Insights into the enigma of oral streptococci in carcinogenesis.

SUMMARYThe genus Streptococcus consists of a taxonomically diverse group of Gram-positive bacteria that have earned significant scientific interest due to their physiological and pathogenic characteristics. Within the genus Streptococcus, viridans group streptococci (VGS) play a significant role in the oral ecosystem, constituting approximately 80% of the oral biofilm. Their primary role as pioneering colonizers in the oral cavity with multifaceted interactions like adherence, metabolic signaling, and quorum sensing contributes significantly to the complex dynamics of the oral biofilm, thus shaping oral health and disease outcomes. Perturbations in oral streptococci composition drive oral dysbiosis and therefore impact host-pathogen interactions, resulting in oral inflammation and representing VGS as an opportunistic pathogen. The association of oral streptococci in tumors across distant organs, spanning the esophagus, stomach, pancreas, and colon, illuminates a potential association between oral streptococci, inflammation, and tumorigenesis. This finding emphasizes the need for further investigations into the role of oral streptococci in mucosal homeostasis and their involvement in carcinogenesis. Hence, here, we review the significance of oral streptococci in biofilm dynamics and how the perturbation may impact mucosal immunopathogenesis in the context of cancer, with a vision of exploiting oral streptococci for cancer intervention and for the development of non-invasive cancer diagnosis.

Biofilm Interactions of Candida albicans and Mitis Group Streptococci in a Titanium-Mucosal Interface Model.

Streptococci from the mitis group (represented mainly by Streptococcus mitis, Streptococcus oralis, Streptococcus sanguinis, and Streptococcus gordonii) form robust biofilms with Candida albicans in different experimental models. These microorganisms have been found in polymicrobial biofilms forming on titanium biomaterial surfaces in humans with peri-implant disease. The purpose of this work was to study mutualistic interactions in biofilms forming on titanium and their effect on the adjacent mucosa, using a relevant infection model. Single and mixed biofilms of C. albicans and each Streptococcus species were grown on titanium disks. Bacterial and fungal biovolume and biomass were quantified in these biofilms. Organotypic mucosal constructs were exposed to preformed titanium surface biofilms to test their effect on secretion of proinflammatory cytokines and cell damage. C. albicans promoted bacterial biofilms of all mitis Streptococcus species on titanium surfaces. This relationship was mutualistic since all bacterial species upregulated the efg1 hypha-associated gene in C. albicans Mixed biofilms caused increased tissue damage but did not increase proinflammatory cytokine responses compared to biofilms comprising Candida alone. Interestingly, spent culture medium from tissues exposed to titanium biofilms suppressed Candida growth on titanium surfaces.IMPORTANCE Our findings provide new insights into the cross-kingdom interaction between C. albicans and Streptococcus species representative of the mitis group. These microorganisms colonize titanium-based dental implant materials, but little is known about their ability to cause inflammation and damage of the adjacent mucosal tissues. Using an in vitro biomaterial-mucosal interface infection model, we showed that mixed biofilms of each species with C. albicans enhance tissue damage. One possible mechanism for this effect is the increased fungal hypha-associated virulence gene expression we observed in mixed biofilms with these species. Interestingly, we also found that the interaction of multispecies biofilms with organotypic mucosal surfaces led to the release of growth-suppressing mediators of Candida, which may represent a homeostatic defense mechanism of the oral mucosa against fungal overgrowth. Thus, our findings provide novel insights into biofilms on biomaterials that may play an important role in the pathogenesis of mucosal infections around titanium implants.

Strain-level analysis of gut-resident pro-inflammatory viridans group Streptococci suppressed by long-term cotrimoxazole prophylaxis among HIV-positive children in Zimbabwe.

Antimicrobials have become a mainstay of healthcare in the past century due to their activity against pathogens. More recently, it has become clear that they can also affect health via their impact on the microbiota and inflammation. This may explain some of their clinical benefits despite global increases in antimicrobial resistance (AMR) and reduced antimicrobial effectiveness. We showed in a randomized controlled trial of stopping versus continuing cotrimoxazole prophylaxis among HIV-positive Zimbabwean children taking antiretroviral therapy (ART), that continuation of cotrimoxazole persistently suppressed gut-resident viridans group streptococcal species (VGS) that were associated with intestinal inflammation. In this addendum, we provide a broader overview of how antibiotics can shape the microbiota and use high read-depth whole metagenome sequencing data from our published study to investigate whether (i) the impact of cotrimoxazole on gut VGS and (ii) VGS associated inflammation, is attributable to strain-level variability. We focus on S. salivarius, the VGS species that was most prevalent in the cohort and for which there was sufficient genome coverage to differentiate strains. We demonstrate that suppression of S. salivarius by cotrimoxazole is not strain specific, nor did stool concentration of the pro-inflammatory mediator myeloperoxidase vary by S. salivarius strain. We also show that gut-resident S. salivarius strains present in this study population are distinct from common oral strains. This is the first analysis of how cotrimoxazole prophylaxis used according to international treatment guidelines for children living with HIV influences the gut microbiome at the strain-level. We also provide a detailed review of the literature on the mechanisms by which suppression of VGS may act synergistically with cotrimoxazole's anti-inflammatory effects to reduce gut inflammation. A greater understanding of the sub-clinical effects of antibiotics offers new insights into their responsible clinical use.

Epidemiological and clinical characteristics of Streptococcus tigurinus endocarditis.

BACKGROUND: Streptococcus tigurinus was recently described as a new streptococcal species within the viridans group streptococci (VGS). The objectives of the present work were to analyse the clinical and microbiological characteristics of S. tigurinus isolated from patients with bacteraemias, to determine the prevalence of S. tigurinus among VGS endocarditis in Spain, and to compare the clinical characteristics and outcomes of endocarditis caused by S. tigurinus and other VGS. METHODS: Retrospective nationwide study, performed between 2008 and 2016 in 9 Spanish hospitals from 7 different provinces comprising 237 cases of infective endocarditis. Streptococcal isolates were identified by sequencing fragments of their 16S rRNA, sodA and groEL genes. Clinical data of patients with streptococcal endocarditis were prospectively collected according to a pre-established protocol. RESULTS: Patients with endocarditis represented 7/9 (77.8%) and 26/86 (30.2%) of the bacteraemias caused by S. tigurinus and other VGS, respectively (p < 0.001), in two of the hospital participants. Among patients with streptococcal endocarditis, 12 different Streptococcus species were recognized being S. oralis, S. tigurinus and S. mitis the three more common. No relevant statistical differences were observed in the clinical characteristics and outcomes of endocarditis caused by the different VGS species. CONCLUSIONS: In this multicenter study performed in Spain, S. tigurinus showed a higher predilection for the endocardial endothelium as compared to other VGS. However, clinical characteristics and outcomes of endocarditis caused by S. tigurinus did not significantly differ from endocarditis caused by other oral streptococci.

Relapsing bloodstream infections during treatment of acute leukemia.

Acute leukemia (AL) patients may experience more than one episode of bloodstream infection (BSI) caused by the same pathogen during the entire chemotherapy program. In order to identify factors influencing BSI recurrence (R-BSI) during subsequent phases of treatment, we analyzed all BSIs occurring to consecutively treated AL patients during a period of active epidemiologic surveillance at our institution between 2004 and 2011. Two hundred and fifty BSIs were observed in 138 patients receiving more than 1 cycle of chemotherapy. BSI due to the same pathogen recurred in 39/138 (28.3 %) patients. Gram-negative rods (GNRs) accounted for 59.6 % and Gram-positive cocci (GPCs) for 34.4 % of BSI. Four pathogens were involved in R-BSI: Escherichia coli, Pseudomonas aeruginosa, coagulase-negative staphylococci, and Streptococcus viridans. GNRs were significantly more frequent among R-BSI compared to non-relapsing BSI (nR-BSI) [69/94 (73.4 %) vs 70/156 (50.6 %), p < 0.0001]; in particular, E. coli accounted for 67 % of R-BSI vs 32.1 % of nR-BSI (p < 0.0001). Receiving more than four chemotherapy courses and having an extended spectrum ß-lactamase (ESBL)-producing E. coli BSI at any time of treatment were significantly associated to R-BSI. A trend toward a higher mortality among R-BSI patients in comparison with nR-BSI was observed (17.9 and 7.1 %, respectively, p = 0.12). Among AL patients, R-BSI is a frequent phenomenon, which may contribute to the shift of epidemiology toward GNR and to a higher mortality. This should significantly impact the strategies of antibiotic prophylaxis and treatment in patients with AL.

Facial paralysis and mediastinitis due to odontogenic infection and poor prognosis.

Cervical necrotizing fasciitis (CNF) is a rare, rapidly advancing infection that involves the skin, the subcutaneous fibrofatty tissue, as well as the superficial and deep fascia and can cause life-threatening complications. The most frequent initiating factors in the head and neck region are a primary odontogenic infection, a peritonsillar infection, as well as posttraumatic or iatrogenic skin and mucosal injuries. Necrotizing fasciitis (NF) can expand within hours, and the reported mortality rate is up to 75% with delay interference. If the patients have any risk factors, poor prognosis can be seen. In this study, 1 patient with CNF with a history of peritonsillar infection and 2 patients with CNF who had a history of odontogenic infection with spreading to the temporal region and the mediastinum were described, with information of the literature and a clinical experience that was gained from 5 patients with NF who were seen at our clinic in the recent year, despite the fact that CNF was not seen up to last year. None of the patients had any risk factors. One of them had a worse clinical state with ascending infection to the temporal region, cranial nerve paralysis, and descending necrotizing mediastinitis, but he recovered from NF. After the oral intake began, dyspnea due to aspiration was seen and he died because of sepsis and multiorgan dysfunction. We aimed to attract attention to the importance of dental pathologies and increased mortality in a healthy patient.

Synergistic interaction between Candida albicans and commensal oral streptococci in a novel in vitro mucosal model.

Candida albicans is a commensal colonizer of the gastrointestinal tract of humans, where it coexists with highly diverse bacterial communities. It is not clear whether this interaction limits or promotes the potential of C. albicans to become an opportunistic pathogen. Here we investigate the interaction between C. albicans and three species of streptococci from the viridans group, which are ubiquitous and abundant oral commensal bacteria. The ability of C. albicans to form biofilms with Streptococcus oralis, Streptococcus sanguinis, or Streptococcus gordonii was investigated using flow cell devices that allow abiotic biofilm formation under salivary flow. In addition, we designed a novel flow cell system that allows mucosal biofilm formation under conditions that mimic the environment in the oral and esophageal mucosae. It was observed that C. albicans and streptococci formed a synergistic partnership where C. albicans promoted the ability of streptococci to form biofilms on abiotic surfaces or on the surface of an oral mucosa analogue. The increased ability of streptococci to form biofilms in the presence of C. albicans could not be explained by a growth-stimulatory effect since the streptococci were unaffected in their growth in planktonic coculture with C. albicans. Conversely, the presence of streptococci increased the ability of C. albicans to invade organotypic models of the oral and esophageal mucosae under conditions of salivary flow. Moreover, characterization of mucosal invasion by the biofilm microorganisms suggested that the esophageal mucosa is more permissive to invasion than the oral mucosa. In summary, C. albicans and commensal oral streptococci display a synergistic interaction with implications for the pathogenic potential of C. albicans in the upper gastrointestinal tract.

Is repetitive intraoperative splash basin use a source of bacterial contamination in total joint replacement?

Splash basins are used in arthroplasty cases to wash instruments. Several studies in the literature have shown these basins being a potential source of bacterial infection. This study assesses the risk of contamination of intraoperative splash basins used to wash and store instruments. A total of 46 random clean primary arthroplasty cases (32 hips, 13 knees, and 1 unicondylar knee) were studied by taking cultures of sterile splash basins as soon as they are opened (controls) and again at wound closure after instruments and debris have come into contact with the sterile water. All cultures were taken with sterile culture swabs and sent to the laboratory for aerobic, anaerobic, and fungal culture. Outcome measured was any positive culture. A total of 92 cultures from 46 cases were tested. Only 1 (2.17%) control culture, which grew Streptococcus viridans, was positive for bacterial growth. One of 46 samples (2.17%) taken at wound closure was positive for coagulase-negative Staphylococcus. Mean time between basin opening and wound closure was 180±45 minutes. For the 1 infected sample taken at the conclusion of the case, it was 240 minutes. Previous studies show contamination rates as high as 74% for splash basins used intraoperatively. Our study contradicts the belief that splash basins are a high source of infection, with only 2.17% of basins showing contamination. Splash basins can be a potential source of contamination, but the risk is not as high as previously cited in the orthopedic literature.

Viridans streptococcal bacteremia-related encephalopathy in childhood with malignancy.

Viridans streptococcal bacteremia is a prognostic factor in pediatric patients with malignant disease accompanied by severe neutropenia. Here the authors describe 4 patients with viridans streptococcal bacteremia-related encephalopathy who showed serious complications, which included seizures and loss of consciousness. Therapy for relief of brain edema on seizures was started quickly, and included the administration of midazolam, dexamethasone, and mannitol with antimicrobial therapy. The treatment was successfully completed without sequelae. The authors registered 28 episodes of viridans streptococcal bacteremia in their hospital. The peak of serum C-reaction protein was higher in viridans streptococcal bacteremia patients with encephalopathy than in those without encephalopathy. The authors concluded that viridans streptococcal bacteremia can induce encephalopathy in pediatric patients with malignancy and that it is crucial to establish an accurate diagnosis and initiate therapy as soon as possible.

Invasion of human aortic endothelial cells by oral viridans group streptococci and induction of inflammatory cytokine production.

Oral viridans group streptococci are the major commensal bacteria of the supragingival oral biofilm and have been detected in human atheromatous plaque. Atherosclerosis involves an ongoing inflammatory response, reportedly involving chronic infection caused by multiple pathogens. The aim of this study was to examine the invasion of human aortic endothelial cells (HAECs) by oral viridans group streptococci and the subsequent cytokine production by viable invaded HAECs. The invasion of HAECs by bacteria was examined using antibiotic protection assays and was visualized by confocal scanning laser microscopy. The inhibitory effects of catalase and cytochalasin D on the invasion of HAECs were also examined. The production of cytokines by invaded or infected HAECs was determined using enzyme-linked immunosorbent assays, and a real-time polymerase chain reaction method was used to evaluate the expression of cytokine messenger RNA. The oral streptococci tested were capable of invading HAECs. The number of invasive bacteria increased with the length of the co-culture period. After a certain co-culture period, some organisms were cytotoxic to the HAECs. Catalase and cytochalasin D inhibited the invasion of HAECs by the organism. HAECs invaded by Streptococcus mutans Xc, Streptococcus gordonii DL1 (Challis), Streptococcus gordonii ATCC 10558 and Streptococcus salivarius ATCC 13419 produced more cytokine(s) (interleukin-6, interleukin-8, monocyte chemoattractant protein-1) than non-invaded HAECs. The HAECs invaded by S. mutans Xc produced the largest amounts of cytokines, and the messenger RNA expression of cytokines by invaded HAECs increased markedly compared with that by non-invaded HAECs. These results suggest that oral streptococci may participate in the pathogenesis of atherosclerosis.

Activation of human valve interstitial cells by a viridians streptococci modulin induces chemotaxis of mononuclear cells.

Infective endocarditis is characterized by inflammatory infiltrates of mononuclear cells in infected cardiac valve leaflets. To delineate the role of valve interstitial cells (VICs) in leukocyte recruitment, we stimulated human VICs with glucosyltransferase, a modulin from viridians streptococci. Interstitial cells were activated directly by glucosyltransferase in a dose-dependent manner through concerted mitogen-activated protein kinase and nuclear factor-kappaB signaling pathways; activation resulted in up-regulation of synthesis and release of interleukin-6, interleukin-8, or monocyte chemoattractant protein-1 and enhanced transwell migration of U937 monocytic cells or primary mononuclear cells. The expression of glucosyltransferases and activation of VICs (nuclear localization of RelA) were detected in a rat model of experimental endocarditis. Proinflammatory cytokines also were detected in VICs from diseased human autopsy specimens but not in VICs from normal specimens. These results indicate that interstitial cells in the cardiac valve can be activated directly by bacterial modulins to recruit and retain mononuclear cells, likely contributing to the persistent inflammation characteristic of infective endocarditis.

Potential oral health benefits of cranberry.

In the past decade, cranberry extracts have been attracting ever-growing attention by dental researchers. The potential benefits of cranberry components in reducing oral diseases, including dental caries and periodontitis, are discussed in this review. A non-dialysable cranberry fraction enriched in high molecular weight polyphenols has very promising properties with respect to cariogenic and periodontopathogenic bacteria, as well as to the host inflammatory response and enzymes that degrade the extracellular matrix. Cranberry components are potential anti-caries agents since they inhibit acid production, attachment, and biofilm formation by Streptococcus mutans. Glucan-binding proteins, extracellular enzymes, carbohydrate production, and bacterial hydrophobicity, are all affected by cranberry components. Regarding periodontal diseases, the same cranberry fraction inhibits host inflammatory responses, production, and activity of enzymes that cause the destruction of the extracellular matrix, biofilm formation, and adherence of Porphyromonas gingivalis, and proteolytic activities and coaggregation of periodontopathogens. The above-listed effects suggest that cranberry components, especially those with high molecular weight, could serve as bioactive molecules for the prevention and/or treatment of oral diseases.

Perspectives on the 2007 AHA Endocarditis Prevention Guidelines.

From 2005 to 2007, the American Heart Association convened a consensus panel of experts to revisit the guidelines for the premedication of patients with cardiac defects prior to dental treatment. Presented in this article is a summary of the guidelines as well as commentary on the process.

Association of a high-molecular weight arginine-binding protein of Fusobacterium nucleatum ATCC 10953 with adhesion to secretory immunoglobulin A and coaggregation with Streptococcus cristatus.

INTRODUCTION: Fusobacterium nucleatum coaggregates with a diverse range of bacterial species, and binds to host tissues and proteins such as immunoglobulin. These interactions may support the attachment of a variety of organisms to oral surfaces and can facilitate the invasion of soft tissues. We hypothesized that coaggregation with streptococci and immunoglobulin binding may occur by a common adhesin sensitive to l-arginine. METHODS: Repeated mixing of F. nucleatum with non-immune secretory immunoglobulin A (S-IgA) and recovery of non-agglutinating cells isolated a spontaneous mutant (isolate 21) of F. nucleatum that was defective in S-IgA binding. Wild-type and mutant F. nucleatum were compared by coaggregation and adhesion assays. RESULTS: Isolate 21 exhibited significantly reduced S-IgA binding and coaggregation with oral streptococci but not with Porphyromonas gingivalis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the mutant was deficient compared to wild-type for a single protein of approximately 360 kilodaltons. The corresponding protein was isolated from wild-type F. nucleatum protein preparations by coprecipitation with arginine-agarose beads. This protein was able to bind both Streptococcus cristatus and S-IgA. Mass spectrometry analysis indicated that this protein was closely related to putative autotransporter proteins in other F. nucleatum strains and was a 100% match to the deduced amino acid sequence of a 10,638-base-pair open reading frame in the incomplete genome sequence of F. nucleatum ATCC 10,953. Peptides identified by MS-MS analysis spanned most of the predicted amino acid sequence, suggesting that the mature protein is not subject to postsecretory cleavage. CONCLUSION: Coaggregation represents a novel function within the autotransporter class of proteins, which are often associated with virulence.

Inflammatory immune responses by water-insoluble alpha-glucans.

Water-insoluble alpha-glucans are synthesized from sucrose by glucosyltransferase-I of mutans streptococci and play an important role in the development of dental plaque. Several types of beta-glucans in fungal cell wall components and water-soluble alpha-glucans from Streptococcus mutans are known to modulate innate immunity. In the present study, we investigated whether water-insoluble alpha-glucans also induced inflammatory innate immune responses. Our results showed that water-insoluble alpha-glucans synthesized by Streptococcus sobrinus activated mouse peritoneal exudate macrophages to produce pro-inflammatory cytokines. The immunological responses were not due to contamination by sucrose, water-soluble alpha-glucan, lipopolysaccharide, or peptidoglycan. Furthermore, human monocytes stimulated by water-insoluble alpha-glucans produced TNF-alpha and IL-8, while human polymorphonuclear cells were activated by water-insoluble alpha-glucans, resulting in chemotaxis and hydrogen peroxide production. The results demonstrated that water-soluble alpha-glucans modulate macrophage- and granulocyte-induced inflammatory immune responses, and suggest that inflammation induced by those alpha-glucans is associated with the development of periodontal diseases.

Secretory IgA, salivary peroxidase, and catalase-mediated microbicidal activity during hydrogen peroxide catabolism in viridans streptococci: pathogen coaggregation.

Viridans streptococci can kill methicillin-resistant Staphylococcus aureus (MRSA) through the production of hydrogen peroxide (H2O2). However, several hundred viridans streptococci cells are necessary to kill 1 cfu of MRSA. We analyzed the potency of bactericidal and fungicidal effector molecules induced by catabolism of H2O2 in the oral cavity. Secretory IgA (SIgA) and an unidentified salivary component bound Streptococcus sanguinis, a viridans streprococcus, and MRSA into coaggregates. In these coaggregates, salivary peroxidase and the MRSA catalase produced singlet molecular oxygen (1O2) from H2O2 produced by viridans streptococci. SIgA converted 1O2 into ozone, which has potent bactericidal and fungicidal activity. We calculated that <10 cfu of Streptococcus sanguinis were necessary to kill 1 cfu of MRSA in the coaggregate. SIgA, Aspergillus niger catalase, and H2O2 in saliva killed Candida albicans, which is highly resistant to reagent H2O2. Together with indigenous bacteria and innate immunity, SIgA potentially constitutes a novel system that may sustain oral homeostasis.

Streptococcus massiliensis sp. nov., isolated from a patient blood culture.

An unidentified strain of the viridans group of streptococci was isolated from a human blood sample. It was distinguished from all other recognized species of the Streptococcus sanguinis group by several biochemical characteristics. Phylogenetic analysis based on 16S rRNA gene sequence comparisons clustered this strain with Streptococcus ferus (mutans group) but phylogenetic analysis based on rpoB and sodA gene sequence comparisons included it in the S. sanguinis group. The isolate showed 95.4 and 95.2 % 16S rRNA gene sequence similarity to S. ferus and S. sanguinis, respectively, confirming it as belonging to a novel taxon, for which the name Streptococcus massiliensis sp. nov. is proposed. The type strain is 4401825T (=CIP 108498T=CCUG 49690T).

Streptococcus sinensis may react with Lancefield group F antiserum.

Lancefield group F streptococci have been found almost exclusively as members of the 'Streptococcus milleri' group, although they have been reported very occasionally in some other streptococcal species. Among 302 patients with bacteraemia caused by viridans streptococci over a 6-year period, three cases were caused by Streptococcus sinensis (type strain HKU4T, HKU5 and HKU6). All three patients had infective endocarditis complicating their underlying chronic rheumatic heart diseases. Gene sequencing showed no base differences between the 16S rRNA gene sequences of HKU5 and HKU6 and that of HKU4T. All three strains were Gram-positive, non-spore-forming cocci arranged in chains. All grew on sheep blood agar as alpha-haemolytic, grey colonies of 0.5-1 mm in diameter after 24 h incubation at 37 degrees C in ambient air. Lancefield grouping revealed that HKU5 and HKU6 were Lancefield group F, but HKU4T was non-groupable with Lancefield groups A, B, C, D, F or G antisera. HKU4T was identified by the Vitek system (GPI), API system (20 STREP) and ATB system (ID32 STREP) as 99 % Streptococcus intermedius, 51.3 % S. intermedius and 99.9 % Streptococcus anginosus, respectively. Using the same tests, HKU5 was identified as 87 % Streptococcus sanguinis/Streptococcus gordonii, 59 % Streptococcus salivarius and 99.6 % S. anginosus, respectively, and HKU6 as 87 % S. sanguinis/S. gordonii, 77 % Streptococcus pneumoniae and 98.3 % S. anginosus, respectively. The present data revealed that a proportion of Lancefield group F streptococci could be S. sinensis. Lancefield group F streptococci should not be automatically reported as 'S. milleri'.