Risk factors for early fatal outcomes among children with hemophagocytic lymphohistiocytosis (HLH): a single-institution case-series in Vietnam.

Hemophagocytic lymphohistiocytosis (HLH) is a rare and fatal hematological syndrome that causes a disturbance of the immune system. Overall mortality of HLH is greater than 50% and the majority of patients who die do so within the first 8 weeks of chemotherapy treatment. To find clinical parameters relating to high-risk HLH patients, this study examined associations between an early fatal outcome and potential prognostic clinical factors and laboratory findings on admission. Eighty-nine pediatric HLH patients were prospectively recruited in Children's Hospital No. 1, Ho-Chi-Minh City, Vietnam, during the period from January 2010 to August 2012. Associations between early fatal outcome and clinical and laboratory findings, including a cerebrospinal fluid examination and virological test on admission, were examined. During the 8-week therapy, 25 (28%) HLH patients died. Persistent fever (>2 weeks), severe thrombocytopenia (<75 × 10(9)/L), hyperbilirubinemia, and prolonged activated partial thromboplastin time (APTT) (>33 sec) were significant risk factors of early fatal outcome. Multivariate logistic regression analysis revealed that thrombocytopenia and prolonged APTT (P for trend was 0.054 and 0.013, respectively) were independently associated with the early fatal outcome. Persistent fever, severe thrombocytopenia, hyperbilirubinemia, and prolonged APTT on admission will be useful and practical predictors to determine high-risk HLH patients.

Cardiac Tamponade Due to Pericardial Effusion Following Peripherally Inserted Central Catheter: A Single-Institution Case Series.

INTRODUCTION: Although the use of peripherally inserted central catheters (PICCs) has many advantages, misplacement can lead to serious life-threatening complications such as pericardial effusion (PCE) and cardiac tamponade (CT). This report aims to describe four cases of CT resulting from misplaced PICC, which were successfully managed. METHODS: Retrospective analysis of neonates who required PICC insertion and had PCE leading to CT in the Neonatal Intensive Care Unit (NICU) at The Children's Hospital 2, Ho Chi Minh City, Vietnam, during the year 2022. RESULTS: Four cases involved preterm infants at 28-30 weeks gestational age, weighing between 900-1,500 grams. The PCE/CT developed between 3 and 24 days following PICC insertion. The abrupt onset with clinical manifestations that showed hemodynamic instability included sudden deterioration, lethargy, apnea, bradycardia, pale skin, and cardiovascular collapse. We use cardiac point of care ultrasound (POCUS) to assess the condition of these patients and guide the pericardiocentesis procedure. The analysis of the aspirated fluid used for PCE/CT treatment is consistent with the component of parenteral nutrition. No deaths were encountered. CONCLUSION: Neonates presenting sudden deterioration following PICC insertion should undergo POCUS to prompt identifying PCE/CT. Timely diagnosis via POCUS, prompt pericardiocentesis, and prevention of misplaced PICC-associated serious complications are crucial. Monitoring of the PICC position twice a week is recommended to avoid life-threatening complications. Additionally, incorporating POCUS for identifying the tip of PICC rather than relying solely on X-ray should be considered in the current protocol.

Progression of Amplitude-Integrated Electroencephalography and Neurological Outcomes in Neonates With Hypoxic-Ischemic Encephalopathy: A Single-Institution Cohort Study in Vietnam.

Background The characteristics of amplitude-integrated electroencephalography (aEEG) are associated with neurological outcomes in neonates with hypoxic-ischemic encephalopathy (HIE). We perform a longitudinal analysis of continuous monitoring of aEEG during therapeutic hypothermia and explore the association between aEEG interpretation and clinical neurological outcomes. Method We conducted a prospective cohort study on HIE neonates undergoing hypothermia with aEEG monitoring. Results A total of 37 HIE infants underwent hypothermia with improved aEEG background activity in 28 (75.7%) neonates, of which 18 (48.6%) neonates had background activity returned to a continuous pattern, and the median recovery time was 26.5 hours. Sleep-wake cycle (SWC) appeared in 14 (37.8%) cases, with a median onset time of 34.5 hours. Seizure activity on aEEG was present in 26 (70.3%) infants. Factors associated with poor outcomes at discharge included low voltage or flat trace background activity, a lack of improvement in background activity after hypothermia, and the absence of SWC. Neonates who took longer than 62 hours to return to continuous background activity (time to normal trace) or did not have SWC before the end of hypothermia were more likely to have unfavorable outcomes at discharge. Conclusions Longitudinal analysis of aEEG during hypothermia should be implemented in neonatal care units. The progression of these features on aEEG may predict neurological outcomes for HIE neonates.

Discovery of DNA operators for TetR and MarR family transcription factors from Burkholderia xenovorans.

Determining transcription factor (TF) recognition motifs or operator sites is central to understanding gene regulation, yet few operators have been characterized. In this study, we used a protein-binding microarray (PBM) to discover the DNA recognition sites and putative regulons for three TetR and one MarR family TFs derived from Burkholderia xenovorans, which are common to the genus Burkholderia. We also describe the development and application of a more streamlined version of the PBM technology that significantly reduced the experimental time. Despite the genus containing many pathogenically important species, only a handful of TF operator sites have been experimentally characterized for Burkholderia to date. Our study provides a significant addition to this knowledge base and illustrates some general challenges of discovering operators on a large scale for prokaryotes.

Structure, mechanism, and substrate profile for Sco3058: the closest bacterial homologue to human renal dipeptidase .

Human renal dipeptidase, an enzyme associated with glutathione metabolism and the hydrolysis of beta-lactams, is similar in sequence to a cluster of approximately 400 microbial proteins currently annotated as nonspecific dipeptidases within the amidohydrolase superfamily. The closest homologue to the human renal dipeptidase from a fully sequenced microbe is Sco3058 from Streptomyces coelicolor. Dipeptide substrates of Sco3058 were identified by screening a comprehensive series of l-Xaa-l-Xaa, l-Xaa-d-Xaa, and d-Xaa-l-Xaa dipeptide libraries. The substrate specificity profile shows that Sco3058 hydrolyzes a broad range of dipeptides with a marked preference for an l-amino acid at the N-terminus and a d-amino acid at the C-terminus. The best substrate identified was l-Arg-d-Asp (k(cat)/K(m) = 7.6 x 10(5) M(-1) s(-1)). The three-dimensional structure of Sco3058 was determined in the absence and presence of the inhibitors citrate and a phosphinate mimic of l-Ala-d-Asp. The enzyme folds as a (beta/alpha)(8) barrel, and two zinc ions are bound in the active site. Site-directed mutagenesis was used to probe the importance of specific residues that have direct interactions with the substrate analogues in the active site (Asp-22, His-150, Arg-223, and Asp-320). The solvent viscosity and kinetic effects of D(2)O indicate that substrate binding is relatively sticky and that proton transfers do not occurr during the rate-limiting step. A bell-shaped pH-rate profile for k(cat) and k(cat)/K(m) indicated that one group needs to be deprotonated and a second group must be protonated for optimal turnover. Computational docking of high-energy intermediate forms of l/d-Ala-l/d-Ala to the three-dimensional structure of Sco3058 identified the structural determinants for the stereochemical preferences for substrate binding and turnover.

The mechanism of the reaction catalyzed by uronate isomerase illustrates how an isomerase may have evolved from a hydrolase within the amidohydrolase superfamily.

Uronate isomerase (URI) catalyzes the reversible isomerization of D-glucuronate to D-fructuronate and of D-galacturonate to D-tagaturonate. URI is a member of the amidohydrolase superfamily (AHS), a highly divergent group of enzymes that catalyze primarily hydrolytic reactions. The chemical mechanism and active site structure of URI were investigated in an attempt to improve our understanding of how an active site template that apparently evolved to catalyze hydrolytic reactions has been reforged to catalyze an isomerization reaction. The pH-rate profiles for k(cat) and k(cat)/K(m) for URI from Escherichia coli are bell-shaped and indicate that one group must be unprotonated and another residue must be protonated for catalytic activity. Primary isotope effects on the kinetic constants with [2-2H]-D-glucuronate and the effects of changes in solvent viscosity are consistent with product release being the rate-limiting step. The X-ray structure of Bh0493, a URI from Bacillus halodurans, was determined in the presence of the substrate D-glucuronate. The bound complex showed that the mononuclear metal center in the active site is ligated to the C-6 carboxylate and the C-5 hydroxyl group of the substrate. This hydroxyl group is also hydrogen bonded to Asp-355 in the same orientation as the hydroxide or water is bound in those members of the AHS that catalyze hydrolytic reactions. In addition, the C-2 and C-3 hydroxyl groups of the substrate are hydrogen bonded to Arg-357 and the carbonyl group at C-1 is hydrogen bonded to Tyr-50. A chemical mechanism is proposed that utilizes a proton transfer from C-2 of D-glucuronate to C-1 that is initiated by the combined actions of Asp-355 from the end of beta-strand 8 and the C-5 hydroxyl of the substrate that is bound to the metal ion. The formation of the proposed cis-enediol intermediate is further facilitated by the shuttling of the proton between the C-2 and C-1 oxygens by the conserved Tyr-50 and/or Arg-355.

Erythritol as a single carbon source improves cultural isolation of Burkholderia pseudomallei from rice paddy soils.

BACKGROUND: Isolation of the soil bacterium Burkholderia pseudomallei from tropical environments is important to generate a global risk map for man and animals to acquire the infectious disease melioidosis. There is increasing evidence, that the currently recommended soil culture protocol using threonine-basal salt solution with colistin (TBSS-C50) for enrichment of B. pseudomallei and Ashdown agar for subsequent subculture lacks sensitivity. We therefore investigated, if the otherwise rarely encountered erythritol catabolism of B. pseudomallei might be exploited to improve isolation of this bacterium from soil. METHODOLOGY/PRINCIPAL FINDINGS: Based on TBSS-C50, we designed a new colistin-containing medium with erythritol as the single carbon source (EM). This medium was validated in various culture protocols by analyzing 80 soil samples from 16 different rice fields in Vietnam. B. pseudomallei enrichment was determined in all culture supernatants by a specific quantitative PCR (qPCR) targeting the type three secretion system 1. 51 out of 80 (63.8%) soil samples gave a positive qPCR signal in at least one of the culture conditions. We observed a significantly higher enrichment shown by lower median cycle threshold values for B. pseudomallei in a two-step culture with TBSS-C50 for 48 h followed by EM for 96h compared to single cultures in TBSS-C50 for either 48h or 144h (p<0.0001, respectively). Accordingly, B. pseudomallei could be isolated on Ashdown agar in 58.8% (30/51) of samples after subcultures from our novel two-step enrichment culture compared to only 9.8% (5/51) after standard enrichment with TBSS-C50 for 48h (p<0.0001) or 25.5% (13/51; p<0.01) after TBSS-C50 for 144h. CONCLUSIONS/SIGNIFICANCE: In the present study, we show that specific exploitation of B. pseudomallei metabolic capabilities in enrichment protocols leads to a significantly improved isolation rate of this pathogen from soil compared to established standard procedures. Our new culture method might help to facilitate the creation of environmental risk maps for melioidosis in the future.

A new bischromanone from the stems of Semecarpus caudata.

From an CHCl3-soluble fraction of the stems of Semecarpus caudata, one new bischromanone named semecarpanone (1), together with 5 known flavonoids (2-6) were isolated. Their structures were elucidated based on interpretation of spectroscopic data. The stereo-configuration of 1 was identified based on the calculated and experimental coupling constants. Compounds 4-6 showed potent tyrosinase inhibitory activity with the IC50 values ranging from 15.0 to 76.3 µM.

At the periphery of the amidohydrolase superfamily: Bh0493 from Bacillus halodurans catalyzes the isomerization of D-galacturonate to D-tagaturonate.

The amidohydrolase superfamily is a functionally diverse set of enzymes that catalyzes predominantly hydrolysis reactions involving sugars, nucleic acids, amino acids, and organophosphate esters. One of the most divergent members of this superfamily, uronate isomerase from Escherichia coli, catalyzes the isomerization of d-glucuronate to d-fructuronate and d-galacturonate to d-tagaturonate and is the only uronate isomerase in this organism. A gene encoding a putative uronate isomerase in Bacillus halodurans (Bh0705) was identified based on sequence similarity to uronate isomerases from other organisms. Kinetic evidence indicates that Bh0705 is relatively specific for the isomerization of d-glucuronate to d-fructuronate, confirming this functional assignment. Despite a low sequence identity to all other characterized uronate isomerases, phylogenetic and network-based analysis suggests that a second gene in this organism, Bh0493, is also a uronate isomerase, although it is an outlier in the group, with <20% sequence identity to any other characterized uronate isomerase from another species. The elucidation of the X-ray structure at a resolution of 2.0 A confirms that Bh0493 is a member of the amidohydrolase superfamily with conserved residues common to other members of the uronate isomerase family. Functional characterization of this protein shows that unlike Bh0705, Bh0493 can utilize both d-glucuronate and d-galacturonate as substrates. In B. halodurans, Bh0705 is found in an operon for the metabolism of d-glucuronate, whereas Bh0493 is in an operon for the metabolism of d-galacturonate. These results provide the first identification of a uronate isomerase that operates in a pathway distinct from that for d-glucuronate. While most organisms that contain this pathway have only one gene for a uronate isomerase, sequence analysis and operon context show that five other organisms also appear to have two genes and one organism appears to have three genes for this activity.