Identification of Small Molecule Inhibitors of Clostridium perfringens ε-Toxin Cytotoxicity Using a Cell-Based High-Throughput Screen

The Clostridium perfringens epsilon toxin, a select agent, is responsible for a severe, often fatal enterotoxemia characterized by edema in the heart, lungs, kidney, and brain. The toxin is believed to be an oligomeric pore-forming toxin. Currently, there is no effective therapy for countering the cytotoxic activity of the toxin in exposed individuals. Using a robust cell-based high-throughput screening (HTS) assay, we screened a 151,616-compound library for the ability to inhibit ε-toxin-induced cytotoxicity. Survival of MDCK cells exposed to the toxin was assessed by addition of resazurin to detect metabolic activity in surviving cells. The hit rate for this screen was 0.6%. Following a secondary screen of each hit in triplicate and assays to eliminate false positives, we focused on three structurally-distinct compounds: an N-cycloalkylbenzamide, a furo[2,3-b]quinoline, and a 6H-anthra[1,9-cd]isoxazol. None of the three compounds appeared to inhibit toxin binding to cells or the ability of the toxin to form oligomeric complexes. Additional assays demonstrated that two of the inhibitory compounds inhibited ε-toxin-induced permeabilization of MDCK cells to propidium iodide. Furthermore, the two compounds exhibited inhibitory effects on cells pre-treated with toxin. Structural analogs of one of the inhibitors identified through the high-throughput screen were analyzed and provided initial structure-activity data. These compounds should serve as the basis for further structure-activity refinement that may lead to the development of effective anti-ε-toxin therapeutics

Genetic Signatures for \u3cem\u3eHelicobacter pylori\u3c/em\u3e Strains of West African Origin

Helicobacter pylori is a genetically diverse bacterial species that colonizes the stomach in about half of the human population. Most persons colonized by H. pylori remain asymptomatic, but the presence of this organism is a risk factor for gastric cancer. Multiple populations and subpopulations of H. pylori with distinct geographic distributions are recognized. Genetic differences among these populations might be a factor underlying geographic variation in gastric cancer incidence. Relatively little is known about the genomic features of African H. pylori strains compared to other populations of strains. In this study, we first analyzed the genomes of H. pylori strains from seven globally distributed populations or subpopulations and identified encoded proteins that exhibited the highest levels of sequence divergence. These included secreted proteins, an LPS glycosyltransferase, fucosyltransferases, proteins involved in molybdopterin biosynthesis, and Clp protease adaptor (ClpS). Among proteins encoded by the cag pathogenicity island, CagA and CagQ exhibited the highest levels of sequence diversity. We then identified proteins in strains of Western African origin (classified as hspWAfrica by MLST analysis) with sequences that were highly divergent compared to those in other populations of strains. These included ATP-dependent Clp protease, ClpS, and proteins of unknown function. Three of the divergent proteins sequences identified in West African strains were characterized by distinct insertions or deletions up to 8 amino acids in length. These polymorphisms in rapidly evolving proteins represent robust genetic signatures for H. pylori strains of West African origin

Genome sequences of three hpAfrica2 strains of Helicobacter pylori

We present the genome sequences of three hpAfrica2 strains of Helicobacter pylori, which are postulated to have evolved in isolation for many millennia in people of San ethnicity. Although previously considered to be ancestral to Helicobacter acinonychis, the hpAfrica2 strains differ markedly from H. acinonychis in their gene arrangement. These data provide new insights into Helicobacter evolution

Helicobacter pylori Exploits a Unique Repertoire of Type IV Secretion System Components for Pilus Assembly at the Bacteria-Host Cell Interface

Colonization of the human stomach by Helicobacter pylori is an important risk factor for development of gastric cancer. The H. pylori cag pathogenicity island (cag PAI) encodes components of a type IV secretion system (T4SS) that translocates the bacterial oncoprotein CagA into gastric epithelial cells, and CagL is a specialized component of the cag T4SS that binds the host receptor α5β1 integrin. Here, we utilized a mass spectrometry-based approach to reveal co-purification of CagL, CagI (another integrin-binding protein), and CagH (a protein with weak sequence similarity to CagL). These three proteins are encoded by contiguous genes in the cag PAI, and are detectable on the bacterial surface. All three proteins are required for CagA translocation into host cells and H. pylori-induced IL-8 secretion by gastric epithelial cells; however, these proteins are not homologous to components of T4SSs in other bacterial species. Scanning electron microscopy analysis reveals that these proteins are involved in the formation of pili at the interface between H. pylori and gastric epithelial cells. ΔcagI and ΔcagL mutant strains fail to form pili, whereas a ΔcagH mutant strain exhibits a hyperpiliated phenotype and produces pili that are elongated and thickened compared to those of the wild-type strain. This suggests that pilus dimensions are regulated by CagH. A conserved C-terminal hexapeptide motif is present in CagH, CagI, and CagL. Deletion of these motifs results in abrogation of CagA translocation and IL-8 induction, and the C-terminal motifs of CagI and CagL are required for formation of pili. In summary, these results indicate that CagH, CagI, and CagL are components of a T4SS subassembly involved in pilus biogenesis, and highlight the important role played by unique constituents of the H. pylori cag T4SS

Prevalence, predictors, and outcomes of poststroke falls in acute hospital setting

Abstract—Falls are a serious medical complication following stroke. The objectives of this study were to (1) confirm the prevalence of falls among patients with stroke during acute hospitalization, (2) identify factors associated with falls during the acute stay, and (3) examine whether in-hospital falls were associated with loss of function after stroke (new dependence at discharge). We completed a secondary analysis of data from a retrospective cohort study of patients with ischemic stroke who were hospitalized at one of four hospitals. We used logistic regression to identify factors associated with inpatient falls and examine the association between falls and loss of function. Among 1,269 patients with stroke, 65 (5%) fell during the acute hospitalization period. We found two characteristics independently associated with falls: greater stroke severity (National Institutes of Health Stroke Scale [NIHSS] 8, adjusted odds ratio [OR] = 3.63, 95% confidence interval [CI]: 1.46–9.00) and history of anxiety (adjusted OR = 4.90, 95% CI: 1.70–13.90). Falls were independently associated with a loss of function (adjusted OR = 9.85, 95% CI: 1.22–79.75) even after adjusting for age, stroke severity, gait abnormalities, and past stroke. Stroke severity (NIHSS 8) may be clinically useful during the acute inpatient setting in identifying those at greatest risk of falling. Given the association between falls and poor patient outcomes, rehabilitation interventions should be implemented to prevent falls poststroke

Auto-titrating continuous positive airway pressure for patients with acute transient ischemic attack: a randomized feasibility trial

BACKGROUND AND PURPOSE: Transient ischemic attack (TIA) patients are at risk of recurrent vascular events. The primary objectives were to evaluate among TIA patients the prevalence of sleep apnea and among patients with sleep apnea auto-titrating continuous positive airway pressure (auto-CPAP) adherence. The secondary objective was to describe among TIA patients with sleep apnea the recurrent vascular event rate by auto-CPAP use category. METHODS: All intervention patients received auto-CPAP for 2 nights, but only intervention patients with evidence of sleep apnea received auto-CPAP for the remainder of the 90-day period. Intervention patients received polysomnography at 90 days after TIA. Control patients received polysomnography at baseline and at 90 days. Acceptable auto-CPAP adherence was defined as >or=4 hours per night for >or=75% of nights. Vascular events included recurrent TIA, stroke, hospitalization for congestive heart failure, myocardial infarction, or death. RESULTS: We enrolled 70 acute TIA patients: 45 intervention and 25 control. The majority of patients had sleep apnea: 57% at baseline and 59% at 90 days. Among the 30 intervention patients with airflow obstruction, 12 (40%) had acceptable auto-CPAP adherence, 18 (60%) had some use, and none had no use. Three intervention patients (12%) had recurrent events compared with 1 (2%;P=0.13) control patient. The vascular event rate was highest among sleep apnea patients with no CPAP use: none, 16%;some, 5%;acceptable adherence 0% (P=0.08). CONCLUSIONS: Sleep apnea is common among acute TIA patients. It appears feasible to provide auto-CPAP in the acute TIA period. Larger studies should evaluate whether a strategy of diagnosing and treating sleep apnea can reduce recurrent vascular events after TIA

Runoff sources and land cover change in the Amazon : an end-member mixing analysis from small watersheds

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Biogeochemistry 105 (2011): 7-18, doi:10.1007/s10533-011-9597-8.The flowpaths by which water moves from watersheds to streams has important consequences for the runoff dynamics and biogeochemistry of surface waters in the Amazon Basin. The clearing of Amazon forest to cattle pasture has the potential to change runoff sources to streams by shifting runoff to more surficial flow pathways. We applied end member mixing analysis (EMMA) to ten small watersheds throughout the Amazon in which solute composition of streamwater and groundwater, overland flow, soil solution, throughfall and rainwater were measured, largely as part of the Large-Scale Biosphere-Atmosphere Experiment in Amazonia. We found a range in the extent to which streamwater samples fell within the mixing space determined by potential flowpath end members, suggesting that some water sources to streams were not sampled. The contribution of overland flow as a source of stream flow was greater in pasture watersheds than in forest watersheds of comparable size. Increases in overland flow contribution to pasture streams ranged in some cases from 0% in forest to 27 to 28% in pasture and were broadly consistent with results from hydrometric sampling of Amazon forest and pasture watersheds that indicate 17- to 18-fold increase in the overland flow contribution to stream flow in pastures. In forest, overland flow was an important contribution to stream flow (45 to 57%) in ephemeral streams where flows were dominated by stormflow. Overland flow contribution to stream flow decreased in importance with increasing watershed area, from 21 to 57% in forest and 60 to 89% in pasture watersheds 100 ha. Soil solution contributions to stream flow were similar across watershed area and groundwater inputs generally increased in proportion to decreases in overland flow. Application of EMMA across multiple watersheds indicated patterns across gradients of stream size and land cover that were consistent with patterns determined by detailed hydrometric sampling.This work was supported by National Science Foundation (DEB-0315656, DEB-0640661), the NASA LBA Program (NCC5-686, NCC5-69, NCC5-705, NNG066E88A) and by grants from Brazilian agencies FAPESP (03/13172-2) and CNPq (20199/2005-5)