Serendipitous Pathways and Elusive Definitions: Leadership in Continuing Professional Development.

INTRODUCTION: Although the Continuing Professional Development (CPD) field has rapidly expanded in scope, breadth, and depth, there is a gap in how we understand CPD leadership and the role of the leader. Previous scholarship indicates that there is neither an agreed on set of competencies for CPD leadership roles nor a distinct pathway towards those roles. This study is aimed at answering the following question: How is leadership described or defined in CPD and what are the contextual issues that are and/or should be shaping its evolution? METHODS: Conducted between 2020 and 2022, CPD leadership program learners and CPD leaders with a range of leadership expertise were identified using convenience and purposive sampling and invited to participate in this study. Semistructured interviews were conducted with consenting participants. Interviews were recorded, transcribed, and analyzed using a qualitative thematic template analysis approach. RESULTS: Seventeen interviews were conducted. There were multiple components identified that were important to CPD leadership, such as being visionary, or having strong collaboration skills with some components, such as adaptability and flexibility appearing more unique to the CPD context. The role of CPD leadership and the pathway to CPD leadership remain highly variable. DISCUSSION: Attaining a CPD leadership position predominantly involves some degree of "serendipity." While CPD leaders may fundamentally need basic and common leadership skills, an essential attribute of the CPD leader is to effectively respond to the context and the unique needs of the health system. We recommend better articulating and valuing the role of the CPD leader within the health system.

Advancing equity, diversity, inclusivity, and accessibility in primary care: The development of an integrated educational experience model.

This article presents the development of the Equity, Diversity, Inclusivity, and Accessibility (EDIA) Cross-Cutting Theme Project within the Team Primary Care (TPC) initiative, aimed at addressing systemic inequities through innovative educational strategies. Grounded in the social accountability of health professions framework, this project aims to equip primary care teams with the knowledge, skills, and attitudes necessary to promote health equity. The EDIA Integrated Educational Experience (IEE) model includes a self-assessment tool, digital learning space, and national mentorship network, providing a comprehensive approach for primary care teams to promote health equity. The IEE model utilizes a layered micro, meso, and macro approach to support cultural transformation within highly complex healthcare environments. Key lessons learned involve trust- and relationship-building processes to help dismantle historical silos and encourage open dialogue. Future efforts focus on implementation, ensuring adaptability, scalability, and sustainability, positioning the model as a catalyst for equitable primary care delivery.

Microbial tryptophan catabolism as an actionable target via diet-microbiome interactions.

In recent years, the role of microbial tryptophan (Trp) catabolism in host-microbiota crosstalk has become a major area of scientific interest. Microbiota-derived Trp catabolites positively contribute to intestinal and systemic homeostasis by acting as ligands of aryl hydrocarbon receptor and pregnane X receptor, and as signaling molecules in microbial communities. Accumulating evidence suggests that microbial Trp catabolism could be therapeutic targets in treating human diseases. A number of bacteria and metabolic pathways have been identified to be responsible for the conversion of Trp in the intestine. Interestingly, many Trp-degrading bacteria can benefit from the supplementation of specific dietary fibers and polyphenols, which in turn increase the microbial production of beneficial Trp catabolites. Thus, this review aims to highlight the emerging role of diets and food components, i.e., food matrix, fiber, and polyphenol, in modulating the microbial catabolism of Trp and discuss the opportunities for potential therapeutic interventions via specifically designed diets targeting the Trp-microbiome axis.

Cholecystitis and Cardiomyopathy in an Immunocompetent Patient With Cytomegalovirus Infection: A Case Report.

In this case report, we present a 53-year-old immunocompetent male exhibiting cholecystitis and cardiomyopathy related to cytomegalovirus (CMV) infection. The initial presentation pointed toward cholecystitis, including epigastric pain, chronic dysgeusia, dyspepsia, and cholelithiasis on ultrasound. A cholecystectomy was performed, and tissue analysis showed subacute cholecystitis. Postsurgical daily fever spikes prompted subsequent evaluation, which revealed CMV infection along with cardiomyopathy as evidenced by a reduced left ventricular ejection fraction, despite no suggestive clinical symptoms. Gastrointestinal symptoms, along with elevated liver enzymes, indicated possible congestive hepatopathy. Preceding symptoms also suggested a viral etiology, including a protracted fever and a possible transient Bell's palsy. Medical management for viral myocarditis was initiated, and the patient has been followed closely after discharge. The case emphasizes the importance of considering viral etiology with comprehensive cardiac workup, even in the absence of overt cardiac symptoms but with abnormal liver enzymes. Surprisingly, the infectious workup showed positive West Nile virus (WNV) and Epstein-Barr virus (EBV) serology, indicating possible co-infection or cross-reactivity.

Repurposing Hsp90 inhibitors as antimicrobials targeting two-component systems identifies compounds leading to loss of bacterial membrane integrity.

The discovery of antimicrobials with novel mechanisms of action is crucial to tackle the foreseen global health crisis due to antimicrobial resistance. Bacterial two-component signaling systems (TCSs) are attractive targets for the discovery of novel antibacterial agents. TCS-encoding genes are found in all bacterial genomes and typically consist of a sensor histidine kinase (HK) and a response regulator. Due to the conserved Bergerat fold in the ATP-binding domain of the TCS HK and the human chaperone Hsp90, there has been much interest in repurposing inhibitors of Hsp90 as antibacterial compounds. In this study, we explore the chemical space of the known Hsp90 inhibitor scaffold 3,4-diphenylpyrazole (DPP), building on previous literature to further understand their potential for HK inhibition. Six DPP analogs inhibited HK autophosphorylation in vitro and had good antimicrobial activity against Gram-positive bacteria. However, mechanistic studies showed that their antimicrobial activity was related to damage of bacterial membranes. In addition, DPP analogs were cytotoxic to human embryonic kidney cell lines and induced the cell arrest phenotype shown for other Hsp90 inhibitors. We conclude that these DPP structures can be further optimized as specific disruptors of bacterial membranes providing binding to Hsp90 and cytotoxicity are lowered. Moreover, the X-ray crystal structure of resorcinol, a substructure of the DPP derivatives, bound to the HK CheA represents a promising starting point for the fragment-based design of novel HK inhibitors. IMPORTANCE: The discovery of novel antimicrobials is of paramount importance in tackling the imminent global health crisis of antimicrobial resistance. The discovery of novel antimicrobials with novel mechanisms of actions, e.g., targeting bacterial two-component signaling systems, is crucial to bypass existing resistance mechanisms and stimulate pharmaceutical innovations. Here, we explore the possible repurposing of compounds developed in cancer research as inhibitors of two-component systems and investigate their off-target effects such as bacterial membrane disruption and toxicity. These results highlight compounds that are promising for further development of novel bacterial membrane disruptors and two-component system inhibitors.

Soil salinity regulates spatial-temporal heterogeneity of seed germination and seedbank persistence of an annual diaspore-trimorphic halophyte in northern China.

BACKGROUND AND AIMS: Seed heteromorphism is a plant strategy that an individual plant produces two or more distinct types of diaspores, which have diverse morphology, dispersal ability, ecological functions and different effects on plant life history traits. The aim of this study was to test the effects of seasonal soil salinity and burial depth on the dynamics of dormancy/germination and persistence/depletion of buried trimorphic diaspores of a desert annual halophyte Atriplex centralasiatica. METHODS: We investigated the effects of salinity and seasonal fluctuations of temperature on germination, recovery of germination and mortality of types A, B, C diaspores of A. centralasiatica in the laboratory and buried diaspores in situ at four soil salinities and three depths. Diaspores were collected monthly from the seedbank from December 2016 to November 2018, and the number of viable diaspores remaining (not depleted) and their germinability were determined. RESULTS: Non-dormant type A diaspores were depleted in the low salinity "window" in the first year. Dormant diaspore types B and C germinated to high percentages at 0.3 and 0.1 mol L-1 soil salinity, respectively. High salinity and shallow burial delayed depletion of diaspore types B and C. High salinity delayed depletion time of the three diaspore types and delayed dormancy release of types B and C diaspores from autumn to spring. Soil salinity modified the response of diaspores in the seedbank by delaying seed dormancy release in autum and winter and by providing a low-salt concentration window for germination of non-dormant diaspores in spring and early summer. CONCLUSIONS: Buried trimorphic diaspores of annual desert halophyte A. centralasiatica exhibited diverse dormancy/germination behavior in respond to seasonal soil salinity fluctuation. Prolonging persistence of the seedbank and delaying depletion of diaspores under salt stress in situ primarily is due to inhibition of dormancy-break. The differences in dormancy/germination and seed persistence in the soil seedbank may be a bet-hadging strategy adapted to stressful temporal and spatial heterogeneity, and allows A. centralasiatica to persist in the unpredictable cold desert enevironment.

Evolutionary reversal of physical dormancy to nondormancy: evidence from comparative seed morphoanatomy of Argyreia species (Convolvulaceae).

Argyreia is the most recently evolved genus in the Convolvulaceae, and available information suggests that most species in this family produce seeds with physical dormancy (PY). Our aim was to understand the evolution of seed dormancy in this family via an investigation of dormancy, storage behaviour, morphology and anatomy of seeds of five Argyreia species from Sri Lanka. Imbibition, germination and dye tracking of fresh intact and manually scarified seeds were studied. Scanning electron micrographs and hand sections of the hilar area and the seed coat away from the hilar area were compared. Scarified and intact seeds of A. kleiniana, A. hirsuta and A. zeylanica imbibed water and germinated to a high percentage, but only scarified seeds of A. nervosa and A. osyrensis did so. Thus, seeds of the three former species are non-dormant (ND), while those of the latter two have physical dormancy (PY); this result was confirmed by dye-tracking experiments. Since >90% of A. kleiniana, A. hirsuta and A. zeylanica seeds survived desiccation to 10% moisture content (MC) and >90% of A. nervosa and A. osyrensis seeds with a dispersal MC of ~12% were viable, seeds of the five species were desiccation-tolerant. A. nervosa and A. osyrensis have a wide geographical distribution and PY, while A. kleiniana, A. hirsuta and A. zeylanica have a restricted distribution and ND. Although seeds of A. kleiniana are ND, their seed coat anatomy is similar to that of A. osyrensis with PY. These observations suggest that the ND of A. kleiniana, A. hirsuta and A. zeylanica seeds is the result of an evolutionary reversal from PY and that ND may be an adaptation of these species to the environmental conditions of their wet aseasonal habitats.

Managing cow's milk protein allergy during the 2022 formula shortage: decision-making among pediatric healthcare providers.

Introduction: Cow's milk protein allergy (CMPA) affects 2%-7% of infants and is managed with hypoallergenic formulas. The 2022 recalls of infant formulas due to factors including contamination led to specialty formula shortages, highlighting CMPA management challenges. Understanding healthcare providers' (HCPs) decision-making in transitioning to alternative formulas during shortages is crucial. Limited attention has been given to how pediatric physicians make these choices. Methods: This study utilized US HCPs' de-identified survey data to assess driving factors when switching extensively hydrolyzed formulas during shortages. Results: 104 eligible HCPs participated, including general pediatrics, pediatric allergy/immunology, and pediatric gastroenterology specialists. Safety, tolerability, and efficacy were identified as top factors for switching formulas. Formula 1 was considered well-tolerated, patient-accepted, and safe by all HCPs. Most expressed strong belief in Formula 1's safety and effectiveness. Discussion: Findings inform CMPA management during shortages, offering guidance to HCPs for suitable formula selection and enhanced infant care.

Translational Research of the Acute Effects of Negative Emotions on Vascular Endothelial Health: Findings From a Randomized Controlled Study.

BACKGROUND: Provoked anger is associated with an increased risk of cardiovascular disease events. The underlying mechanism linking provoked anger as well as other core negative emotions including anxiety and sadness to cardiovascular disease remain unknown. The study objective was to examine the acute effects of provoked anger, and secondarily, anxiety and sadness on endothelial cell health. METHODS AND RESULTS: Apparently healthy adult participants (n=280) were randomized to an 8-minute anger recall task, a depressed mood recall task, an anxiety recall task, or an emotionally neutral condition. Pre-/post-assessments of endothelial health including endothelium-dependent vasodilation (reactive hyperemia index), circulating endothelial cell-derived microparticles (CD62E+, CD31+/CD42-, and CD31+/Annexin V+) and circulating bone marrow-derived endothelial progenitor cells (CD34+/CD133+/kinase insert domain receptor+ endothelial progenitor cells and CD34+/kinase insert domain receptor+ endothelial progenitor cells) were measured. There was a group×time interaction for the anger versus neutral condition on the change in reactive hyperemia index score from baseline to 40 minutes (P=0.007) with a mean±SD change in reactive hyperemia index score of 0.20±0.67 and 0.50±0.60 in the anger and neutral conditions, respectively. For the change in reactive hyperemia index score, the anxiety versus neutral condition group by time interaction approached but did not reach statistical significance (P=0.054), and the sadness versus neutral condition group by time interaction was not statistically significant (P=0.160). There were no consistent statistically significant group×time interactions for the anger, anxiety, and sadness versus neutral condition on endothelial cell-derived microparticles and endothelial progenitor cells from baseline to 40 minutes. CONCLUSIONS: In this randomized controlled experimental study, a brief provocation of anger adversely affected endothelial cell health by impairing endothelium-dependent vasodilation.

Environmental and seed-position effects on viability and germination of buried seeds of an invasive diaspore-heteromorphic annual grass.

Environmental factors, such as temperature and moisture, and plant factors, such as seed position on the mother plant, can affect seed viability and germination. However, little is known about the viability and germination of seeds in different positions on the mother plant after burial in soil under natural environmental conditions. Here, diaspores from three positions on a compound spike and seeds from two/three positions in a diaspore of the invasive diaspore-heteromorphic annual grass Aegilops tauschii were buried at four depths for more than 2 years (1-26 months) under natural conditions and viability and germination monitored monthly. Viability of seeds in each diaspore/seed position decreased as burial depth and duration increased and was associated with changes in soil temperature and moisture. Germination was highest at 2 cm and lowest at 10 cm soil depths, with peaks and valleys in autumn/spring and winter/summer, respectively. Overall, seeds in distal diaspore and distal seed positions had higher germination percentages than those in basal diaspore and basal seed positions, but basal ones lived longer than distal ones. Chemical content of fresh diaspores/seeds was related to diaspore/seed position effects on seed germination and viability during burial. We conclude that seeds in distal diaspores/seed positions have a 'high risk' strategy and those in basal positions a 'low risk' strategy. The two risk strategies may act as a bet-hedging strategy that spreads risks of germination failure in the soil seed bank over time, thereby facilitating the survival and invasiveness of A. tauschii.

Concurrent cecal lipoma and Crohn's disease in a pediatric patient: A conservative approach.

We report the case of a 14-year-old patient with a known history of Crohn's disease who was incidentally diagnosed with an asymptomatic cecal lipoma. A routine surveillance colonoscopy as part of the management of the patient's Crohn's Disease revealed a well-defined, submucosal, yellowish mass in the patient's cecum. Histopathological examination of a biopsy specimen revealed submucosal adipose tissue, consistent with the endoscopic images showing the characteristic appearance of the lipoma. A computed tomography examination further confirmed the diagnosis. While colonic lipomas are infrequent and typically manifest later in life, few cases report the coexistence of a cecal lipoma with Crohn's disease, particularly in the pediatric population. In this case, managing this dual condition posed a notable challenge. Here, we present the conservative approach to managing a pediatric patient with cecal lipoma and Crohn's disease. The decision to leave the lipoma in situ was based on the absence of symptoms and potential risks associated with surgical removal.

Microbial responses to long-term warming differ across soil microenvironments.

Soil carbon loss is likely to increase due to climate warming, but microbiomes and microenvironments may dampen this effect. In a 30-year warming experiment, physical protection within soil aggregates affected the thermal responses of soil microbiomes and carbon dynamics. In this study, we combined metagenomic analysis with physical characterization of soil aggregates to explore mechanisms by which microbial communities respond to climate warming across different soil microenvironments. Long-term warming decreased the relative abundances of genes involved in degrading labile compounds (e.g. cellulose), but increased those genes involved in degrading recalcitrant compounds (e.g. lignin) across aggregate sizes. These changes were observed in most phyla of bacteria, especially for Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, and Planctomycetes. Microbial community composition was considerably altered by warming, leading to declined diversity for bacteria and fungi but not for archaea. Microbial functional genes, diversity, and community composition differed between macroaggregates and microaggregates, indicating the essential role of physical protection in controlling microbial community dynamics. Our findings suggest that microbes have the capacity to employ various strategies to acclimate or adapt to climate change (e.g. warming, heat stress) by shifting functional gene abundances and community structures in varying microenvironments, as regulated by soil physical protection.

Oral tryptophan activates duodenal aryl hydrocarbon receptor in healthy subjects: a crossover randomized controlled trial.

Tryptophan is an essential amino acid transformed by host and gut microbial enzymes into metabolites that regulate mucosal homeostasis through aryl hydrocarbon receptor (AhR) activation. Alteration of tryptophan metabolism has been associated with chronic inflammation; however, whether tryptophan supplementation affects the metabolite repertoire and AhR activation under physiological conditions in humans is unknown. We performed a randomized, double blind, placebo-controlled, crossover study in 20 healthy volunteers. Subjects on a low tryptophan background diet were randomly assigned to a 3-wk l-tryptophan supplementation (3 g/day) or placebo, and after a 2-wk washout switched to opposite interventions. We assessed gastrointestinal and psychological symptoms by validated questionnaires, AhR activation by cell reporter assay, tryptophan metabolites by liquid chromatography and high-resolution mass spectrometry, cytokine production in isolated monocytes by ELISA, and microbiota profile by 16S rRNA Illumina technique. Oral tryptophan supplementation was well tolerated, with no changes in gastrointestinal or psychological scores. Compared with placebo, tryptophan increased AhR activation capacity by duodenal contents, but not by feces. This was paralleled by higher urinary and plasma kynurenine metabolites and indoles. Tryptophan had a modest impact on fecal microbiome profiles and no significant effect on cytokine production. At the doses used in this study, oral tryptophan supplementation in humans induces microbial indole and host kynurenine metabolic pathways in the small intestine, known to be immunomodulatory. The results should prompt tryptophan intervention strategies in inflammatory conditions of the small intestine where the AhR pathway is impaired.NEW & NOTEWORTHY We demonstrate that in healthy subjects, orally administered tryptophan activates microbial indole and host kynurenine pathways in the small intestine, the primary metabolic site for dietary components, and the richest source of immune cells along the gut. This study provides novel insights in how to optimally activate immunomodulatory AhR pathways and indole metabolism in the small intestine, serving as basis for future therapeutic trials using l-tryptophan supplementation in chronic inflammatory conditions affecting the small intestine.

Contrast-enhanced ultrasound (CEUS) for the characterization of intra-scrotal lesions.

Contrast-enhanced ultrasound (CEUS) has emerged as a promising imaging modality for the characterization of hepatic and renal lesions. However, there is a paucity of data describing the use of CEUS for the evaluation of intra-scrotal pathology. In the following review, we describe the clinical utility of CEUS for the characterization and differentiation of common and uncommon intra-scrotal conditions, including testicular torsion, infection, trauma, and benign and malignant intratesticular and extratesticular neoplasms. In addition, we outline key principles of CEUS and provide case examples from our institution.

Mis-expression of GATA6 re-programs cell fate during early hematopoiesis.

The traditional view of hematopoiesis is that myeloid cells derive from a common myeloid progenitor (CMP), whereas all lymphoid cell populations, including B, T, and natural killer (NK) cells and possibly plasmacytoid dendritic cells (pDCs), arise from a common lymphoid progenitor (CLP). In Max41 transgenic mice, nearly all B cells seem to be diverted into the granulocyte lineage. Here, we show that these mice have an excess of myeloid progenitors, but their CLP compartment is ablated, and they have few pDCs. Nevertheless, T cell and NK cell development proceeds relatively normally. These hematopoietic abnormalities result from aberrant expression of Gata6 due to serendipitous insertion of the transgene enhancer (Eµ) in its proximity. Gata6 mis-expression in Max41 transgenic progenitors promoted the gene-regulatory networks that drive myelopoiesis through increasing expression of key transcription factors, including PU.1 and C/EBPa. Thus, mis-expression of a single key regulator like GATA6 can dramatically re-program multiple aspects of hematopoiesis.

Natural airway as an alternative to intubation for pediatric endoscopic esophageal foreign body removal: A retrospective cohort study of 326 patients.

BACKGROUND: Anesthesia is required for endoscopic removal of esophageal foreign bodies (EFBs) in children. Historically, endotracheal intubation has been the de facto gold standard for airway management in these cases. However, as more elective endoscopic procedures are now performed under propofol sedation with natural airway, there has been a move toward using similar Monitored Anesthesia Care (MAC) for select patients who require endoscopic removal of an EFB. METHODS: In this single-center retrospective cohort study, we compared endoscopic EFB removal with either MAC or endotracheal intubation. Descriptive statistics summarized factors stratified by initial choice of airway technique, including intra- and postanesthesia complications and the frequency of mid-procedure conversion to endotracheal intubation in those initially managed with MAC. To demonstrate the magnitude of associations between these factors and the anesthesiologist's choice of airway technique, univariable Firth logistic and quantile regressions were used to estimate odds ratios (95% CI) and beta coefficients (95% CI). RESULTS: From the initial search, 326 patients were identified. Among them, 23% (n = 75) were planned for intubation and 77% (n = 251) were planned for MAC. Three patients (0.9%) who were initially planned for MAC required conversion to endotracheal intubation after induction. Two (0.6%) of these children were admitted to the hospital after the procedure and treated for ongoing airway reactivity. No patient experienced reflux of gastric contents to the mouth or dislodgement of the foreign body to the airway, and no patient required administration of vasoactive medications or cardiopulmonary resuscitation. Patients had higher odds that the anesthesiologist chose to utilize MAC if the foreign body was a coin (OR, 3.3; CI, 1.9-5.7, p < .001) or if their fasting time was >6 h. Median total operating time was 15 min greater in intubated patients (11 vs. 26 min, p < .001). CONCLUSIONS: This study demonstrates that MAC may be considered for select pediatric patients undergoing endoscopic removal of EFB, especially those who have ingested coins, who do not have reactive airways, who have fasted for >6 h, and in whom the endoscopic procedure is expected to be short and uncomplicated. Prospective multi-site studies are needed to confirm these findings.

Impact of the 2022 national formula shortage on clinical decision-making of healthcare providers in switching amino acid formulas for infants with cow's milk protein allergy: a survey-based study.

Background: In 2022, the United States experienced a national shortage of infant formula due to a global supply chain crisis and a large-scale domestic formula recall. The existing literature on healthcare providers' (HCPs) clinical decision-making during formula shortages is limited. This study aims to analyze the factors influencing pediatric HCP clinical decision-making when switching between amino acid formulas (AAF) for managing cow's milk protein allergy (CMPA) in infants under 24 months of age during an unprecedented national formula shortage. Methods: The study included pediatric HCPs with experience managing CMPA in infants and toddlers under 24 months during the formula shortage from January 2022 to November 2022. A de-identified survey comprising 26 questions examining driving factors used in clinical decision-making was administered to pediatric HCPs using a real-time mobile data collection tool. Results: Among the surveyed pediatric HCPs (n = 75), the factors most frequently considered as "extremely important" when switching to another AAF included safety (85%), tolerability (73%), and efficacy (83%). No statistically significant differences were found in HCP ratings among the listed examined factors of the four AAFs. The availability of specific formulas was the only factor that exhibited a statistically significant difference in perceived performance among pediatric HCPs when comparing the four AAFs (p < 0.05). Discussion: This study elucidates the crucial aspects that influenced pediatric HCPs' selection of AAFs for CMPA management during the 2022 formula shortage. The findings highlight the significance of safety, tolerability, efficacy, and availability in the pediatric HCP decision-making processes.

Neutron diffraction from a microgravity-grown crystal reveals the active site hydrogens of the internal aldimine form of tryptophan synthase.

Pyridoxal 5'-phosphate (PLP), the biologically active form of vitamin B6, is an essential cofactor in many biosynthetic pathways. The emergence of PLP-dependent enzymes as drug targets and biocatalysts, such as tryptophan synthase (TS), has underlined the demand to understand PLP-dependent catalysis and reaction specificity. The ability of neutron diffraction to resolve the positions of hydrogen atoms makes it an ideal technique to understand how the electrostatic environment and selective protonation of PLP regulates PLP-dependent activities. Facilitated by microgravity crystallization of TS with the Toledo Crystallization Box, we report the 2.1 Å joint X-ray/neutron (XN) structure of TS with PLP in the internal aldimine form. Positions of hydrogens were directly determined in both the α- and ß-active sites, including PLP cofactor. The joint XN structure thus provides insight into the selective protonation of the internal aldimine and the electrostatic environment of TS necessary to understand the overall catalytic mechanism.

Identification of plasminogen-binding sites in Streptococcus suis enolase that contribute to bacterial translocation across the blood-brain barrier.

Streptococcus suis is an emerging zoonotic pathogen that can cause invasive disease commonly associated with meningitis in pigs and humans. To cause meningitis, S. suis must cross the blood-brain barrier (BBB) comprising blood vessels that vascularize the central nervous system (CNS). The BBB is highly selective due to interactions with other cell types in the brain and the composition of the extracellular matrix (ECM). Purified streptococcal surface enolase, an essential enzyme participating in glycolysis, can bind human plasminogen (Plg) and plasmin (Pln). Plg has been proposed to increase bacterial traversal across the BBB via conversion to Pln, a protease which cleaves host proteins in the ECM and monocyte chemoattractant protein 1 (MCP1) to disrupt tight junctions. The essentiality of enolase has made it challenging to unequivocally demonstrate its role in binding Plg/Pln on the bacterial surface and confirm its predicted role in facilitating translocation of the BBB. Here, we report on the CRISPR/Cas9 engineering of S. suis enolase mutants eno261, eno252/253/255, eno252/261, and eno434/435 possessing amino acid substitutions at in silico predicted binding sites for Plg. As expected, amino acid substitutions in the predicted Plg binding sites reduced Plg and Pln binding to S. suis but did not affect bacterial growth in vitro compared to the wild-type strain. The binding of Plg to wild-type S. suis enhanced translocation across the human cerebral microvascular endothelial cell line hCMEC/D3 but not for the eno mutant strains tested. To our knowledge, this is the first study where predicted Plg-binding sites of enolase have been mutated to show altered Plg and Pln binding to the surface of S. suis and attenuation of translocation across an endothelial cell monolayer in vitro.