Prospective multicenter evaluation of real time PCR Kit prototype for early diagnosis of congenital Chagas disease.

BACKGROUND: Current algorithm for Congenital Chagas Disease (cCD) diagnosis is unsatisfactory due to low sensitivity of the parasitological methods. Moreover, loss to follow-up precludes final serodiagnosis after nine months of life in many cases. A duplex TaqMan qPCR kit for Trypanosoma cruzi DNA amplification was prospectively evaluated in umbilical cord (UCB) and peripheral venous blood (PVB) of infants born to CD mothers at endemic and non-endemic sites of Argentina. METHODS: We enrolled and followed-up 370 infants; qPCR was compared to gold-standard cCD diagnosis following studies of diagnostic accuracy guidelines. FINDINGS: Fourteen infants (3·78%) had cCD. The qPCR sensitivity and specificity were higher in PVB (72·73%, 99·15% respectively) than in UCB (66·67%, 96·3%). Positive and negative predictive values were 80 and 98·73% and 50 and 98·11% for PVB and UCB, respectively. The Areas under the Curve (AUC) of ROC analysis for qPCR and micromethod (MM) were 0·81 and 0·67 in UCB and 0·86 and 0·68 in PVB, respectively. Parasitic loads ranged from 37·5 to 23,709 parasite equivalents/mL. Discrete typing Unit Tc V was identified in five cCD patients and in six other cCD cases no distinction among Tc II, Tc V or Tc VI was achieved. INTERPRETATION: This first prospective field study demonstrated that qPCR was more sensitive than MM for early cCD detection and more accurate in PVB than in UCB. Its use, as an auxiliary diagnostic tool to MM will provide more accurate records on cCD incidence. FUNDING: FITS SALUD 001-CHAGAS (FONARSEC, MINCyT, Argentina) to the Public-Private Consortium (INGEBI-CONICET, INP-ANLIS MALBRAN and Wiener Laboratories); ERANET-LAC-HD 328 to AGS and PICT 2015-0074 (FONCYT, MinCyT) to AGS and FA.

Molecular Diversity by Olefin Cross-Metathesis on Solid Support. Generation of Libraries of Biologically Promising ß-Lactam Derivatives.

The application of the reagent-based diversification strategy for generation of libraries of biologically promising ß-lactam derivatives is described. Key features are the versatility of the linker used and the cross-metathesis functionalization at the cleavage step. From an immobilized primary library, diversity was expanded by applying different cleavage conditions, leading to a series of cholesterol absorption inhibitor analogues together with interesting hybrid compounds through incorporation of a chalcone moiety.

The non-metathetic role of Grubbs' carbene complexes: from hydrogen-free reduction of α,ß-unsaturated alkenes to solid-supported sequential cross-metathesis/reduction.

An efficient and high-yielding "hydrogen-free" reduction of α,ß-unsaturated alkenes was carried out employing Grubbs' catalyst in a non-metathetic role and Et(3)SiH. Conditions were optimized under microwave irradiation. Application to the solid-phase organic synthesis allows a facile construction of sp(3)-sp(3) carbon bonds through a sequential cross metathesis/olefin reduction.

Unravelling the olefin cross metathesis on solid support. Factors affecting the reaction outcome.

Olefin cross metathesis on solid support under a variety of conditions is described. A comprehensive analysis considering diverse factors governing the reaction outcome gives a series of patterns for the application of this useful methodology in organic synthesis. If the intrasite reaction is not possible, homodimerization of the soluble olefin is crucial. When the homodimer is less reactive than its monomer, reaction outcome depends on the homodimerization rate, which, in turn, depends on the precatalyst used and the reaction conditions. If the site-site interaction is a feasible process, the cross metathesis product is obtained exclusively when the newly-formed double bond is resilient to further metathetic events. Taking into account these considerations, we have demonstrated that excellent results in terms of cross metathesis coupling can be obtained under the optimized conditions, and that microwave irradiation is also an interesting alternative for the development of a practical and energy-efficient cross metathesis on solid support.

Trapping and characterization of a reaction intermediate in carbapenem hydrolysis by B. cereus metallo-beta-lactamase.

Metallo-beta-lactamases hydrolyze most beta-lactam antibiotics. The lack of a successful inhibitor for them is related to the previous failure to characterize a reaction intermediate with a clinically useful substrate. Stopped-flow experiments together with rapid freeze-quench EPR and Raman spectroscopies were used to characterize the reaction of Co(II)-BcII with imipenem. These studies show that Co(II)-BcII is able to hydrolyze imipenem in both the mono- and dinuclear forms. In contrast to the situation met for penicillin, the species that accumulates during turnover is an enzyme-intermediate adduct in which the beta-lactam bond has already been cleaved. This intermediate is a metal-bound anionic species with a novel resonant structure that is stabilized by the metal ion at the DCH or Zn2 site. This species has been characterized based on its spectroscopic features. This represents a novel, previously unforeseen intermediate that is related to the chemical nature of carbapenems, as confirmed by the finding of a similar intermediate for meropenem. Since carbapenems are the only substrates cleaved by B1, B2, and B3 lactamases, identification of this intermediate could be exploited as a first step toward the design of transition-state-based inhibitors for all three classes of metallo-beta-lactamases.

Solid-supported cross metathesis and the role of the homodimerization of the non-immobilized olefin.

We have prepared immobilized olefins as models for the cross metathesis using different olefin partners in the presence of second generation Grubbs and Hoveyda-Grubbs precatalysts. We have demonstrated that solid-phase cross metathesis is strongly dependent on the degree of homodimerization of the non-immobilized olefin and the reactivity of such a homodimer. As in the homogeneous phase, the Hoveyda-Grubbs precatalyst was better for immobilized alpha,beta-unsaturated carbonyl compounds.

A minimalistic approach to identify substrate binding features in B1 Metallo-beta-lactamases.

The 2-oxoazetidinylacetate sodium salt was synthesized as a model of a minimal beta-lactam drug. This compound and the monobactam aztreonam were assayed as substrates of the Metallo-beta-lactamase BcII. None of them was hydrolyzed by the enzyme. While the azetidinone was not able to bind BcII, aztreonam was shown to bind in a nonproductive mode. These results provide an explanation for the unability of Metallo-beta-lactamases to inactive monobactams and give some clues for inhibitor design.