Classification and identification of the viridans streptococci

Streptococcus intermedius: an underestimated pathogen in brain infection?

Streptococcus intermedius is an oral commensal organism belonging to the Streptococcus anginosus group (SAG). S. intermedius causes periodontitis as well as invasive, pyogenic infection of the central nervous system, pleural space or liver. Compared with other SAG organisms, S. intermedius has a higher mortality as well as a predilection for intracranial infection, suggesting it is likely to possess virulence factors that mediate specific interactions with the host resulting in bacteria reaching the brain. The mechanisms involved are not well described. Intracranial suppuration (ICS) due to S. intermedius infection can manifest as an abscess within the brain parenchyma, or a collection of pus (empyema) in the sub- or extra-dural space. These infections necessitate neurosurgery and prolonged antibiotic treatment and are associated with a considerable burden of morbidity and mortality. The incidence of ICS is increasing in several settings, with SAG species accounting for an increasing proportion of cases. There is a paucity of published literature regarding S. intermedius pathogenesis as well as few published genomes, hampering molecular epidemiological research. This perspective evaluates what is known about the clinical features and pathogenesis of ICS due to S. intermedius and explores hypothetical explanations why the incidence of these infections may be increasing.

EvoraPlus Oral Probiotic Tablet: New paradigm for Caries Prevention in Children

Background

According to the World Health Organization, probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit to the host. The use of oral probiotics in children to improve oral health may lead to nonpathogenic bacteria replacing cariogenic bacteria. The Evora Plus oral probiotics tablet is the first such oral probiotics tablet containing a proprietary blend of three select species of naturally occurring oral bacteria, each with a specific function for maintaining a healthy oral environment. These strains include Streptococcus oralis KJ3sm, Streptococcus uberis KJ2sm, and Streptococcus rattus JH145.

Aim

To compare the levels of salivary total bacterial count, salivary pH levels, and salivary S. mutans count before and after consumption of the Evora Plus oral probiotic tablet.

Materials and methods

Around 40 caries-free schoolchildren from Daksh International School, Gadarwara, Madhya Pradesh, India, aged 12-14 years, were selected and divided equally into two groups-group A, in which total salivary bacterial count and pH were evaluated, and group B, in which salivary S. mutans count and pH were evaluated. These groups were further subdivided into group A1 and group B1, which served as the control groups not receiving the Evora Plus oral probiotic tablet, and group A2 and group B2, which were the test groups consuming the Evora Plus oral probiotic tablet for 30 days. Assessment of salivary samples for total bacterial count was done at baseline and after 30 days for groups A1 and B1. Salivary pH estimation was done at baseline and after 30 days for the entire group, and salivary S. mutans count was done at baseline and after 30 days for groups A2 and B2. Salivary pH level was checked using a digital pH meter; nutrient agar was used for salivary total bacterial count, while Mitis salivarius bacitracin agar was used for salivary S. mutans count. The number of colonies was counted and subjected to statistical analysis using unpaired and paired Student's t-test.

Results

The study showed a significant reduction in salivary total bacterial count and salivary S. mutans counts, as well as a significant increase in salivary pH after 30 days in the Evora Plus oral probiotic group compared with the group not receiving the Evora Plus oral probiotic tablet.

Conclusion

Cariogenic microorganisms could be reduced by an oral probiotic formulation. Thus, the use of the Evora Plus oral probiotic tablet could be recommended for the prevention of enamel demineralization.

How to cite this article

Mishra A, Saurabh S. EvoraPlus Oral Probiotic Tablet: New paradigm for Caries Prevention in Children. Int J Clin Pediatr Dent 2024;17(9):1044-1048.

Brain Abscess Caused by Oral Cavity Bacteria: A Nationwide, Population-based Cohort Study

BACKGROUND

Oral cavity bacteria are the most frequent etiology of brain abscess. Yet, data on the clinical presentation and outcome are scarce.

METHODS

We performed a nationwide, population-based study comprising all adults (aged ≥18 years) with brain abscess due to oral cavity bacteria in Denmark from 2007 through 2020. Prognostic factors for unfavorable outcome (Glasgow outcome scale, 1-4) were examined using modified Poisson regression to compute adjusted relative risks (RRs) with 95% confidence intervals (CIs).

RESULTS

Among 287 identified patients, the median age was 58 years (interquartile range, 47-66), and 96 of 287 (33%) were female. Preexisting functional impairment was absent or mild in 253 of 280 (90%), and risk factors for brain abscess included immunocompromise in 95 of 287 (33%), dental infection in 68 of 287 (24%), and ear-nose-throat infection in 33 of 287 (12%). Overall, a neurological deficit was present in 246 of 276 (86%) and in combination with headache and fever in 64 of 287 (22%). Identified microorganisms were primarily the Streptococcus anginosus group, Fusobacterium, Actinomyces, and Aggregatibacter spp., and 117 of 287 (41%) were polymicrobial. Unfavorable outcome occurred in 92 of 246 (37%) at 6 months after discharge and was associated with antibiotics before neurosurgery (RR, 3.28; 95% CI, 1.53-7.04), rupture (RR, 1.89; 95% CI, 1.34-2.65), and immunocompromise (RR, 1.80; 95% CI, 1.29-2.51), but not with specific targeted antibiotic regimens. Identified dental infection was associated with favorable prognosis (RR, 0.58; 95% CI, .36-.93).

CONCLUSIONS

Brain abscess due to oral cavity bacteria often occurred in previously healthy individuals without predisposing dental infections. Important risk factors for unfavorable outcome were rupture and immunocompromise. However, outcome was not associated with specific antibiotic regimens supporting carbapenem-sparing strategies.

Peritoneal Dialysis-associated Peritonitis Due to Streptococcus oralis Three Weeks after Peritoneal Dialysis Initiation

A 60-year-old man with end-stage renal disease due to nephrosclerosis had a peritoneal dialysis catheter (PD) embedded with stepwise initiation of peritoneal dialysis using Moncrief and Popovich's technique three months ago. PD was initiated three weeks after creating an exit site. He presented with abdominal pain and fever a day before admission and was diagnosed with PD-associated peritonitis caused by Streptococcus oralis. Medical consultation after admission revealed a history of wisdom tooth extraction following PD catheter placement, resulting in delayed wound healing. Transient bacteremia can occur after tooth extraction, leading to PD-associated peritonitis. Contemplating the oral milieu in patients undergoing PD is pertinent.

Streptococcus viridans Liver Abscess and Septicemia Likely Secondary to a Swallowed Dental Bridge

Pyogenic liver abscesses are relatively rare in developed countries such as the United States, and, when they do occur, they are typically secondary to direct or hematogenous spread of intra-abdominal pathologies. Gastrointestinal pathogens such as Escherichia coli and Enterococcus species are typically implicated. Conversely, the Streptococcus viridans group is a rare cause of bacteremia and abscess formation, especially in immunocompetent patients. We present a case of a 53-year-old male who presented with S. viridans liver abscess that was found to be secondary to a swallowed dental bridge that was lodged in the patient's descending colon. The patient was treated with intravenous antibiotics, percutaneous drainage, and colonoscopy for removal of the foreign body; the patient had a good response to treatment and was discharged on oral antibiotics. In any patient who has fever and abnormal liver function tests, hepatobiliary sepsis including liver abscess should always be excluded. Additionally, it is important to suspect unusual pathogens and sources of infection. We suggest empiric broad-spectrum antibiotic coverage when liver abscess is suspected and tailoring treatment as the specific organism and susceptibilities are identified. Moreover, we suggest the importance of removing any foreign bodies promptly upon discovery as they may serve as an important nidus of infection.

Antimicrobial activity of probiotic Streptococcus salivarius LAB813 on in vitro cariogenic biofilms

OBJECTIVE

To investigate the antimicrobial activity of a novel commensal strain of Streptococcus salivarius, LAB813, against Streptococcus mutans biofilms.

METHODS

The inhibitory activity of LAB813 towards S. mutans was tested using mono-, dual-, and multi-species cariogenic biofilms formed on three types of orthodontic appliances (metal, ceramic, aligner). The activity of the commercially available probiotic, BLIS M18™ was used as control.

RESULTS

LAB813 significantly inhibited S. mutans biofilms with cell killing approximating 99% for all materials. LAB813 showed effectiveness at inhibiting S. mutans in more complex multi-species biofilms with cell killing approximating 90% for all three materials. When comparing the killing kinetics of the probiotics, LAB813 had a faster rate of killing biofilms than M18. Experiments conducted with cell-free culture supernatant confirmed the presence of an inhibitory substance of proteinaceous nature. The addition of xylitol, a common sugar substitute used for human consumption, potentiated the inhibitory effects of LAB813 against S. mutans embedded in a more complex fungal-bacterial biofilm.

CONCLUSIONS

LAB813 possesses strong antimicrobial activity, potent anti-biofilm properties, and enhanced antimicrobial activity in the presence of xylitol. The identification and characterization of strain LAB813 exhibiting antimicrobial activity towards S. mutans hold exciting promise for this novel strain to be developed as an oral probiotic for use in the prevention of dental caries.

C-Reactive Protein: Pathophysiology, Diagnosis, False Test Results and a Novel Diagnostic Algorithm for Clinicians

The current literature provides a body of evidence on C-Reactive Protein (CRP) and its potential role in inflammation. However, most pieces of evidence are sparse and controversial. This critical state-of-the-art monography provides all the crucial data on the potential biochemical properties of the protein, along with further evidence on its potential pathobiology, both for its pentameric and monomeric forms, including information for its ligands as well as the possible function of autoantibodies against the protein. Furthermore, the current evidence on its potential utility as a biomarker of various diseases is presented, of all cardiovascular, respiratory, hepatobiliary, gastrointestinal, pancreatic, renal, gynecological, andrological, dental, oral, otorhinolaryngological, ophthalmological, dermatological, musculoskeletal, neurological, mental, splenic, thyroid conditions, as well as infections, autoimmune-supposed conditions and neoplasms, including other possible factors that have been linked with elevated concentrations of that protein. Moreover, data on molecular diagnostics on CRP are discussed, and possible etiologies of false test results are highlighted. Additionally, this review evaluates all current pieces of evidence on CRP and systemic inflammation, and highlights future goals. Finally, a novel diagnostic algorithm to carefully assess the CRP level for a precise diagnosis of a medical condition is illustrated.

Vertebral osteomyelitis secondary to Streptococcus cristatus infection

A 66-year-old male with a history of low back pain was found to have discitis and osteomyelitis. Biopsy and PCR testing revealed Streptococcus cristatus infection. This bacteria does not typically cause disease, and only a few cases in the literature have reported it to cause infection in the bones or joints. This case illustrates that vertebral osteomyelitis with a rare causative agent, S. cristatus, is possible and can be identified with PCR. Treatment typically requires long-term antibiotics tailored to the causative agent for a minimum of 6 weeks and can sometimes include surgical management.

Novel Multilocus Sequence Typing and Global Sequence Clustering Schemes for Characterizing the Population Diversity of Streptococcus mitis

Streptococcus mitis is a common oral commensal and an opportunistic pathogen that causes bacteremia and infective endocarditis; however, the species has received little attention compared to other pathogenic streptococcal species. Effective and easy-to-use molecular typing tools are essential for understanding bacterial population diversity and biology, but schemes specific for S. mitis are not currently available. We therefore developed a multilocus sequence typing (MLST) scheme and defined sequence clusters or lineages of S. mitis using a comprehensive global data set of 322 genomes (148 publicly available and 174 newly sequenced). We used internal 450-bp sequence fragments of seven housekeeping genes (accA, gki, hom, oppC, patB, rlmN, and tsf) to define the MLST scheme and derived the global S. mitis sequence clusters using the PopPUNK clustering algorithm. We identified an initial set of 259 sequence types (STs) and 258 global sequence clusters. The schemes showed high concordance (100%), capturing extensive S. mitis diversity with strains assigned to multiple unique STs and global sequence clusters. The tools also identified extensive within- and between-host S. mitis genetic diversity among isolates sampled from a cohort of healthy individuals, together with potential transmission events, supported by both phylogeny and pairwise single nucleotide polymorphism (SNP) distances. Our novel molecular typing and strain clustering schemes for S. mitis allow for the integration of new strain data, are electronically portable at the PubMLST database (https://pubmlst.org/smitis), and offer a standardized approach to understanding the population structure of S. mitis. These robust tools will enable new insights into the epidemiology of S. mitis colonization, disease and transmission.

Oral mitis group streptococci: A silent majority in our oral cavity

Members of the oral mitis group streptococci including Streptococcus oralis, Streptococcus sanguinis, and Streptococcus gordonii are the most abundant inhabitants of human oral cavity and dental plaque, and have been implicated in infectious complications such as bacteremia and infective endocarditis. Oral mitis group streptococci are genetically close to Streptococcus pneumoniae; however, they do not produce cytolysin (pneumolysin), which is a key virulence factor of S. pneumoniae. Similar to S. pneumoniae, oral mitis group streptococci possess several cell surface proteins that bind to the cell surface components of host mammalian cells. S. sanguinis expresses long filamentous pili that bind to the matrix proteins of host cells. The cell wall-anchored nuclease of S. sanguinis contributes to the evasion of the neutrophil extracellular trap by digesting its web-like extracellular DNA. Oral mitis group streptococci produce glucosyltransferases, which synthesize glucan (glucose polymer) from sucrose of dietary origin. Neuraminidase (NA) is a virulent factor in oral mitis group streptococci. Influenza type A virus (IAV) relies on viral NA activity to release progeny viruses from infected cells and spread the infection, and NA-producing oral streptococci elevate the risk of IAV infection. Moreover, oral mitis group streptococci produce hydrogen peroxide (H₂ O₂ ) as a by-product of sugar metabolism. Although the concentrations of streptococcal H₂ O₂ are low (1-2 mM), they play important roles in bacterial competition in the oral cavity and evasion of phagocytosis by host macrophages and neutrophils. In this review, we intended to describe the diverse pathogenicity of oral mitis group streptococci.

Oral mitis group streptococci reduce infectivity of influenza A virus via acidification and H2O2 production

Members of the mitis group streptococci are the most abundant inhabitants of the oral cavity and dental plaque. Influenza A virus (IAV), the causative agent of influenza, infects the upper respiratory tract, and co-infection with Streptococcus pneumoniae is a major cause of morbidity during influenza epidemics. S. pneumoniae is a member of mitis group streptococci and shares many features with oral mitis group streptococci. In this study, we investigated the effect of viable Streptococcus oralis, a representative member of oral mitis group, on the infectivity of H1N1 IAV. The infectivity of IAV was measured by a plaque assay using Madin-Darby canine kidney cells. When IAV was incubated in growing culture of S. oralis, the IAV titer decreased in a time- and dose-dependent manner and became less than 100-fold, whereas heat-inactivated S. oralis had no effect. Other oral streptococci such as Streptococcus mutans and Streptococcus salivarius also reduced the viral infectivity to a lesser extent compared to S. oralis and Streptococcus gordonii, another member of the oral mitis group. S. oralis produces hydrogen peroxide (H2O2) at a concentration of 1–2 mM, and its mutant deficient in H2O2 production showed a weaker effect on the inactivation of IAV, suggesting that H2O2 contributes to viral inactivation. The contribution of H2O2 was confirmed by an inhibition assay using catalase, an H2O2-decomposing enzyme. These oral streptococci produce short chain fatty acids (SCFA) such as acetic acid as a by-product of sugar metabolism, and we also found that the inactivation of IAV was dependent on the mildly acidic pH (around pH 5.0) of these streptococcal cultures. Although inactivation of IAV in buffers of pH 5.0 was limited, incubation in the same buffer containing 2 mM H2O2 resulted in marked inactivation of IAV, which was similar to the effect of growing S. oralis culture. Taken together, these results reveal that viable S. oralis can inactivate IAV via the production of SCFAs and H2O2. This finding also suggests that the combination of mildly acidic pH and H2O2 at low concentrations could be an effective method to inactivate IAV.

The findings of glucosyltransferase enzymes derived from oral streptococci

Glucosyltransferase enzymes (Gtfs) distribute among some streptococcal species in oral cavity and are known as key enzymes contributing to the development of oral biofilm such as dental plaque. In 18 streptococcal species, 45 glucosyltransferase genes (gtf) are detected from genome database. Gtfs catalyze the synthesis of the glucans, which are polymers of glucose, from sucrose and they are main component of oral biofilm. Especially, the Gtfs from Streptococcus mutans are recognized as one of dental caries pathogens since they contribute to the formation of dental plaque and the establishment of S. mutans in the tooth surface. Therefore, Gtfs has been studied particularly by many researchers in the dentistry field to develop the anti- caries vaccine. However, it is not still accomplished. In these days, the phylogenetic and crystal structure analyses of Gtfs were performed and the study of Gtfs will enter new situation from the technique in the past old viewpoint. The findings from those analyses will affect the development of the anti-caries vaccine very much after this.　In this review, we summarize the findings of oral streptococcal Gtfs and consider the perspectives of the dental caries prevention which targeted Gtf.

Amyloid Aggregates Are Localized to the Nonadherent Detached Fraction of Aging Streptococcus mutans Biofilms

The number of bacterial species recognized to utilize purposeful amyloid aggregation within biofilms continues to grow. The oral pathogen Streptococcus mutans produces several amyloidogenic proteins, including adhesins P1 (also known as AgI/II, PAc) and WapA, whose truncation products, namely, AgII and AgA, respectively, represent the amyloidogenic moieties. Amyloids demonstrate common biophysical properties, including recognition by Thioflavin T (ThT) and Congo red (CR) dyes that bind to the cross β-sheet quaternary structure of amyloid aggregates. Previously, we observed amyloid formation to occur only after 60 h or more of S. mutans biofilm growth. Here, we extend those findings to investigate where amyloid is detected within 1- and 5-day-old biofilms, including within tightly adherent compared with those in nonadherent fractions. CR birefringence and ThT uptake demonstrated amyloid within nonadherent material removed from 5-day-old cultures but not within 1-day-old or adherent samples. These experiments were done in conjunction with confocal microscopy and immunofluorescence staining with AgII- and AgA-reactive antibodies, including monoclonal reagents shown to discriminate between monomeric protein and amyloid aggregates. These results also localized amyloid primarily to the nonadherent fraction of biofilms. Lastly, we show that the C-terminal region of P1 loses adhesive function following amyloidogenesis and is no longer able to competitively inhibit binding of S. mutans to its physiologic substrate, salivary agglutinin. Taken together, our results provide new evidence that amyloid aggregation negatively impacts the functional activity of a widely studied S. mutans adhesin and are consistent with a model in which amyloidogenesis of adhesive proteins facilitates the detachment of aging biofilms. IMPORTANCE Streptococcus mutans is a keystone pathogen and causative agent of human dental caries, commonly known as tooth decay, the most prevalent infectious disease in the world. Like many pathogens, S. mutans causes disease in biofilms, which for dental decay begins with bacterial attachment to the salivary pellicle coating the tooth surface. Some strains of S. mutans are also associated with bacterial endocarditis. Amyloid aggregation was initially thought to represent only a consequence of protein mal-folding, but now, many microorganisms are known to produce functional amyloids with biofilm environments. In this study, we learned that amyloid formation diminishes the activity of a known S. mutans adhesin and that amyloid is found within the nonadherent fraction of older biofilms. This finding suggests that the transition from adhesin monomer to amyloid facilitates biofilm detachment. Knowing where and when S. mutans produces amyloid will help in developing therapeutic strategies to control tooth decay and other biofilm-related diseases.

Unusual cases of peritonitis: A case series of five patients

INTRODUCTION

Peritonitis is a complication in patients on peritoneal dialysis that frequently results from touch contamination. Most cases of peritoneal dialysis-related peritonitis are caused by skin organisms. Herein, we are presenting a series of peritonitis cases with unusual organisms in a single home dialysis center at an academic hospital in New York City.

METHODS

The records of five patients with an unusual cause of peritonitis were reviewed by a clinician. We have chronologically tabulated the cell count of the dialysate, microbiologic cultures, and antibiotics received by each patient. Additionally, both a table and figure detail the microbiologic organisms that our dialysis unit encountered over the 3-year period concurrent with the infections reported.

RESULTS

The first patient presented with refractory polymicrobial peritonitis due to a liver abscess. Another patient presented with diverticulitis and developed enteric peritonitis with various organisms. The following patient had peritonitis in the setting of bowel pathologies and from Rhizobium after exposure to plants. The next patient developed Pasteurella peritonitis from his cat. The final patient developed multiple episodes of peritonitis from organisms including flora native to soil and water.

CONCLUSION

These uncommon cases of peritonitis with unusual circumstances bring awareness to various elements that can lead to peritonitis.

Secondary streptococcal infection following influenza

Secondary bacterial infection following influenza A virus (IAV) infection is a major cause of morbidity and mortality during influenza epidemics. Streptococcus pneumoniae has been identified as a predominant pathogen in secondary pneumonia cases that develop following influenza. Although IAV has been shown to enhance susceptibility to the secondary bacterial infection, the underlying mechanism of the viral-bacterial synergy leading to disease progression is complex and remains elusive. In this review, cooperative interactions of viruses and streptococci during co- or secondary infection with IAV are described. IAV infects the upper respiratory tract, therefore, streptococci that inhabit or infect the respiratory tract are of special interest. Since many excellent reviews on the co-infection of IAV and S. pneumoniae have already been published, this review is intended to describe the unique interactions between other streptococci and IAV. Both streptococcal and IAV infections modulate the host epithelial barrier of the respiratory tract in various ways. IAV infection directly disrupts epithelial barriers, though at the same time the virus modifies the properties of infected cells to enhance streptococcal adherence and invasion. Mitis group streptococci produce neuraminidases, which promote IAV infection in a unique manner. The studies reviewed here have revealed intriguing mechanisms underlying secondary streptococcal infection following influenza. This article is protected by copyright. All rights reserved.

Aeromonas species obtained from different farmed aquatic species in India and Taiwan show high phenotypic relatedness despite species diversity

Objectives

Aeromonads cause severe diseases in farmed aquatic organisms. Herein, we examined 28 isolates causing disease in farmed aquatic organisms from India (n = 24) and Taiwan (n = 4) to gain insight of their genotypic and phenotypic properties.

Results

API 20NE biochemical phenotyping showed ≥ 90% similarity classifying all isolates as Aeromonas hydrophila. 16S rRNA genotyping showed ≥ 98% homology among all isolates with A. sobria (NR119044.1ATCC), A. veronii (MK990549.1), A. caviae (NR029252.1) and A. hydrophila (MG984625.1ATCC) and other reference strains. In contrast, gyrB showed a higher intraspecies diversity (≥ 96%) than 16S rRNA delineating the 28 isolates into three groups. Group-I consisted of seven Indian isolates clustered with A. sobria (MK484163.1ATCC), group-II comprised of five Indian and two Taiwanese isolates clustered with A. veronii AF417626.1ATCC while group-III had 11 Indian and three Taiwanese isolates grouped with A. hydrophila (AY987520.1 and DQ519366.1) reference strains. None of our isolates clustered with A. caviae (AJ868400.1ATCC) reference strain. These findings suggest that A. sobria, A. veronii and A. hydrophila could be the etiological agents of diseases observed in farmed fish and soft-shelled turtles (Pelodiscus sinensis) examined in this study. Overall, our findings accentuate the importance of combining phenotyping with genotyping for correct taxonomic classification of Aeromonas spp. in Aquaculture.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-021-05716-3.

Streptococcal Infections in Marine Mammals

Marine mammals are sentinels for the marine ecosystem and threatened by numerous factors including infectious diseases. One of the most frequently isolated bacteria are beta-hemolytic streptococci. However, knowledge on ecology and epidemiology of streptococcal species in marine mammals is very limited. This review summarizes published reports on streptococcal species, which have been detected in marine mammals. Furthermore, we discuss streptococcal transmission between and adaptation to their marine mammalian hosts. We conclude that streptococci colonize and/or infect marine mammals very frequently, but in many cases, streptococci isolated from marine mammals have not been further identified. How these bacteria disseminate and adapt to their specific niches can only be speculated due to the lack of respective research. Considering the relevance of pathogenic streptococci for marine mammals as part of the marine ecosystem, it seems that they have been neglected and should receive scientific interest in the future.

Does the Application of a Semiocclusive Dressing Alter the Microflora of Healthy Intact Skin on the Foot?

BACKGROUND

The skin on human feet presents unique environments for the proliferation of potentially pathogenic commensals. This study examined microflora changes on healthy intact skin under a semiocclusive dressing on the medial longitudinal arch of the foot to determine changes in growth, distribution, and frequency of microflora under the dressing.

METHODS

Nine human participants wore a low-adherent, absorbent, semiocclusive dressing on the medial longitudinal arch of the left foot for 2 weeks. An identical location on the right foot was swabbed and used as a control. Each foot was swabbed at baseline, week 1, and week 2. The swabs were cultured for 48 hours. Visual identification, Gram staining, DNase test agar, and a latex slide agglutination test were used to identify genera and species.

RESULTS

Microflora growth was categorized as scant (0-10 colony-forming units [CFU]), light (11-50 CFU), moderate (51-100 CFU), or heavy (>100 CFU). Scant and light growth decreased and moderate and heavy growth increased under the dressing compared with the control. Seven different genera of bacteria were identified. Coagulase-negative Staphylococcus spp appeared most frequently, followed by Corynebacterium spp.

CONCLUSIONS

Changes in microflora distribution, frequency, and growth were found under the dressing, supporting historical studies. Microflora changes were identified as an increase in bioburden and reduction in diversity. The application of similar methods, using more sophisticated identification and analysis techniques and a variety of dressings, could lead to a better understanding of bacterial and fungal growth under dressings, informing better dressing selection to assist the healing process of wounds and prevent infection.

Hydrogen Peroxide Production by Streptococcus pneumoniae Results in Alpha-hemolysis by Oxidation of Oxy-hemoglobin to Met-hemoglobin

There is a misconception that alpha-hemolysis observed on blood agar plate cultures of Streptococcus pneumoniae and other alpha-hemolytic streptococci is produced by a hemolysin or, alternatively, by lysis of erythrocytes caused by hydrogen peroxide. We noticed in the course of our investigations that wild-type S. pneumoniae strains and hemolysin (e.g., pneumolysin) knockout mutants produced the alpha-hemolytic halo on blood agar plates.

Streptococcus pneumoniae and other streptococci produce a greenish halo on blood agar plates referred to as alpha-hemolysis. This phenotype is utilized by clinical microbiology laboratories to report culture findings of alpha-hemolytic streptococci, including S. pneumoniae, and other bacteria. The alpha-hemolysis halo on blood agar plates has been related to the hemolytic activity of pneumococcal pneumolysin (Ply) or, to a lesser extent, to lysis of erythrocytes by S. pneumoniae-produced hydrogen peroxide. We investigated the molecular basis of the alpha-hemolysis halo produced by S. pneumoniae. Wild-type strains TIGR4, D39, R6, and EF3030 and isogenic derivative Δply mutants produced similar alpha-hemolytic halos on blood agar plates, while cultures of hydrogen peroxide knockout ΔspxB ΔlctO mutants lacked this characteristic halo. Moreover, in the presence of catalase, the alpha-hemolysis halo was absent in cultures of the wild-type (wt) and Δply mutant strains. Spectroscopic studies demonstrated that culture supernatants of TIGR4 released hemoglobin-bound heme (heme-hemoglobin) from erythrocytes and oxidized oxy-hemoglobin to met-hemoglobin within 30 min of incubation. As expected, given Ply hemolytic activity and that hydrogen peroxide contributes to the release of Ply, TIGR4Δply and ΔspxB ΔlctO isogenic mutants had significantly decreased release of heme-hemoglobin from erythrocytes. However, TIGR4Δply that produces hydrogen peroxide oxidized oxy-hemoglobin to met-hemoglobin, whereas TIGR4ΔspxB ΔlctO failed to produce oxidation of oxy-hemoglobin. Studies conducted with all other wt strains and isogenic mutants resulted in similar findings. We demonstrated that the so-called alpha-hemolysis halo is caused by the oxidation of oxy-hemoglobin (Fe⁺²) to a non-oxygen-binding met-hemoglobin (Fe⁺³) by S. pneumoniae-produced hydrogen peroxide.

IMPORTANCE There is a misconception that alpha-hemolysis observed on blood agar plate cultures of Streptococcus pneumoniae and other alpha-hemolytic streptococci is produced by a hemolysin or, alternatively, by lysis of erythrocytes caused by hydrogen peroxide. We noticed in the course of our investigations that wild-type S. pneumoniae strains and hemolysin (e.g., pneumolysin) knockout mutants produced the alpha-hemolytic halo on blood agar plates. In contrast, hydrogen peroxide-defective mutants prepared in four different strains lacked the characteristic alpha-hemolysis halo. We also demonstrated that wild-type strains and pneumolysin mutants oxidized oxy-hemoglobin to met-hemoglobin. Hydrogen peroxide knockout mutants, however, failed to oxidize oxy-hemoglobin. Therefore, the greenish halo formed on cultures of S. pneumoniae and other so-called alpha-hemolytic streptococci is caused by the oxidation of oxy-hemoglobin produced by hydrogen peroxide. Oxidation of oxy-hemoglobin to the nonbinding oxygen form, met-hemoglobin, might occur in the lungs during pneumococcal pneumonia.

Pyogenic Liver Abscess and Sepsis Caused by Streptococcus constellatus in the Immunocompetent Host

Streptococcus constellatus is a member of Streptococcus milleri group which is a subgroup of Viridans streptococci, first described by Guthof in 1956 after being isolated from dental abscesses. S. constellatus, a gram positive, non-sporing, non-motile, catalase negative cocci, is the normal flora of the oropharyngeal, gastrointestinal and urogenital tract. It is not a commonly encountered pathogen but has a propensity to form abscesses and cause bacteremia in the immunocompromised patient. Here, we report a 78-year-old man with sepsis due to Streptococcus constellatus liver abscess. The patient had a history of hypertension, stroke, benign prostatic hyperplasia, vascular dementia and myocardial infarction status post coronary artery bypass grafting. There has been no particular link between any of these conditions to S. constellatus. However, immunocompromised status predisposes to fulminant infection and formation of abscesses. The patient was febrile with a temperature of 99.1°F, blood pressure of 143/73 mmHg and the heart rate (HR) of 98. Labs revealed a leukocytosis of 16.90 K/uL, hemoglobin 11.8 g/dL, hematocrit 35.8%, total bilirubin 1.7 mg/dL, direct bilirubin 1.0 mg/dL, aspartate aminotransferase (AST) 44 IU/L, alanine aminotransferase (ALT) 28 IU/L, alkaline phosphatase (ALKP) 176 IU/L and lactate dehydrogenase (LDH) was 290 IU/L. He was started on intravenous Maxipime and Unasyn which was switched to Rocephin and Clindamycin based on the Infectious disease recommendations. Metronidazole was also started and the serologies were sent for Entamoeba histolytica. Computerized tomography (CT) scan showed an abscess in the right lobe of the liver which was finally drained using an interventional radiology (IR)-guided approach. The cultures from the fluid and blood yielded S. constellatus and thus Metronidazole was discontinued. The patient improved after a few days and the drainage catheter was pulled out and the patient discharged in stable condition.

Streptococcal H2O2 inhibits IgE-triggered degranulation of RBL-2H3 mast cell/basophil cell line by inducing cell death

Mast cells and basophils are central players in allergic reactions triggered by immunoglobulin E (IgE). They have intracellular granules containing allergic mediators (e.g., histamine, serotonin, inflammatory cytokines, proteases and β-hexosaminidase), and stimulation by IgE-allergen complex leads to the release of such allergic mediators from the granules, that is, degranulation. Mast cells are residents of mucosal surfaces, including those of nasal and oral cavities, and play an important role in the innate defense system. Members of the mitis group streptococci such as Streptococcus oralis, are primary colonizers of the human oral cavity. They produce hydrogen peroxide (H₂O₂) as a by-product of sugar metabolism. In this study, we investigated the effects of streptococcal infection on RBL-2H3 mast cell/basophil cell line. Infection by oral streptococci did not induce degranulation of the cells. Stimulation of the RBL-2H3 cells with anti-dinitrophenol (DNP) IgE and DNP-conjugated human serum albumin triggers degranulation with the release of β-hexosaminidase. We found that S. oralis and other mitis group streptococci inhibited the IgE-triggered degranulation of RBL-2H3 cells. Since mitis group streptococci produce H₂O₂, we examined the effect of S. oralis mutant strain deficient in producing H₂O_2, and found that they lost the ability to suppress the degranulation. Moreover, H₂O₂ alone inhibited the IgE-induced degranulation. Subsequent analysis suggested that the inhibition of degranulation was related to the cytotoxicity of streptococcal H₂O₂. Activated RBL-2H3 cells produce interleukin-4 (IL-4); however, IL-4 production was not induced by streptococcal H₂O₂. Furthermore, an in vivo study using the murine pollen-induced allergic rhinitis model suggested that the streptococcal H₂O₂ reduces nasal allergic reaction. These findings reveal that H₂O₂ produced by oral mitis group streptococci inhibits IgE-stimulated degranulation by inducing cell death. Consequently, streptococcal H₂O₂ can be considered to modulate the allergic reaction in mucosal surfaces.

Repurposing the Streptococcus mutans CRISPR-Cas9 System to Understand Essential Gene Function

A recent genome-wide screen identified ~300 essential or growth-supporting genes in the dental caries pathogen Streptococcus mutans. To be able to study these genes, we built a CRISPR interference tool around the Cas9 nuclease (Cas9Smu) encoded in the S. mutans UA159 genome. Using a xylose-inducible dead Cas9Smu with a constitutively active single-guide RNA (sgRNA), we observed titratable repression of GFP fluorescence that compared favorably to that of Streptococcus pyogenes dCas9 (Cas9Spy). We then investigated sgRNA specificity and proto-spacer adjacent motif (PAM) requirements. Interference by sgRNAs did not occur with double or triple base-pair mutations, or if single base-pair mutations were in the 3' end of the sgRNA. Bioinformatic analysis of >450 S. mutans genomes allied with in vivo assays revealed a similar PAM recognition sequence as Cas9Spy. Next, we created a comprehensive library of sgRNA plasmids that were directed at essential and growth-supporting genes. We discovered growth defects for 77% of the CRISPRi strains expressing sgRNAs. Phenotypes of CRISPRi strains, across several biological pathways, were assessed using fluorescence microscopy. A variety of cell structure anomalies were observed, including segregational instability of the chromosome, enlarged cells, and ovococci-to-rod shape transitions. CRISPRi was also employed to observe how silencing of cell wall glycopolysaccharide biosynthesis (rhamnose-glucose polysaccharide, RGP) affected both cell division and pathogenesis in a wax worm model. The CRISPRi tool and sgRNA library are valuable resources for characterizing essential genes in S. mutans, some of which could prove to be promising therapeutic targets.

Exploring the putative interactions between chronic kidney disease and chronic periodontitis

Chronic kidney disease (CKD) and chronic periodontitis (CP) are both common diseases, which are found disproportionately comorbid with each other and have been reported to have a detrimental effect on the progression of each respective disease. They have an overlap in risk factors and both are a source of systemic inflammation along with a wide selection of immunological and non-specific effects that can affect the body over the lifespan of the conditions. Previous studies have investigated the directionality of the relationship between these two diseases; however, there is a lack of literature that has examined how these diseases may be interacting at the localized and systemic level. This review discusses how oral microorganisms have the ability to translocate and have distal effects and provides evidence for microbial involvement in a systemic disease. Furthermore, it summarizes the reported local and systemic effects of CKD and CP and discusses how the interaction of these effects may be responsible for directionality associations reported.

Erythromycin-resistant lactic acid bacteria in the healthy gut of vegans, ovo-lacto vegetarians and omnivores

Diet can affect the diversity and composition of gut microbiota. Usage of antibiotics in food production and in human or veterinary medicine has resulted in the emergence of commensal antibiotic resistant bacteria in the human gut. The incidence of erythromycin-resistant lactic acid bacteria (LAB) in the feces of healthy vegans, ovo-lacto vegetarians and omnivores was analyzed. Overall, 155 LAB were isolated and characterized for their phenotypic and genotypic resistance to erythromycin. The isolates belonged to 11 different species within the Enterococcus and Streptococcus genera. Enterococcus faecium was the dominant species in isolates from all the dietary categories. Only 97 out of 155 isolates were resistant to erythromycin after Minimum Inhibitory Concentration (MIC) determination; among them, 19 isolates (7 from vegans, 4 from ovo-lacto vegetarians and 8 from omnivores) carried the erm(B) gene. The copresence of erm(B) and erm(A) genes was only observed in Enterococcus avium from omnivores. Moreover, the transferability of erythromycin resistance genes using multidrug-resistant (MDR) cultures selected from the three groups was assessed, and four out of six isolates were able to transfer the erm(B) gene. Overall, isolates obtained from the omnivore samples showed resistance to a greater number of antibiotics and carried more tested antibiotic resistance genes compared to the isolates from ovo-lacto vegetarians and vegans. In conclusion, our results show that diet does not significantly affect the occurrence of erythromycin-resistant bacteria and that commensal strains may act as a reservoir of antibiotic resistance (AR) genes and as a source of antibiotic resistance spreading.

The Significance of Lactoperoxidase System in Oral Health: Application and Efficacy in Oral Hygiene Products

Lactoperoxidase (LPO) present in saliva are an important element of the nonspecific immune response involved in maintaining oral health. The main role of this enzyme is to oxidize salivary thiocyanate ions (SCN^-) in the presence of hydrogen peroxide (H₂O₂) to products that exhibit antimicrobial activity. LPO derived from bovine milk has found an application in food, cosmetics, and medical industries due to its structural and functional similarity to the human enzyme. Oral hygiene products enriched with the LPO system constitute an alternative to the classic fluoride caries prophylaxis. This review describes the physiological role of human salivary lactoperoxidase and compares the results of clinical trials and in vitro studies of LPO alone and complex dentifrices enriched with bovine LPO. The role of reactivators and inhibitors of LPO is discussed together with the possibility of using nanoparticles to increase the stabilization and activity of this enzyme.

An Update on the Evolution of Glucosyltransferase (Gtf) Genes in Streptococcus

In many caries-promoting Streptococcus species, glucosyltransferases (Gtfs) are recognized as key enzymes contributing to the modification of biofilm structures, disruption of homeostasis of healthy microbiota community and induction of caries development. It is therefore of great interest to investigate how Gtf genes have evolved in Streptococcus. In this study, we conducted a comprehensive survey of Gtf genes among 872 streptococci genomes of 37 species and identified Gtf genes from 364 genomes of 18 species. To clarify the relationships of these Gtf genes, 45 representative sequences were used for phylogenic analysis, which revealed two clear clades. Clade I included 12 Gtf genes from nine caries-promoting species of the Mutans and Downei groups, which produce enzymes known to synthesize sticky, water-insoluble glucans (WIG) that are critical for modifying biofilm structures. Clade II primarily contained Gtf genes responsible for synthesizing water-soluble glucans (WSG) from all 18 species, and this clade further diverged into three subclades (IIA, IIB, and IIC). An analysis of 16 pairs of duplicated Gtf genes revealed high divergence levels at the C-terminal repeat regions, with ratios of the non-synonymous substitution rate (dN) to synonymous substitution rate (dS) ranging from 0.60 to 1.03, indicating an overall relaxed constraint in this region. However, among the clade I Gtf genes, some individual repeat units possessed strong functional constraints by the same criterion. Structural variations in the repeat regions were also observed, with detection of deletions or recent duplications of individual repeat units. Overall, by establishing an updated phylogeny and further elucidating their evolutionary patterns, this work enabled us to gain a greater understanding of the origination and divergence of Gtf genes in Streptococcus.

Veillonella Catalase Protects the Growth of Fusobacterium nucleatum in Microaerophilic and Streptococcus gordonii-Resident Environments

The oral biofilm is a multispecies community in which antagonism and mutualism coexist among friends and foes to keep an ecological balance of community members. The pioneer colonizers, such as Streptococcus gordonii, produce H₂O₂ to inhibit the growth of competitors, like the mutans streptococci, as well as strict anaerobic middle and later colonizers of the dental biofilm. Interestingly, Veillonella species, as early colonizers, physically interact (coaggregate) with S. gordonii A putative catalase gene (catA) is found in most sequenced Veillonella species; however, the function of this gene is unknown. In this study, we characterized the ecological function of catA from Veillonella parvula PK1910 by integrating it into the only transformable strain, Veillonella atypica OK5, which is catA negative. The strain (OK5-catA) became more resistant to H₂O₂ Further studies demonstrated that the catA gene expression is induced by the addition of H₂O₂ or coculture with S. gordonii Mixed-culture experiments further revealed that the transgenic OK5-catA strain not only enhanced the growth of Fusobacterium nucleatum, a strict anaerobic periodontopathogen, under microaerophilic conditions, but it also rescued F. nucleatum from killing by S. gordonii A potential role of catalase in veillonellae in biofilm ecology and pathogenesis is discussed here.IMPORTANCEVeillonella species, as early colonizers, can coaggregate with many bacteria, including the initial colonizer Streptococcus gordonii and periodontal pathogen Fusobacterium nucleatum, during various stages of oral biofilm formation. In addition to providing binding sites for many microbes, our previous study also showed that Veillonella produces nutrients for the survival and growth of periodontal pathogens. These findings indicate that Veillonella plays an important "bridging" role in the development of oral biofilms and the ecology of the human oral cavity. In this study, we demonstrated that the reducing activity of Veillonella can rescue the growth of Fusobacterium nucleatum not only under microaerophilic conditions, but also in an environment in which Streptococcus gordonii is present. Thus, this study will provide a new insight for future studies on the mechanisms of human oral biofilm formation and the control of periodontal diseases.

First Detection and Characterization of Streptococcus dentapri from Caries Active Subject

INTRODUCTION

Mutans streptococci (MS) are a group of oral bacteria generally regarded as the principal agents in the pathogenesis of dental caries.

AIM

The study aimed was characterize S. dentapri based on phylogenetic analysis and phenotypic methods from Caries Active Subject.

MATERIALS AND METHODS

While sequencing MS species which were isolated from 65 caries active subjects, one strain of S. dentapri was detected. Dental plaque samples were processed and cultured on mitis salivarius bacitracin agar. S. dentapri was characterized using phylogenetic analysis, colony morphology characterization and biotyping.

RESULTS

Among the study population, one strain designated as H14 was identified as S. dentapri by 16S rDNA sequencing. Morphologically, S. dentapri could not differentiate from other species of MS. S. dentapri H14 demonstrated biotype II biochemical characteristics of MS. The phylogenetic analysis showed S. dentapri is closely related to S. macacae.

CONCLUSION

The study concludes that S. dentapri can inhabit the human oral cavity and therefore further investigations are warranted to determine its role in caries.

Microarray analysis of macrophage response to infection with Streptococcus oralis reveals the immunosuppressive effect of hydrogen peroxide

Oral streptococci including mitis group streptococci are commensal residents and are also the first to colonize the oral cavity. However, various species of these oral streptococci have the potential to invade the host and occasionally lead to severe infectious disease such as cardiovascular diseases. Oral streptococci have close interactions with the host immune system including macrophages at the oral mucosal surface. One notable common trait of oral streptococcus including Streptococcus oralis (S. oralis) is the production of hydrogen peroxide (H₂O₂). Using a comprehensive microarray approach, we sought to understand the innate immune response profiling affected by H₂O₂ production from oral streptococci. We compared the gene expression patterns of macrophages infected with S. oralis wild type (WT) and streptococcal pyruvate oxidase knockout (SpxB-KO), a strain that does not produce H₂O₂. We found that H₂O₂ from S. oralis suppressed proinflammatory gene expression such as TNF-α, that is induced in response to infection, and activated the cellular stress genes such as Egr-1 in response to oxidative stress. A comparative gene ontology analysis of S. oralis WT and SpxB-KO strains revealed that during infection, down regulated genes were closely related to the processes involved in the host defense reaction and up regulated genes were related with the cellular stress responses. Using qPCR analysis, we also confirmed the same pattern of expression changes such as TNF-α, IL-6 and Egr-1. Furthermore, supernatant from SpxB-KO could not suppress the expression of TNF-α in macrophages stimulated with LPS. These findings suggested that H₂O₂ production from S. oralis leads to the suppression of inflammatory responses and NF-κB signaling pathways in macrophages as well as the induction of the oxidative stress response. We concluded that streptococcal H₂O₂ production has the beneficial effects of modulating the innate immune response, thereby stabilizing streptococcal colonization at the mucosal surface and even in the bloodstream leading to cardiovascular disease after invasion, in addition to the commensal role to compete other bacterial species as initial colonizer at oral cavity.

Streptococcal Diversity of Human Milk and Comparison of Different Methods for the Taxonomic Identification of Streptococci

BACKGROUND

The genus Streptococcus is 1 of the dominant bacterial groups in human milk, but the taxonomic identification of some species remains difficult.

OBJECTIVE

The objective of this study was to investigate the discriminatory ability of different methods to identify streptococcal species in order to perform an assessment of the streptococcal diversity of human milk microbiota as accurately as possible.

METHODS

The identification of 105 streptococcal strains from human milk was performed by 16S rRNA, tuf, and sodA gene sequencing, phylogenetic analysis, and Matrix Assisted Laser Desorption Ionization-Time of Flight (MALDI-TOF) mass spectrometry.

RESULTS

Streptococcus salivarius, Streptococcus mitis, and Streptococcus parasanguinis were the streptococcal dominant species in the human milk microbiota. Sequencing of housekeeping genes allowed the classification of 96.2% (16S rRNA), 84.8% ( sodA), and 88.6% ( tuf) of the isolates. Phylogenetic analysis showed 3 main streptococcal clusters corresponding with the mitis (73 isolates), salivarius (29), mutans (1)-pyogenic (2) groups, but many of the mitis group isolates (36) could not be assigned to any species. The application of the MALDI-TOF Bruker Biotyper system resulted in the identification of 56 isolates (53.33%) at the species level, but it could not discriminate between S pneumoniae and S mitis isolates, in contrast to the Vitek-MS system.

CONCLUSION

There was a good agreement among the different methods assessed in this study to identify those isolates of the salivarius, mutans, and pyogenic groups, whereas unambiguous discrimination could not be achieved concerning some species of the mitis group ( S mitis, S pneumoniae, S pseudopneumoniae, S oralis).

Antimicrobial Activity of Protamine against Oral Microorganisms

Protamine is an arginine-rich polycationic protein extracted from sperm cells of vertebrates including fishes such as salmon. The purpose of this study was to investigate the suppressive effects of protamine on the growth of oral pathogens for possible usage in dental materials. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were determined by the microdilution method. Twelve strains of oral viridans streptococci, Actinomyces naeslundii, Actinomyces odontolyticus, Enterococcus faecalis, Lactobacillus acidophilus, Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Porphyromonas gingivalis and Candida albicans were suppressed by protamine. MIC and MBC values were between 0.009 ～ 20 mg/mL and 0.019 ～ 80 mg/mL, respectively. The bactericidal activities of protamine against susceptible bacterial species were dependent on the concentration of protamine and incubation time. Based on the results of this study, protamine would be a useful compound for the development of antimicrobial agents against oral pathogens in dental materials.

Streptococcus oralis Induces Lysosomal Impairment of Macrophages via Bacterial Hydrogen Peroxide

Streptococcus oralis, an oral commensal, belongs to the mitis group of streptococci and occasionally causes opportunistic infections, such as bacterial endocarditis and bacteremia. Recently, we found that the hydrogen peroxide (H2O2) produced by S. oralis is sufficient to kill human monocytes and epithelial cells, implying that streptococcal H2O2 is a cytotoxin. In the present study, we investigated whether streptococcal H2O2 impacts lysosomes, organelles of the intracellular digestive system, in relation to cell death. S. oralis infection induced the death of RAW 264 macrophages in an H2O2-dependent manner, which was exemplified by the fact that exogenous H2O2 also induced cell death. Infection with either a mutant lacking spxB, which encodes pyruvate oxidase responsible for H2O2 production, or Streptococcus mutans, which does not produce H2O2, showed less cytotoxicity. Visualization of lysosomes with LysoTracker revealed lysosome deacidification after infection with S. oralis or exposure to H2O2, which was corroborated by acridine orange staining. Similarly, fluorescent labeling of lysosome-associated membrane protein-1 gradually disappeared during infection with S. oralis or exposure to H2O2 The deacidification and the following induction of cell death were inhibited by chelating iron in lysosomes. Moreover, fluorescent staining of cathepsin B indicated lysosomal destruction. However, treatment of infected cells with a specific inhibitor of cathepsin B had negligible effects on cell death; instead, it suppressed the detachment of dead cells from the culture plates. These results suggest that streptococcal H2O2 induces cell death with lysosomal destruction and then the released lysosomal cathepsins contribute to the detachment of the dead cells.

Comparing Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry and Phenotypic and Molecular Methods for Identification of Species within the Streptococcus anginosus Group

The heterogeneity of members of the Streptococcus anginosus group (SAG) has traditionally hampered their correct identification. Recently, the group was subdivided into 6 taxa whose prevalence among human infections is poorly described. We evaluated the accuracy of the Rapid ID32 Strep test, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), and a PCR multiplex method to identify 212 SAG isolates recovered from human infections to the species and subspecies level by using multilocus sequence analysis (MLSA) as the gold standard. We also determined the antimicrobial susceptibilities of the isolates. Representatives of all SAG taxa were found among our collection. MALDI-TOF MS and the Rapid ID32 Strep test correctly identified 92% and 68% of the isolates to the species level, respectively, but showed poor performance at the subspecies level, and the latter was responsible for major identification errors. The multiplex PCR method results were in complete agreement with the MLSA identifications but failed to distinguish the subspecies Streptococcus constellatus subsp. pharyngis and S. constellatus subsp. viborgensis. A total of 145 MLSA sequence types were present in our collection, indicating that within each taxon a number of different lineages are capable of causing infection. Significant antibiotic resistance was observed only to tetracycline, erythromycin, and clindamycin and was present in most taxa. MALDI-TOF MS is a reliable method for routine SAG species identification, while the need for identification to the subspecies level is not clearly established.

Oral Streptococci Biofilm Formation on Different Implant Surface Topographies

The establishment of the subgingival microbiota is dependent on successive colonization of the implant surface by bacterial species. Different implant surface topographies could influence the bacterial adsorption and therefore jeopardize the implant survival. This study evaluated the biofilm formation capacity of five oral streptococci species on two titanium surface topographies. In vitro biofilm formation was induced on 30 titanium discs divided in two groups: sandblasted acid-etched (SAE- n = 15) and as-machined (M- n = 15) surface. The specimens were immersed in sterilized whole human unstimulated saliva and then in fresh bacterial culture with five oral streptococci species: Streptococcus sanguinis, Streptococcus salivarius, Streptococcus mutans, Streptococcus sobrinus, and Streptococcus cricetus. The specimens were fixed and stained and the adsorbed dye was measured. Surface characterization was performed by atomic force and scanning electron microscopy. Surface and microbiologic data were analyzed by Student's t-test and two-way ANOVA, respectively (P < 0.05). S. cricetus, S. mutans, and S. sobrinus exhibited higher biofilm formation and no differences were observed between surfaces analyzed within each species (P > 0.05). S. sanguinis exhibited similar behavior to form biofilm on both implant surface topographies, while S. salivarius showed the lowest ability to form biofilm. It was concluded that biofilm formation on titanium surfaces depends on surface topography and species involved.

Prevalence of Heptavalent Vaccine-related Pneumococcal Serotypes in Nasopharyngeal carrier in children under five years old in Shahrekord, Iran by Multiplex-PCR during 2010- 2011

BACKGROUND

Heptavalent pneumococcal vaccine which included pneumococcal serotypes 4, 6B, 9V,14, 18C, 19F and 23F has been regularly used and is effective on preventing invasive pneumococcal infection. This study aimed to determine vaccine-related serotype distribution in nasopharyngeal carrier and healthy children under five years old.

MATERIALS AND METHODS

In this cross-sectional study from September 2010 to September 2011, 363 nasopharyngeal specimens were collected from healthy children in day care centers. In positive cultures of streptococcus pneumoniae (S. pneumonia) distribution, serotypes were detected by Multiplex polymerase chain reaction (PCR). Electrophoresis of PCR products was used for detection of serotypes of S. pneumoniae.

RESULTS

The carrier rate of S. pneumoniae was 29.5% with 95% confidence interval as 24.8- 34.5%. Electrophoresis of PCR products for detection of serotypes of S. pneumonia revealed 430, 220, 753, 189, 573, 304, and 384 bp (s) for 4, 6B, 9V, 14, 18C, 19F, and 23F serotypes of S. pneumoniae, respectively. The frequency of 23F, 6B, 19F, and 18C serotypes were 43%, 34%, 18%, and 5% respectively, but other serotypes (4, 9V and 14) were not detected.

CONCLUSION

Based on the 30% carrier rate and high prevalence of most of heptavalent pneumococcal conjugate vaccine serotypes in our study, this vaccine should be used for prevention of invasive infection in Iranian children.

Acute septicemia caused by Streptococcus gallolyticus subsp. pasteurianus in turkey poults

Streptococcus gallolyticus, previously known as Streptococcus bovis biotypes I and II/2, is a well-known cause of sepsis and meningitis in humans and birds. The present case report describes an outbreak of fatal septicemia associated with S. gallolyticus subsp. pasteurianus (S. bovis biotype II/2) in 11 turkey flocks in Pennsylvania between 2010 and 2013. Affected poults were 2-3 wk of age. Major clinical observation was sudden increase in mortality among turkey poults without any premonitory clinical signs. Postmortem examination findings revealed acute septicemia with lesions such as fibrinous pericarditis, meningitis, splenic multifocal fibrinoid necrosis, hepatitis, osteochondritis, myositis, and airsacculitis. Gram-positive cocci were isolated from several organs by routine bacterial culture. Biotyping identified bacteria as streptococci, whereas 16S ribosomal RNA gene sequencing identified them as S. gallolyticus subsp. pasteurianus. Antibiotic susceptibility profiles revealed that all the strains isolated were sensitive to penicillin and erythromycin with different sensitivity profiles for other antibacterial agents tested. The present study reports the first confirmed case of acute septicemia in turkey poults caused by S. gallolyticus subsp. pasteurianus.

Bacteraemia due to Streptococcus gallolyticus subspecies pasteurianus is associated with digestive tract malignancies and resistance to macrolides and clindamycin

OBJECTIVES

This study was intended to delineate the association between digestive tract malignancies and bacteraemia due to Streptococcus gallolyticus subspecies pasteurianus.

METHODS

We reviewed the medical records and microbiological results of patients with bacteraemia due to Streptococcus bovis during the period 2000-2012. Species and subspecies identification of isolates originally classified as S. bovis was confirmed by 16S rRNA sequencing and PCR restriction fragment length polymorphism (PCR-RFLP) assays. Minimum inhibitory concentrations of antimicrobial agents were determined by the broth microdilution method.

RESULTS

Of the 172 S. bovis complex isolates obtained from 172 patients (age range, <1-94 years, median age, 66) with bacteraemia, 31 isolates were identified to be S. gallolyticus subspecies gallolyticus, 126 were S. gallolyticus subspecies pasteurianus, and 15 were shown to be Streptococcus infantarius. The majority (n = 104, 60%) of patients were male and had underlying malignancies (n = 87, 51%). Bacteraemia due to S. gallolyticus subspecies gallolyticus was significantly associated with endocarditis while S. gallolyticus subspecies pasteurianus was more likely to be associated with malignancies of the digestive tract, including gastric, pancreatic, hepatobiliary and colorectal cancers. Septic shock at presentation was the only factor associated with mortality among patients with bacteraemia due to either subspecies of S. bovis. Isolates of S. gallolyticus subspecies pasteurianus had higher rates of resistance to macrolides and clindamycin than isolates of S. gallolyticus subspecies gallolyticus.

CONCLUSION

Extensive diagnostic work-up for digestive tract malignancies and trans-esophageal echocardiogram should be investigated in patients with bacteraemia caused by S. gallolyticus.

Hydrogen peroxide contributes to the epithelial cell death induced by the oral mitis group of streptococci

Members of the mitis group of streptococci are normal inhabitants of the commensal flora of the oral cavity and upper respiratory tract of humans. Some mitis group species, such as Streptococcus oralis and Streptococcus sanguinis, are primary colonizers of the human oral cavity. Recently, we found that hydrogen peroxide (H₂O₂) produced by S. oralis is cytotoxic to human macrophages, suggesting that streptococcus-derived H₂O₂ may act as a cytotoxin. Since epithelial cells provide a physical barrier against pathogenic microbes, we investigated their susceptibility to infection by H₂O₂-producing streptococci in this study. Infection by S. oralis and S. sanguinis was found to stimulate cell death of Detroit 562, Calu-3 and HeLa epithelial cell lines at a multiplicity of infection greater than 100. Catalase, an enzyme that catalyzes the decomposition of H₂O₂, inhibited S. oralis cytotoxicity, and H₂O₂ alone was capable of eliciting epithelial cell death. Moreover, S. oralis mutants lacking the spxB gene encoding pyruvate oxidase, which are deficient in H₂O₂ production, exhibited reduced cytotoxicity toward Detroit 562 epithelial cells. In addition, enzyme-linked immunosorbent assays revealed that both S. oralis and H₂O₂ induced interleukin-6 production in Detroit 562 epithelial cells. These results suggest that streptococcal H₂O₂ is cytotoxic to epithelial cells, and promotes bacterial evasion of the host defense systems in the oral cavity and upper respiratory tracts.

High Frequency of Isolation of Antibiotic-Resistant Oral Viridans Streptococci from Children in Kuwait

Antimicrobial resistance among the Viridans group of streptococci (VGS) has emerged as a hindrance to effective antibiotic therapy. Our objective was to evaluate the prevalence of antibiotic-resistant VGS in healthy children. Plaque samples were collected from tooth and tongue surfaces of 102 healthy subjects. Serially diluted samples were inoculated onto BHI agar plates and Mitis Salivarius Agar (MSA) plates and incubated as appropriate. Representative colonies were identified to species level by standard methods. Susceptibility of the VGS was performed by determining the minimum inhibitory concentrations (MICs) of 11 antibiotics using Etest. Of the 540 VGS isolates from both sites, 58% were from the tooth surfaces and 42% from the tongue. The most prevalent were S. salivarius (21.5%) and S. sanguis (16.3%). Imipenem and vancomycin had excellent activities. Resistance rates to trimethoprim, amoxicillin, piperacillin, erythromycin, cefuroxime and cephalothin, were 60.7, 40.8, 34.7, 32.6, 27.5 and 25.3%, respectively. Resistance rates to penicillin and clindamycin were 15.9% and 15.4%, respectively. The majority of the erythromycin-resistant isolates were from the tongue; 41% versus 29%. At the species level, 26% and 23% of S. salivarius and 23% and 14% of S. mutans from the tooth and tongue, respectively were resistant to penicillin. The data show species-related and site-related variations in the susceptibility pattern and an emerging high prevalence of antibiotic-resistant VGS. The difference in the susceptibilities between the species underscores the importance of accurate-identification and the need for surveillance of antimicrobial resistance among clinical isolates in our hospitals.

Dynamics of Microbial Colonization of the Oral Cavity in Newborns

The host defense mechanisms are not well developed in neonates. The aim of this study was to evaluate the dynamics of microbial colonization of the oral cavity in newborns. Eighty-one samples of the oral microbiota were obtained from 51 healthy newborns 10 min to 53 h after birth by gently rubbing sterile swabs onto the surface of the tongue, cheek mucosa, alveolar process and palate. After microbiological processing, counting of the colony forming units of streptococci, staphylococci and Gram-negative aerobic bacilli was performed. Between 10 min and 8 h, Staphylococcus epidermidis was detected in 30.7% of the samples; between 8 and 16 h, S. epidermidis was detected in 69.5% of the samples and streptococci in 56.5% of the samples; between 16 and 24 h, S. epidermidis, streptococci and S. aureus were detected in 77.78%, 85.18% and 37.03% of the samples, respectively. Between 24 and 53 h, S. epidermidis was detected in 88.89%, streptococci in 94.4% and S. aureus in 33.3% of the samples. Mutans streptococci were not detected in any of the samples. The adoption of strict hygienic measures by the mother and the nursing staff should be emphasized to avoid or at least delay the occurrence of infections caused by microorganisms in newborns. In addition, hospital procedures must be aseptic and invasive interventions must be minimized.

Hydrogen peroxide produced by oral Streptococci induces macrophage cell death

Hydrogen peroxide (H₂O₂) produced by members of the mitis group of oral streptococci plays important roles in microbial communities such as oral biofilms. Although the cytotoxicity of H₂O₂ has been widely recognized, the effects of H₂O₂ produced by oral streptococci on host defense systems remain unknown. In the present study, we investigated the effect of H₂O₂ produced by Streptococcus oralis on human macrophage cell death. Infection by S. oralis was found to stimulate cell death of a THP-1 human macrophage cell line at multiplicities of infection greater than 100. Catalase, an enzyme that catalyzes the decomposition of H₂O₂, inhibited the cytotoxic effect of S. oralis. S. oralis deletion mutants lacking the spxB gene, which encodes pyruvate oxidase, and are therefore deficient in H₂O₂ production, showed reduced cytotoxicity toward THP-1 macrophages. Furthermore, H₂O₂ alone was capable of inducing cell death. The cytotoxic effect seemed to be independent of inflammatory responses, because H₂O₂ was not a potent stimulator of tumor necrosis factor-α production in macrophages. These results indicate that streptococcal H₂O₂ plays a role as a cytotoxin, and is implicated in the cell death of infected human macrophages.

Enumeration of Salivary Streptococci and Lactobacilli in Children with Differing Caries Experiences in a Rural Indian Population

Objectives. Compare the total salivary Streptococci and Lactobacilli counts in cleft and noncleft children with differing caries experiences, correlate the bacterial counts with dmft/DMFT status and identify the different biotypes of Mutans Streptococci (MS). Patients. Group I included thirty subjects with dental caries (DC) and cleft lip and palate (CL/P); Group II had thirty subjects with DC but without CL/P. Group III comprised a control of thirty subjects with neither DC nor CL/P. Methodology. Enumeration of total salivary Streptococci and Lactobacilli was done by the plate count method and correlation of counts with dmft/ DMFT status examined. Differences in biochemical reactions were used to identify the biotypes. Results. Streptococci colonies in CL/P children with caries (64.30 ± 24.52) was significantly higher than in children with no CL/P or caries (45.57 ± 16.73). No significant differences in the Lactobacilli count were observed. dmft/DMFT status and Streptococci counts showed a strong positive correlation whereas Lactobacilli counts showed a moderate correlation. S. mutans was the predominant biotype. Conclusions. Higher total salivary Streptococci and Lactobacilli counts exist in cleft subjects with caries than in the non-cleft subjects. Positive correlation between dmft/DMFT scores and salivary Streptococci reinforces its role in DC. S. mutans and S. sobrinus are the biotypes more frequently associated with dental caries in children.