Enhanced Automatic Segmentation for Superficial White Matter Fiber Bundles for Probabilistic Tractography Datasets.

This paper presents an enhanced algorithm for automatic segmentation of superficial white matter (SWM) bundles from probabilistic dMRI tractography datasets, based on a multi-subject bundle atlas. Previous segmentation methods use the maximum Euclidean distance between corresponding points of the subject fibers and the atlas centroids. However, this scheme might include noisy fibers. Here, we propose a three step approach to discard noisy fibers improving the identification of fibers. The first step applies a fiber clustering and the segmentation is performed between the centroids of the clusters and the atlas centroids. This step removes outliers and enables a better identification of fibers with similar shapes. The second step applies a fiber filter based on two different fiber similarities. One is the Symmetrized Segment-Path Distance (SSPD) over 2D ISOMAP and the other is an adapted version of SSPD for 3D space. The last step eliminates noisy fibers by removing those that connect regions that are far from the main atlas bundle connections. We perform an experimental evaluation using ten subjects of the Human Connectome (HCP) database. The evaluation only considers the bundles connecting precentral and postcentral gyri, with a total of seven bundles per hemisphere. For comparison, the bundles of the ten subjects were manually segmented. Bundles segmented with our method were evaluated in terms of similarity to manually segmented bundles and the final number of fibers. The results show that our approach obtains bundles with a higher similarity score than the state-of-the-art method and maintains a similar number of fibers.Clinical relevance-Many brain pathologies or disorders can occur in specific regions of the SWM automatic segmentation of reliable SWM bundles would help applications to clinical research.

Impact of serpentinized peridotite mine waste on the composition and quality of sediments in the Ría de Ortigueira (Galicia, NW Spain).

The Ría de Ortigueira is an environmentally well conserved; however, the sediments show high concentrations of toxic elements. In some zones, the concentrations of Ni (60-1080 mg kg-1) and Cr (9-567 mg kg-1) were extremely high, while the concentrations of other toxic elements were within normal ranges. PCA revealed that metal enrichment was due to dumping of waste sludge from a peridotite mine. The study of marine currents showed that the exit of the contaminated waste towards the external zone is restricted by the low energy of the residual currents, and the sludge therefore remains trapped in the internal zones. The potential ecological risk was moderate for all areas of the ría, reaching high values close to the mouth of the river Landoi. Finally, geochemical fractioning showed that most of the metals are associated with Fe oxyhydroxides which can become unstable and release adsorbed or coprecipitated metals, especially Ni.

The effect of the number of fibers in tractography reconstruction of white matter bundles.

The study of white matter (WM) through diffusion Magnetic Resonance Imaging (dMRI) is crucial to obtain a better understanding of human brain connections and functions, at a macroscopic level. A large number of works have focused on long range brain connections, while recently, several studies have also analyzed superficial WM connectivity. In recent years, with the massive use of HCP database, and its processing with known softwares like DSI Studio and MRtrix, it is necessary to evaluate the influence of tractography parameters on the reconstruction of fiber bundles and further analyses. We study the effect of the number of fibers, for whole brain tractography, on the reconstruction of deep and superficial WM bundles based on their segmentation using multi-subject bundle atlases. For DSI Studio (deterministic algorithm), a value of 1M fibers could reconstruct most of deep white matter (DWM) bundles, while a value of 1.5M was required for superficial white matter (SWM) bundles. In the case of MRtrix (probabilistic algorithm), a value of 3M fibers was found to be suitable for the study of both kinds of fibers. Furthermore, we found the tracking of SWM bundles to be more sensitive to several parameters than DWM, for DSI Studio.

Consenso de VIH: tratamiento antirretroviral en adultos

Consenso para el tratamiento antirretroviral en adultos

Antiretroviral Adult treatment Consensus

Consenso de VIH-2: tratamiento antirretroviral en niños, adolescentes y embarazadas

Consenso para el tratamiento antirretroviral de las mujeres embarazadas, los adolescentes y los niños

Consensus of Antiretroviral treatment of pregnant women, adolescents and children

Consenso de VIH-3: adherencia al tratamiento antirretroviral y consideraciones en situaciones especiales

Consenso acerca de la adherencia al tratamiento antirretroviral en situaciones especiales

Consensus about the antiretroviral treatment adherence in special situations

HRTEM Microstructural Characterization of ß-WO3 Thin Films Deposited by Reactive RF Magnetron Sputtering.

Though tungsten trioxide (WO3) in bulk, nanosphere, and thin film samples has been extensively studied, few studies have been dedicated to the crystallographic structure of WO3 thin films. In this work, the evolution from amorphous WO3 thin films to crystalline WO3 thin films is discussed. WO3 thin films were fabricated on silicon substrates (Si/SiO2) by RF reactive magnetron sputtering. Once a thin film was deposited, two successive annealing treatments were made: an initial annealing at 400 °C for 6 h was followed by a second annealing at 350 °C for 1 h. Film characterization was carried out by X-ray diffraction (XRD), high-resolution electron transmission microscopy (HRTEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) techniques. The ß-WO3 final phase grew in form of columnar crystals and its growth plane was determined by HRTEM.

Whole genome sequencing of Shigella sonnei through PulseNet Latin America and Caribbean: advancing global surveillance of foodborne illnesses.

OBJECTIVES: Shigella sonnei is a globally important diarrhoeal pathogen tracked through the surveillance network PulseNet Latin America and Caribbean (PNLA&C), which participates in PulseNet International. PNLA&C laboratories use common molecular techniques to track pathogens causing foodborne illness. We aimed to demonstrate the possibility and advantages of transitioning to whole genome sequencing (WGS) for surveillance within existing networks across a continent where S. sonnei is endemic. METHODS: We applied WGS to representative archive isolates of S. sonnei (n = 323) from laboratories in nine PNLA&C countries to generate a regional phylogenomic reference for S. sonnei and put this in the global context. We used this reference to contextualise 16 S. sonnei from three Argentinian outbreaks, using locally generated sequence data. Assembled genome sequences were used to predict antimicrobial resistance (AMR) phenotypes and identify AMR determinants. RESULTS: S. sonnei isolates clustered in five Latin American sublineages in the global phylogeny, with many (46%, 149 of 323) belonging to previously undescribed sublineages. Predicted multidrug resistance was common (77%, 249 of 323), and clinically relevant differences in AMR were found among sublineages. The regional overview showed that Argentinian outbreak isolates belonged to distinct sublineages and had different epidemiologic origins. CONCLUSIONS: Latin America contains novel genetic diversity of S. sonnei that is relevant on a global scale and commonly exhibits multidrug resistance. Retrospective passive surveillance with WGS has utility for informing treatment, identifying regionally epidemic sublineages and providing a framework for interpretation of prospective, locally sequenced outbreaks.

Spatial normalization of brain images and beyond.

The deformable atlas paradigm has been at the core of computational anatomy during the last two decades. Spatial normalization is the variant endowing the atlas with a coordinate system used for voxel-based aggregation of images across subjects and studies. This framework has largely contributed to the success of brain mapping. Brain spatial normalization, however, is still ill-posed because of the complexity of the human brain architecture and the lack of architectural landmarks in standard morphological MRI. Multi-atlas strategies have been developed during the last decade to overcome some difficulties in the context of segmentation. A new generation of registration algorithms embedding architectural features inferred for instance from diffusion or functional MRI is on the verge to improve the architectural value of spatial normalization. A better understanding of the architectural meaning of the cortical folding pattern will lead to use some sulci as complementary constraints. Improving the architectural compliance of spatial normalization may impose to relax the diffeomorphic constraint usually underlying atlas warping. A two-level strategy could be designed: in each region, a dictionary of templates of incompatible folding patterns would be collected and matched in a way or another using rare architectural information, while individual subjects would be aligned using diffeomorphisms to the closest template. Manifold learning could help to aggregate subjects according to their morphology. Connectivity-based strategies could emerge as an alternative to deformation-based alignment leading to match the connectomes of the subjects rather than images.

Similar white matter but opposite grey matter changes in schizophrenia and high-functioning autism.

OBJECTIVE: High-functioning autism (HFA) and schizophrenia (SZ) are two of the main neurodevelopmental disorders, sharing several clinical dimensions and risk factors. Their exact relationship is poorly understood, and few studies have directly compared both disorders. Our aim was thus to directly compare neuroanatomy of HFA and SZ using a multimodal MRI design. METHODS: We scanned 79 male adult subjects with 3T MRI (23 with HFA, 24 with SZ and 32 healthy controls, with similar non-verbal IQ). We compared them using both diffusion-based whole-brain tractography and T1 voxel-based morphometry. RESULTS: HFA and SZ groups exhibited similar white matter alterations in the left fronto-occipital inferior fasciculus with a decrease in generalized fractional anisotropy compared with controls. In grey matter, the HFA group demonstrated bilateral prefrontal and anterior cingulate increases in contrast with prefrontal and left temporal reductions in SZ. CONCLUSION: HFA and SZ may share common white matter deficits in long-range connections involved in social functions, but opposite grey matter abnormalities in frontal regions that subserve complex cognitive functions. Our results are consistent with the fronto-occipital underconnectivity theory of HFA and the altered connectivity hypothesis of SZ and suggest the existence of both associated and diametrical liabilities to these two conditions.

Creation of a whole brain short association bundle atlas using a hybrid approach.

The Human brain connection map is far from being complete. In particular the study of the superficial white matter (SWM) is an unachieved task. Its description is essential for the understanding of human brain function and the study of pathogenesis triggered by abnormal connectivity. In this work we expanded a previously developed method for the automatic creation of a whole brain SWM bundle atlas. The method is based on a hybrid approach. First a cortical parcellation is used to extract fibers connecting two regions. Then an intra-and inter-subject hierarchical clustering are applied to find well-defined SWM bundles reproducible across subjects. In addition to the fronto-parietal and insula regions of the left hemisphere, the analysis was extended to the temporal and occipital lobes, including all their internal regions, for both hemispheres. Validation steps are performed in order to test the robustness of the method and the reproducibility of the obtained bundles. First the method was applied to two independent groups of subjects, in order to discard bundles without match across the two independent atlases. Then, the resulting intersection atlas was projected on a third independent group of subjects in order to filter out bundles without reproducible and reliable projection. The final multi-subject U-fiber atlas is composed of 100 bundles in total, 50 per hemisphere, from which 35 are common to both hemispheres. The atlas can be used in clinical studies for segmentation of the SWM bundles in new subjects, and measure DW values or complement functional data.

Short association bundle atlas based on inter-subject clustering from HARDI data.

This paper is focused on the study of short brain association fibers. We present an automatic method to identify short bundles of the superficial white matter based on inter-subject hierarchical clustering. Our method finds clusters of similar fibers, belonging to the different subjects, according to a distance measure between fibers. First, the algorithm obtains representative bundles and subsequently we perform an automatic labeling based on the anatomy, of the most stable connections. The analysis was applied to two independent groups of 37 subjects. Results between the two groups were compared, in order to keep reproducible connections for the atlas creation. The method was applied using linear and non-linear registration, where the non-linear registration showed significantly better results. A final atlas with 35 bundles in the left hemisphere and 27 in the right hemisphere from the whole brain was obtained. Finally results were validated using the atlas to segment 26 new subjects from another HARDI database.

Automatic segmentation of short association bundles using a new multi-subject atlas of the left hemisphere fronto-parietal brain connections.

Human brain connection map is far from being complete. In particular the study of the superficial white matter (SWM) is an unachieved task. Its description is essential for the understanding of human brain function and the study of the pathogenesis associated to it. In this work we developed a method for the automatic creation of a SWM bundle multi-subject atlas. The atlas generation method is based on a cortical parcellation for the extraction of fibers connecting two different gyri. Then, an intra-subject fiber clustering is applied, in order to divide each bundle into sub-bundles with similar shape. After that, a two-step inter-subject fiber clustering is used in order to find the correspondence between the sub-bundles across the subjects, fuse similar clusters and discard the outliers. The method was applied to 40 subjects of a high quality HARDI database, focused on the left hemisphere fronto-parietal and insula brain regions. We obtained an atlas composed of 44 bundles connecting 22 pair of ROIs. Then the atlas was used to automatically segment 39 new subjects from the database.

Antígenos HLA de clase ii en pacientes con artritis reumatoide ecuatorianos y asociación con el factor reumatoide, anticuerpos anti-citrulinados y nódulos reumatoides / HLA antigens class ii in patients with ecuadorian rheumatoid arthritis and association with the rheumatoid factor, anti-citrulinated antibodies and rheumatoid nodules

Objetivo Determinar los antígenos de Clase II en 52 pacientes con artritis reumatoide (AR) y 52 controles, y establecer la asociación de los antígenos de Clase II DRB1* con el factor reumatoide (FR), anticuerpos anti-péptido cíclico citrulinados (anti-CCP) y nódulos reumatoides. Material y Métodos Estudio de casos y controles, realizado en pacientes del Hospital Vicente Corral Moscoso y José Carrasco Arteaga de la ciudad de Cuenca-Ecuador; se incluyeron 52 pacientes con AR que cumplen los criterios del Colegio Americano de Reumatología (ACR) y 52 controles. Se identificaron a través de la Reacción en Cadena de la Polimerasa (PCR), los diferentes tipos de HLA que tienen cada uno de los 52 pacientes con AR y controles. Se buscó asociación de los HLA-DR1* con la AR y las pruebas de laboratorio: FR, anticuerpos anti-CCP y con nódulos reumatoides. El análisis estadístico se realizó con el cálculo de OR (IC 95%) y 2 de Pearson con corrección de Fisher y la información se procesó en SPSS v15. Resultados Los alelos más frecuentes fueron HLA-DRB1*09 (17,3%) OR 3,42 (IC95% 1,21 ­ 10,14) y HLADRB1*04 (32,7%) OR 1,81 (IC95% 0,93 ­ 3,55). Tanto el factor reumatoide como los anticuerpos anti-péptido cíclico citrulinados estuvieron presentes en el 82,7% de pacientes con artritis reumatoide y los nódulos reumatoides se detectaron en el 19,2% de pacientes con AR. Se encontró asociación entre los nódulos reumatoides con valores altos de FR y anti-CCP y estos a su vez con los alelos HLA-DRB1*14 y HLADRB1*04. La mayoría de pacientes con alelos HLA-DRB1*09 con predominio heterocigoto tuvieron anticuerpos anti-CCP y FR positivo. Conclusión La presencia de los alelos HLA-DRB1*04 y HLADRB1*09 está relacionada con la susceptibilidad de presentar AR en pacientes ecuatorianos, además se relaciona con valores elevados de factor reumatoide y anticuerpos anti-péptido cíclico citrulinados.

Objective To determine Class II antigens in 52 patients with rheumatoid arthritis (RA) and 52 controls and establish the association of Class II antigens DRB1* with rheumatoid anti- cyclic citrullinated peptide (anti-CCP) rheumatoid factor (RF), and antibodies rheumatoid nodules. Methods and Materials Case and control study in patients from the Hospital Vicente Corral Moscoso and José Carrasco Arteaga of Cuenca-Ecuador; 52 patients with rheumatoid arthritis who satisfy the criteria of ACR-American College of Rheumatology and 52 healthy patients. The different types of HLA from each 52 patients with rheumatoid arthritis and controls were identified through PCR - Polymerase Chain Reaction. Association of HLA-DR1* with rheumatoid arthritis and rheumatoid factor, anti-citrullinated and rheumatoid nodules. The statistical analysis was done by the OR (IC 95%) and 2 of Pearson with Fisher correction and the information was processed in SPSS v15. Results The most frequency alleles were HLA-DRB1*09 (17,3%) OR 3,42 (IC95% 1,21 ­ 10,14) and HLADRB1*04 (32,7%) OR 1,81 (IC95% 0,93 ­ 3,55). The rheumatoid factor and anti-cyclic citrullinated peptide antibodies were presented in 82,7% of patients with rheumatoid arthritis and rheumatoid nodules was detected in the 19.2% of patients with rheumatoid arthritis . An association between rheumatoid nodules with high values of rheumatoid factor and anti-ccp and these in turn with HLA-DRB1*14 y HLA-DRB1*04 alleles were found. The majority of patients with HLA-DRB1*09 alleles with heterozygote predomination had positive anti-ccp and rheumatoid factor. Conclusion The presence of HLA-DRB1*04 and HLA-DRB1*09 alleles is related with the susceptibility of present rheumatoid arthritis in Ecuadorian patients, and it is related with higher values of rheumatoid factor and anti-cyclic citrullinated peptide.

Automatic fiber bundle segmentation in massive tractography datasets using a multi-subject bundle atlas.

This paper presents a method for automatic segmentation of white matter fiber bundles from massive dMRI tractography datasets. The method is based on a multi-subject bundle atlas derived from a two-level intra-subject and inter-subject clustering strategy. This atlas is a model of the brain white matter organization, computed for a group of subjects, made up of a set of generic fiber bundles that can be detected in most of the population. Each atlas bundle corresponds to several inter-subject clusters manually labeled to account for subdivisions of the underlying pathways often presenting large variability across subjects. An atlas bundle is represented by the multi-subject list of the centroids of all intra-subject clusters in order to get a good sampling of the shape and localization variability. The atlas, composed of 36 known deep white matter bundles and 47 superficial white matter bundles in each hemisphere, was inferred from a first database of 12 brains. It was successfully used to segment the deep white matter bundles in a second database of 20 brains and most of the superficial white matter bundles in 10 subjects of the same database.

Infecciones urinarias adquiridas en la comunidad: epidemiología a los antimicrobianos y opciones terapéuticas / Urinary infections acquired in community: epidemiology resistance to antibiotics and therapeutic options

Las infecciones del tracto urinario (ITU) constituyen uno de los principales motivos de consulta en el ámbito de atención primaria. En los últimos años se han producido cambios sustanciales en los patrones de sensibilidad de los principales patógenos urinarios, lo que ha condicionado cambios en el tratamiento empírico de éstas. El objetivo de este trabajo fue caracterizar las ITU en pacientes de la comunidad. La muestra estuvo conformada por 71 pacientes de ambos sexos mayores de 18 años. El género más afectado fue el femenino (80,28%). Los signos y síntomas más frecuentes fueron dolor lumbar, disuria y dolor abdominal. La presencia de cálculos renales fue el más importante factor predisponente (39,43%), seguido de la menopausia (23,94%). El 63,38% de los pacientes presentaron ITU previas. Escherichia coli fue el agente causal más frecuente (63,89%), seguido de Proteus mirabilis (6,94%). Las enterobacterias aisladas presentaron elevados niveles de resistencia a ampicilina, cefalotina y norfloxacina. El 51,52% de las enterobacterias presentaron resistencia a las fluoroquinolonas y en el 16,67% se demostró la producción de ß-lactamasas de espectro expandido (BLEE). La mayoría de los agentes causales fueron sensibles a la nitrofurantoína independientemente de la presencia de mecanismos de resistencia que afectan a otros grupos de antimicrobianos

Urinary tract infections (UTI) are one of the main reasons for consultation in primary care. In recent years, there have been substantial changes in susceptibility patterns for major urinary tract pathogens, which have conditioned changes in their empirical treatment. The aim of this study was to characterize UTI in patients from the community. The sample consisted of 71 patients of both sexes over 18 years of age. The most affected sex was the female (80.28%). The signs and symptoms were lumbar pain, dysuria and abdominal pain. The presence of kidney stones was the most important predisposing factor (39.43%), followed by menopause (23.94%); 63.38% of the patients had a previous UTI. Escherichia coli was the most common agent (63.89%), followed by Proteus mirabilis (6.94%). Isolates showed high levels of resistance to ampicillin, cephalothin and norfloxacin. 51.52% of the Enterobacteriaceae were resistant to fluoroquinolones and 16.67% showed production of extended spectrum ß-lactamases (ESBL). Most of the agents were susceptible to nitrofurantoin, regardless of the presence of resistance mechanisms affecting other antibiotic groups

Reflujo gastroesofágico en pediatría / Gastro esophageal reflux disease in pediatrics

Gastro Esophageal Reflux (GER) is the passage of gastric content to the esophagus with or without vomitus or regurgitation. GER is a physiological process that occurs in 50 percent of newborns, spontaneously resolving at 12 to 14 months of age. When this retrograde gastric content reaches the esophagus and produces uncomfortable symptoms or complications, a disease is produced, named Gastro Esophageal Reflux Disease or GERD. Reflux episodes occur due to transient relaxation of the inferior esophagic sphincter, triggered by distension of the gastric fundus. Nursing children show higher frequency of episodes of relaxation due to a higher frequency of feeding than older children do. Most frequent symptoms include frequent regurgitation, with out without vomit, weight loss or poor weight gain, irritability, pyrosis, hematemesis, dysphagia, odinophagia, sibillances, stridor, cough, dysphonia, among others. These are very inespecific symptoms. Studies for GERD include 24 H pHmeasurement, which permits the study of associatrion between one of these symptoms and reflux, as well as the study of those patients with poor response to medical treatment. Unfortunately, it does not detect non-acid reflux. Multichannel intraluminal pH impedance measurement is a relatively new exam that measures the movement of fluids, gas or solids by a change in electric impedance through the esophagus. It allows to detect small volumes, type of content, acid and non acid and correlated with symptoms of GERD. Other useful exams include endoscopy with biopsy of the esophagus for diagnosis of esophagitis, esophageal mannometry for specific cases and gastroesophagic scintigram for pulmonary aspiration. Treatment include change in lifestyle (feeding, position, habits), pharmacological treatment and surgery. Medical treatment includes antacids, PPIs, most frequently omeprazole, H2 blockers such as ranitidine have a lower rate of healing of esophagitis than omeprazole, and appears to show tachyph...

El reflujo gastroesofagico (RGE) es el paso del contenido gástrico hacia el esófago con o sin vómitos o regurgitación. El RGE es un proceso normal fisiológico que ocurre en el 50 por ciento de los lactantes, resolviéndose espontáneamente a los 12 a 14 meses de edad. Cuando este contenido retrógrado gástrico alcanza al esófago y produce síntomas molestos o complicaciones se produce la enfermedad por RGE o ERGE. Los episodios de reflujo se producen principalmente por relajaciones transitorias del esfínter esofágico inferior (LES) gatillado por distensión del fondo gástrico. Los lactantes presentan mayor numero de episodios de relajación del LES debido a que se alimentan con más frecuencia que los niños mayores. Los síntomas más frecuentes asociados con reflujo patológico son regurgitaciones frecuentes con o sin vómitos, pérdida de peso o pobre ganancia de peso, irritabilidad, pirosis, hematemesis, disfagia, odinofagia, sibilancias, estridor, tos, disfonía entre otros, estos síntomas son poco específicos en lactantes y niños menores. Los exámenes para el estudio de ERGE son la pH metría de 24 hrs que permite estudiar la asociación entre un síntoma y el reflujo, también es útil para estudiar aquellos pacientes con mala respuesta al tratamiento médico, sin embargo, tiene el inconveniente que no detecta episodios de reflujo no ácidos. La pH-Impedanciometria Intraluminal multicanal (pH IIM) es un examen relativamente nuevo mide los movimientos de fluidos, gas o sólidos a través de cambios en la impe-dancia eléctrica a lo largo del esófago; permite distinguir pequeños volúmenes refluidos y el tipo de contenido, detecta reflujo acido y no acido y correlaciona síntomas con ERGE. Otros exámenes útiles son la endoscopia con biopsia de esófago para estudio de esofagitis. La Manometría esofágica tiene sus indicaciones específicas y la Cintigrafía gastroesofágica que es otro examen que se utiliza principalmente para estudiar aspiración pulmonar. El tratamiento incluye cambi...

Robust clustering of massive tractography datasets.

This paper presents a clustering method that detects the fiber bundles embedded in any MR-diffusion based tractography dataset. Our method can be seen as a compressing operation, capturing the most meaningful information enclosed in the fiber dataset. For the sake of efficiency, part of the analysis is based on clustering the white matter (WM) voxels rather than the fibers. The resulting regions of interest are used to define subset of fibers that are subdivided further into consistent bundles using a clustering of the fiber extremities. The dataset is reduced from more than one million fiber tracts to about two thousand fiber bundles. Validations are provided using simulated data and a physical phantom. We see our approach as a crucial preprocessing step before further analysis of huge fiber datasets. An important application will be the inference of detailed models of the subdivisions of white matter pathways and the mapping of the main U-fiber bundles.

Metaloenzimas tipo VIM detectadas en aislamientos clínicos en Pseudomonas aeruginosa en cuatro hospitales en Venezuela / VIM- type metalloenzymes detected in clinical isolates of Pseudomonas aeruginosa in four Venezuelan hospitals

En los últimos años se ha observado mundialmente un incremento del aislamiento de cepas de Pseudomonas aeruginosa resistentes a múltiples antibióticos, siendo la producción de β-lactamasas la principal causa de resistencia a los antibióticos β-lactámicos, los cuales constituyen la única opción terapéutica en muchos casos. Las metalo-β-lactamasas (MBLs) son una familia de enzimas degradadoras de β-lactámicos que recientemente han emergido como determinantes de resistencia de importancia clínica y que son activas contra los carbapenem; no hidrolizan a los monobactámicos; son inhibidas por agentes quelantes de iones metálicos como el EDTA y el ácido dipicolínico; no son inhibidas por el ácido clavulánico, sulbactan ni tazobactan y presentan uno o dos iones de zinc en su sitio activo. Este reporte describe la detección de MBLs tipo VIM mediante ensayos fenotípicos y moleculares en nueve cepas de Pseudomonas aeruginosa resistentes a carbapenems aisladas de muestras clínicas de cuatro hospitales de Venezuela. Por métodos fenotípicos se evidenció que 100% de las cepas eran productoras de MBLs, y por PCR todas las MBLs resultaron ser de la familia VIM, las cuales confieren alto nivel de resistencia a los antibióticos β-lactámicos, con excepción del Aztreonam, único antibiótico al cual se observó sensibilidad, complicando así las opciones terapéuticas.

In recent years there has been a worldwide raise in the isolation of Pseudomonas aeruginosa strains with resistance to multiple antibiotics, being β-lactamase production the main cause of resistance to β-lactamic antibiotic (which are the only therapeutic option in many cases). The MBLs are an β-lactamic- degrading enzymatic family that have emerged as clinically relevant resistance determinants and are active against carbapemens, don´t hydrolise monobactams, have one or two zinc ions in its active site and are inhibited by metallic ions chelating agents such as EDTA and dipicolinic acid, but aren´t inhibited by β-lactamase inhibitors such as clavulanic acid, sulbactam or tazobactam. This report describes the detection of VIM-type MBLs by phenotypic and molecular methods in 9 carbapenemsresistant Pseudomonas aeruginosa strains isolated from clinical samples of four Venezuelan hospitals. By phenotypic methods it was evidenced that 100% of the strains were MBLs producers, and by final- point PCR it was determined that all the MBLs were from the VIM family, which confer high- level resistance to the β-lactamic antibiotics (except Aztreonam), and because they are carried by plasmids with the ability to transfer horizontally to other bacterial families, they can be responsible for therapeutic complications in an individual or the patients collective.