Modular and Molecular Optimization of a LOV (Light-Oxygen-Voltage)-Based Optogenetic Switch in Yeast.

Optogenetic switches allow light-controlled gene expression with reversible and spatiotemporal resolution. In Saccharomyces cerevisiae, optogenetic tools hold great potential for a variety of metabolic engineering and biotechnology applications. In this work, we report on the modular optimization of the fungal light-oxygen-voltage (FUN-LOV) system, an optogenetic switch based on photoreceptors from the fungus Neurospora crassa. We also describe new switch variants obtained by replacing the Gal4 DNA-binding domain (DBD) of FUN-LOV with nine different DBDs from yeast transcription factors of the zinc cluster family. Among the tested modules, the variant carrying the Hap1p DBD, which we call "HAP-LOV", displayed higher levels of luciferase expression upon induction compared to FUN-LOV. Further, the combination of the Hap1p DBD with either p65 or VP16 activation domains also resulted in higher levels of reporter expression compared to the original switch. Finally, we assessed the effects of the plasmid copy number and promoter strength controlling the expression of the FUN-LOV and HAP-LOV components, and observed that when low-copy plasmids and strong promoters were used, a stronger response was achieved in both systems. Altogether, we describe a new set of blue-light optogenetic switches carrying different protein modules, which expands the available suite of optogenetic tools in yeast and can additionally be applied to other systems.

Analysis of the photoreceptors involved in the light-depending basidiocarp formation in Ustilago maydis.

We have described that formation of basidiocarps by Ustilago maydis requires illumination. In the current research, we have proceeded to analyze what kind of light receptors are involved in this phenomenon. Accordingly, we investigated whether the homologues of the White Collar (WC), and the phytochrome (PHY) genes played a role in this process. Mutants deficient in either one of the three U. maydis WC homologue genes (WCO1a, WCO1b, WCO2), or the phytochrome-encoding the PHY gene were obtained. Phenotypic analysis of the mutants showed that ∆wco1a mutants formed similar numbers of basidiocarps than wild-type strain, whereas ∆wco1b mutants were severely affected in basidiocarp formation when illuminated with white, blue or red light. ∆wco2 and ∆phy1 mutants did not form basidiocarps under any illumination condition. These data indicate that Wco1a is the main blue light receptor, and Wco1b may operate as a secondary blue light receptor; Phy1 is the red light receptor, and Wco2 the transcription factor that controls the photo stimulation of the genes involved in the formation of fruiting bodies. It is suggested that effectiveness of the light receptors depends on the whole structure of the complex, possibly, because their association is necessary to maintain their functional structure.

Bacterial Photosensory Proteins and Their Role in Plant-pathogen Interactions.

Light is an important environmental signal for almost all living organisms. The light perception is achieved by photoreceptor proteins. As can be observed from the great number of bacterial genomes sequenced, plant pathogenic bacteria encode for a large number of photoreceptor proteins. The physiological implications of these photoreceptors are still poorly characterized. However, recent studies revealed the participation of these photosensory proteins in the pathogenic process. Here, we summarize what is known about these proteins and their role during the virulence process, concluding that the light environment modulates the plant-pathogen interaction.

Optogenetic switches for light-controlled gene expression in yeast.

Light is increasingly recognized as an efficient means of controlling diverse biological processes with high spatiotemporal resolution. Optogenetic switches are molecular devices for regulating light-controlled gene expression, protein localization, signal transduction and protein-protein interactions. Such molecular components have been mainly developed through the use of photoreceptors, which upon light stimulation undergo conformational changes passing to an active state. The current repertoires of optogenetic switches include red, blue and UV-B light photoreceptors and have been implemented in a broad spectrum of biological platforms. In this review, we revisit different optogenetic switches that have been used in diverse biological platforms, with emphasis on those used for light-controlled gene expression in the budding yeast Saccharomyces cerevisiae. The implementation of these switches overcomes the use of traditional chemical inducers, allowing precise control of gene expression at lower costs, without leaving chemical traces, and positively impacting the production of high-value metabolites and heterologous proteins. Additionally, we highlight the potential of utilizing this technology beyond laboratory strains, by optimizing it for use in yeasts tamed for industrial processes. Finally, we discuss how fungal photoreceptors could serve as a source of biological parts for the development of novel optogenetic switches with improved characteristics. Although optogenetic tools have had a strong impact on basic research, their use in applied sciences is still undervalued. Therefore, the invitation for the future is to utilize this technology in biotechnological and industrial settings.

Functional Characterization of a LOV-Histidine Kinase Photoreceptor from Xanthomonas citri subsp. citri.

The blue-light (BL) absorbing protein Xcc-LOV from Xanthomonas citri subsp. citri is composed of a LOV-domain, a histidine kinase (HK) and a response regulator. Spectroscopic characterization of Xcc-LOV identified intermediates and kinetics of the protein's photocycle. Measurements of steady state and time-resolved fluorescence allowed determination of quantum yields for triplet (ΦT  = 0.68 ± 0.03) and photoproduct formation (Φ390  = 0.46 ± 0.05). The lifetime for triplet decay was determined as τT  = 2.4-2.8 µs. Fluorescence of tryptophan and tyrosine residues was unchanged upon light-to-dark conversion, emphasizing the absence of significant conformational changes. Photochemistry was blocked upon cysteine C76 (C76S) mutation, causing a seven-fold longer lifetime of the triplet state (τT  = 16-18.5 µs). Optoacoustic spectroscopy yielded the energy content of the triplet state. Interestingly, Xcc-LOV did not undergo the volume contraction reported for other LOV domains within the observation time window, although the back-conversion into the dark state was accompanied by a volume expansion. A radioactivity-based enzyme function assay revealed a larger HK activity in the lit than in the dark state. The C76S mutant showed a still lower enzyme function, indicating the dark state activity being corrupted by a remaining portion of the long-lived lit state.

Photoreceptors in Chemotrophic Prokaryotes: The Case of Acinetobacter spp. Revisited.

A comprehensive description of blue light using flavin (BLUF) photosensory proteins, including preferred domain architectures and the molecular mechanism of their light activation and signal generation, among chemotrophic prokaryotes is presented. Light-regulated physiological responses in Acinetobacter spp. from environmental and clinically relevant strains are discussed. The twitching motility response in A. baylyi sp. ADP1 and the joint involvement of three of the four putative BLUF-domain-containing proteins in this response, in this species, is presented as an example of remarkable photoreceptor redundancy.

The LOV protein of Xanthomonas citri subsp. citri plays a significant role in the counteraction of plant immune responses during citrus canker.

Pathogens interaction with a host plant starts a set of immune responses that result in complex changes in gene expression and plant physiology. Light is an important modulator of plant defense response and recent studies have evidenced the novel influence of this environmental stimulus in the virulence of several bacterial pathogens. Xanthomonas citri subsp. citri is the bacterium responsible for citrus canker disease, which affects most citrus cultivars. The ability of this bacterium to colonize host plants is influenced by bacterial blue-light sensing through a LOV-domain protein and disease symptoms are considerably altered upon deletion of this protein. In this work we aimed to unravel the role of this photoreceptor during the bacterial counteraction of plant immune responses leading to citrus canker development. We performed a transcriptomic analysis in Citrus sinensis leaves inoculated with the wild type X. citri subsp. citri and with a mutant strain lacking the LOV protein by a cDNA microarray and evaluated the differentially regulated genes corresponding to specific biological processes. A down-regulation of photosynthesis-related genes (together with a corresponding decrease in photosynthesis rates) was observed upon bacterial infection, this effect being more pronounced in plants infected with the lov-mutant bacterial strain. Infection with this strain was also accompanied with the up-regulation of several secondary metabolism- and defense response-related genes. Moreover, we found that relevant plant physiological alterations triggered by pathogen attack such as cell wall fortification and tissue disruption were amplified during the lov-mutant strain infection. These results suggest the participation of the LOV-domain protein from X. citri subsp. citri in the bacterial counteraction of host plant defense response, contributing in this way to disease development.

LOV-domain photoreceptor, encoded in a genomic island, attenuates the virulence of Pseudomonas syringae in light-exposed Arabidopsis leaves.

In Arabidopsis thaliana, light signals modulate the defences against bacteria. Here we show that light perceived by the LOV domain-regulated two-component system (Pst-Lov) of Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) modulates virulence against A. thaliana. Bioinformatic analysis and the existence of an episomal circular intermediate indicate that the locus encoding Pst-Lov is present in an active genomic island acquired by horizontal transfer. Strains mutated at Pst-Lov showed enhanced growth on minimal medium and in leaves of A. thaliana exposed to light, but not in leaves incubated in darkness or buried in the soil. Pst-Lov repressed the expression of principal and alternative sigma factor genes and their downstream targets linked to bacterial growth, virulence and quorum sensing, in a strictly light-dependent manner. We propose that the function of Pst-Lov is to distinguish between soil (dark) and leaf (light) environments, attenuating the damage caused to host tissues while releasing growth out of the host. Therefore, in addition to its direct actions via photosynthesis and plant sensory receptors, light may affect plants indirectly via the sensory receptors of bacterial pathogens.

Assessing the effects of light on differentiation and virulence of the plant pathogen Botrytis cinerea: characterization of the White Collar Complex.

Organisms are exposed to a tough environment, where acute daily challenges, like light, can strongly affect several aspects of an individual's physiology, including pathogenesis. While several fungal models have been widely employed to understand the physiological and molecular events associated with light perception, various other agricultural-relevant fungi still remain, in terms of their responsiveness to light, in the dark. The fungus Botrytis cinerea is an aggressive pathogen able to cause disease on a wide range of plant species. Natural B. cinerea isolates exhibit a high degree of diversity in their predominant mode of reproduction. Thus, the majority of naturally occurring strains are known to reproduce asexually via conidia and sclerotia, and sexually via apothecia. Studies from the 1970's reported on specific developmental responses to treatments with near-UV, blue, red and far-red light. To unravel the signaling machinery triggering development--and possibly also connected with virulence--we initiated the functional characterization of the transcription factor/photoreceptor BcWCL1 and its partner BcWCL2, that form the White Collar Complex (WCC) in B. cinerea. Using mutants either abolished in or exhibiting enhanced WCC signaling (overexpression of both bcwcl1 and bcwcl2), we demonstrate that the WCC is an integral part of the mentioned machinery by mediating transcriptional responses to white light and the inhibition of conidiation in response to this stimulus. Furthermore, the WCC is required for coping with excessive light, oxidative stress and also to achieve full virulence. Although several transcriptional responses are abolished in the absence of bcwcl1, the expression of some genes is still light induced and a distinct conidiation pattern in response to daily light oscillations is enhanced, revealing a complex underlying photobiology. Though overlaps with well-studied fungal systems exist, the light-associated machinery of B. cinerea appears more complex than those of Neurospora crassa and Aspergillus nidulans.

Light regulates attachment, exopolysaccharide production, and nodulation in Rhizobium leguminosarum through a LOV-histidine kinase photoreceptor.

Rhizobium leguminosarum is a soil bacterium that infects root hairs and induces the formation of nitrogen-fixing nodules on leguminous plants. Light, oxygen, and voltage (LOV)-domain proteins are blue-light receptors found in higher plants and many algae, fungi, and bacteria. The genome of R. leguminosarum bv. viciae 3841, a pea-nodulating endosymbiont, encodes a sensor histidine kinase containing a LOV domain at the N-terminal end (R-LOV-HK). R-LOV-HK has a typical LOV domain absorption spectrum with broad bands in the blue and UV-A regions and shows a truncated photocycle. Here we show that the R-LOV-HK protein regulates attachment to an abiotic surface and production of flagellar proteins and exopolysaccharide in response to light. Also, illumination of bacterial cultures before inoculation of pea roots increases the number of nodules per plant and the number of intranodular bacteroids. The effects of light on nodulation are dependent on a functional lov gene. The results presented in this work suggest that light, sensed by R-LOV-HK, is an important environmental factor that controls adaptive responses and the symbiotic efficiency of R. leguminosarum.

In vitro anticancer activity of microbial isolates from diverse habitats / In vitro atividade anticancerígena de isolados microbianos de diversos habitats

Extracts from natural products, especially microorganisms, have served as a valuable source of diverse molecules in many drug discovery efforts and led to the discovery of several important drugs. Identification of microbial strains having promising biological activities and purifying the bio-molecules responsible for the activities, have led to the discovery of many bioactive molecules. Extracellular, as well as intracellular, extracts of the metabolites of thirty-six bacterial and twenty-four fungal isolates, grown under unusual conditions such as high temperature, high salt and low sugar concentrations, were in vitro tested for their cytotoxic potential on various cancer cell lines. The extracts were screened on HeLa and MCF-7 cell lines to study the cytotoxic potential. Nuclear staining and flow cytometric studies were carried out to assess the potential of the extracts in arresting the cell cycle. The crude ethylacetate extract of isolate F-21 showed promising results by MTT assay with IC50 as low as 20.37±0.36 µg/mL on HeLa, and 44.75±0.81 µg/mL on MCF-7 cells, comparable with Cisplatin. The isolate F-21 was identified as Aspergillus sp. Promising results were also obtained with B-2C and B-4E strains. Morphological studies, biochemical tests and preliminary chemical investigation of the extracts were also carried out.

Extratos de produtos naturais, especialmente de microrganismos, constituíram-se em fonte valiosa de diversas moléculas em muitas descobertas de fármacos e levaram à descoberta de fármacos importantes. A identificação de espécies microbianas que apresentam atividade biológica e a purificação de biomoléculas responsáveis pelas atividades levou à descoberta de muitas moléculas bioativas. Extratos extracelulares tanto quanto intracelulares de metabólitos de 36 isolados de bactérias e 24 isolados de fungos, que cresceram sob condições não usuais, como alta temperatura, alta concentração de sal e baixa concentração de açúcar, foram testados in vitro quanto ao seu potencial citotóxico em várias linhagens de câncer. Os extratos foram ensaiados em células HeLa e MCF-7 para o estudo do potencial citotóxico. A coloração nuclear e os estudos de citometria de fluxo foram realizados para avaliar o potencial dos extratos em bloquear o ciclo celular. O extrato bruto em acetato de etila do isolado F-21 mostrou resultados promissores no ensaio de MTT, com IC50 de 20,37±0,36 µg/mL em células HeLa e 44,.75±0,81 µg/mL em células MCF-7, comparativamente à cisplatina. O isolado F-21 foi identificado como Aspergillus sp. Resultados promissores foram obtidos com cepas B-2C e B-4E. Realizaram-se, também, estudos morfológicos, testes bioquímicos e investigação química preliminar dos extratos.

Crucial factors of the light perception machinery and their impact on growth and cellulase gene transcription in Trichoderma reesei.

In Trichoderma reesei light stimulates transcription of cellulase genes and this regulation has been found to occur, at least in part, through the protein ENVOY. Here we analyzed the role of the BLR photoreceptor complex (BLR1/BLR2) in photoconidiation and the regulation of gene expression. Both responses were dependent on both BLR proteins. Analyses of Deltablr1, Deltablr2 and Deltaenv1 mutants showed that the BLR proteins regulate growth under illumination. Analysis of env1 mutant strains indicated that ENVOY allows the fungus to tolerate continuous exposure to light, damped the capacity of Trichoderma to perceive changes in light intensity, and suggested that it participates in a negative regulatory feedback. Its activity as repressor establishes a period of insensitivity to a second light treatment. Interestingly, the stimulation of cellulase gene expression by light was also modulated by both blr1 and blr2, indicating a key role of the BLR proteins in this pathway.

Sensibilidad a los antimicrobianos de cepas de Salmonella aisladas en granjas porcinas del estado Zulia / Antimicrobial susceptibility of Salmonella strains isolated from pig herds in Zulia state

El objetivo de este estudio fue determinar los patrones de resistencia a los antimicrobianos de diferentes cepas de Salmonella aisladas en granjas de cerdos del estado Zulia. Para este fin se evaluaron mediante la técnica de Bauer-Kirby, 126 cepas de Salmonella aisladas de heces de cerdos portadores asintomáticos. Las pruebas de sensibilidad antimicrobiana demostraron que los más altos niveles de resistencia fueron frente a la sulfamida (54 por ciento), tetraciclina (40 por ciento), ácido nalidíxico (29 por ciento) y ampicilina (23 por ciento). Sin embargo, sensibilidad superior al 95 por ciento fue encontrada frente a la ceftriaxona, gentamicina, apramicina y colistina. El treinta por ciento de las cepas mostraron multirresistencia (MR) a los antimicrobianos, siendo el patrón de resistencia ASuT (7,14 por ciento) el más frecuente. Los resultados obtenidos indican que la proporción de cepas de Salmonella de origen porcino con características de multirresistencia a los agentes antimicrobianos es medianamente elevada (30 por ciento) y esta multirresistencia puede afectar a cualquier serotipo. Desde ese punto de vista, la infección de las personas por cepas de Salmonella de origen porcino conlleva a un riesgo potencial de presentar dificultades en el tratamiento específico.

The aim of this study was to determine antimicrobial resintance paterns of different strains of Salmonella isolated in pig farms of the Zulia State. To achieve these goals 126 strain Salmonella were screened by Kirby-Bauer method, colleted from heces of pigs asymptomatic. Antimicrobial susceptibility tests showed that the highest level of resistance was against Sulphonamides (54%), Tetracycline (40%), Nalidixic acid (29%) and Amplicillin (23%). However, susceptibility superior to 95% was found to Ceftriaxone, Gentamycin, Apramycin and Colistin. Thrity percent of the strains showed multirresitance, being the patterns resistance ASuT (7.14%) the most frequent. The results indicate the proportion of strain of Salmonella of pig origin with characteristics of multiresistance to the antimicrobial agents is elevated (30%) and this multiresistance could affect to anyone serotype. From this point of view, the infection of the people by isolates of Salmonella from swine origin entails a potential risk to present difficulties in the specific treatment.

Caracterización fenotípica y susceptibilidad antimicrobiana de cepas clínicas de Stenotrophomonas maltophilia / Phenotypic characterization and antimicrobial susceptibility in clinical strains of Stenotrophomonas maltophilia

Stenotrophomonas maltophilia, anteriormente conocida como Xanthomonas maltophilia y Pseudomonas maltophilia es un bacilo Gram negativo no fermentador de la glucosa, reconocido como agente causal de diversas infecciones nosocomiales, además de presentar resistencia a múltiples agentes antimicrobianos. El objetivo del presente estudio fué identificar y caracterizar fenotípicamente cepas clínicas de S. maltophilia así como también establecer un patrón de actividad in vitro a diferentes antimicrobianos. Los aislados bacterianos, fueron suministrados por el laboratorio de Bacteriología del Hospital de Cumaná para ser identificadas a través de pruebas bioquímicas convencionales y de un método comercial empleando las galerias API ID32GN. Se determinó la CMI de los antimicrobianos mediante la técnica de dilución en agar Mueller Hinton siguiendo las normas del CLSI. Se identificaron fenotípicamente 24 cepas de S. maltophilia. La identificación fue 100 por ciento coincidente con ambas técnicas. Se mantuvo un patrón uniforme entre las cepas excepto para oxidasa donde 17 (70,83 por ciento) fueron positivas y 7 (29,17 por ciento) negativas. Los resultados de las pruebas de identificación mostraron la presencia de 5 fenotipos prevaleciendo el patrón típico del microorganismo (fenotipo I, 14 aislados). Las cepas mostraron 10 por ciento de resistencia a Imipenem, cefepime, amikacina y ácido nalidixico, 95,83 por ciento a cefotaxima, ceftazidima y ampicilina sulbactam, 91,67 por ciento a ceftriaxona y ciprofloxacina y 75 por ciento a piperacilina tazobactam, siendo más susceptibles a trimetoprim sulfametoxazol (91,67 por ciento), levofloxacina (75 por ciento) y rifampicina (95,83 por ciento)

Salmonella spp. y Shigella spp. asociados con síndrome diarreico agudo en niños menores de seis años de edad / Salmonella spp. and shigella spp. associated with acute diahrreic syndrome from children under six year of age

Con el propósito de determinar la presencia de aislados de Salmonella spp. y Shigella spp. y su asociación con manifestaciones clínicas de síndrome diarreico agudo, en niños menores de seis años de edad, se analizaron mediante coprocultivos 96 muestras de heces, entre los meses de julio a octubre de 2002, procedentes de pacientes, asistidos en el Servicio Autónomo Hospital Universitario "Antonio Patricio de Alcalá", Cumaná-estado Sucre. Se obtuvieron 50 casos positivos (52,08 por ciento)de los cuales 16,00 por ciento correspondieron a Shigella spp. aislándose Shigella sonnei en 50,00 por ciento mientras que Salmonella spp. se identificó en el 10,00 por ciento de los aislamientos. Salmonella agona y Salmonella enteritidis presentaron una frecuencia de 40,00 por ciento. En relación a Shigella spp., el análisis estadístico mostró una asociación altamente significativa (p<0,001) y significativa (p<0,05) en los pacientes con disentería y pujo, respectivamente. Asimismo, los resultados indican que existe asociación estadística muy significativa (p<0,01) entre la presencia de Salmonella spp. y el dolor abdominal y, asociación significativa (p<0,05) con la manifestación de pujo y fiebre. La actividad antimicrobiana in vitro, mostró que Shigella spp. presentó 62,50 por ciento de resistencia para ampicilina y 12,50 por ciento para cloranfenicol. Salmonella spp. fue resistente en un 20,00 por ciento a ampicilina, ciprofloxacina y gentamicina

BLR-1 and BLR-2, key regulatory elements of photoconidiation and mycelial growth in Trichoderma atroviride.

In fungi, phototropism, the induction of carotenogenesis and reproductive structures, and resetting of the circadian rhythm are controlled by blue light. Trichoderma atroviride, a fungus used in biological control, sporulates in a synchronized manner following a brief pulse of blue light. Due to its apparent simplicity, this response was chosen for pursuing photoreceptor isolation. Two genes were cloned, blue-light regulators 1 and 2 (blr-1 and blr-2), similar to the Neurospora crassa white-collar 1 and 2, respectively. The BLR-1 protein has all the characteristics of a blue-light photoreceptor, whereas the structure of the deduced BLR-2 protein suggests that it interacts with BLR-1 through PAS domains to form a complex. Disruption of the corresponding genes demonstrated that they are essential for blue-light-induced conidiation. blr-1 and blr-2 were also shown to be essential for the light-induced expression of the photolyase-encoding gene (phr-1). Mechanical injury of mycelia was found to trigger conidiation of T. atroviride, a response not described previously. This response was not altered in the mutants. A novel effect of both red and blue light on mycelial growth was found involving another light receptor, which is compensated by the BLR proteins.

Sensibilidad antimicrobiana de uropatógenos identificados en pacientes adultos con infección urinaria / Antibiotics sensibility of uropathogens indentified in adult patients with urinary tract infections

Las infecciones urinarias después de las respiratorias representan el grupo de infecciones que más afectan al humano. Evaluar, describir y analizar la sensibilidad antimicrobiana de los uropatógenos que con mayor frecuencia se identifican en pacientes atendidos en el Hospital Universitario de Caracas. Se efectuó un estudio de vigilancia bacteriológica de los uropatógenos identificados en la sección de Bacteriología. Diariamente se revisaban los aislamientos de uropatógenos y su sensibilidad antimocrobiana y posteriormente se relacionaban con antecedentes demográficos de los pacientes a quienes pertenecían. Se evaluaron los urocultivos de 738 pacientes: 70 por ciento del sexo femenino. Pertenecientes a la Consulta Ambulatoria el 23 por ciento, al Servicio de Urología el 17 por ciento y al Servicio de Obstetricia el 13 por ciento. Escherichia coli (55 por ciento) fue la bacteria más identificada seguida Klebsiella pneumoniae (9 por ciento). Escherichia coli fue 100 por ciento sensible a imipenem. La sensibilidad de Klebsiella pneumoniae fue: imipemen 100 por ciento, cefepima 88 por ciento, y ciprofloxacina 87 por ciento; Enterococus spp: vancomicina 100 por ciento trimetropim/sulfametaxol 100 por ciento y ampicilina 95 por ciento; Pseudonomas aeruginosa: cefepima 75 por ciento, piperacilina/ tazobactam 74 por ciento amikacina 61 por ciento; Staphylococus saprophyticus: ciprofloxacina, nitrofurantoína y rifampicina 100 por ciento. Se concluye recomendando la evaluación sistemática de los aislamientos de uropatógenos y de sus patrones de sensibilidad antimicobiana en las instituciones dispensadoras de salud, con la finalidad de mantener referencias estadísticas que permitan el tratamiento empírico de una infección urinaria mientras se espera el resultado del urocultivo correspondiente

Resistencia bacteriana en el Hospital Universitario de Caracas: año 1997 en cepas de diferentes procedencia / Resistance bacterial at the Universitary Caracas Hospital: year 1997 in straing differeat

A medida que la resistencia bacteriana (RB) se incrementa, se intensifican las investigaciones a fin de explicar sus causas y lograr su controlû. La relación entre el uso de antimicrobianos y la RB parece obvia a primera vista; sin embargo, el problema es complejo, ya que varios estudios no muestran claramente tal asociación. Entre 25 y 40 por ciento de todos los pacientes hospitalizados reciben antimicrobianos². El objetivo de este trabajo es comparar los porcentajes de resistencia de varios microorganismos (S.aureus, S. epidermidis, Enterobacter sp. K. pneumoniae, P. aeruginosa, A. baumannii y A. Iwoffii) provenientes de tres fuentes diferentes (Terapia intensiva= UTI; Hospital= IH; y Comunidad = IC) a distintos antimicrobianos (oxacilina = OXA; clindamicina = CC; vancomicina = VA; amikacina = AMK; ceftazidima = CAZ; cefoperazona-sulbactam= SLP; piperacilina tazobactam = TZP; cefepima = FEP; aztreonam = ATM; imipenem = IMP; ciprofioxacina = CIP.). Al analizar los resultados, encontramos diferencias importantes en la sensibilidad de todos los microoganismos a casi todos los antimicrobianos probados (resultados expresados en gráficos de barras). Estos resultados apoyan aparentemente la relación entre uso de antimicrobianos y selección de cepas resistentes en nuestro hospital

Resistencia bacteriana a los antimicrobianos / Bacterial resistance to the antimicrobials

Mediante la revisión de la literatura médica se realiza una actualización de la resistencia bacteriana a los antimicrobianos, problema que cada día preocupa más a los especialistas en el área de las enfermedades infecciosas y la micribiología, a los gerentes y directivos de las instituciones dispensadoras de salud, por los costos crecientes que conlleva a la compra de nuevos y eficientes antibióticos y antimicrobianos, para el tratamiento de las infecciones por agentes con nuevos mecanismos de resistencia. Se insiste en la clasificación y definición de los mecanismos de resistencia de los microorganismos responsables, tratando en lo posible de hacerlo de la manera más sencilla, sin que se comprometa la profundidad y el análisis de este problema, que hoy día es uno de los importantes en Salud Pública