An intact S-layer is advantageous to Clostridioides difficile within the host.

Clostridioides difficile is responsible for substantial morbidity and mortality in antibiotically-treated, hospitalised, elderly patients, in which toxin production correlates with diarrhoeal disease. While the function of these toxins has been studied in detail, the contribution of other factors, including the paracrystalline surface layer (S-layer), to disease is less well understood. Here, we highlight the essentiality of the S-layer in vivo by reporting the recovery of S-layer variants, following infection with the S-layer-null strain, FM2.5. These variants carry either correction of the original point mutation, or sequence modifications which restored the reading frame, and translation of slpA. Selection of these variant clones was rapid in vivo, and independent of toxin production, with up to 90% of the recovered C. difficile population encoding modified slpA sequence within 24 h post infection. Two variants, subsequently named FM2.5varA and FM2.5varB, were selected for study in greater detail. Structural determination of SlpA from FM2.5varB indicated an alteration in the orientation of protein domains, resulting in a reorganisation of the lattice assembly, and changes in interacting interfaces, which might alter function. Interestingly, variant FM2.5varB displayed an attenuated, FM2.5-like phenotype in vivo compared to FM2.5varA, which caused disease severity more comparable to that of R20291. Comparative RNA sequencing (RNA-Seq) analysis of in vitro grown isolates revealed large changes in gene expression between R20291 and FM2.5. Downregulation of tcdA/tcdB and several genes associated with sporulation and cell wall integrity may account for the reported attenuated phenotype of FM2.5 in vivo. RNA-seq data correlated well with disease severity with the more virulent variant, FM2.5varA, showing s similar profile of gene expression to R20291 in vitro, while the attenuated FM2.5varB showed downregulation of many of the same virulence associated traits as FM2.5. Cumulatively, these data add to a growing body of evidence that the S-layer contributes to C. difficile pathogenesis and disease severity.

d-Serine induces distinct transcriptomes in diverse Escherichia coli pathotypes.

Appropriate interpretation of environmental signals facilitates niche specificity in pathogenic bacteria. However, the responses of niche-specific pathogens to common host signals are poorly understood. d-Serine (d-ser) is a toxic metabolite present in highly variable concentrations at different colonization sites within the human host that we previously found is capable of inducing changes in gene expression. In this study, we made the striking observation that the global transcriptional response of three Escherichia coli pathotypes - enterohaemorrhagic E. coli (EHEC), uropathogenic E. coli (UPEC) and neonatal meningitis-associated E. coli (NMEC) - to d-ser was highly distinct. In fact, we identified no single differentially expressed gene common to all three strains. We observed the induction of ribosome-associated genes in extraintestinal pathogens UPEC and NMEC only, and the induction of purine metabolism genes in gut-restricted EHEC, and UPEC indicating distinct transcriptional responses to a common signal. UPEC and NMEC encode dsdCXA - a genetic locus required for detoxification and hence normal growth in the presence of d-ser. Specific transcriptional responses were induced in strains accumulating d-ser (WT EHEC and UPEC/NMEC mutants lacking the d-ser-responsive transcriptional activator DsdC), corroborating the notion that d-ser is an unfavourable metabolite if not metabolized. Importantly, many of the UPEC-associated transcriptome alterations correlate with published data on the urinary transcriptome, supporting the hypothesis that d-ser sensing forms a key part of urinary niche adaptation in this pathotype. Collectively, our results demonstrate distinct pleiotropic responses to a common metabolite in diverse E. coli pathotypes, with important implications for niche selectivity.

Setting defensible standards in small cohort OSCEs: Understanding better when borderline regression can 'work'.

Introduction: Borderline regression (BRM) is considered problematic in small cohort OSCEs (e.g. n < 50), with institutions often relying on item-centred standard setting approaches which can be resource intensive and lack defensibility in performance tests.Methods: Through an analysis of post-hoc station- and test-level metrics, we investigate the application of BRM in three different small-cohort OSCE contexts: the exam for international medical graduates wanting to practice in the UK, senior sequential undergraduate exams, and Physician associates exams in a large UK medical school.Results: We find that BRM provides robust metrics and concomitantly defensible cut scores in the majority of stations (percentage of problematic stations 5, 14, and 12%, respectively across our three contexts). Where problems occur, this is generally due to an insufficiently strong relationship between global grades and checklist scores to be confident in the standard set by BRM in these stations.Conclusion: This work challenges previous assumptions about the application of BRM in small test cohorts. Where there is sufficient spread of ability, BRM will generally provide defensible standards, assuming careful design of station-level scoring instruments. However, extant station cut-scores are preferred as a substitute where BRM standard setting problems do occur.

Shining a spotlight on scoring in the OSCE: Checklists and item weighting.

Introduction: There has been a long-running debate about the validity of item-based checklist scoring of performance assessments like OSCEs. In recent years, the conception of a checklist has developed from its dichotomous inception into a more 'key-features' and/or chunked approach, where 'items' have the potential to become weighted differently, but the literature does not always reflect these broader conceptions.Methods: We consider theoretical, design and (clinically trained) assessor issues related to differential item weighting in checklist scoring of OSCEs stations. Using empirical evidence, this work also compares candidate decisions and psychometric quality of different item-weighting approaches (i.e. a simple 'unweighted' scheme versus a differentially weighted one).Results: The impact of different weighting schemes affect approximately 30% of the key borderline group of candidates, and 3% of candidates overall. We also find that measures of overall assessment quality are a little better under the differentially weighted scoring system.Discussion and conclusion: Differentially weighted modern checklists can contribute to valid assessment outcomes, and bring a range of additional benefits to the assessment. Judgment about weighting of particular items should be considered a key design consideration during station development and must align to clinical assessor expectations of the relative importance of sub-tasks.

The journeys of three ASPIRE winning medical schools toward excellence in student assessment.

Introduction: ASPIRE Excellence Awards in Student Assessment are offered to medical schools with innovative and comprehensive assessment programmes adjudged by international experts, using evidence-based criteria. The journeys of three ASPIRE-winning medical schools toward "assessment excellence" are presented. These schools include Aga Khan University Medical College (AKU-MC), Pakistan, Southern Illinois University School of Medicine (SIUSOM), USA, and University of Leeds School of Medicine, UK. Methods: The unfolding journeys highlighting achievements, innovations, and essential components of each assessment programme were compared to identify differences and commonalities. Results: Cultural contextual differences included developed-versus-developing country, east-west, type of regulatory bodies, and institutional-versus-national certifying/licensing examinations, which influence curricula and assessments. In all, 12 essential commonalities were found: alignment with institutional vision; sustained assessment leadership; stakeholder engagement; communication between curriculum and assessment; assessment-for-learning and feedback; longitudinal student profiling of outcome achievement; assessment rigor and robustness; 360° feedback from-and-to assessment; continuous enrichment through rigorous quality assurance; societal sensitivity; influencing others; and a "wow factor." Conclusions: Although the journeys of the three medical schools were undertaken in different cultural contexts, similar core components highlight strong foundations in student assessment. The journeys continue as assessment programmes remain dynamic and measurement science expands. This article may be helpful to other institutions pursuing excellence in assessment.

Managing extremes of assessor judgment within the OSCE.

CONTEXT: There is a growing body of research investigating assessor judgments in complex performance environments such as OSCE examinations. Post hoc analysis can be employed to identify some elements of "unwanted" assessor variance. However, the impact of individual, apparently "extreme" assessors on OSCE quality, assessment outcomes and pass/fail decisions has not been previously explored. This paper uses a range of "case studies" as examples to illustrate the impact that "extreme" examiners can have in OSCEs, and gives pragmatic suggestions to successfully alleviating problems. METHOD AND RESULTS: We used real OSCE assessment data from a number of examinations where at station level, a single examiner assesses student performance using a global grade and a key features checklist. Three exemplar case studies where initial post hoc analysis has indicated problematic individual assessor behavior are considered and discussed in detail, highlighting both the impact of individual examiner behavior and station design on subsequent judgments. CONCLUSIONS: In complex assessment environments, institutions have a duty to maximize the defensibility, quality and validity of the assessment process. A key element of this involves critical analysis, through a range of approaches, of assessor judgments. However, care must be taken when assuming that apparent aberrant examiner behavior is automatically just that.

D-Serine reduces the expression of the cytopathic genotoxin colibactin.

Some Escherichia coli strains harbour the pks island, a 54 kb genomic island encoding the biosynthesis genes for a genotoxic compound named colibactin. In eukaryotic cells, colibactin can induce DNA damage, cell cycle arrest and chromosomal instability. Production of colibactin has been implicated in the development of colorectal cancer (CRC). In this study, we demonstrate the inhibitory effect of D-Serine on the expression of the pks island in both prototypic and clinically-associated colibactin-producing strains and determine the implications for cytopathic effects on host cells. We also tested a comprehensive panel of proteinogenic L-amino acids and corresponding D-enantiomers for their ability to modulate clbB transcription. Whilst several D-amino acids exhibited the ability to inhibit expression of clbB, D-Serine exerted the strongest repressing activity (>3.8-fold) and thus, we focussed additional experiments on D-Serine. To investigate the cellular effect, we investigated if repression of colibactin by D-Serine could reduce the cytopathic responses normally observed during infection of HeLa cells with pks + strains. Levels of γ-H2AX (a marker of DNA double strand breaks) were reduced 2.75-fold in cells infected with D-Serine treatment. Moreover, exposure of pks + E. coli to D-Serine during infection caused a reduction in cellular senescence that was observable at 72 h post infection. The recent finding of an association between pks-carrying commensal E. coli and CRC, highlights the necessity for the development of colibactin targeting therapeutics. Here we show that D-Serine can reduce expression of colibactin, and inhibit downstream cellular cytopathy, illuminating its potential to prevent colibactin-associated disease.

Non-traumatic dental presentations at accident and emergency departments in the UK: a systematic review.

Objective Attendance at accident and emergency departments (A&E) for non-traumatic dental conditions (NTDC) is increasing in high-income countries. Not all NTDC visits to A&E are inappropriate; however, those that are take up capacity with conditions which are adding to the pressure regarding cost and healthcare utilisation for A&E departments. The scale of this problem is yet to be understood in the United Kingdom (UK). The aim of this study was to systematically review the literature to identify peer-reviewed research publications reporting non-traumatic dental presentations at A&E departments in the UK.Data sources A structured search of Cochrane Library, EMBASE, MEDLINE, CINAHL, PsycINFO, Scopus and Web of Science databases from their earliest date to May 2018. Hand-searching of identified articles that met the inclusion criteria was also reviewed.Data selection Publications were included if they were primary research on A&E users in the UK with NTDC as the primary reason for the A&E visit.Data extraction Data were extracted on the study, patient and visit characteristics.Data synthesis Studies were assessed for methodological quality and the analysis took the form of a narrative review.Conclusion There is limited evidence, of variable quality, to inform on the extent of inappropriate presentations of patients with non-urgent NTDC to A&E departments in the UK. The evidence supports the hypothesis that dental patients are inappropriately seeking care for NTDC at A&E departments and this may be a driver of unnecessary antibiotic prescriptions. Further research should focus on the reasons for this occurrence.

A Practitioner's Guide to Performing a Holistic Evaluation of Technology-Enhanced Learning in Medical Education.

Technology-enhanced learning (TEL) is now a common mode of educational delivery within medical education. Despite this upsurge, there remains a paucity in comprehensive evaluation of TEL efficacy. In order to make meaningful and evidence-informed decisions on 'how' and 'when' to utilise technology within a course, 'useful knowledge' is required to support faculty in these decision-making processes. In this monograph, a series of pragmatic and achievable approaches for conducting a holistic evaluation of a TEL resource intervention are detailed. These suggestions are based on an established TEL evaluation framework, as well as the author's own experience and that of the broader literature. The approaches cover development of an appropriate research question that is based on the availability of existing TEL resources alongside the peer-reviewed literature; the development of an appropriate team as well as recommendations for navigating ethical approval; conducting small-scale quantitative and qualitative measure; and performing a large-scale mixed methods assessment to understand the holistic impact of the TEL resource.

Impact of goal priority and goal conflict on the intention-health-behavior relationship: Tests on physical activity and other health behaviors.

OBJECTIVES: Goal intentions are the key proximal determinant of behavior in a number of key models applied to predicting health behavior. However, relatively little previous research has examined how characteristics of goals moderate the intention-health-behavior relations. The present research examined the effects of goal priority and goal conflict as moderators of the intention-health-behavior relationship. METHOD: The main outcome measures were self-reported performance of physical activity (Studies 1, 2, and 3) and other health behaviors (Study 4), and objectively measured physical activity (Study 3). Studies 1 and 4 used prospective correlational designs to predict later behavior from earlier cognitions. Studies 2 and 3 were experimental studies manipulating goal priority and goal conflict. Studies 1 and 2 used between-subjects designs while Studies 3 and 4 used within-subjects designs. RESULTS: Goal priority significantly moderated the intention-health-behavior relationship for physical activity (Study 1) and a range of protective and risk health behaviors (Study 4). Manipulations of goal priority significantly increased the intention-physical-activity relationship when self-reported (Study 2) and objectively measured (Study 3). In contrast, inconsistent effects were observed for goal conflict as an intention-behavior moderator. CONCLUSIONS: When goal priority is high, then intentions are strong predictors of health behaviors. Further studies testing manipulations of goal conflict and in particular goal priority in combination with goal intentions are required to confirm their value as a means to change health behavior. (PsycINFO Database Record