diabetic patients who underwent cataract surgery and developed endophthalmitis postoperatively. Material and methods . This is a retrospective case series of diabetic patients who underwent cataract surgery and developed endophthalmitis postoperatively between September 2015 and August 2016. The medical records were retrieved from the system, and data was collected. Results . The patients eventually had different visual outcomes depending on the severity of endophthalmitis. Case 1. The patient developed delayed subtle postoperative endophthalmitis at 8 weeks post cataract operation, with underlying foot cellulitis and poor blood sugar control. The patient responded well to topical and systemic antibiotics and stabilization of blood sugar. Case 2. The patient presented with delayed postoperative endophthalmitis secondary to a suture abscess of the cataract wound at 7 months post implantation of an anterior chamber intraocular lens. There was complete resolution of the infection after administration of topical, intravitreal and systemic antibiotics, with a good control of blood sugar. Case 3. The patient presented with acute severe postoperative endophthalmitis with the presence of hypopyon at day 5 following cataract surgery. There were no obvious risk factors besides poor control of blood sugar, but Streptococcus mitis was isolated from the vitreous specimen. The endophthalmitis worsened in spite of topical, intravitreal and systemic antibiotics, as well as vitrectomy. Evisceration was eventually performed for the painful blind eye. Conclusions . Although endophthalmitis following cataract surgery is rare, the incidence and complications are much higher in diabetic patients.

Jinmann Chon,1 Moosang Kim2 1Department of Rehabilitation Medicine, Kyung Hee University Hospital, Kyung Hee University School of Medicine, Seoul, 2Department of Ophthalmology, School of Medcine, Kangwon National University, Chuncheon, Korea Abstract: Endophthalmitis following intraocular surgery can be devastating. This case report demonstrates successful management of late-onset Streptococcus mitis endophthalmitis treated by vitrectomy, panretinal photocoagulation (PRP) and silicone oil tamponade. A 75-year-old man presented with painful vision loss in his right eye. The patient had uneventful phacoemulsification and intraocular lens implantation in the right eye at an outside clinic 6 weeks prior. Examination disclosed hypopyon and vitritis, as well as discrete inflammatory collections in the vitreous. The patient underwent vitrectomy with PRP and silicone oil tamponade. Vitreous cultures were positive for S. mitis, a pathogen associated with severe tissue damage and poor clinical outcomes. One month after the surgery, intraocular inflammation was stabilized, and visual acuity was improved from light perception to 20/200. Aggressive surgical management may play a role in improving outcomes in these patients. Keywords: late-onset endophthalmitis, Streptococcus mitis, vitrectomy

Abstract Background Our previous research on the diversity of microbiota in the endotracheal tubes (ETTs) of neonates in the neonatal intensive care unit found that Pseudomonas aeruginosa (P. aeruginosa) and Streptococcus mitis (S. mitis) were the dominant bacteria on the ETT surface and the existence of S. mitis could promote biofilm formation and pathogenicity of P. aeruginosa. Toll-like receptor 4 (TLR4), which has been widely detected on the surface of airway epithelial cells, is the important component of the innate immune system. Therefore, we hypothesized that the co-existence of these two bacteria might impact the host immune system through TLR4 signaling. Results S. mitis rarely caused inflammation, whereas P. aeruginosa caused the most severe inflammation accompanied by increases in the number of inflammatory cells, interleukin (IL)-6 and tumor necrosis factor (TNF)-α expression, and total cell counts in BALF (p

S. mitis is an abundant member of the commensal microbiota of the oral cavity and pharynx, which has the potential to promote systemic infections. By analyzing a collection of S. mitis strains isolated from the oral cavity at commensal states or from systemic infections (blood strains), we established that S. mitis ubiquitously express the surface immunodominant protein, PcsB (also called GbpB), required for binding to sucrose-derived exopolysaccharides (EPS). Immuno dot blot assays with anti-PcsB antibodies and RT-qPCR transcription analyses revealed strain-specific profiles of PcsB production associated with diversity in pcsB transcriptional activities. Additionally, blood strains showed significantly higher levels of PcsB expression compared to commensal isolates. Because Streptococcus mutans co-colonizes S. mitis dental biofilms, and secretes glucosyltransferases (GtfB/C/D) for the synthesis of highly insoluble EPS from sucrose, profiles of S. mitis binding to EPS, biofilm formation and evasion of the complement system were assessed in sucrose-containing BHI medium supplemented or not with filter-sterilized S. mutans culture supernatants. These analyses showed significant S. mitis binding to EPS and biofilm formation in the presence of S. mutans supernatants supplemented with sucrose, compared to BHI or BHI-sucrose medium. In addition, these phenotypes were abolished if strains were grown in culture supernatants of a gtfBCD-defective S. mutans mutant. Importantly, GtfB/C/D-associated phenotypes were enhanced in high PcsB-expressing strains, compared to low PcsB producers. Increased PcsB expression was further correlated with increased resistance to deposition of C3b/iC3b of the complement system after exposure to human serum, when strains were previously grown in the presence of S. mutans supernatants. Finally, analyses of PcsB polymorphisms and bioinformatic prediction of epitopes with significant binding to MHC class II alleles revealed that blood isolates harbor PcsB polymorphisms in its functionally conserved CHAP-domain, suggesting antigenic variation. These findings reveal important roles of PcsB in S. mitis-host interactions under commensal and pathogenic states, highlighting the need for studies to elucidate mechanisms regulating PcsB expression in this species.

ABSTRACT From a common ancestor, Streptococcus pneumoniae and Streptococcus mitis evolved in parallel into one of the most important pathogens and a mutualistic colonizer of humans, respectively. This evolutionary scenario provides a unique basis for studies of both infection-associated properties and properties important for harmonious coexistence with the host. We performed detailed comparisons of 60 genomes of S. pneumoniae, S. mitis, Streptococcus pseudopneumoniae, the three Streptococcus oralis subspecies oralis, tigurinus, and dentisani, and Streptococcus infantis. Nonfunctional remnants of ancestral genes in both S. pneumoniae and in S. mitis support the evolutionary model and the concept that evolutionary changes on both sides were required to reach their present relationship to the host. Confirmed by screening of >7,500 genomes, we identified 224 genes associated with virulence. The striking difference to commensal streptococci was the diversity of regulatory mechanisms, including regulation of capsule production, a significantly larger arsenal of enzymes involved in carbohydrate hydrolysis, and proteins known to interfere with innate immune factors. The exclusive presence of the virulence factors in S. pneumoniae enhances their potential as vaccine components, as a direct impact on beneficial members of the commensal microbiota can be excluded. In addition to loss of these virulence-associated genes, adaptation of S. mitis to a mutualistic relationship with the host apparently required preservation or acquisition of 25 genes lost or absent from S. pneumoniae. Successful adaptation of S. mitis and other commensal streptococci to a harmonious relationship with the host relied on genetic stability and properties facilitating life in biofilms. IMPORTANCE Streptococcus pneumoniae is one of the most important human pathogens but is closely related to Streptococcus mitis, with which humans live in harmony. The fact that the two species evolved from a common ancestor provides a unique basis for studies of both infection-associated properties and properties important for harmonious coexistence with the host. By detailed comparisons of genomes of the two species and other related streptococci, we identified 224 genes associated with virulence and 25 genes unique to the mutualistic species. The exclusive presence of the virulence factors in S. pneumoniae enhances their potential as vaccine components, as a direct impact on beneficial members of the commensal microbiota can be excluded. Successful adaptation of S. mitis and other commensal streptococci to a harmonious relationship with the host relied on genetic stability and properties facilitating life in biofilms.

Bacteria utilize quorum sensing (QS) to coordinate many group behaviors. As such, QS has attracted significant attention as a potential mean to attenuate bacterial infectivity without introducing selective pressure for resistance development. Streptococcus mitis, a human commensal, acts as a genetic diversity reservoir for Streptococcus pneumoniae, a prevalent human pathogen. S. mitis possesses a typical comABCDE competence regulon QS circuitry; however, the competence-stimulating peptide (CSP) responsible for QS activation and the regulatory role of the competence regulon QS circuitry in S. mitis are yet to be explored. We set out to delineate the competence regulon QS circuitry in S. mitis, including confirming the identity of the native CSP signal, evaluating the molecular mechanism that governs CSP interactions with histidine kinase receptor ComD leading to ComD activation, and defining the regulatory roles of the competence regulon QS circuitry in initiating various S. mitis phenotypes. Our analysis revealed important structure-activity relationship insights of the CSP signal and facilitated the development of novel CSP-based QS modulators. Our analysis also revealed the involvement of the competence regulon in modulating competence development and biofilm formation. Furthermore, our analysis revealed that the native S. mitis CSP signal can modulate QS response in S. pneumoniae. Capitalizing on this crosstalk, we developed a multispecies QS modulator that activates both the pneumococcus ComD receptors and the S. mitis ComD-2 receptor with high potencies. The novel scaffolds identified herein can be utilized to evaluate the effects temporal QS modulation has on S. mitis as it inhabits its natural niche., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

S. mitis is an abundant member of the commensal microbiota of the oral cavity and pharynx, which has the potential to promote systemic infections. By analyzing a collection of S. mitis strains isolated from the oral cavity at commensal states or from systemic infections (blood strains), we established that S. mitis ubiquitously express the surface immunodominant protein, PcsB (also called GbpB), required for binding to sucrose-derived exopolysaccharides (EPS). Immuno dot blot assays with anti-PcsB antibodies and RT-qPCR transcription analyses revealed strain-specific profiles of PcsB production associated with diversity in pcsB transcriptional activities. Additionally, blood strains showed significantly higher levels of PcsB expression compared to commensal isolates. Because Streptococcus mutans co-colonizes S. mitis dental biofilms, and secretes glucosyltransferases (GtfB/C/D) for the synthesis of highly insoluble EPS from sucrose, profiles of S. mitis binding to EPS, biofilm formation and evasion of the complement system were assessed in sucrose-containing BHI medium supplemented or not with filter-sterilized S. mutans culture supernatants. These analyses showed significant S. mitis binding to EPS and biofilm formation in the presence of S. mutans supernatants supplemented with sucrose, compared to BHI or BHI-sucrose medium. In addition, these phenotypes were abolished if strains were grown in culture supernatants of a gtfBCD -defective S. mutans mutant. Importantly, GtfB/C/D-associated phenotypes were enhanced in high PcsB-expressing strains, compared to low PcsB producers. Increased PcsB expression was further correlated with increased resistance to deposition of C3b/iC3b of the complement system after exposure to human serum, when strains were previously grown in the presence of S. mutans supernatants. Finally, analyses of PcsB polymorphisms and bioinformatic prediction of epitopes with significant binding to MHC class II alleles revealed that blood isolates harbor PcsB polymorphisms in its functionally conserved CHAP-domain, suggesting antigenic variation. These findings reveal important roles of PcsB in S. mitis -host interactions under commensal and pathogenic states, highlighting the need for studies to elucidate mechanisms regulating PcsB expression in this species. [ABSTRACT FROM AUTHOR]

Septic arthritis is a serious medical condition that can lead to significant complications if misdiagnosed or mismanaged. A rare case of a 1st metatarso-phalangeal joint septic arthritis in a native joint is presented in a patient with no significant risk factors. A 41-year-old patient was referred by his general practitioner owing to ongoing pain and swelling over his native 1st metatarso-phalangeal joint with difficulty on weightbearing for three months. After a series of investigations, including blood tests and a foot magnetic resonance imaging, which were inconclusive, the patient was led to the operating theatre for sampling and washout of his joint. The samples taken in the theatres revealed septic arthritis with Streptococcus mitis as the causative microorganism. The patient was treated with six weeks of oral antibiotics with a good functional outcome. This case report illuminates this rare condition and makes foot and ankle surgeons aware of its existence. A high suspicion for this condition can prevent misdiagnosis and mismanagement. [ABSTRACT FROM AUTHOR]

Taxonomic and phylogenetic relationships of Streptococcus mitis and Streptococcus oralis have been difficult to establish biochemically and genetically. We used core-genome analyses of S. mitis and S. oralis, as well as the closely related species Streptococcus pneumoniae and Streptococcus parasanguinis, to clarify the phylogenetic relationships between S. mitis and S. oralis, as well as within subclades of S. oralis. All S. mitis (n  = 67), S. oralis (n  = 89), S. parasanguinis (n  = 27), and 27 S. pneumoniae genome assemblies were downloaded from NCBI and reannotated. All genes were delineated into homologous clusters and maximum-likelihood phylogenies built from putatively nonrecombinant core gene sets. Population structure was determined using Bayesian genome clustering, and patristic distance was calculated between populations. Population-specific gene content was assessed using a phylogenetic-based genome-wide association approach. Streptococcus mitis and S. oralis formed distinct clades, but species mixing suggests taxonomic misassignment. Patristic distance between populations suggests that S. oralis subsp. dentisani is a distinct species, whereas S. oralis subsp. tigurinus and subsp. oralis are supported as subspecies, and that S. mitis comprises two subspecies. None of the genes within the pan-genomes of S. mitis and S. oralis could be statistically correlated with either, and the dispensable genomes showed extensive variation among isolates. These are likely important factors contributing to established overlap in biochemical characteristics for these taxa. Based on core-genome analysis, the substructure of S. oralis and S. mitis should be redefined, and species assignments within S. oralis and S. mitis should be made based on whole-genome analysis to be robust to misassignment. [ABSTRACT FROM AUTHOR]

Background/Objectives: The pathogenesis of preadolescent acne has not been well studied, and it is uncertain if Cutibacterium acnes is a predominant organism in the microbiome in this age group. The aim of this study was to analyze the microbiome of preadolescent females and to assess whether benzoyl peroxide impacts the microbiome. Methods: The study enrolled girls, aged 7‐12 years, with evidence of at least six acne lesions who had not been previously treated. Participants' skin surface of forehead, cheeks, nose, chin, left retroauricular crease, and extruded contents of a comedonal lesion were sampled at baseline. Participants used benzoyl peroxide 4% wash for 6‐8 weeks and returned for skin surface sampling and extraction collection. Microbiome analysis was performed using 16S ribosomal RNA gene amplicon sequencing on all swab and lesional extraction samples. Results: Fifty‐one participants were enrolled with a median IGA score of 2 (mild). Changes in microbiome diversity were associated with increasing age and number of acne lesions (P = 0.001). C. acnes had higher abundances on forehead and nose, as opposed to cheeks and chin (P = 0.009). Bacterial diversity (alpha diversity) of the skin microbiome was comparable between preadolescent at baseline and after treatment with benzoyl peroxide. Conclusion: This is the first large assessment characterizing female acne microbiome in early and late preadolescence. Results show that preadolescent acne can vary in its microbial profile, reflecting surrounding changes associated with the onset of puberty. Although benzoyl peroxide use was associated with decreased acne counts, its effect on microbial diversity was not demonstrated in our study. [ABSTRACT FROM AUTHOR]

The use of medicinal plants as natural antimicrobial agents has recently gained popularity. Many naturally occurring compounds found in medicinal plants, herbs, and spices have been shown to possess antimicrobial activity against different pathogenic bacteria. Of these medicinal plants, Hibiscus sabdariffa has been found to have significant antimicrobial properties. This study aimed to investigate the effect of Hibiscus SabdariffaH sabdariffa ethanol extract on Streptococcus Mitismitis and Streptococcus Oralisoralis. In vitro antibacterial effects of three types of extracts (ethanol, acidic water, and aqueous) of the dry calyces of H sabdariffa were investigated against S mitis and S oralis. Well diffusion technique was used on solid nutrient agar at different concentrations of these extracts (0.0, 50, 100, 150, 200, and 250) µg/mL. Around 0.2% of chlorhexidine (CHX) was used as positive control. The minimum inhibitory concentration and minimum bactericidal concentration of the plant extracts on the test isolates were determined using the micro broth dilution method. The phytochemical analysis was carried out using standard methods to determine the most effective substances like (glycoside, alkaloids, flavonoids, and phenols). The antibacterial activity of the three extracts compared with the positive control (CHX) showed that acidic water and ethanol extracts of calyces of H sabdariffa have strong antibacterial characteristics and are more efficient than CHX. The inhibition rate of CHX was 29.1% in S mitis and 63.23% in S oralis , whereas the inhibition rate reached 91.2% and 92% in S mitis, and 91.34% and 94.53% in S oralis for the ethanol and acidic water extracts, respectively with significant differences (P ≤ 0.05). Phytochemical analyses revealed the presence of flavonoids, glycosides, phenols, and alkaloids. The 70% ethanol extract or acidified aqueous extract had higher antimicrobial activity than the aqueous extract in a concentration-dependent manner. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this study was to evaluate the association of the common root canal pathogens namely; Streptococcus mitis and Enterococcus faecalis with specific endodontic signs and symptoms. Materials and Methods: Sixty subjects scheduled for endodontic treatment were divided into two groups comprising of 30 subjects with primary endodontic infections and 30 subjects with failed endodontic treatment. The endodontic signs and symptoms of the subjects were assessed using clinical and radiographic methods. Root canal samples were collected using sterile paper point. Advanced microbiological culture techniques were used to isolate S. mitis and E. faecalis from the root canal samples. The presence of root canal pathogens was then correlated with the corresponding endodontic signs and symptoms. Statistical analysis was done using Student′s t-test and Fisher′s exact test. Results: S. mitis was significantly associated with pain and periapical lesions in primary and retreatment cases (P = 0.04). E. faecalis had a strong correlation with tenderness on percussion in retreatment cases (P = 0.016). Conclusion: Association of S. mitis with pain and periapical lesion, as well as E. faecalis with tenderness on percussion, suggests a correlation between endodontic signs and symptoms with specific root canal bacterial species. Knowledge regarding the association of root canal pathogens and specific endodontic signs and symptoms could help in better understanding and a predictable therapeutic management of root canal infections.

Cyclic di-adenosine monophosphate (c-di-AMP) has emerged as an important bacterial signaling molecule that functions both as an intracellular second messenger in bacterial cells and an extracellular ligand involved in bacteria-host cross-talk. In this study, we identify and characterize proteins involved in controlling the c-di-AMP concentration in the oral commensal and opportunistic pathogen Streptococcusmitis (S. mitis). We identified three known types of c-di-AMP turnover proteins in the genome of S. mitis CCUG31611: a CdaA-type diadenylate cyclase as well as GdpP-, and DhhP-type phosphodiesterases. Biochemical analyses of purified proteins demonstrated that CdaA synthesizes c-di-AMP from ATP whereas both phosphodiesterases can utilize c-di-AMP as well as the intermediary metabolite of c-di-AMP hydrolysis 5′-phosphadenylyl-adenosine (pApA) as substrate to generate AMP, albeit at different catalytic efficiency. Using deletion mutants of each of the genes encoding c-di-AMP turnover proteins, we show by high resolution MS/MS that the intracellular concentration of c-di-AMP is increased in deletion mutants of the phosphodiesterases and non-detectable in the cdaA-mutant. We also detected pApA in mutants of the DhhP-type phosphodiesterase. Low and high levels of c-di-AMP were associated with longer and shorter chains of S. mitis, respectively indicating a role in regulation of cell division. The deletion mutant of the DhhP-type phosphodiesterase displayed slow growth and reduced rate of glucose metabolism.

Current vaccines against Streptococcus pneumoniae, a bacterial species that afflicts people by causing a wide spectrum of diseases, do not protect against all pneumococcal serotypes. Thus, alternative vaccines to fight pneumococcal infections that target common proteins are under investigation. One promising strategy is to take advantage of immune cross-reactivity between commensal and pathogenic microbes for cross-protection. In this study, we examined the antibody-mediated cross-reactivity between S. pneumoniae and Streptococcus mitis, a commensal species closely related to S. pneumoniae. Western blot analysis showed that rabbit antisera raised against S. mitis reacted with multiple proteins of virulent S. pneumoniae strains (6B, TIGR4, and D39). Rabbit anti-S. pneumoniae IgG antibodies also showed binding to S. mitis antigens. Incubation of rabbit antisera raised against S. mitis with heterologous or homologous bacterial lysates resulted in marked inhibition of the developments of bands in the Western blots. Furthermore, plasma IgG antibodies from adult human volunteers intranasally inoculated with S. pneumoniae 6B revealed enhanced S. mitis-specific IgG titers compared with the pre-inoculation samples. Using an on-chip protein microarray representing a number of selected membrane and extracellular S. pneumoniae proteins, we identified choline-binding protein D (CbpD), cell division protein (FtsH), and manganese ABC transporter or manganese-binding adhesion lipoprotein (PsaA) as common targets of the rabbit IgG antibodies raised against S. mitis or S. pneumoniae. Cumulatively, these findings provide evidence on the antibody-mediated cross-reactivity of proteins from S. mitis and S. pneumoniae, which may have implications for development of effective and wide-range pneumococcal vaccines.

We report a case of Streptococcus mitis endocarditis associated with early gastric carcinoma. A 71-year-old man who had been diagnosed with aortic regurgitation (AR) two years previously was referred for valve surgery and evaluation of elevated inflammatory markers. Four months previously, atrophic gastritis, early gastric adenocarcinoma, and colon polyp had been identified in the patient during endoscopy. However, Helicobacter pylori testing was negative. On admission, he had no dental diseases or recent oral procedures. Echocardiography demonstrated severe AR and mobile vegetation on the aortic valve. Magnetic resonance imaging revealed cerebral embolism and spondylodiscitis. Blood cultures grew Streptococcus mitis. At surgery, destruction of the left cusp with vegetation and a perforation of the non-coronary cusp were found; in addition, aortic valve replacement was performed. Although the association between Streptococcus bovis bacteremia and colon neoplasm is well recognized, the association between Streptococcus mitis endocarditis and gastrointestinal carcinoma should also be kept in mind.

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 .

Endophthalmitis is an acute inflammatory intraocular condition that can cause permanent vision loss. The treatment strategy and visual outcome partly depend on the identification of the agents of pathogens. In this study, metagenomic sequencing was conducted to investigate the microbial and antibiotic resistance genes (ARGs) composition in the vitreous (intraocular body fluid) of an endophthalmitis patient, who progressed rapidly and accompanied by severe pain. Metagenomic sequencing data revealed that the vitreous sample was predominated by Streptococcus, with a low-diversity microbiome in the vitreous. This strain harbor's the ARGs mainly against beta-lactam, macrolide-lincosamide-streptogramin, and multidrug. Additionally, metagenome-assembled genome sequence of Streptococcus sp. v1. nov. was identified. The Tetra Correlation Search (TCS) analysis uncovered that the closest relative of the Streptococcus sp. v1. nov. was Streptococcus mitis SK321. Pan/core genome analysis for Streptococcus sp. v1. nov. and TCS top 25 hits strains revealed that most unique genes of Streptococcus sp. v1. nov. were linked to ATP-binding cassette transport system, which could indicate unique virulence and pathogenic potentials of Streptococcus sp. v1. nov. In addition, a total of 7 virulence factors were identified, and the overwhelming of them were classified into "offensive virulence factors". The high pathogenicity of Streptococcus sp. v1. nov. could be a reason for the patient's rapid disease progression. Our study was first isolated an ocular pathogen with highly virulent based on metagenomic sequencing and bioinformatics analysis, which has important reference value for revealing the composition and genome characteristics of pathogens in endophthalmitis patient in the future., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

This study investigated how the physiological states of Aggregatibacter actinomycetemcomitans (Aa) and Streptococcus mitis affect their intracellular invasion capabilities and the resulting host cell responses. The physiological states included two forms of planktonic states, floating or sedimented (by centrifugation) and the biofilm state (with centrifugation). Confluent epithelial Ca9-22 cells were challenged with floating or sedimented planktonic cultures, or with 24-h biofilms for 3 h. The results show that intracellular invasion efficiencies were clearly affected by the bacterial physiological states. For both bacterial species, the sedimented-cells displayed 2-10 times higher invasion efficiency than the floating-cells (p < 0.05). The invasion efficiency of Aa biofilms was three fold lower than sedimented cells, whereas those of S. mitis biofilms were similar to sedimented cells. Unlike invasion, the metabolic activities of Ca9-22 were unaffected by different bacterial physiological states. However, Aa biofilms induced higher IL-1β expression than planktonic cultures. In conclusion, different bacterial physiological states can affect the outcomes of (in vitro) host-microbe interaction in different ways. [ABSTRACT FROM AUTHOR]

Background: In streptococci of the mitis group, competence for natural transformation is a transient physiological state triggered by competence stimulating peptides (CSPs). Although low transformation yields and the absence of a widespread functional competence system have been reported for Streptococcus mitis, recent studies revealed that, at least for some strains, high efficiencies can be achieved following optimization protocols. To gain a deeper insight into competence in this species, we used RNA-seq, to map the global CSP response of two transformable strains: the type strain NCTC12261T and SK321. Results: All known genes induced by ComE in Streptococcus pneumoniae, including sigX, were upregulated in the two strains. Likewise, all sets of streptococcal SigX core genes involved in extracellular DNA uptake, recombination, and fratricide were upregulated. No significant differences in the set of induced genes were observed when the type strain was grown in rich or semi-defined media. Five upregulated operons unique to S. mitis with a SigX-box in the promoter region were identified, including two specific to SK321, and one specific to NCTC12261T. Two of the strain-specific operons coded for different bacteriocins. Deletion of the unique S. mitis sigX regulated genes had no effect on transformation. Conclusions: Overall, comparison of the global transcriptome in response to CSP shows the conservation of the ComE and SigX-core regulons in competent S. mitis isolates, as well as species and strain-specific genes. Although some S. mitis exhibit truncations in key competence genes, this study shows that in transformable strains, competence seems to depend on the same core genes previously identified in S. pneumoniae. [ABSTRACT FROM AUTHOR]

Current vaccines against Streptococcus pneumoniae, a bacterial species that afflicts people by causing a wide spectrum of diseases, do not protect against all pneumococcal serotypes. Thus, alternative vaccines to fight pneumococcal infections that target common proteins are under investigation. One promising strategy is to take advantage of immune cross-reactivity between commensal and pathogenic microbes for cross-protection. In this study, we examined the antibody-mediated cross-reactivity between S. pneumoniae and Streptococcus mitis, a commensal species closely related to S. pneumoniae. Western blot analysis showed that rabbit antisera raised against S. mitis reacted with multiple proteins of virulent S. pneumoniae strains (6B, TIGR4, and D39). Rabbit anti-S. pneumoniae IgG antibodies also showed binding to S. mitis antigens. Incubation of rabbit antisera raised against S. mitis with heterologous or homologous bacterial lysates resulted in marked inhibition of the developments of bands in the Western blots. Furthermore, plasma IgG antibodies from adult human volunteers intranasally inoculated with S. pneumoniae 6B revealed enhanced S. mitis-specific IgG titers compared with the pre-inoculation samples. Using an on-chip protein microarray representing a number of selected membrane and extracellular S. pneumoniae proteins, we identified choline-binding protein D (CbpD), cell division protein (FtsH), and manganese ABC transporter or manganese-binding adhesion lipoprotein (PsaA) as common targets of the rabbit IgG antibodies raised against S. mitis or S. pneumoniae. Cumulatively, these findings provide evidence on the antibody-mediated cross-reactivity of proteins from S. mitis and S. pneumoniae, which may have implications for development of effective and wide-range pneumococcal vaccines. [ABSTRACT FROM AUTHOR]

Background Subdural empyema can present as a spinal subdural empyema (SSE) or a cranial subdural empyema (CSE). Although they differ somewhat in epidemiology, etiology, pathophysiology, and symptomatology and occur separately, they rarely manifest together. The aim of this article is to review the literature concerning the clinical presentation, clinical course, and treatment options for managing concurrently occurring SSE and CSE. Methods The literature in the Medline database was reviewed with key words including but not limited to subdural empyema, retroclival empyema, and Streptococcus mitis . No similar reports were found in the database involving infection with this type of microorganism in this anatomical region. Results Only 3 cases with concurrent CSE and SSE were found in the literature caused by various etiologic agents. Two of the patients recovered with no neurologic deficit, whereas one fatality was reported. One new illustrative case caused by Streptococcus mitis is also presented. Conclusions CSE and SSE are neurosurgical emergencies, often requiring prompt surgical evacuation. Although very rare, Streptococcus mitis can cause spinal subdural empyema or retroclival abscesses. Natural history of this disease is grave without treatment. Delays in diagnosis and treatment are directly related to mortality and severe morbidity in patients with intracranial and spinal subdural empyema. Prompt recognition and treatment are essential to preclude severe neurologic disabilities or in rare cases a fatal outcome. A treatment paradigm for cranio-spinal empyema is proposed. [ABSTRACT FROM AUTHOR]

Background. Endophthalmitis post cataract surgery is rare, but the incidence and complications are higher in diabetics. Objectives. We present 3 diabetic patients who underwent cataract surgery and developed endophthalmitis postoperatively. Material and methods. This is a retrospective case series of diabetic patients who underwent cataract surgery and developed endophthalmitis postoperatively between September 2015 and August 2016. The medical records were retrieved from the system, and data was collected. Results. The patients eventually had different visual outcomes depending on the severity of endophthalmitis. Case 1. The patient developed delayed subtle postoperative endophthalmitis at 8 weeks post cataract operation, with underlying foot cellulitis and poor blood sugar control. The patient responded well to topical and systemic antibiotics and stabilization of blood sugar. Case 2. The patient presented with delayed postoperative endophthalmitis secondary to a suture abscess of the cataract wound at 7 months post implantation of an anterior chamber intraocular lens. There was complete resolution of the infection after administration of topical, intravitreal and systemic antibiotics, with a good control of blood sugar. Case 3. The patient presented with acute severe postoperative endophthalmitis with the presence of hypopyon at day 5 following cataract surgery. There were no obvious risk factors besides poor control of blood sugar, but Streptococcus mitis was isolated from the vitreous specimen. The endophthalmitis worsened in spite of topical, intravitreal and systemic antibiotics, as well as vitrectomy. Evisceration was eventually performed for the painful blind eye. Conclusions. Although endophthalmitis following cataract surgery is rare, the incidence and complications are much higher in diabetic patients. [ABSTRACT FROM AUTHOR]

The genetically diverse viridans group streptococci (VGS) are increasingly recognized as the cause of a variety of human diseases. We used a recently developed multilocus sequence analysis scheme to define the species of 118 unique VGS strains causing bacteremia in patients with cancer; Streptococcus mitis (68 patients) and S. oralis (22 patients) were the most frequently identified strains. Compared with patients infected with non–S. mitis strains, patients infected with S. mitis strains were more likely to have moderate or severe clinical disease (e.g., VGS shock syndrome). Combined with the sequence data, whole-genome analyses showed that S. mitis strains may more precisely be considered as >2 species. Furthermore, we found that multiple S. mitis strains induced disease in neutropenic mice in a dose-dependent fashion. Our data define the prominent clinical effect of the group of organisms currently classified as S. mitis and lay the groundwork for increased understanding of this understudied pathogen.