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INTRODUCTION: Coronavirus disease 2019 (COVID-19) was declared a global pandemic in March 2020. Since then, several studies have found COVID-19 patients with recurrent viral polymerase chain reaction (PCR) positivity. METHODS: On May 6, 2021, an exhaustive literature search of the Web of Science, PubMed, Cochrane Library, Chinese National Knowledge Infrastructure databases, Embase, Wan Fang Data, VIP database, Sinomed database, BioRxiv, MedRxiv, and Research Square was conducted to find describing the laboratory indicators of recurrent and non-recurrent viral PCR positivity in patients with COVID-19. The data were statistically analyzed using STATA version 15.0. RESULTS: In total, 22 studies-comprising 5154 laboratory-confirmed COVID-19 cases-were included in the analyses. Patients with less severe COVID-19 illness (i.e. those clinically classified as mild or common-type) seemed to exhibit recurrent PCR positivity more commonly than patients with more severe illness (i.e. those classified as severe or critical). There were also significant differences between the two groups in terms of the rates of headaches and dizziness, in addition to the levels of aspartate aminotransferase, C reactive protein, interleukin-6, and lactate dehydrogenase. Further, there were variations in the ratio of CD4+ T cells/CD8+ T cells on admission to the hospital. CONCLUSION: In comparison to COVID-19 patients with non-recurrent viral PCR positivity, patients with recurrent virus PCR positivity seem to experience more severe immune function suppression upon hospital admission.
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Prueba de COVID-19/métodos , COVID-19/diagnóstico , COVID-19/inmunología , Inmunidad Celular/inmunología , Reacción en Cadena de la Polimerasa/métodos , COVID-19/epidemiología , Prueba de COVID-19/tendencias , Humanos , Reacción en Cadena de la Polimerasa/tendencias , RecurrenciaRESUMEN
BACKGROUND: The promoter hypermethylation of the methylguanine-DNA methyltransferase gene is a frequently used biomarker in daily clinical practice as it is associated with a favorable prognosis in glioblastoma patients treated with temozolamide. Due to the absence of adequately standardized techniques, international harmonization of the MGMT methylation biomarker is still an unmet clinical need for the diagnosis and treatment of glioblastoma patients. RESULTS: In this study we carried out a clinical validation of a quantitative assay for MGMT methylation detection by comparing a novel quantitative MSP using double-probe (dp_qMSP) with the conventional MSP in 100 FFPE glioblastoma samples. We performed both technologies and established the best cutoff for the identification of positive-methylated samples using the quantitative data obtained from dp_qMSP. Kaplan-Meier curves and ROC time dependent curves were employed for the comparison of both methodologies. CONCLUSIONS: We obtained similar results using both assays in the same cohort of patients, in terms of progression free survival and overall survival according to Kaplan-Meier curves. In addition, the results of ROC(t) curves showed that dp_qMSP increases the area under curve time-dependent in comparison with MSP for predicting progression free survival and overall survival over time. We concluded that dp_qMSP is an alternative methodology compatible with the results obtained with the conventional MSP. Our assay will improve the therapeutic management of glioblastoma patients, being a more sensitive and competitive alternative methodology that ensures the standardization of the MGMT-biomarker making it reliable and suitable for clinical use.
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Biomarcadores de Tumor/genética , Neoplasias Encefálicas/patología , Glioblastoma/diagnóstico , Glioblastoma/genética , Adulto , Anciano , Anciano de 80 o más Años , Antineoplásicos Alquilantes/uso terapéutico , Neoplasias Encefálicas/mortalidad , Estudios de Cohortes , Islas de CpG , Metilación de ADN , Metilasas de Modificación del ADN/genética , Enzimas Reparadoras del ADN/genética , Epigenómica , Femenino , Glioblastoma/tratamiento farmacológico , Glioblastoma/cirugía , Humanos , Estimación de Kaplan-Meier , Masculino , Persona de Mediana Edad , Reacción en Cadena de la Polimerasa/métodos , Reacción en Cadena de la Polimerasa/tendencias , Pronóstico , Supervivencia sin Progresión , Regiones Promotoras Genéticas/genética , Estudios Prospectivos , Curva ROC , Sensibilidad y Especificidad , Temozolomida/uso terapéutico , Proteínas Supresoras de Tumor/genéticaRESUMEN
AIM: To determine the mitochondrial microsatellite instability (mtMSI) status in a series of Malaysian patients with brain tumors. Furthermore, we analyzed whether the mtMSI status is associated with the clinicopathological features of the patients. MATERIAL AND METHODS: Forty fresh frozen tumor tissues along with blood samples of brain tumor patients were analyzed for mtMSI by PCR amplification of genomic DNAs, and the amplicons were directly sequenced in both directions using Sanger sequencing. RESULTS: Microsatellite analysis revealed that 20% (8 out of 40) of the tumors were mtMSI positive with a total of 8 mtMSI changes. All mtMSI markers were detected in D310 and D16184 of the D-loop region. Additionally, no significant association was observed between mtMSI status and clinicopathological features. CONCLUSION: The variations, specifically the mtMSI, suggest that the mitochondrial DNA (mtDNA) can be targeted for genomic alteration in brain tumors. Therefore, the specific role of mtDNA alteration in brain tumor development and prognosis requires further investigation.
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Neoplasias Encefálicas/epidemiología , Neoplasias Encefálicas/genética , ADN Mitocondrial/genética , Inestabilidad de Microsatélites , Adolescente , Adulto , Anciano , Neoplasias Encefálicas/diagnóstico , Neoplasias del Sistema Nervioso Central/diagnóstico , Neoplasias del Sistema Nervioso Central/epidemiología , Neoplasias del Sistema Nervioso Central/genética , Niño , Preescolar , Femenino , Humanos , Malasia/epidemiología , Masculino , Repeticiones de Microsatélite/genética , Persona de Mediana Edad , Mitocondrias/genética , Reacción en Cadena de la Polimerasa/tendencias , Adulto JovenRESUMEN
Over the past few decades, PCR has been the gold standard for detecting nucleic acids (NAs) in various biomedical fields. However, there are several limitations associated with conventional PCR, such as complicated operation, need for bulky equipment, and, in particular, long thermocycling time. Emerging nanomaterials with photothermal effects have shown great potential for developing a new generation of PCR: ultrafast photonic PCR. Here, we review recent applications of photothermal nanomaterials in ultrafast photonic PCR. First, we introduce emerging photothermal nanomaterials and their light-to-heat energy conversion process in photonic PCR. We then review different photothermal nanomaterial-based photonic PCRs and compare their merits and drawbacks. Finally, we summarize existing challenges with photonic PCR and hypothesize its promising future research directions.
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Nanoestructuras/química , Óptica y Fotónica/métodos , Reacción en Cadena de la Polimerasa/tendencias , Humanos , Terapia Fototérmica/tendenciasRESUMEN
This review is the second part of the workshop on digital PCR (dPCR) proposed by the working group of the French society of clinical biology. The first part of the paper discusses the advantages and limitations of dPCR for the search of different molecular abnormalities such as point mutations, copy number variants, DNA methylation, RNA analysis and a more innovative application, the single-cell dPCR. This synthesis makes it possible to propose a positioning of the dPCR compared to the other available technologies in a medical laboratory. In a second part, the main current applications of the dPCR will be addressed including the oncology of solid tumors and liquid biopsies, oncohematology and the follow-up of hemopathies treatments by hematopoietic stem cell transplantation. We will also detail non-invasive prenatal diagnosis and diagnosis of mosaic genetic disease, using the example of McCune-Albright syndrome. Several French specialists in the field who have implemented these techniques in their laboratory have written these different examples of applications jointly. In summary, this manuscript offers an up-to-date view of the positioning of dPCR in relation to other existing technologies in order to best meet the expectations of precision medicine.
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Técnicas de Diagnóstico Molecular/métodos , Reacción en Cadena de la Polimerasa/métodos , Pautas de la Práctica en Medicina , Medicina de Precisión , Femenino , Displasia Fibrosa Poliostótica/diagnóstico , Displasia Fibrosa Poliostótica/genética , Displasia Fibrosa Poliostótica/terapia , Trasplante de Células Madre Hematopoyéticas , Humanos , Técnicas de Diagnóstico Molecular/estadística & datos numéricos , Técnicas de Diagnóstico Molecular/tendencias , Neoplasias/diagnóstico , Neoplasias/genética , Neoplasias/terapia , Reacción en Cadena de la Polimerasa/estadística & datos numéricos , Reacción en Cadena de la Polimerasa/tendencias , Pautas de la Práctica en Medicina/estadística & datos numéricos , Pautas de la Práctica en Medicina/tendencias , Medicina de Precisión/métodos , Medicina de Precisión/estadística & datos numéricos , Medicina de Precisión/tendencias , Embarazo , Diagnóstico Prenatal/métodosRESUMEN
BACKGROUND: Clinical tuberculosis diagnosis and empiric treatment have traditionally been common among patients with negative bacteriologic test results. Increasing availability of rapid molecular diagnostic tests, including Xpert MTB/RIF and the new Xpert Ultra cartridge, may alter the role of empiric treatment. METHODS: We prospectively enrolled outpatients age > = 15 who were evaluated for pulmonary tuberculosis at three health facilities in Kampala, Uganda. Using sputum mycobacterial culture, interviews, and clinical record abstraction, we estimated the accuracy of clinical diagnosis relative to Xpert and sputum culture and assessed the contribution of clinical diagnosis to case detection. RESULTS: Over a period of 9 months, 99 patients were diagnosed with pulmonary tuberculosis and subsequently completed sputum culture; they were matched to 196 patients receiving negative tuberculosis evaluations in the same facilities. Xpert was included in the evaluation of 291 (99%) patients. Compared to culture, Xpert had a sensitivity of 92% (95% confidence interval 83-97%) and specificity of 95% (92-98%). Twenty patients with negative Xpert were clinically diagnosed with tuberculosis and subsequently had their culture status determined; two (10%) were culture-positive. Considering all treated patients regardless of Xpert and culture data completeness, and considering treatment initiations before a positive Xpert (N = 4) to be empiric, 26/101 (26%) tuberculosis treatment courses were started empirically. Compared to sputum smear- or Xpert-positive patients with positive cultures, empirically-treated, Xpert-negative patients with negative cultures had higher prevalence of HIV (67% versus 37%), shorter duration of cough (median 4 versus 8 weeks), and lower inflammatory markers (median CRP 7 versus 101 mg/L). CONCLUSION: Judged against sputum culture in a routine care setting of high HIV prevalence, the accuracy of Xpert was high. Clinical judgment identified a small number of additional culture-positive cases, but with poor specificity. Although clinicians should continue to prescribe tuberculosis treatment for Xpert-negative patients whose clinical presentations strongly suggest pulmonary tuberculosis, they should also carefully consider alternative diagnoses.
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Antibióticos Antituberculosos/uso terapéutico , Pruebas Diagnósticas de Rutina , Técnicas de Diagnóstico Molecular/métodos , Mycobacterium tuberculosis/genética , Esputo/microbiología , Tuberculosis Pulmonar/diagnóstico , Tuberculosis Pulmonar/tratamiento farmacológico , Adulto , Antibióticos Antituberculosos/clasificación , Estudios de Casos y Controles , Pruebas Diagnósticas de Rutina/métodos , Pruebas Diagnósticas de Rutina/tendencias , Farmacorresistencia Bacteriana/genética , Femenino , Humanos , Masculino , Técnicas Microbiológicas/métodos , Mycobacterium tuberculosis/aislamiento & purificación , Reacción en Cadena de la Polimerasa/métodos , Reacción en Cadena de la Polimerasa/tendencias , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Tiempo de Tratamiento/estadística & datos numéricos , Tuberculosis Resistente a Múltiples Medicamentos/diagnóstico , Tuberculosis Resistente a Múltiples Medicamentos/genética , Tuberculosis Resistente a Múltiples Medicamentos/prevención & control , Tuberculosis Pulmonar/epidemiología , Tuberculosis Pulmonar/microbiología , Uganda/epidemiologíaRESUMEN
The incidence of opportunistic yeast infections in humans has been increasing over recent years. These infections are difficult to treat and diagnose, in part due to the large number and broad diversity of species that can underlie the infection. In addition, resistance to one or several antifungal drugs in infecting strains is increasingly being reported, severely limiting therapeutic options and showcasing the need for rapid detection of the infecting agent and its drug susceptibility profile. Current methods for species and resistance identification lack satisfactory sensitivity and specificity, and often require prior culturing of the infecting agent, which delays diagnosis. Recently developed high-throughput technologies such as next generation sequencing or proteomics are opening completely new avenues for more sensitive, accurate and fast diagnosis of yeast pathogens. These approaches are the focus of intensive research, but translation into the clinics requires overcoming important challenges. In this review, we provide an overview of existing and recently emerged approaches that can be used in the identification of yeast pathogens and their drug resistance profiles. Throughout the text we highlight the advantages and disadvantages of each methodology and discuss the most promising developments in their path from bench to bedside.
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Secuenciación de Nucleótidos de Alto Rendimiento/métodos , Secuenciación de Nucleótidos de Alto Rendimiento/tendencias , Micosis/diagnóstico , Patología Molecular/métodos , Patología Molecular/tendencias , Levaduras/genética , Antifúngicos/farmacología , Antifúngicos/uso terapéutico , Farmacorresistencia Fúngica Múltiple , Humanos , Micosis/tratamiento farmacológico , Micosis/microbiología , Sistemas de Atención de Punto/tendencias , Reacción en Cadena de la Polimerasa/tendencias , Proteómica , Secuenciación Completa del Genoma/tendencias , Levaduras/efectos de los fármacos , Levaduras/patogenicidadRESUMEN
Dengue virus is an important arbovirus infection which transmitted by the Aedes female mosquitoes. The attempt to control and early detection of this infection is a global public health issue at present. Because of the clinical importance of its detection, the main focus of this review is on all of the methods that can offer the new diagnosis strategies. The advantages and disadvantages of reported methods have been discussed comprehensively from different aspects like biomarkers type, sensitivity, accuracy, rate of detection, possibility of commercialization, availability, limit of detection, linear range, simplicity, mechanism of detection, and ability of usage for clinical applications. The optical, electrochemical, microfluidic, enzyme linked immunosorbent assay (ELISA), and smartphone-based biosensors are the main approaches which developed for detection of different biomarkers and serotypes of Dengue virus. Future efforts in miniaturization of these methods open the horizons for development of commercial biosensors for early-diagnosis of Dengue virus infection. Graphical abstract Transmission of Dengue virus by the biting of an Aedes aegypti mosquito, the symptoms of Dengue hemorrhagic fever and the structure of Dengue virus and application of biosensors for its detection.
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Biomarcadores/sangre , Técnicas Biosensibles/métodos , Virus del Dengue/aislamiento & purificación , Técnicas Electroquímicas/métodos , Ensayo de Inmunoadsorción Enzimática/métodos , Reacción en Cadena de la Polimerasa/métodos , Técnicas Biosensibles/instrumentación , Técnicas Biosensibles/tendencias , Técnicas Electroquímicas/tendencias , Ensayo de Inmunoadsorción Enzimática/tendencias , Humanos , Reacción en Cadena de la Polimerasa/tendencias , Teléfono InteligenteRESUMEN
INTRODUCTION: The ongoing improvement and development of state-of-the-art diagnostic methods indicate that we are in an era of revolution in clinical microbiological diagnosis of infectious diseases. Non-culture-based methods have the possibility to play a central role in delivering personalized microbiological diagnoses of severe infections. The PCR electrospray ionization mass spectrometry (PCR/ESI-MS) system is built on the principle of universal detection and specific identification. The performance studies using PCR/ESI-MS on whole blood samples, as well as our experiences, indicate that this method provides useful clinical information. These types of modern molecular methods deserve further development for broad implementation into clinical practices. Areas covered: The review describes briefly hitherto developed molecular assays in detection of microorganisms directly from whole blood and focuses on the clinical implementation of PCR/ESI-MS. Expert opinion: The detection of an extensive broad-spectrum of microorganisms directly from whole blood samples with a series of tests that are run automatically with a turn-around time of 8 h would be a desirable diagnostic tool for the clinical microbiology laboratories. We believe that the clinical experience with PCR-ESI MS may guide the development and establishment of similar state-of-the-art diagnostic technologies in medicine in the future.
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Bacterias/aislamiento & purificación , Infecciones Bacterianas/sangre , Técnicas Microbiológicas/tendencias , Espectrometría de Masa por Ionización de Electrospray/tendencias , Bacterias/patogenicidad , Infecciones Bacterianas/diagnóstico , Infecciones Bacterianas/microbiología , Humanos , Reacción en Cadena de la Polimerasa/tendenciasRESUMEN
Co-amplification at lower denaturation temperature-polymerase chain reaction (COLD-PCR) is a novel form of PCR that selectively denatures and amplifies low-abundance mutations from mixtures of wild-type and mutation-containing sequences, enriching the mutation 10 to 100 folds. Due to the slightly altered melting temperature (Tm) of the double-stranded DNA and the formation of the mutation/wild-type heteroduplex DNA, COLD-PCR methods are sensitive, specific, accurate, cost-effective and easy to maneuver, and can enrich mutations of any type and at any position, even unknown mutations within amplicons. COLD-PCR and its improved methods are now applied in cancer, microorganisms, prenatal screening, animals and plants. They are extremely useful for early diagnosis, monitoring the prognosis of disease and the efficiency of the treatment, drug selection, prediction of prognosis, plant breeding and etc. In this review, we introduce the principles, key techniques, derived methods and applications of COLD-PCR.
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Reacción en Cadena de la Polimerasa/métodos , Animales , Análisis Mutacional de ADN , Humanos , Reacción en Cadena de la Polimerasa/instrumentación , Reacción en Cadena de la Polimerasa/tendencias , TemperaturaRESUMEN
After years of development, the use of nanopore as a sensor to sequence DNA molecules is now a viable and promising possibility. Single base pair detection during DNA transport enables to record ultra-long threads with high parallelization and rates. I will present in this review the current methodologies based on electrical detection and biological nanopores and the new methods based on solid state nanopores and optical detection.
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Nanoporos , Nanotecnología/tendencias , Análisis de Secuencia de ADN/métodos , Análisis de Secuencia de ADN/tendencias , Potenciales de Acción/fisiología , Animales , Comercio , Conductividad Eléctrica , Secuenciación de Nucleótidos de Alto Rendimiento/economía , Secuenciación de Nucleótidos de Alto Rendimiento/métodos , Humanos , Nanotecnología/economía , Nanotecnología/métodos , Reacción en Cadena de la Polimerasa/métodos , Reacción en Cadena de la Polimerasa/tendencias , Análisis de Secuencia de ADN/economíaRESUMEN
Background: Novel molecular techniques, such as the Biofire FilmArray Meningitis/Encephalitis (ME) panel, are increasingly used to improve pathogen detection and time to detection (TtD). The Brooke Army Medical Center antibiotic stewardship program evaluated the impact of the ME panel on empiric antimicrobial usage. Methods: Negative ME panels were analyzed for days of therapy (DOT). The ME panel became available at Brooke Army Medical Center on January 1, 2016 and a retrospective chart review was performed on all hospitalized patients tested by ME panel through April 30, 2016. Demographic data, cerebral spinal fluid (CSF) leukocyte count, immunocompromised status, and intensive care unit admission status were collected. TtD by ME panel and CSF culture were compared and DOT for common antimicrobials were quantified. Positive ME panels were analyzed for same demographic data, diagnoses, and microbiologic workup including CSF cultures and send out polymerase chain reactions. Results: Of the 77 ME panels performed during the study period, 54 (70%) were conducted on inpatients and included in the analysis. The majority of patients were males (n = 29, 54%) and the median age was 24 yr (interquartile range [IQR] 45; range 1 d to 83 yr). A total of eight (15%) patients were immunocompromised and 17 (31%) required intensive care unit level of care. The median TtD with the ME panel and CSF culture was 2.75 (IQR 2.16, 3.64) and 68.5 (IQR 63.87, 78.37) h, respectively. For negative ME panels, the overall median DOT for antimicrobials was 3 (IQR 1.5, 4.0) d, whereas the median DOT for individual agents was 2 (IQR 1.0, 4.0) d for vancomycin (n = 15), 1.5 (IQR 1.0, 2.25) d for ceftriaxone (n = 16), 3 (IQR 3.0, 4.0) d for ampicillin (n = 15), 3.5 (IQR 2.75, 4.0) d for gentamicin (n = 8), 3.5 (IQR 2.25, 4.0) d for cefotaxime (n = 6), and 5 (IQR 3.0, 5.5) d for acyclovir (n = 7); the median CSF leukocyte is of 2 cells/mm3 (IQR 1.0, 7.5). DOT excluded cases of positive ME panels: human herpes virus-6 (n = 2), herpes simplex virus-2 (n = 3), enterovirus (n = 1), and Streptococcus pneumoniae (n = 1). Of these, there were two discordance diagnoses between ME panel and convention microbiologic methods. S. pneumonia was detected on the ME panel and not on the CSF culture. One bone marrow transplant recipient had symptoms of encephalitis caused by human herpes virus-6 detected only by the ME panel, the send out human herpes virus-6 polymerase chain reaction was negative. Conclusion: The ME panel appears to improve diagnostic yield in our facility, and there is potential for improvement in decreasing empiric antimicrobial usage, particularly in patients with a negative ME panel and absence of CSF pleocytosis. This demonstrates the need for antibiotic stewardship program involvement to assist in implementation of rapid diagnostic tests through methods such as education, clinical guidelines, and prospective audit and feedback to improve meningitis and encephalitis management.
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Programas de Optimización del Uso de los Antimicrobianos/normas , Encefalitis/diagnóstico , Meningitis/diagnóstico , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Programas de Optimización del Uso de los Antimicrobianos/métodos , Niño , Preescolar , Femenino , Humanos , Lactante , Recién Nacido , Masculino , Persona de Mediana Edad , Reacción en Cadena de la Polimerasa/métodos , Reacción en Cadena de la Polimerasa/tendencias , Estudios Retrospectivos , Centros de Atención Terciaria/organización & administración , Centros de Atención Terciaria/estadística & datos numéricos , TexasRESUMEN
Digital PCR (dPCR) approaches have been developed for the detection of nucleic acids of low abundance, such as cell-free DNA, and represent an attractive and sensitive alternative to conventional methods, particularly in the field of non-invasive prenatal diagnosis (NIPD). In this review, we present the principle of dPCR and its applications in the field of prenatal diagnosis from current and emerging uses, such as fetal gender determination, rhesus blood group D antigen genotyping, or monogenic disorders prenatal testing, to future applications, such as the diagnosis and monitoring of pregnancy-related disorders. We also address considerations for implementation of the method in a clinical laboratory and discuss the competiveness of dPCR over other technologies such as quantitative PCR or massively parallel sequencing.
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Reacción en Cadena de la Polimerasa/métodos , Reacción en Cadena de la Polimerasa/tendencias , Diagnóstico Prenatal/métodos , Diagnóstico Prenatal/tendencias , Enfermedades Fetales/diagnóstico , HumanosRESUMEN
O sistema de secreção tipo IV (T4SS) da família de bactérias Xanthomonadaceae transfere efetores (X-Tfes) com a capacidade de matar outras bactérias, conferindo uma vantagem em comunidades bacterianas mistas para colonizar diferentes nichos como o solo ou as superfícies das plantas. Os X-Tfes possuem diferentes domínios putativos com atividades hidrolíticas contra componentes do envelope celular bacteriano do tipo: glicohidrolases, transglicosilases, amidases e lipases. Os X-Tfes por sua atividade biológica inata podem ocasionar dano intracelular para a bactéria que os produz. Para se proteger contra estas atividades, também são produzidas lipoproteínas com função inibitoria (X-Tfis) localizadas no periplasma. Os genes que codificam os X-Tfes e os X-Tfis estão organizados em operons, o que permite gerar os pares efetor/inibidor simultaneamente. Entre os potenciais X-Tfes do fitopatógeno Xanthomonas citri estão Xac1918 e Xac0574. Xac1918 é uma proteína com um domínio da superfamília da lisozima e um domínio conhecido como RTX (Repeats in Toxin) de ligação ao cálcio, enquanto Xac0574 tem um domínio da superfamília da lipase 3. Os seus possíveis inibidores, Xac1917 e Xac0573 respectivamente, apresentam um peptídeo sinal no N-terminal contendo o lipobox representativo das lipoproteínas. As proteínas Xac0574 e Xac0573 são monômeros em solução que formam um complexo estável 1:1, favorecido termodinamicamente (ΔG°= -12 Kcal/mol) com uma constante de dissociação de 2,45 nM, garantindo que a bactéria fique protegida contra os efeitos nocivos de Xac0574 quando é produzida intracelularmente. Xac0574 é uma fosfolipase A1, sem atividade lisofosfolipase, com a capacidade de hidrolisar os três fosfolipídios majoritários que compõem a membrana celular bacteriana, fosfatidilglicerol (PG), cardiolipina e fosfatidiletanolamina (PE), mostrando uma aparente preferência pelo último. A atividade enzimática de Xac0574 explica a forte inibição do crescimento celular em E. coli após da sua indução heteróloga, já que gera uma diminuição de quase 10 vezes da população celular comparada com a cultura não induzida com a mesma construção. Poroutro lado, Xac0573 inibe efetivamente a atividade enzimática de Xac0574 ao formar o complexo, além de não ter atividade fosfolipase nem lisofosfolipase. Foram produzidos cristais da Xac1918 e Xac0573 que difrataram com uma resolução de 3,0 e 2,5 Å, respectivamente. Porém, só foi gerado um modelo de Xac0573. Xac0573 está composta por duas folhas ß antiparalelas com uma topologia característica de ß sanduíche Com uma pequena hélice e duas voltas. Um alinhamento de homólogos de Xac0573 identificou nas extremidades da proteína as regiões conservadas, constituindo duas possíveis interfaces de interação que podem ser as responsáveis por bloquear o acesso dos fosfolipídios ao sítio catalítico ou impedir os rearranjos estruturais de Xac0574 que são necessários para a sua atividade enzimática. Adicionalmente, a topologia da Xac0573 é semelhante do domínio C2, conhecido em eucariotos como domínio de ligação ao lipídio e ao cálcio, e está envolvido em processos de sinalização de segundos mensageiros lipídicos, proteínas de trafego de membranas e mecanismos de fusão de membranas. Nossos resultados apontam para uma nova função biológica do domínio C2 como um inibidor enzimático intracelular em bactérias
The type IV secretion system (T4SS) of the bacteria family Xanthomonadaceae transfers effectors (X-Tfes) with that can kill other bacterial cells, conferring an advantage to the bacterial community during colonization of different niches in the soil or on the plant surface. The X-Tfes possess different putative domains with hydrolytic activity against components of the bacterial cellular envelope, including glycohydrolase, transglycolase, amidase and lipase domain. The innate biological activity of X-Tfes can cause intracellular damage. Therefore, the bacteria that produce them also produce lipoproteins with inhibitor function (X-Tfis) located in the periplasm for their protection. The genes that code for X-Tfes and X-Tfis are organized in operons that allow for their simultaneous expression. Among the X-Tfes of the phytopathogen Xanthomonas citri are Xac1918 and Xac0574. Xac1918 is carries a lysozyme superfamily domain, as well as a domain known as RTX (Repeats in Toxic) predict to bind calcium, while, Xac0574 has a domain belonging to the lipase 3 superfamily. Their possible inhibitors, Xac1917 e Xac0573 respectively, carry an N-terminal signal peptide containing a lipobox found in bacterial lipoproteins. The Xac0574 and Xac0573 proteins are both monomers in solution, They can form a stable 1:1 complex, that is thermodynamically favored (ΔG°= -12 Kcal/mol) with a dissociation constant of 2,45 nM. This affinity ensure that the bacterium is protected against the harmful effects of Xac0574 when it is produced intracellularly. We show that Xac0574 is a phospholipase A1, without lisophospholipase activity, and is able to hydrolyze the three most common phospholipids found in the membranes of Gram negative bacteria, namely phosphatidylglycerol (PG), cardiolipin and phosphatidylethanolamine (PE), presenting an apparent preference for PE. The enzymatic activity of Xac0574 explains the strong inhibition of growth of E. coli cells after its heterologous induction: a nearly 10-fold decrease in the cell population is observed when compared to the non-induced culture with the same construct. On the other hand, Xac0573 effectively inhibits the enzymatic activity of Xac0574. Furthermore, Xac0573 does not possess when forming the complex, besides not having phospholipase nor lysophospholipase activity.Crystals of Xac1918 and Xac0573 were produced which diffracted with to resolution of 3.0 and 2.5 Å, respectively. However, we were able to resolve the structure of only Xac0573. Xac0573 is composed of two anti-parallel sheet that form a ß-sandwich with three small helices. An alignment to Xac0573 homologs identified conserved regions at the ends of the protein that constitute two possible interfaces of interaction that may be responsible for blocking the access of the phospholipids to the catalytic site or impede the structural rearrangements of Xac0574 that are necessary for its enzymatic activity. Additionally, the topology of Xac0573 is similar to that to C2 domains, known in eukaryotes to bind lipids and calcium and to be involved in signaling processes mediated by lipid second messengers, membrane trafficking and membrane fusion mechanisms. Our results point to a new biological function of the C2 domain as an intracellular enzyme inhibitor in bacteria
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Plantas , Suelo , Xanthomonas/clasificación , Sistemas de Secreción Tipo IV/análisis , Reacción en Cadena de la Polimerasa/tendencias , Biología Molecular/clasificaciónRESUMEN
Infections of the nervous system are an important and challenging aspect of clinical neurology. Immediate correct diagnosis enables to introduce effective therapy, in conditions that without diagnosis may leave the patient with severe neurological incapacitation and sometimes even death. The cerebrospinal fluid (CSF) is a mirror that reflects nervous system pathology and can promote early diagnosis and therapy. The present chapter focuses on the CSF findings in neuro-infections, mainly viral and bacterial. Opening pressure, protein and glucose levels, presence of cells and type of the cellular reaction should be monitored. Other tests can also shed light on the causative agent: serology, culture, staining, molecular techniques such as polymerase chain reaction. Specific examination such as panbacterial and panfungal examinations should be examined when relevant. Our chapter is a guide-text that combines clinical presentation and course with CSF findings as a usuaful tool in diagnosis of neuroinfections.
Asunto(s)
Líquido Cefalorraquídeo/microbiología , Enfermedades Transmisibles/líquido cefalorraquídeo , Enfermedades Transmisibles/diagnóstico , Enfermedad Aguda , Animales , Enfermedad Crónica , Enfermedades Transmisibles/fisiopatología , Electroencefalografía/tendencias , Humanos , Reacción en Cadena de la Polimerasa/tendenciasRESUMEN
New applications are driving the need for faster, higher fidelity PCR. Nathan Blow looks at some clever modifications taking PCR to the next level.
Asunto(s)
Reacción en Cadena de la Polimerasa , Humanos , Reacción en Cadena de la Polimerasa/métodos , Reacción en Cadena de la Polimerasa/tendenciasRESUMEN
Today, we have access to excellent and advanced molecular methods that are already widely used. This requires rules to control the quality of the methods as well as the laboratory. Both aspects will be discussed in the article. Following the isolation of nucleic acids they are used for genotyping which allows to address several questions: diagnosis of inherited diseases, inherited predispositions, forensic analyses, identification and typing of bacteria or viruses, elucidation of evolutionary aspects. Importantly, it has to be realized that the type and heterogeneity of phenotypically relevant mutations determines the method used for testing. Today, most laboratories use either PCR analyses or Sanger sequencing for diagnostic applications. However, increasingly next generation sequencing (NGS) is applied. The clinical use of NGS is still very challenging, but we can expect that the switch to regular application of this method will be coming in the very near future. The price for NGS has gone down to approx. USD 1000,- which makes the routine diagnostic use feasible. Nevertheless, several challenges have yet to be solved, such as the processing of the large data volume as well as storage of the data. Supporting data bases exist already and some will be discussed in the article. The understanding of the clinical relevance of many polymorphisms is another issue that has yet to be solved, particularly as in the context of personalized medicine polymorphisms have become increasingly important.
Asunto(s)
Predisposición Genética a la Enfermedad/genética , Pruebas Genéticas/tendencias , Secuenciación de Nucleótidos de Alto Rendimiento/tendencias , Técnicas de Diagnóstico Molecular/tendencias , Reacción en Cadena de la Polimerasa/tendencias , Análisis de Secuencia de ADN/tendencias , Humanos , Medicina de PrecisiónRESUMEN
Timely and accurate identification and determination of the antimicrobial susceptibility of uropathogens is central to the management of UTIs. Urine dipsticks are fast and amenable to point-of-care testing, but do not have adequate diagnostic accuracy or provide microbiological diagnosis. Urine culture with antimicrobial susceptibility testing takes 2-3 days and requires a clinical laboratory. The common use of empirical antibiotics has contributed to the rise of multidrug-resistant organisms, reducing treatment options and increasing costs. In addition to improved antimicrobial stewardship and the development of new antimicrobials, novel diagnostics are needed for timely microbial identification and determination of antimicrobial susceptibilities. New diagnostic platforms, including nucleic acid tests and mass spectrometry, have been approved for clinical use and have improved the speed and accuracy of pathogen identification from primary cultures. Optimization for direct urine testing would reduce the time to diagnosis, yet these technologies do not provide comprehensive information on antimicrobial susceptibility. Emerging technologies including biosensors, microfluidics, and other integrated platforms could improve UTI diagnosis via direct pathogen detection from urine samples, rapid antimicrobial susceptibility testing, and point-of-care testing. Successful development and implementation of these technologies has the potential to usher in an era of precision medicine to improve patient care and public health.