RESUMEN
In Enterobacteriaceae, the blaNDM genes have been found in many different genetic contexts, and a wide diversity of plasmid scaffolds bearing those genes has been found. In August 2013, we identified NDM-1-producing Escherichia coli and Enterobacter hormaechei strains from a single rectal swab sample from a patient hospitalized in Rio de Janeiro, Brazil, who had no history of travel abroad. Complete DNA sequencing using the Illumina platform and annotation of the two plasmids harboring the blaNDM-1 gene, one from each strain, showed that they belonged to incompatibility groups IncFIIK and IncX3 and harbored a novel transposon named Tn3000. Similar genetic structures have been identified among other isolates in Brazil but also on plasmids from other continents. Our findings suggest that the blaNDM-1 gene may be transmitted by Tn3000 in different parts of the world.
Asunto(s)
Elementos Transponibles de ADN/genética , Enterobacter/aislamiento & purificación , Escherichia coli/aislamiento & purificación , beta-Lactamasas/metabolismo , Antibacterianos/farmacología , Aztreonam/farmacología , Proteínas Bacterianas/genética , Secuencia de Bases , Brasil , Conjugación Genética , Secuencia Conservada , Enterobacter/efectos de los fármacos , Enterobacter/genética , Enterobacter/metabolismo , Infecciones por Enterobacteriaceae/microbiología , Escherichia coli/efectos de los fármacos , Escherichia coli/genética , Escherichia coli/metabolismo , Fosfomicina/farmacología , Humanos , India , Pruebas de Sensibilidad Microbiana , Marruecos , Nepal , Plásmidos , Recto/microbiología , beta-Lactamasas/genéticaRESUMEN
Total mercury, at µg kg(-1) level, was determined in different types of nuts (cashew nut, Brazil nuts, almond, pistachio, peanut, walnut) using a direct mercury analyser after previous sample defatting and by cold vapour atomic fluorescence spectrometry. There is not enough sensitivity in the second approach to determine Hg in previously digested samples due to the strong matrix effect. Mercury levels in 25 edible nut samples from Brazil and Spain were found in the range from 0.6 to 2.7µg kg(-1) by using the pyrolysis of sample after the extraction of the nut fat. The accuracy of the proposed method was confirmed by analysing certified reference materials of Coal Fly Ash-NIST SRM 1633b, Fucus-IAEA 140 and three unpolished Rice Flour NIES-10. The observed results were in good agreement with the certified values. The recoveries of different amounts of mercury added to nut samples ranged from 94 to 101%. RSD values corresponding to three measurements varied between 2.0 and 14% and the limit of detection and quantification of the method were 0.08 and 0.3µg kg(-1), respectively.
Asunto(s)
Mercurio/análisis , Nueces/química , Calibración , Límite de Detección , Espectrometría de Fluorescencia/métodosRESUMEN
A cold vapor atomic fluorescence spectrometry method (CV-AFS) has been developed for the determination of Hg in rice samples at a few ngg(-1) concentration level. The method is based on the previous digestion of samples in a microwave oven with HNO(3) and H(2)O(2) followed by dilution with water containing KBr/KBrO(3) and hydroxylamine and reduction with SnCl(2) in HCl using external calibration. The matrix interferences and the effect of nitrogen oxide vapors have been evaluated and the method validated using a certified reference material. The limit of detection of the method was 0.9ngg(-1) with a recovery percentage of 95+/-4% at an added concentration of 5ngg(-1). The concentration level of Hg found in 24 natural rice samples from different origin ranged between 1.3 and 7.8ngg(-1).
Asunto(s)
Gases/química , Mercurio/análisis , Microondas , Oryza/química , Espectrometría de Fluorescencia/métodos , Frío , Peróxido de Hidrógeno/química , Ácido Nítrico/química , Compuestos de Estaño/químicaRESUMEN
Quantifying cocaine in apprehended samples is important to the Brazilian Federal Police because the concentration can indicate the origin of the drug and consequently the traffic route. In addition to the other risks of using this drug is the variability in cocaine concentration, which makes large doses lethal. Gas Chromatography with a Flame Ionization Detector (GC-FID) and a Mass Selective Detector (GC-MS) are the techniques usually employed, but these systems are not available in all police laboratories, due to the relatively high cost. In the present work, a flow-system procedure for the spectrophotometric determination of cocaine using cobalt thiocyanate as a complexing reagent was developed. In this reaction, two phases are formed: the superior (pink) contains an excess of cobalt thiocyanate solution and the lower layer (blue) contains the complex cocaine-cobalt thiocyanate. Samples and reagent are inserted through a sequential-injection valve between two air bubbles inside a reaction chamber. An optic fiber sensor connected to the chamber recorded the absorbance at 630 nm signal. The detection and quantification limits were 29.4 mg L(-1) and 98 mg L(-1), respectively. Relative standard deviation was 4.9% for solutions containing 400 mg L(-1) (n=10), with stable baselines. The analytical throughput was 12 determinations per hour.
