Burkholderia pseudomallei is a gram-negative bacterium that causes the serious human disease, melioidosis. There is no vaccine against melioidosis and it can be fatal if not treated with a specific ...antibiotic regimen, which typically includes the third-generation cephalosporin, ceftazidime (CAZ). There have been several resistance mechanisms described for B. pseudomallei, of which the best described are amino acid changes that alter substrate specificity in the highly conserved class A β-lactamase, PenA. In the current study, we sequenced penA from isolates sequentially derived from two melioidosis patients with wild-type (1.5 µg/mL) and, subsequently, resistant (16 or ≥256 µg/mL) CAZ phenotypes. We identified two single-nucleotide polymorphisms (SNPs) that directly increased CAZ hydrolysis. One SNP caused an amino acid substitution (C69Y) near the active site of PenA, whereas a second novel SNP was found within the penA promoter region. In both instances, the CAZ resistance phenotype corresponded directly with the SNP genotype. Interestingly, these SNPs appeared after infection and under selection from CAZ chemotherapy. Through heterologous cloning and expression, and subsequent allelic exchange in the native bacterium, we confirmed the role of penA in generating both low-level and high-level CAZ resistance in these clinical isolates. Similar to previous studies, the amino acid substitution altered substrate specificity to other β-lactams, suggesting a potential fitness cost associated with this mutation, a finding that could be exploited to improve therapeutic outcomes in patients harboring CAZ resistant B. pseudomallei. Our study is the first to functionally characterize CAZ resistance in clinical isolates of B. pseudomallei and to provide proven and clinically relevant signatures for monitoring the development of antibiotic resistance in this important pathogen.
Finding food and remaining at a food source are crucial survival strategies. We show how neural circuits and signaling molecules regulate these food-related behaviors in Caenorhabditis elegans. In ...the absence of food, AVK interneurons release FLP-1 neuropeptides that inhibit motorneurons to regulate body posture and velocity, thereby promoting dispersal. Conversely, AVK photoinhibition promoted dwelling behavior. We identified FLP-1 receptors required for these effects in distinct motoneurons. The DVA interneuron antagonizes signaling from AVK by releasing cholecystokinin-like neuropeptides that potentiate cholinergic neurons, in response to dopaminergic neurons that sense food. Dopamine also acts directly on AVK via an inhibitory dopamine receptor. Both AVK and DVA couple to head motoneurons by electrical and chemical synapses to orchestrate either dispersal or dwelling behavior, thus integrating environmental and proprioceptive signals. Dopaminergic regulation of food-related behavior, via similar neuropeptides, may be conserved in mammals.
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•Presence or absence of food promotes the dwelling or dispersal behavior of C. elegans•Dopamine signals to peptidergic interneurons in response to food•Peptidergic interneurons antagonize each other to inhibit or excite motoneurons•Cholecystokinin and RFamide modulate motoneurons to generate food response behavior
In this study of C. elegans food response behavior, the underlying circuitry is identified by dopaminergic neurons signaling the presence of food to interneurons that release neuropeptides and regulate locomotion by conferring distinct motoneuron responses via specific neuropeptide receptor expression.
Background The risk of death in dialysis patients is high, but varies significantly among patients. No prediction tool is used widely in current clinical practice. We aimed to predict long-term ...mortality in incident dialysis patients using easily obtainable variables. Study Design Prospective nationwide multicenter cohort study in the United Kingdom (UK Renal Registry); models were developed using Cox proportional hazards. Setting & Participants Patients initiating hemodialysis or peritoneal dialysis therapy in 2002-2004 who survived at least 3 months on dialysis treatment were followed up for 3 years. Analyses were restricted to participants for whom information for comorbid conditions and laboratory measurements were available (n = 5,447). The data set was divided into data sets for model development (n = 3,631; training) and validation (n = 1,816) using random selection. Predictors Basic patient characteristics, comorbid conditions, and laboratory variables. Outcomes All-cause mortality censored for kidney transplant, recovery of kidney function, and loss to follow-up. Results In the training data set, 1,078 patients (29.7%) died within the observation period. The final model for the training data set included patient characteristics (age, race, primary kidney disease, and treatment modality), comorbid conditions (diabetes, history of cardiovascular disease, and smoking), and laboratory variables (hemoglobin, serum albumin, creatinine, and calcium levels); reached a C statistic of 0.75 (95% CI, 0.73-0.77); and could discriminate accurately among patients with low (6%), intermediate (19%), high (33%), and very high (59%) mortality risk. The model was applied further to the validation data set and achieved a C statistic of 0.73 (95% CI, 0.71-0.76). Limitations Number of missing comorbidity data and lack of an external validation data set. Conclusions Basic patient characteristics, comorbid conditions, and laboratory variables can predict 3-year mortality in incident dialysis patients with sufficient accuracy. Identification of subgroups of patients according to mortality risk can guide future research and subsequently target treatment decisions in individual patients.
Summary Background Yersinia pestis has caused at least three human plague pandemics. The second (Black Death, 14–17th centuries) and third (19–20th centuries) have been genetically characterised, but ...there is only a limited understanding of the first pandemic, the Plague of Justinian (6–8th centuries). To address this gap, we sequenced and analysed draft genomes of Y pestis obtained from two individuals who died in the first pandemic. Methods Teeth were removed from two individuals (known as A120 and A76) from the early medieval Aschheim-Bajuwarenring cemetery (Aschheim, Bavaria, Germany). We isolated DNA from the teeth using a modified phenol-chloroform method. We screened DNA extracts for the presence of the Y pestis -specific pla gene on the pPCP1 plasmid using primers and standards from an established assay, enriched the DNA, and then sequenced it. We reconstructed draft genomes of the infectious Y pestis strains, compared them with a database of genomes from 131 Y pestis strains from the second and third pandemics, and constructed a maximum likelihood phylogenetic tree. Findings Radiocarbon dating of both individuals (A120 to 533 AD plus or minus 98 years; A76 to 504 AD plus or minus 61 years) places them in the timeframe of the first pandemic. Our phylogeny contains a novel branch (100% bootstrap at all relevant nodes) leading to the two Justinian samples. This branch has no known contemporary representatives, and thus is either extinct or unsampled in wild rodent reservoirs. The Justinian branch is interleaved between two extant groups, 0.ANT1 and 0.ANT2, and is distant from strains associated with the second and third pandemics. Interpretation We conclude that the Y pestis lineages that caused the Plague of Justinian and the Black Death 800 years later were independent emergences from rodents into human beings. These results show that rodent species worldwide represent important reservoirs for the repeated emergence of diverse lineages of Y pestis into human populations. Funding McMaster University, Northern Arizona University, Social Sciences and Humanities Research Council of Canada, Canada Research Chairs Program, US Department of Homeland Security, US National Institutes of Health, Australian National Health and Medical Research Council.
The glycosphingolipid GM1 binds cholera toxin (CT) on host cells and carries it retrograde from the plasma membrane (PM) through endosomes, the trans-Golgi (TGN), and the endoplasmic reticulum (ER) ...to induce toxicity. To elucidate how a membrane lipid can specify trafficking in these pathways, we synthesized GM1 isoforms with alternate ceramide domains and imaged their trafficking in live cells. Only GM1 with unsaturated acyl chains sorted efficiently from PM to TGN and ER. Toxin binding, which effectively crosslinks GM1 lipids, was dispensable, but membrane cholesterol and the lipid raft-associated proteins actin and flotillin were required. The results implicate a protein-dependent mechanism of lipid sorting by ceramide structure and provide a molecular explanation for the diversity and specificity of retrograde trafficking by CT in host cells.
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► Cells sort the glycosphingolipid GM1 by the structure of its ceramide domain (76/89) ► Only unsaturated GM1 ceramides sort retrograde all the way to the ER (64/78) ► GM1 is the vehicle that carries cholera toxin from plasma membrane to ER (61/74) ► Flotillin, cholesterol, and actin are required for GM1 sorting (55/64)
Chinnapen et al. examine how membrane lipids are sorted in mammalian cells and how the membrane glycosphingolipid GM1 can direct cholera toxin trafficking from cell surface into the ER of host cells to cause disease. Their results implicate a protein-dependent mechanism of sorting GM1, determined by its unsaturated ceramide domain.
Leptospirosis, caused by Leptospira bacteria, is a common zoonosis worldwide, especially in the tropics. Reservoir species and risk factors have been identified but surveys for environmental sources ...are rare. Furthermore, understanding of environmental Leptospira containing virulence associated genes and possibly capable of causing disease is incomplete, which may convolute leptospirosis diagnosis, prevention, and epidemiology.
We collected environmental samples from 22 sites in Puerto Rico during three sampling periods over 14-months (Dec 2018-Feb 2020); 10 water and 10 soil samples were collected at each site. Samples were screened for DNA from potentially pathogenic Leptospira using the lipL32 PCR assay and positive samples were sequenced to assess genetic diversity. One urban site in San Juan was sampled three times over 14 months to assess persistence in soil; live leptospires were obtained during the last sampling period. Isolates were whole genome sequenced and LipL32 expression was assessed in vitro. We detected pathogenic Leptospira DNA at 15/22 sites; both soil and water were positive at 5/15 sites. We recovered lipL32 sequences from 83/86 positive samples (15/15 positive sites) and secY sequences from 32/86 (10/15 sites); multiple genotypes were identified at 12 sites. These sequences revealed significant diversity across samples, including four novel lipL32 phylogenetic clades within the pathogenic P1 group. Most samples from the serially sampled site were lipL32 positive at each time point. We sequenced the genomes of six saprophytic and two pathogenic Leptospira isolates; the latter represent a novel pathogenic Leptospira species likely belonging to a new serogroup.
Diverse and novel pathogenic Leptospira are widespread in the environment in Puerto Rico. The disease potential of these lineages is unknown but several were consistently detected for >1 year in soil, which could contaminate water. This work increases understanding of environmental Leptospira diversity and should improve leptospirosis surveillance and diagnostics.
Robust Power Flow and Three-Phase Power Flow Analyses Pandey, Amritanshu; Jereminov, Marko; Wagner, Martin R. ...
IEEE transactions on power systems,
2019-Jan., 2019-1-00, 20190101, Letnik:
34, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Robust simulation is essential for reliable operation and planning of transmission and distribution power grids. At present, disparate methods exist for steady-state analysis of the transmission ...(power flow) and distribution power grid (three-phase power flow). Due to the nonlinear nature of the problem, it is difficult for alternating current power flow and three-phase power flow analyses to ensure convergence to the correct physical solution, particularly from arbitrary initial conditions, or when evaluating a change (e.g., contingency) in the grid. In this paper, we describe our equivalent circuit formulation approach with current and voltage variables, which models both the positive sequence network of the transmission grid and three-phase network of the distribution grid without loss of generality. The proposed circuit models and formalism enables the extension and application of circuit simulation techniques to solve for the steady-state solution with excellent robustness of convergence. Examples for positive sequence transmission and three-phase distribution systems, including actual 75k+ nodes Eastern Interconnection transmission test cases and 8k+ nodes taxonomy distribution test cases, are solved from arbitrary initial guesses to demonstrate the efficacy of our approach.
Diffuse cutaneous leishmaniasis (DCL) is a rare form of leishmaniasis where parasites grow uncontrolled in diffuse lesions across the skin. Meta-transcriptomic analysis of biopsies from DCL patients ...infected with Leishmania amazonensis demonstrated an infiltration of atypical B cells producing a surprising preponderance of the IgG4 isotype. DCL lesions contained minimal CD8+ T cell transcripts and no evidence of persistent TH2 responses. Whereas localized disease exhibited activated (so-called M1) macrophage presence, transcripts in DCL suggested a regulatory macrophage (R-Mϕ) phenotype with higher levels of ABCB5, DCSTAMP, SPP1, SLAMF9, PPARG, MMPs, and TM4SF19. The high levels of parasite transcripts in DCL and the remarkable uniformity among patients afforded a unique opportunity to study parasite gene expression in this disease. Patterns of parasite gene expression in DCL more closely resembled in vitro parasite growth in resting macrophages, in the absence of T cells. In contrast, parasite gene expression in LCL revealed 336 parasite genes that were differently upregulated, relative to DCL and in vitro macrophage growth, and these transcripts may represent transcripts that are produced by the parasite in response to host immune pressure.
Disinfection by-products (DBPs) are formed when disinfectants (chlorine, ozone, chlorine dioxide, or chloramines) react with naturally occurring organic matter, anthropogenic contaminants, bromide, ...and iodide during the production of drinking water. Here we review 30 years of research on the occurrence, genotoxicity, and carcinogenicity of 85 DBPs, 11 of which are currently regulated by the U.S., and 74 of which are considered emerging DBPs due to their moderate occurrence levels and/or toxicological properties. These 74 include halonitromethanes, iodo-acids and other unregulated halo-acids, iodo-trihalomethanes (THMs), and other unregulated halomethanes, halofuranones (MX 3-chloro-4-(dichloromethyl)-5-hydroxy-2(
5H)-furanone and brominated MX DBPs), haloamides, haloacetonitriles, tribromopyrrole, aldehydes, and
N-nitrosodimethylamine (NDMA) and other nitrosamines. Alternative disinfection practices result in drinking water from which extracted organic material is less mutagenic than extracts of chlorinated water. However, the levels of many emerging DBPs are increased by alternative disinfectants (primarily ozone or chloramines) compared to chlorination, and many emerging DBPs are more genotoxic than some of the regulated DBPs. Our analysis identified three categories of DBPs of particular interest. Category 1 contains eight DBPs with some or all of the toxicologic characteristics of human carcinogens: four regulated (bromodichloromethane, dichloroacetic acid, dibromoacetic acid, and bromate) and four unregulated DBPs (formaldehyde, acetaldehyde, MX, and NDMA). Categories 2 and 3 contain 43 emerging DBPs that are present at moderate levels (sub- to low-μg/L): category 2 contains 29 of these that are genotoxic (including chloral hydrate and chloroacetaldehyde, which are also a rodent carcinogens); category 3 contains the remaining 14 for which little or no toxicological data are available. In general, the brominated DBPs are both more genotoxic and carcinogenic than are chlorinated compounds, and iodinated DBPs were the most genotoxic of all but have not been tested for carcinogenicity. There were toxicological data gaps for even some of the 11 regulated DBPs, as well as for most of the 74 emerging DBPs. A systematic assessment of DBPs for genotoxicity has been performed for ∼60 DBPs for DNA damage in mammalian cells and 16 for mutagenicity in
Salmonella. A recent epidemiologic study found that much of the risk for bladder cancer associated with drinking water was associated with three factors: THM levels, showering/bathing/swimming (i.e., dermal/inhalation exposure), and genotype (having the
GSTT1-1 gene). This finding, along with mechanistic studies, highlights the emerging importance of dermal/inhalation exposure to the THMs, or possibly other DBPs, and the role of genotype for risk for drinking-water-associated bladder cancer. More than 50% of the total organic halogen (TOX) formed by chlorination and more than 50% of the assimilable organic carbon (AOC) formed by ozonation has not been identified chemically. The potential interactions among the 600 identified DBPs in the complex mixture of drinking water to which we are exposed by various routes is not reflected in any of the toxicology studies of individual DBPs. The categories of DBPs described here, the identified data gaps, and the emerging role of dermal/inhalation exposure provide guidance for drinking water and public health research.
: Tularemia is a disease caused by several subspecies of Francisella tularensis, although the severity of the disease varies greatly from subspecies to subspecies. Currently, there are four ...recognized subspecies (tularensis, holarctica, mediasiatica, and novicida), in addition to a second Francisella species, F. philomiragia. It is clear from molecular sampling of the environment that these human pathogens are a mere fraction of the Francisella diversity. Taxonomic nomenclature is now being based upon several DNA‐sequence‐based approaches and this advance provides for robust phylogenetic models that are guiding the systematics of this genus. This in turn allows for better molecular epidemiological investigations and more precise ecological analysis. Tularemia ecology is still only partially understood, with many knowledge gaps about the disease reservoir and vectors. Molecular analysis has identified a major population split within F. tularensis subsp. tularensis that points toward distinctive ecological adaptations, vectors, and host species. Current medical practice does not rely upon subspecies or subpopulation identification, although this information may have predictive value for clinical outcome, especially in the United States. Combined molecular and epidemiological analyses suggest that the population split in F. tularensis subsp. tularensis matches two distinct human diseases in the United States with different mortality rates. DNA‐sequence‐based typing of F. tularensis subsp. holarctica from tularemia outbreaks in Europe and the United States proves regional identity among isolates and also demonstrates that this subspecies successfully disseminated worldwide in recent evolutionary time.
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