Recurrent Annular Thrombosis and Embolism Following Mitral Valve Repair.

A patient without evident systemic thrombophilia developed recurrent ischemic stroke following surgical mitral valve repair. Thromboembolism proved resistant to anticoagulation; however, following explantation of the prosthesis, she became asymptomatic with normal valve function. We postulate that an unusual reaction to prosthetic material was the source of thromboembolism.

Ancestry and somatic profile predict acral melanoma origin and prognosis.

Acral melanoma, which is not ultraviolet (UV)-associated, is the most common type of melanoma in several low- and middle-income countries including Mexico. Latin American samples are significantly underrepresented in global cancer genomics studies, which directly affects patients in these regions as it is known that cancer risk and incidence may be influenced by ancestry and environmental exposures. To address this, here we characterise the genome and transcriptome of 128 acral melanoma tumours from 96 Mexican patients, a population notable because of its genetic admixture. Compared with other studies of melanoma, we found fewer frequent mutations in classical driver genes such as BRAF, NRAS or NF1. While most patients had predominantly Amerindian genetic ancestry, those with higher European ancestry had increased frequency of BRAF mutations and a lower number of structural variants. These BRAF-mutated tumours have a transcriptional profile similar to cutaneous non-volar melanocytes, suggesting that acral melanomas in these patients may arise from a distinct cell of origin compared to other tumours arising in these locations. KIT mutations were found in a subset of these tumours, and transcriptional profiling defined three expression clusters; these characteristics were associated with overall survival. We highlight novel low-frequency drivers, such as SPHKAP, which correlate with a distinct genomic profile and clinical characteristics. Our study enhances knowledge of this understudied disease and underscores the importance of including samples from diverse ancestries in cancer genomics studies.

Dual diagnosis of UQCRFS1-related mitochondrial complex III deficiency and recessive GJA8-related cataracts.

Biallelic pathogenic variants in UQCRFS1 underlie a rare form of isolated mitochondrial complex III deficiency associated with lactic acidosis and a distinctive scalp alopecia previously described in two unrelated probands. Here, we describe a participant in the Undiagnosed Diseases Network (UDN) with a dual diagnosis of two autosomal recessive disorders revealed by genome sequencing: UQCRFS1-related mitochondrial complex III deficiency and GJA8-related cataracts. Both pathogenic variants have been reported before: UQCRFS1 (NM_006003.3:c.215-1 G>C, p.Val72_Thr81del10) in a case with mitochondrial complex III deficiency and GJA8 (NM 005267.5:c.736 G>T, p.Glu246*) as a somatic change in aged cornea leading to decreased junctional coupling. A multi-modal approach combining enzyme assays and cellular proteomics analysis provided clear evidence of complex III respiratory chain dysfunction and low abundance of the Rieske iron-sulfur protein, validating the pathogenic effect of the UQCRFS1 variant. This report extends the genotypic and phenotypic spectrum for these two rare disorders and highlights the utility of deep phenotyping and genomics data to achieve diagnosis and insights into rare disease.

Stratification of Wilms tumor patients using physicochemical properties of the adaptive immune receptor polypeptides, IGL and TRG.

INTRODUCTION: Wilms tumor (WT) is the most common pediatric renal malignancy. Current guidelines that stratify WT risk and determine treatment courses are inadequate, as over 60 % of WT survivors develop treatment-related complications. Recently, numerous advances in establishing patient sub-groups with different clinical features have been realized by evaluating the adaptive immune receptor (IR) complementarity determining region-3 (CDR3) amino acid (AA) sequences, a reasonable series of successes, given the prominent role of the CDR3 in antigen binding, including tumor antigen binding. However, the possibility that adaptive IR chemical variability correlates with distinct survival outcomes for WT has not yet been explored. OBJECTIVE: The goal of this study was to isolate the T-cell receptor and B-cell receptor recombination, sequencing reads from WT RNAseq files, representing the actual tumor tissue, translate the sequences to AAs, identify the adaptive IR CDR3 domains, and determine whether the physicochemical properties of those CDR3 AA sequences correlated with survival probability distinctions. STUDY DESIGN: WT RNA-seq files were mined to obtain the CDR3 AAs for various adaptive IRs. The physicochemical properties of these CDR3s were examined for trends in how those properties correlated with survival probabilities for WT patients, using a Kaplan-Meier analyses, verified via several approaches. RESULTS: The above processes indicated the association of the (a) IGL CDR3s' instability index and the (b) TRG CDR3s' fraction disorder promoting features with better outcomes. Additionally, the IGL CDR3 data were assessed using the Predictor of Natural Disordered Regions web tool, which strengthened the evidence for the association with the IGL CDR3 instability index with a better outcome. DISCUSSION: The approaches described here indicate that greater adaptive IR CDR3 instability and flexibility may serve as prognostic indicators; and may indicate the flexibility of CDR3 domains provides for greater opportunity to bind tumor antigens. CONCLUSION: Further exploration and development of these approaches and findings may lead to new guidelines for more precise treatment regimens, or even watchful waiting periods, that could thereby decrease the lifetime occurrence of adverse events.

Comprehensive mutational profiling identifies new driver events in cutaneous leiomyosarcoma.

BACKGROUND: Cutaneous leiomyosarcoma (cLMS) is a rare soft tissue neoplasm, showing smooth muscle differentiation, that arises from the mesenchymal cells of the dermis. To-date, genetic investigation of these tumours has involved studies with small sample sizes and limited analyses that identified recurrent somatic mutations in RB1 and TP53, copy number gain of MYCOD and IGF1R, and copy number loss of PTEN. OBJECTIVES: To better understand the molecular pathogenesis of cLMS, we comprehensively explored the mutational landscape of these rare tumours to identify candidate driver events. METHODS: In this retrospective, multi-institutional study, we performed whole-exome sequencing and RNA sequencing on 38 cases of cLMS. RESULTS: TP53 and RB1 were identified as significantly mutated, thus, represent validated driver genes of cLMS. COSMIC mutational signatures SBS7a/b and DBS1 were recurrent, thus, ultraviolet light exposure may be an aetiological factor driving cLMS. Analysis of significantly recurrent somatic copy number alterations, which represent candidate driver events, found focal (<10Mb) deletions encompassing TP53 and KDM6B, and amplifications encompassing ZMYM2, MYOCD, MAP2K4 and NCOR1. A larger (24 Mb) recurrent deletion encompassing CYLD was also identified as significant. Significantly recurrent broad copy number alterations, involving at least half of a chromosome arm, included deletions of 6p/q, 10p/q, 11q, 12q, 13q and 16p/q, and amplification of 15q. Notably PTEN is located on 10q, RB1 on 13q and IGFR1 on 15q. Fusion gene analysis identified recurrent CRTC1/3::MAML2 fusions, as well as many novel fusions in individual samples. CONCLUSIONS: Our analysis of the largest number of cLMS cases to-date highlights the importance of large cohort sizes and the exploration beyond small targeted gene panels when performing molecular analyses, as it allowed a comprehensive exploration of the mutational landscape of these tumours and identification of novel candidate driver events. It also uniquely afforded the opportunity to compare the molecular phenotype of cLMS with LMS of other tissue types, such as uterine and soft tissue LMS. Given that molecular profiling has resulted in the development of novel targeted treatment approaches for uterine and soft tissue LMS, our study now allows the same opportunities to become available for patients with cLMS.

Clinical factors associated with genetic diagnosis in suspected neurogenetic disorders in a tertiary care clinic.

PURPOSE: This study aimed to identify phenotypic factors associated with genetic diagnoses in patients with neurodevelopmental disorders and generate a decision tree to assist clinicians in identifying patients most likely to receive a positive result on genetic testing. METHODS: We retrospectively reviewed the charts of 316 patients evaluated in a neurodevelopmental clinic between 2014 and 2019. Patients were categorized based on genetic test results. Analyses were performed to identify variables that discriminate between patients with and without a genetic diagnosis. RESULTS: Patients with a genetic diagnosis were more likely to be female and have a history of motor delay, hypotonia, congenital heart disease, and early intervention. Classification and regression tree analysis revealed that 75% of patients with motor delay had a genetic diagnosis. In patients without motor delay, hypotonia, age of walking, and age at initial evaluation were important indicators of a genetic diagnosis. CONCLUSION: Our findings suggest that motor delay and hypotonia are associated with genetic diagnoses in children with neurodevelopmental disorders. The decision tree highlights patient subsets at greater risk and suggests possible phenotypic screens. Future studies could develop validated decision trees based on phenotypic data to assist clinicians in stratifying patients for genetic testing.

Polyclonality overcomes fitness barriers in Apc-driven tumorigenesis.

Loss-of-function mutations in the tumour suppressor APC are an initial step in intestinal tumorigenesis1,2. APC-mutant intestinal stem cells outcompete their wild-type neighbours through the secretion of Wnt antagonists, which accelerates the fixation and subsequent rapid clonal expansion of mutants3-5. Reports of polyclonal intestinal tumours in human patients and mouse models appear at odds with this process6,7. Here we combine multicolour lineage tracing with chemical mutagenesis in mice to show that a large proportion of intestinal tumours have a multiancestral origin. Polyclonal tumours retain a structure comprising subclones with distinct Apc mutations and transcriptional states, driven predominantly by differences in KRAS and MYC signalling. These pathway-level changes are accompanied by profound differences in cancer stem cell phenotypes. Of note, these findings are confirmed by introducing an oncogenic Kras mutation that results in predominantly monoclonal tumour formation. Further, polyclonal tumours have accelerated growth dynamics, suggesting a link between polyclonality and tumour progression. Together, these findings demonstrate the role of interclonal interactions in promoting tumorigenesis through non-cell autonomous pathways that are dependent on the differential activation of oncogenic pathways between clones.

Tricuspid transcatheter edge-to-edge repair for severe tricuspid regurgitation: 1-year outcomes from the TRILUMINATE randomized cohort.

BACKGROUND: Tricuspid regurgitation (TR) is a right-sided valvular disease independently associated with morbidity and mortality. The TRILUMINATE Pivotal trial is the first randomized, controlled trial assessing the impact of TR reduction with tricuspid transcatheter edge-to-edge repair (T-TEER). OBJECTIVE: Outcomes from the full randomized cohort of the TRILUMINATE Pivotal trial have not been previously reported, and the additional enrollment may further support the safety and effectiveness of T-TEER through 1 year. METHODS: The TRILUMINATE Pivotal trial is an international RCT of T-TEER with the TriClip device in patients with symptomatic, severe TR. Adaptive trial design allowed enrollment past the primary analysis population. The primary outcome was a hierarchical composite of all-cause mortality or tricuspid valve surgery, heart failure hospitalizations (HFH), and quality-of-life improvement measured by Kansas City Cardiomyopathy Questionnaire (KCCQ) at 1 year. RESULTS: Between August 21, 2019 and June 29, 2022, 572 subjects were randomized, including the primary cohort (n=350) and subsequent enrollment (n=222). Subjects were elderly (78.1±7.8 years) and predominantly female (58.9%), with atrial fibrillation (87.8%) and prior HFH (23.8%). The primary endpoint was met for the full cohort (win ratio=1.84, p<0.0001). Freedom from all-cause mortality and tricuspid valve surgery through 12 months was 90.6% and 89.9% for the device and control groups, respectively (p=0.82). Annualized HFH rate was comparable between device and control subjects (0.17 vs 0.20 events/patient-year, p=0.40). A significant treatment effect was observed for change in quality of life with 49.5% of device subjects achieving a ≥15-point KCCQ score improvement (compared to 25.6% of control subjects, p<0.0001). All secondary endpoints favored T-TEER: moderate or less TR at 30 days (88.9% vs 5.3%, p<0.0001), KCCQ change at 1 year (13.0±1.4 vs -0.5±1.4 points, p<0.0001), and six-minute walk distance change at 1 year (1.7±7.5 vs -27.4±7.4 meters, p<0.0001). Freedom from major adverse events was 98.9% for T-TEER (vs. performance goal: 90%, p<0.0001). CONCLUSIONS: TriClip was safe and effective in the full randomized cohort of TRILUMINATE Pivotal with significant TR reduction and improvements in six-minute walk distance and health status. Rates of all-cause mortality or TV surgery and HFH through 1 year were not reduced by T-TEER.

Development of an Intravenously Stable Disulfide-Rich Peptide for the Treatment of Chemotherapy-Induced Neuropathic Pain.

α-conotoxins (α-Ctxs), a class of disulfide-rich conopetides, are excellent drug leads due to their small size, high selectivity, and potency for specific membrane receptors and ion channels involved in pain transmission. However, their high susceptibility to proteolytic degradation limits their therapeutic potential. In this study, we designed and synthesized a series of conformationally stable analogues of α-Ctx Mr1.1[S4Dap] using various structural optimization strategies. The Mr1.1[S4Dap, C16Pen] analogue maintained potency at human α9α10 nicotinic acetylcholine receptors, with a half-maximal inhibitory concentration (IC50) of 4 nM. It exhibited over a 5-fold increase in serum stability compared to Mr1.1[S4Dap], without disrupting its overall conformation. Furthermore, intravenous application of Mr1.1[S4Dap, C16Pen] showed potent analgesic activity in oxaliplatin-induced cold allodynia, indicating a high potential for drug development. Overall, the results from this study provide valuable insights for optimizing the serum stability of disulfide-rich peptides in future therapeutic applications.

N-Terminal Capping of the αO-Conotoxin Analogue GeX-2 Improves the Serum Stability and Selectivity toward the Human α9α10 Nicotinic Acetylcholine Receptor.

α9α10 nicotinic acetylcholine receptors (nAChRs) are a promising nonopioid analgesic target, with α9α10 nAChR antagonists showing efficacy against chemotherapy-induced hyperalgesia and allodynia. GeX-2, a potent analgesic conotoxin antagonist of α9α10 nAChRs, has limited serum stability. This study improved GeX-2 stability by capping its N-terminal with fatty acids or polyethylene glycol chains, which enhanced its serum stability but eliminated activity at G protein-coupled γ-aminobutyric acid type B (GABAB) receptor-coupled CaV2.2 channels while preserving activity at α9α10 nAChRs. In vivo, α9α10 nAChRs antagonism alone did not alleviate neuropathic pain, highlighting the importance of GABAB receptor-coupled CaV2.2 channels in GeX-2's antinociceptive effects in the chronic constriction injury rat model. The GeX-2 analogue, with an N-terminal methyl group, showed improved activity and selectivity for α9α10 nAChRs, increased serum half-life, and strong analgesic effects in oxaliplatin-induced cold allodynia models. AlphaFold3 and molecular dynamics simulations provided insights into the binding modes and the effects of N-terminal capping, which informed future peptide therapeutic developments.

Generation and characterization of two iPSC lines derived from subjects with Free Sialic Acid Storage Disorder (FSASD).

Free sialic acid storage disorder (FSASD) is a rare, autosomal recessive, neurodegenerative disorder caused by biallelic mutations in SLC17A5, encoding the lysosomal transmembrane sialic acid exporter, SLC17A5. Defects in SLC17A5 lead to lysosomal accumulation of free sialic acid and other acid hexoses. The clinical spectrum of FSASD ranges from mild (Salla disease) to severe infantile forms. The pathobiology underlying FSASD remains elusive. In this study, two induced pluripotent stem cell (iPSC) lines were generated from a mild and an intermediate FSASD patient and characterized to provide much-needed additional models for basic and translational studies.

Biallelic PI4KA Mutations Disrupt B-Cell Metabolism and Cause B-Cell Lymphopenia and Hypogammaglobulinemia.

PURPOSE: PI4KA-related disorder is a highly clinically variable condition characterized by neurological (limb spasticity, developmental delay, intellectual disability, seizures, ataxia, nystagmus) and gastrointestinal (inflammatory bowel disease and multiple intestinal atresia) manifestations. Although features consistent with immunodeficiency (autoimmunity/autoinflammation and recurrent infections) have been reported in a subset of patients, the burden of B-cell deficiency and hypogammaglobulinemia has not been extensively investigated. We sought to describe the clinical presentation and manifestations of patients with PI4KA-related disorder and to investigate the metabolic consequences of biallelic PI4KA variants in B cells. METHODS: Clinical data from patients with PI4KA variants were obtained. Multi-omics analyses combining transcriptome, proteome, lipidome and metabolome analyses in conjunction with functional assays were performed in EBV-transformed B cells. RESULTS: Clinical and laboratory data of 13 patients were collected. Recurrent infections (7/13), autoimmune/autoinflammatory manifestations (5/13), B-cell deficiency (8/13) and hypogammaglobulinemia (8/13) were frequently observed. Patients' B cells frequently showed increased transitional and decreased switched memory B-cell subsets. Pathway analyses based on differentially expressed transcripts and proteins confirmed the central role of PI4KA in B cell differentiation with altered B-cell receptor (BCR) complex and signalling. By altering lipids production and tricarboxylic acid cycle regulation, and causing increased endoplasmic reticulum stress, biallelic PI4KA mutations disrupt B cell metabolism inducing mitochondrial dysfunction. As a result, B cells show hyperactive PI3K/mTOR pathway, increased autophagy and deranged cytoskeleton organization. CONCLUSION: By altering lipid metabolism and TCA cycle, impairing mitochondrial activity, hyperactivating mTOR pathway and increasing autophagy, PI4KA-related disorder causes a syndromic inborn error of immunity presenting with B-cell deficiency and hypogammaglobulinemia.

Impact of Renal and Liver Function on Clinical Outcomes Following Tricuspid Valve Transcatheter Edge-to-Edge Repair.

BACKGROUND: The TRILUMINATE Pivotal trial is a prospective, randomized, controlled study of patients with severe tricuspid regurgitation (TR). Venous congestion due to TR may lead to end-organ dysfunction and failure. The potential to reverse or stop further deterioration in end-organ function is an important goal of treatment. OBJECTIVES: This study sought to examine changes in end-organ function after tricuspid transcatheter edge-to-edge repair (TEER) and assess the association of baseline end-organ function with heart failure (HF) hospitalizations and mortality. METHODS: Subjects were randomized 1:1 to either the TEER group (TriClip System + medical therapy) or control group (medical therapy alone). Laboratory assessments and TR grading were performed at baseline and at all follow-up visits (discharge, 30 days, 6 months, and 12 months). An independent echocardiography core laboratory assessed TR severity and an independent clinical events committee adjudicated adverse events. RESULTS: A total of 572 subjects were enrolled and randomized (285 TEER, 287 control patients). Patients with moderate-to-severe end-organ impairment (estimated glomerular ejection fraction [eGFR] <45 mL/min/1.73 m2 or Model for End-Stage Liver Disease excluding INR [MELD-XI] >15) at baseline had increased incidence of HF hospitalization and death through 12 months, regardless of treatment. There were no statistically significant differences between TEER and control patients in eGFR or MELD-XI at 12 months. In subgroup analyses examining only successful TEER patients (moderate or less TR at discharge) compared with control patients, as well as when censoring patients with normal baseline values, both eGFR (+3.55 ± 1.04 mL/min/1.73 m2 vs 0.07 ± 1.10 mL/min/1.73 m2; P = 0.022) and MELD-XI (-0.52 ± 0.18 vs 0.34 ± 0.18; P = 0.0007) improved. CONCLUSIONS: Baseline end-organ function was associated with HF hospitalization and death in patients with severe TR. At 12 months, eGFR and MELD-XI scores were not statistically significantly different between the overall TEER and control groups. In patients who had successful TEER, statistically significant, yet small, favorable changes occurred for both eGFR and MELD-XI. Further investigation is needed to assess whether these changes in end-organ function after successful TEER are clinically meaningful and reduce HF hospitalization or death. (Clinical Trial to Evaluate Cardiovascular Outcomes In Patients Treated With the Tricuspid Valve Repair System Pivotal [TRILUMINATE Pivotal]; NCT03904147).

High-resolution functional mapping of RAD51C by saturation genome editing.

Pathogenic variants in RAD51C confer an elevated risk of breast and ovarian cancer, while individuals homozygous for specific RAD51C alleles may develop Fanconi anemia. Using saturation genome editing (SGE), we functionally assess 9,188 unique variants, including >99.5% of all possible coding sequence single-nucleotide alterations. By computing changes in variant abundance and Gaussian mixture modeling (GMM), we functionally classify 3,094 variants to be disruptive and use clinical truth sets to reveal an accuracy/concordance of variant classification >99.9%. Cell fitness was the primary assay readout allowing us to observe a phenomenon where specific missense variants exhibit distinct depletion kinetics potentially suggesting that they represent hypomorphic alleles. We further explored our exhaustive functional map, revealing critical residues on the RAD51C structure and resolving variants found in cancer-segregating kindred. Furthermore, through interrogation of UK Biobank and a large multi-center ovarian cancer cohort, we find significant associations between SGE-depleted variants and cancer diagnoses.

Impact of essential genes on the success of genome editing experiments generating 3313 new genetically engineered mouse lines.

The International Mouse Phenotyping Consortium (IMPC) systematically produces and phenotypes mouse lines with presumptive null mutations to provide insight into gene function. The IMPC now uses the programmable RNA-guided nuclease Cas9 for its increased capacity and flexibility to efficiently generate null alleles in the C57BL/6N strain. In addition to being a valuable novel and accessible research resource, the production of 3313 knockout mouse lines using comparable protocols provides a rich dataset to analyze experimental and biological variables affecting in vivo gene engineering with Cas9. Mouse line production has two critical steps - generation of founders with the desired allele and germline transmission (GLT) of that allele from founders to offspring. A systematic evaluation of the variables impacting success rates identified gene essentiality as the primary factor influencing successful production of null alleles. Collectively, our findings provide best practice recommendations for using Cas9 to generate alleles in mouse essential genes, many of which are orthologs of genes linked to human disease.

The intra-aortic balloon pump as a rescue device: Do we need to shift our strategy for cardiogenic shock rescue after cardiac surgery?

OBJECTIVE: The intra-aortic balloon pump (IABP) is widely used to rescue patients from complications following cardiac surgery. Given improvements in rescue strategies over the past decade, the appropriateness of IABP must be reexamined. This study assessed the risk factors, outcomes, and predictors of survival of rescue IABP placement. METHODS: Patients receiving an isolated rescue IABP during or after cardiac surgery from 2012 to 2020 were studied. All adult patients undergoing cardiac surgery except transplantation and primary mechanical circulatory support (MCS) procedures were included. RESULTS: Of 10,591 patients, 397 (3.7%) received a perioperative IABP, including 182 (45.8%) with rescue IABP placement. The indications for rescue IABP were postcardiotomy shock (n = 66; 36.3%), failure to wean off cardiopulmonary bypass (n = 58; 31.9%), myocardial ischemia (n = 30; 16.5%), cardiac arrest (n = 25; 13.7%), and ventricular arrhythmia (n = 3; 1.6%). The in-hospital failure to rescue rate was 17.6% (n = 32 of 182) with a 90-day survival of 80.8% and 1-year survival of 76.9%. The most common etiology of mortality was ongoing cardiogenic shock (61.9%; n = 26 of 42). IABP use for >4 days and cardiac arrest as an indication for IABP were risk factors for 1-year mortality (adjusted hazard ratio, 2.68 [95% confidence interval (CI), 1.31-5.50] and 2.69 [95% CI, 1.11-6.54], respectively). CONCLUSIONS: Rescue IABP following cardiac surgery is associated with increased early and 1-year mortality. Prolonged IABP use beyond 4 days or cardiac arrest as an indication portended a significantly worse prognosis. Rescue IABP may not be the optimal first-line temporary MCS for all patients, as the level of support provided might not match the severity of cardiogenic shock. Alternative MCS strategies should be considered early.

Nonamyloidogenic TTR gene variants c.76G>A and c.337-18G>C are not associated with idiopathic small-fiber neuropathy.

BACKGROUND AND PURPOSE: Small-fiber neuropathy (SFN) affects only unmyelinated and thin myelinated fibers. It may be caused by amyloidogenic mutations of the transthyretin (TTR) gene, but not all TTR gene variants are pathogenic. The nonamyloidogenic c.76G>A (rs1800458) and c.337-18G>C (rs36204272) variants of TTR were recently reported to be associated with SFN. We investigated this putative association by analyzing TTR gene sequencing data retrospectively for two cohorts of patients, one with SFN and a control group. METHODS: In this retrospective single-center study, we analyzed the frequency of the c.76G>A and c.337-18G>C TTR gene variants in a cohort of patients meeting a strict definition of SFN, with or without dysautonomia, a control cohort of patients investigated for nonneurological conditions, and the gnomAD international database. RESULTS: We included 55 SFN patients in this study, 17 of whom had dysautonomia. The allelic frequencies of the two variants in our cohort of 55 SFN patients were 7.27% for c.76G>A TTR and 5.25% for c.337-18G>C. The frequencies of both variants were statistically similar in the 337 control patients and the gnomAD database. CONCLUSIONS: The c.76G>A and c.337-18G>C TTR gene variants are not associated with SFN.

A Retrospective Analysis of Intravenous Push versus Extended Infusion Meropenem in Critically Ill Patients.

Meropenem is a broad-spectrum antibiotic used for the treatment of multi-drug-resistant infections. Due to its pharmacokinetic profile, meropenem's activity is optimized by maintaining a specific time the serum concentration remains above the minimum inhibitory concentration (MIC) via extended infusion (EI), continuous infusion, or intermittent infusion dosing strategies. The available literature varies regarding the superiority of these dosing strategies. This study's primary objective was to determine the difference in time to clinical stabilization between intravenous push (IVP) and EI administration. We performed a retrospective pilot cohort study of 100 critically ill patients who received meropenem by IVP (n = 50) or EI (n = 50) during their intensive care unit (ICU) admission. There was no statistically significant difference in the overall achievement of clinical stabilization between IVP and EI (48% vs. 44%, p = 0.17). However, the median time to clinical stability was shorter for the EI group (20.4 vs. 66.2 h, p = 0.01). EI administration was associated with shorter hospital (13 vs. 17 days; p = 0.05) and ICU (6 vs. 9 days; p = 0.02) lengths of stay. Although we did not find a statistically significant difference in the overall time to clinical stabilization, the results of this pilot study suggest that EI administration may produce quicker clinical resolutions than IVP.

Vibrio cholerae pathogenicity island 2 encodes two distinct types of restriction systems.

In response to predation by bacteriophages and invasion by other mobile genetic elements such as plasmids, bacteria have evolved specialized defense systems that are often clustered together on genomic islands. The O1 El Tor strains of Vibrio cholerae responsible for the ongoing seventh cholera pandemic (7PET) contain a characteristic set of genomic islands involved in host colonization and disease, many of which contain defense systems. Notably, Vibrio pathogenicity island 2 contains several characterized defense systems as well as a putative type I restriction-modification (T1RM) system, which, interestingly, is interrupted by two genes of unknown function. Here, we demonstrate that the T1RM system is active, methylates the host genomes of a representative set of 7PET strains, and identify a specific recognition sequence that targets non-methylated plasmids for restriction. We go on to show that the two genes embedded within the T1RM system encode a novel two-protein modification-dependent restriction system related to the GmrSD family of type IV restriction enzymes. Indeed, we show that this system has potent anti-phage activity against diverse members of the Tevenvirinae, a subfamily of bacteriophages with hypermodified genomes. Taken together, these results expand our understanding of how this highly conserved genomic island contributes to the defense of pandemic V. cholerae against foreign DNA. IMPORTANCE: Defense systems are immunity systems that allow bacteria to counter the threat posed by bacteriophages and other mobile genetic elements. Although these systems are numerous and highly diverse, the most common types are restriction enzymes that can specifically recognize and degrade non-self DNA. Here, we show that the Vibrio pathogenicity island 2, present in the pathogen Vibrio cholerae, encodes two types of restriction systems that use distinct mechanisms to sense non-self DNA. The first system is a classical Type I restriction-modification system, and the second is a novel modification-dependent type IV restriction system that recognizes hypermodified cytosines. Interestingly, these systems are embedded within each other, suggesting that they are complementary to each other by targeting both modified and non-modified phages.