Mating system induced lags in rates of range expansion for different simulated mating systems and dispersal strategies: a modelling study.

Mismatches between current and potential species distributions are commonplace due to lags in the response of populations to changing environmental conditions. The prevailing mating system may contribute to such lags where it leads to mating failure at the range edge, but how active dispersers might mitigate these lags using social information to inform dispersal strategies warrants greater exploration. We used an individual-based model to explore how different mating systems for species that actively search for habitat can impose a filter on the ability to colonise empty, fragmented landscapes, and explored how using social information during dispersal can mitigate the lags caused by more constrained mating systems. The mate-finding requirements implemented in two-sex models consistently led to slower range expansion compared to those that were not mate limited (i.e., female only models), even when mating was polygynous. A mate-search settlement strategy reduced the proportion of unmated females at the range edge but had little impact on rate of spread. In contrast, a negative density-dependent settlement strategy resulted in much faster spread, which could be explained by a greater number of long-distance dispersal events. Our findings suggest that even low rates of mating failure at the range edge can lead to considerable lags in range expansion, though dispersal strategies that favour colonising more distant, sparsely occupied habitat patches may effectively mitigate these lags.

Development of a highly sensitive and specific intact proviral DNA assay for HIV-1 subtype B and C.

INTRODUCTION: HIV reservoir quantification is essential for evaluation of HIV curative strategies and may provide valuable insights about reservoir dynamics during antiretroviral therapy. The Intact Proviral DNA Assay (IPDA) provides the unique opportunity to quantify the intact and defective reservoir. The current IPDA is optimized for HIV-1 subtype B, the dominant subtype in resource-rich settings. However, subtype C is dominant in Sub-Saharan Africa, jointly accounting for around 60% of the pandemic. We developed an assay capable of quantifying intact and defective proviral HIV-1 DNA of subtype B and C. METHODS: Primer and probe sequences were strategically positioned at conserved regions in psi and env and adapted to subtype B&C. In silico analysis of 752 subtype B and 697 subtype C near-full length genome sequences (nFGS) was performed to predict  the specificity and sensitivity. Gblocks were used to determine the limit of blank (LoB), limit of detection (LoD), and different annealing temperatures were tested to address impact of sequence variability. RESULTS: The in silico analysis showed that the HIV-1 B&C IPDA correctly identified 100% of the intact subtype B, and 86% of the subtype C sequences. In contrast, the original IPDA identified 86% and 12% of these subtype B and C sequences as intact. Furthermore, the HIV-1 B&C IPDA correctly identified hypermutated (87% and 88%) and other defective sequences (73% and 66%) for subtype B and C with comparable specificity as the original IPDA for subtype B (59% and 63%). Subtype B cis-acting sequences were more frequently identified as intact by the HIV-1 B&C IPDA compared to the original IPDA (39% and 2%). The LoB for intact proviral DNA copies was 0, and the LoD for intact proviral DNA copies was 6 (> 95% certainty) at 60 °C. Quantification of 2-6 copies can be performed with > 80% certainty. Lowering the annealing temperature to 55 °C slightly lowered the specificity but prevented exclusion of samples with single mutations in the primer/probe region. CONCLUSIONS: We developed a robust and sensitive assay for the quantification of intact and defective HIV-1 subtype B and C proviral DNA, making this a suitable tool to monitor the impact of (large-scale) curative interventions.

Automated patterns of head dynamics are associated with psychopathic traits in incarcerated women.

Men with elevated psychopathic traits have been characterized by unique patterns of nonverbal communication, including more fixed and focused head positions during clinical interviews, compared to men scoring low on measures of psychopathy. However, it is unclear whether similar patterns of head dynamics help characterize women scoring high on psychopathic traits. Here, we utilized an automated detection algorithm to assess head position and dynamics during a videotaped clinical interview (i.e., the Psychopathy Checklist - Revised [PCL-R]) in a sample of n = 213 incarcerated women. PCL-R Total, Factor 1 (i.e., interpersonal and affective psychopathic traits), and Factor 2 (i.e., lifestyle/behavioral and antisocial/developmental psychopathic traits) scores were associated with a pattern of head dynamics indicative of a rigid head position. The current study extends analyses of nonverbal behavior studies in men to women and highlights how individuals with elevated psychopathic traits demonstrate unique nonverbal behaviors relative to individuals who score low on psychopathic traits. The implications and clinical value of these findings are discussed.

Identifying core components of a radiotherapy comfort intervention package using nominal group technique.

INTRODUCTION: A comfortable treatment position in radiotherapy may promote patient stability and improve outcomes such as accuracy. The aim of this study was to identify, prioritise and determine the feasibility of delivery of intervention components as part of a radiotherapy comfort intervention package. METHODS: Prior research, consisting of a systematic review and qualitative interviews with patient and therapeutic radiographers, was triangulated and 15 intervention components developed. An online nominal group technique consensus meeting with 7 patients who received radiotherapy exceeding 10 min for one of three anatomical cancer sites and 3 therapeutic radiographers (TRs) participated. Four activities were undertaken: 1) discussion of comfort intervention components; 2) initial vote; 3) prioritisation of intervention components; and 4) discussion of feasibility in radiotherapy and were analysed using established quantitative and qualitative methods. RESULTS: One intervention component was added from initial discussions to the 15 pre-determined components being discussed. 11 components were recommended as 'accepted' (n = 5) or 'accepted with caution' (n = 6) to proceed to development. The highest scoring intervention components were 'Compassionate & empathetic communication training for TRs' and 'Tailored information, e.g., TRs provide the required information only as part of preparation for treatment'. Anther that followed closely was 'Adjustments & supports provided for arms or legs during treatment by TRs'. Those 'accepted with caution' included 'Soft pads/mattress under the body to alleviate body discomfort managed by TRs'. Qualitative analysis highlighted concerns over the radiation environment and emphasised the importance of resources such as equipment, training, and time. CONCLUSION: The recommended comfort interventions have potential to improve patient comfort during radiotherapy and should be considered to incorporate into positioning and immobilisation guidelines. However, specific intervention strategies to address these components will need to be developed and robustly evaluated. IMPLICATIONS FOR PRACTICE: Comfort interventions might help patients relax and stay still during treatment, which could improve treatment accuracy and efficacy. Introducing these comfort interventions in practice have potential to lead to a more positive patient experience and improved overall quality of care during radiotherapy.

Nursing, midwifery, and allied health professions research capacities and cultures: a survey of staff within a university and acute healthcare organisation.

BACKGROUND: There is an increasing focus on the development of research capacity and culture in Nursing, Midwifery and Allied Health Professions (NMAHP). However, better understanding of the existing research success and skills, motivators, barriers, and development needs of NMAHP professionals is required to inform this development. This study sought to identify such factors within a university and an acute healthcare organisation. METHODS: An online survey, incorporating the Research Capacity and Culture tool, was administered to NMAHP professionals and students at a university and an acute healthcare organisation in the United Kingdom. Ratings of success/skill levels of teams and individuals were compared between professional groups using Mann-Whitney U tests. Motivators, barriers, and development needs were reported using descriptive statistics. Descriptive thematic analysis was used for open-ended text responses. RESULTS: A total of 416 responses were received (N&M n = 223, AHP n = 133, Other n = 60). N&M respondents were more positive than their AHP counterparts about the success/skill levels of their teams. There were no significant differences between N&M and AHP in their ratings of individual successes/skills. Finding and critically reviewing relevant literature were identified as specific individual strengths; with weaknesses in securing research funding, submitting ethics applications, writing for publication, and advising less experienced researchers. The main motivators for research were to develop skills, increased job satisfaction, and career advancement; whilst barriers included lack of time for research and other work roles taking priority. Key support needs identified included mentorship (for teams and individuals) and in-service training. Open-ended questions generated main themes of 'Employment & staffing', 'Professional services support', 'Clinical & academic management', 'Training & development', 'Partnerships' and 'Operating principles'. Two cross-cutting themes described issues common to multiple main themes: 'Adequate working time for research' and 'Participating in research as an individual learning journey'. CONCLUSIONS: Rich information was generated to inform the development of strategies to enhance research capacity and culture in NMAHP. Much of this can be generic but some nuances may be required to address some specific differences between professional groups, particularly related to perceived team success/skills and priorities identified for support and development.

Online activity - A beaming good initiative! Delivering alternative exercise opportunities for people with cystic fibrosis.

BACKGROUND: Increasing physical activity in people with Cystic Fibrosis (pwCF) can positively influence their physical and mental wellbeing. Online activities provide opportunity for outpatient CF populations to enhance physical activity. METHODS: PwCF within a large Scottish CF unit were invited to participate in a pilot study of online exercise and education sessions. Those participating shared opinions on motivation, fitness habits, types of activities enjoyed pre and during shielding, and desirable goals for online activity. Subsequently, an online activity timetable was created offering daily exercise classes. Educational presentations driven by patient request were delivered in context appropriate to health, wellbeing, and infection control needs during the pandemic and the advent of modulator therapies. Twenty-eight group exercise sessions and 12 educational sessions occurred over the six-week pilot, following which, a post-pilot questionnaire was sent to those who had participated in the sessions. Risk assessment and exercise modifications ensured safe practice and accommodation for all levels of respiratory disease. RESULTS: Twenty-six pwCF attended one or more exercise sessions and 37 pwCF attended one or more education sessions. Group exercise and education improved time efficiency compared to in-person face-to-face delivery. The post-pilot questionnaire demonstrated increases in motivation and perceived fitness, with positive comments regarding peer support and enhanced socialization. Personal fitness goals were fully or partially achieved by 91% of participants. CONCLUSION: Patient feedback suggested the implementation of online exercise and education sessions for pwCF was a satisfactory and convenient way to deliver exercise allowing for optimization and progression of personal goals.

Clozapine-induced gastrointestinal hypomotility: presenting features and outcomes, UK pharmacovigilance reports, 1992-2017.

BACKGROUND: Clozapine-induced gastrointestinal hypomotility (CIGH) affects some 75% of patients treated with clozapine. AIMS: To document the incidence of potentially harmful CIGH in the UK. METHOD: We studied spontaneous UK pharmacovigilance reports recorded as clozapine-related gastrointestinal adverse drug reactions, 1992-2017. RESULTS: There were 527 patients reported with potentially harmful CIGH; 33% (n = 172) died. Deaths averaged 1 per year 1992-1999, 5 per year 2000-2009 and 15 per year 2010-2017. Those who died were older (median 52 years v. 49 years) and had been prescribed clozapine for longer than those who recovered (median 11.3 years v. 4.8 years), but there was no difference in prescribed dose. Within the first 4 years of clozapine treatment, there were 169 reports of CIGH, of which 3% (n = 5) were fatal. At 10-14 years there were 63 reports of CIGH, of which 25% (n = 16) were fatal. Among the deaths, males were younger (median 51, range 22-89 v. median 57, range 24-89 years) with higher clozapine doses (median 450, range 100-900 v. median 300, range 12.5-800 mg/d) than females. In non-fatal CIGH, surgery was the most frequent outcome (n = 92). The procedures included appendectomy, ileostomy, total/partial colectomy, colostomy/stoma and proctosigmoidectomy. Clozapine dosage was reduced in 6 patients, stopped and restarted in 23, 'continued' in 6 and discontinued permanently in at least 76 patients. CONCLUSIONS: The risk of serious morbidity/mortality from CIGH is substantial. The need to actively monitor bowel function and give laxatives to patients treated with clozapine is clear.

Quantitative Head Dynamics Associated with Interpersonal (Grandiose-Manipulative) Psychopathic Traits in Incarcerated Youth.

Clinicians have long noted that individuals with elevated psychopathic traits can be characterized by unique interpersonal styles, including prolonged eye contact, invasion of interpersonal space, and frequent use of hand gestures. Such forms of nonverbal communication can be measured via hand, body, and head position and dynamics. Previous studies have developed an automated algorithm designed to capture head position and dynamics from digital recordings of clinical interviews in a sample of incarcerated adult men. We observed that higher psychopathy scores were associated with stationary head dwell time. Here, we applied a similar automated algorithm to assess head position and dynamics on videotaped clinical interviews assessing psychopathic traits from n = 242 youth housed at a maximum-security juvenile correctional facility. We observed that higher psychopathy scores (assessed via the Hare Psychopathy Checklist: Youth Version [PCL:YV]) were associated with unique patterns of head dynamics. Specifically, PCL:YV Total, Factor 1 (measuring grandiose-manipulative and callous-unemotional traits), and Facet 1 (measuring grandiose-manipulative traits) scores were associated with a higher proportion of time spent in a head dynamics pattern consisting of moderate movement away from the average head position. This study lays the groundwork for future investigations to apply quantitative methods to better understand patterns of nonverbal communication styles in clinical populations characterized by severe antisocial behavior.

The Christchurch mosque shooting, the media, and subsequent gun control reform in New Zealand: a descriptive analysis.

In March 2019, a mass shooting at two Christchurch mosques, livestreamed to Facebook, resulted in the deaths of 51 people. Psychologically, this served as a focusing event with high threat salience, shocking a country unused to gun violence despite its comparatively lax firearm legislation. The unprecedented reluctance by the New Zealand media to feature the shooter as a protagonist or even publish his name, concentrating instead on victims and societal issues, helped promote a sense of collective responsibility for change. This was strongly modeled by political leaders. Within weeks, new gun control laws were introduced with bipartisan support. We present this as a national case study, considering psychological and societal enablers for legislative reform in response to extreme gun violence. The shooting also raised the intractable problem of the internet allowing terrorists to promulgate violent content and extremist ideology with regulation in this area harder to achieve than gun control.

Dimensions of impulsivity related to psychopathic traits and homicidal behavior among incarcerated male youth offenders.

Despite impulsivity being included as scoring criteria within several measures of youth psychopathic traits, the relationship between psychopathic traits and dimensions of impulsivity among high-risk youth is not well-understood. Here we assessed psychopathic traits via total, factor, and facet scores from the Psychopathy Checklist: Youth Version (PCL:YV) and impulsivity through total, three-factor, and six-factor model scores from the Barratt Impulsiveness Scale (BIS-11) in incarcerated male youth offenders. Correlational analyses indicated PCL:YV total, Factor 2, Facet 3, and Facet 4 scores were significantly positively correlated with BIS-11 total scores. Additionally, psychopathy scores were significantly positively correlated with specific scores from the three-factor model of the BIS-11 (e.g. Motor and Non-Planning Impulsivity scores) and the six-factor model of the BIS-11 (e.g., Attention, Self-Control, and Cognitive Complexity Impulsivity scores). Secondary analyses suggest that participants who had previously committed homicide scored higher on lifestyle/antisocial psychopathic traits and specific dimensions of impulsivity (e.g., BIS-11 Non-Planning and Self-Control Impulsivity factor scores) compared to youth who had not previously committed homicide. Our results improve our understanding of the specific forms of impulsivity significantly correlated with youth psychopathic traits and how specific factors underlying both constructs potentially characterize youth associated with severe forms of antisocial behavior.

Variable but not random: temporal pattern coding in a songbird brain area necessary for song modification.

Practice of a complex motor gesture involves motor exploration to attain a better match to target, but little is known about the neural code for such exploration. We examine spiking in a premotor area of the songbird brain critical for song modification and quantify correlations between spiking and time in the motor sequence. While isolated spikes code for time in song during performance of song to a female bird, extended strings of spiking and silence, particularly bursts, code for time in song during undirected (solo) singing, or "practice." Bursts code for particular times in song with more information than individual spikes, and this spike-spike synergy is significantly higher during undirected singing. The observed pattern information cannot be accounted for by a Poisson model with a matched time-varying rate, indicating that the precise timing of spikes in both bursts in undirected singing and isolated spikes in directed singing code for song with a temporal code. Temporal coding during practice supports the hypothesis that lateral magnocellular nucleus of the anterior nidopallium neurons actively guide song modification at local instances in time.NEW & NOTEWORTHY This paper shows that bursts of spikes in the songbird brain during practice carry information about the output motor pattern. The brain's code for song changes with social context, in performance versus practice. Synergistic combinations of spiking and silence code for time in the bird's song. This is one of the first uses of information theory to quantify neural information about a motor output. This activity may guide changes to the song.

Second international guidelines for the diagnosis and management of hereditary hemorrhagic telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disease with an estimated prevalence of 1 in 5000 that is characterized by the presence of vascular malformations (VMs). These result in chronic bleeding, acute hemorrhage, and complications from shunting through VMs. The goal of the Second International HHT Guidelines process was to develop evidence-based consensus guidelines for the management and prevention of HHT-related symptoms and complications. The guidelines were developed using the AGREE II (Appraisal of Guidelines for Research and Evaluation II) framework and GRADE (Grading of Recommendations Assessment, Development and Evaluation) methodology. The guidelines expert panel included expert physicians (clinical and genetic) in HHT from 15 countries, guidelines methodologists, health care workers, health care administrators, patient advocacy representatives, and persons with HHT. During the preconference process, the expert panel generated clinically relevant questions in 6 priority topic areas. A systematic literature search was done in June 2019, and articles meeting a priori criteria were included to generate evidence tables, which were used as the basis for recommendation development. The expert panel subsequently convened during a guidelines conference to conduct a structured consensus process, during which recommendations reaching at least 80% consensus were discussed and approved. The expert panel generated and approved 6 new recommendations for each of the following 6 priority topic areas: epistaxis, gastrointestinal bleeding, anemia and iron deficiency, liver VMs, pediatric care, and pregnancy and delivery (36 total). The recommendations highlight new evidence in existing topics from the first International HHT Guidelines and provide guidance in 3 new areas: anemia, pediatrics, and pregnancy and delivery. These recommendations should facilitate implementation of key components of HHT care into clinical practice.

Clozapine in the treatment of refractory schizophrenia: a practical guide for healthcare professionals.

BACKGROUND: Clozapine remains the only medication licensed for treating refractory schizophrenia. However, it remains underutilized in part due to concerns regarding adverse events. SOURCES OF DATA: Published literature. AREAS OF AGREEMENT: Common adverse events during clozapine treatment include sedation, hypersalivation, postural hypotension, dysphagia, gastrointestinal hypomotility, weight gain, diabetes mellitus and dyslipidaemia. Rare but serious events include agranulocytosis, cardiomyopathy, myocarditis, pneumonia, paralytic ileus and seizure. AREAS OF CONTROVERSY: It remains unclear how best to minimize clozapine-induced morbidity/mortality (i) during dose titration, (ii) from hypersalivation and (iii) from gastrointestinal hypomotility. It is also unclear how clozapine pharmacokinetics are affected by (i) gastrointestinal hypomotility, (ii) systemic infection and (iii) passive exposure to cigarette smoke. Whether monthly haematological monitoring needs to continue after 12 months of uninterrupted therapy is also a subject of debate. GROWING POINTS: There is a need for better management of serious clozapine-related adverse events in addition to agranulocytosis. There is also a need for better education of patients and carers, general practitioners, A&E and ITU staff and others of the problems posed in using clozapine safely. AREAS TIMELY FOR DEVELOPING RESEARCH: There is a need for more research on assessing clozapine dosage (i) as patients get older, (ii) with respect to exposure to cigarette smoke and (iii) optimizing response if adverse events or other factors limit dosage.

A systematic review of effectiveness of interventions applicable to radiotherapy that are administered to improve patient comfort, increase patient compliance, and reduce patient distress or anxiety.

OBJECTIVES: The aim of this review was to search existing literature to identify comfort interventions that can be used to assist an adult patient to undergo complex radiotherapy requiring positional stability for periods greater than 10 min. The objectives of this review were to; 1) identify comfort interventions used for clinical procedures that involve sustained inactivity similar to radiotherapy; 2) define characteristics of comfort interventions for future practice; and 3) determine the effectiveness of identified comfort interventions. The Preferred Reporting Items for Systematic Reviews and meta-analyses statement and the Template-for-Intervention-Description-and Replication guide were used. KEY FINDINGS: The literature search was performed using PICO criteria with five databases (AMED, CINAHL EMBASE, MEDLINE, PsycINFO) identifying 5269 titles. After screening, 46 randomised controlled trials met the inclusion criteria. Thirteen interventions were reported and were grouped into four categories: Audio-visual, Psychological, Physical, and Other interventions (education/information and aromatherapy). The majority of aromatherapy, one audio-visual and one educational intervention were judged to be clinically significant for improving patient comfort based on anxiety outcome measures (effect size ≥ 0.4, mean change is greater than the Minimal-Important-Difference and low-risk-of-bias). Medium to large effect sizes were reported in many interventions where differences did not exceed the Minimal-Important-Difference for the measure. These interventions were deemed worthy of further investigation. CONCLUSION: Several interventions were identified that may improve comfort during radiotherapy assisting patients to sustain and endure the same position over time. This is crucial for the continual growth of complex radiotherapy requiring a need for comfort to ensure stability for targeted treatment. IMPLICATIONS FOR PRACTICE: Further investigation of comfort interventions is warranted, including tailoring interventions to patient choice and determining if multiple interventions can be used concurrently to improve effectiveness.

Photoresponsivity and motility in the planarian Schmidtea mediterranea vary diurnally.

The planarian flatworm has become one of the leading animal model systems for studying stem cell behavior and tissue regeneration. Recent studies have shown that components of the circadian clockwork have important roles in tissue homeostasis and repair. However, it remains unknown whether planarians exhibit circadian or diurnal rhythms in physiology or behavior. Here, we developed a behavioral assay to evaluate diurnal activity in planarians based upon their well-established propensity to swim away from light (negative phototaxis). We show evidence that the planarian Schmidtea mediterranea has diurnal variability in negative phototaxis as a function of daily variation in motility. We also demonstrate that variation in planarian motility over 48 h occurs with 24-h periodicity. Our data suggest that S. mediterranea may be a useful model for studying the interplay between the circadian system and tissue regeneration.

The Biology of Streptococcus mutans.

As a major etiological agent of human dental caries, Streptococcus mutans resides primarily in biofilms that form on the tooth surfaces, also known as dental plaque. In addition to caries, S. mutans is responsible for cases of infective endocarditis with a subset of strains being indirectly implicated with the onset of additional extraoral pathologies. During the past 4 decades, functional studies of S. mutans have focused on understanding the molecular mechanisms the organism employs to form robust biofilms on tooth surfaces, to rapidly metabolize a wide variety of carbohydrates obtained from the host diet, and to survive numerous (and frequent) environmental challenges encountered in oral biofilms. In these areas of research, S. mutans has served as a model organism for ground-breaking new discoveries that have, at times, challenged long-standing dogmas based on bacterial paradigms such as Escherichia coli and Bacillus subtilis. In addition to sections dedicated to carbohydrate metabolism, biofilm formation, and stress responses, this article discusses newer developments in S. mutans biology research, namely, how S. mutans interspecies and cross-kingdom interactions dictate the development and pathogenic potential of oral biofilms and how next-generation sequencing technologies have led to a much better understanding of the physiology and diversity of S. mutans as a species.

Can quantitative computed tomography detect bone morphological changes associated with catastrophic proximal sesamoid bone fracture in Thoroughbred racehorses?

BACKGROUND: Fracture of the proximal sesamoid bones continues to be the most common fatal musculoskeletal injury in US racehorses. Identifying factors that influence fracture risk could lead to screening techniques to reduce catastrophic injury rates and improve animal welfare. OBJECTIVES: To identify morphological differences between proximal sesamoid bones of the contralateral limb of fracture and control horses and assess the feasibility of computed tomography (CT) to detect traits associated with proximal sesamoid bone fracture. We hypothesised that horses with proximal sesamoid bone fracture would have greater bone density. STUDY DESIGN: Cross-sectional cadaver morphological study. METHODS: Proximal sesamoid bone morphology was measured using high-resolution micro-CT images from 16 Thoroughbred racehorses (eight fracture, eight control) euthanised on New York racetracks. Nominal logistic regression models and receiver operating characteristic curves were created to assess the ability of CT-derived morphological traits to accurately classify fracture horses vs. controls. RESULTS: Bone volume fraction was greater in the fracture group (90.39 ± 1.76%) as compared to controls (87.20 ± 2.79%, P<0.0001). Bone volume fraction, bone width, trabecular thickness and degree of anisotropy were significantly different between fracture and control horses. Receiver operating characteristic curves showed that a combined model that incorporates bone volume fraction and width can identify fracture from control horses with an area under the curve of 0.938, indicating high accuracy at classifying fracture horses from controls. MAIN LIMITATIONS: The number of horses per group is small, although the total number of sesamoids imaged is reasonable (n = 62). In vivo CT at the resolution performed in this study is currently unattainable; however, density and width could be measured with quantitative CT. CONCLUSIONS: Differences in proximal sesamoid bone morphology were identified between fracture and control horses. As improved technology becomes accessible, quantitative CT could potentially be used as a clinical imaging technique to estimate proximal sesamoid bone fracture risk in Thoroughbred racehorses.

Biology of Oral Streptococci.

Bacteria belonging to the genus Streptococcus are the first inhabitants of the oral cavity, which can be acquired right after birth and thus play an important role in the assembly of the oral microbiota. In this article, we discuss the different oral environments inhabited by streptococci and the species that occupy each niche. Special attention is given to the taxonomy of Streptococcus, because this genus is now divided into eight distinct groups, and oral species are found in six of them. Oral streptococci produce an arsenal of adhesive molecules that allow them to efficiently colonize different tissues in the mouth. Also, they have a remarkable ability to metabolize carbohydrates via fermentation, thereby generating acids as byproducts. Excessive acidification of the oral environment by aciduric species such as Streptococcus mutans is directly associated with the development of dental caries. However, less acid-tolerant species such as Streptococcus salivarius and Streptococcus gordonii produce large amounts of alkali, displaying an important role in the acid-base physiology of the oral cavity. Another important characteristic of certain oral streptococci is their ability to generate hydrogen peroxide that can inhibit the growth of S. mutans. Thus, oral streptococci can also be beneficial to the host by producing molecules that are inhibitory to pathogenic species. Lastly, commensal and pathogenic streptococci residing in the oral cavity can eventually gain access to the bloodstream and cause systemic infections such as infective endocarditis.