ABSTRACT Introduction. This paper summarizes the contribution by the Technical Group for Modelling and Epidemiology to face COVID-19. The objective was to create knowledge and scientific evidence to support the Government’s decision making, the health system and other sectors. Methods . Implementation research from a transdisciplinary perspective was carried out, with epidemiology providing the guidelines. Tools were developed to identify the magnitude and dissemination of COVID-19 in the country, as well as the analysis of the risk to get sick and severity; also, tools for the evaluation of the measures implemented. Results and Discussion. Improvements were made to the information systems and the Covid19CubaData platform was created to standardize and visualize the data. Prognosis mathematical models were developed. Geographical information systems were used to identify vulnerable population groups and stratify interventions. The impact of the actions was evaluated with a clinical-epidemiological analysis, as well as the use of big data techniques on mobility and real time estimation of the effective reproductive number. Multilevel and artificial intelligence models allowed for comparing the behavior of the pandemic in Cuba and the world. Indicators were brought forward for the de-escalation of the actions. The equity in the country’s response to COVID-19 was evaluated. It was concluded that the epidemiological research done, supported by modelling and the information systems, was useful for the government and the Ministry of Public Health to effectively respond to COVID-19.

RESUMEN Introducción. Este trabajo resume el aporte del Grupo Técnico de Modelación y Epidemiología para el enfrentamiento de la COVID-19. El objetivo del trabajo fue generar conocimiento y evidencias científicas en apoyo a la toma de decisiones del Gobierno, el sistema de salud y otros sectores. Método. Se realizó investigación de implementación con un enfoque transdisciplinar, con la epidemiología como guía. Se desarrollaron herramientas que permitieron la identificación de la magnitud y la diseminación de la COVID-19 en el país, el análisis de riesgo de enfermar y de severidad, así como para la evaluación de las medidas implementadas. Resultados . Se realizaron mejoras a los sistemas de información y se creó la plataforma Covid19CubaData para la estandarización y visualización de los datos. Se desarrollaron modelos matemáticos de pronósticos. Se emplearon los Sistemas de Información Geográfica para identificar grupos poblacionales vulnerables y estratificar intervenciones. El impacto de las acciones fue evaluada desde el análisis clínico-epidemiológico, el uso de técnicas de big data de la movilidad y la estimación en tiempo real del número reproductivo efectivo. Modelos multinivel y de inteligencia artificial permitieron la comparación del comportamiento de la pandemia en Cuba y el mundo. Se propusieron indicadores para el des-escalado de las acciones y se evaluó la equidad en la respuesta del país ante la COVID-19. En conclusión, la investigación epidemiológica realizada, con el apoyo de la modelación y los sistemas de información, sirvieron para la toma de decisiones del Gobierno y el Ministerio de Salud Pública en el enfrentamiento efectivo a la COVID-19.

ABSTRACT The basic SIR (Susceptible-Infected-Recovered) model of Kermack-McKendrick is a compartmental model in which the population under study is divided into epidemiological classes, in between which a flow is described. A robust health system that provides reliable data to the model and combined with coherent public health policies contributes to controlling the impacts of epidemic contingencies. Hence, the objective of this study is to apply the SIR model, without delving into the mathematical apparatus that accompanies it, to know the impact of COVID-19 in Cuba, with an emphasis on Havana, as the center of the epidemic in the country in the period from March 11 to July 16, 2020. To do this, the model is shown with variable coefficients over time, together with its usefulness as a dynamic model to make projections in epidemic situations. It is applied to specific local regions and its potentialities to analyze outbreaks are manifested by the onset of local events that are far from the foreseen predictions. This work is part of the efforts that, in all orders, the Cuban Ministry of Public Health has developed to confront the COVID-19 pandemic.

RESUMEN El modelo básico SIR (Susceptibles-Infectados-Recuperados) de Kermack y McKendrick, es un modelo de compartimentos donde la población bajo estudio se divide en clases epidemiológicas y se describe un flujo entre ellas. Un sistema sanitario robusto que proporcione al modelo datos confiables y aunados a políticas públicas de salud coherentes, contribuye a controlar los impactos de contingencias epidémicas. De ahí que el objetivo del presente estudio sea aplicar el modelo SIR, sin profundizar en el aparato matemático que lo acompaña, para conocer el impacto de la COVID-19 en Cuba, con énfasis en La Habana, como centro de la epidemia en el país en el período del 11 de marzo al 16 de julio de 2020. Para ello se muestra el modelo con coeficientes variables en el tiempo y su utilidad como modelo dinámico para hacer proyecciones en situaciones epidémicas; se aplica a regiones locales específicas y se manifiestan sus potencialidades para analizar rebrotes por la aparición de eventos locales que se alejan de las predicciones previstas. Este trabajo es parte de los esfuerzos que, en todos los órdenes, ha desarrollado el Ministerio de Salud Pública de Cuba para enfrentar la pandemia de la COVID-19.

ABSTRACT The basic SIR (Susceptible-Infected-Recovered) model of Kermack-McKendrick is a compartmental model in which the population under study is divided into epidemiological classes, in between which a flow is described. A robust health system that provides reliable data to the model and combined with coherent public health policies contributes to controlling the impacts of epidemic contingencies. Hence, the objective of this study is to apply the SIR model, without delving into the mathematical apparatus that accompanies it, to know the impact of COVID-19 in Cuba, with an emphasis on Havana, as the center of the epidemic in the country in the period from March 11 to July 16, 2020. To do this, the model is shown with variable coefficients over time, together with its usefulness as a dynamic model to make projections in epidemic situations. It is applied to specific local regions and its potentialities to analyze outbreaks are manifested by the onset of local events that are far from the foreseen predictions. This work is part of the efforts that, in all orders, the Cuban Ministry of Public Health has developed to confront the COVID-19 pandemic.

RESUMEN El modelo básico SIR (Susceptibles-Infectados-Recuperados) de Kermack y McKendrick, es un modelo de compartimentos donde la población bajo estudio se divide en clases epidemiológicas y se describe un flujo entre ellas. Un sistema sanitario robusto que proporcione al modelo datos confiables y aunados a políticas públicas de salud coherentes, contribuye a controlar los impactos de contingencias epidémicas. De ahí que el objetivo del presente estudio sea aplicar el modelo SIR, sin profundizar en el aparato matemático que lo acompaña, para conocer el impacto de la COVID-19 en Cuba, con énfasis en La Habana, como centro de la epidemia en el país en el período del 11 de marzo al 16 de julio de 2020. Para ello se muestra el modelo con coeficientes variables en el tiempo y su utilidad como modelo dinámico para hacer proyecciones en situaciones epidémicas; se aplica a regiones locales específicas y se manifiestan sus potencialidades para analizar rebrotes por la aparición de eventos locales que se alejan de las predicciones previstas. Este trabajo es parte de los esfuerzos que, en todos los órdenes, ha desarrollado el Ministerio de Salud Pública de Cuba para enfrentar la pandemia de la COVID-19.

ABSTRACT The danger of the occurrence of endemic COVID-19 worries the Cuban government as well as epidemiologists. Knowledge about a metric that influences its emergence is a very useful tool to prevent it. The purpose of the study was to prove through dynamic models and the qualitative theory of differential equations that the basic reproduction number R0 is a metric influencing the occurrence of these events. A SIR model was used, which was adjusted to Cuban conditions. Results showed that a mathematical response may be provided to conditions potentially causing a fresh outbreak of the disease. We recommend to maintain activated the epidemiological measures referred to in the paper, which help keep under control the confirmed cases occurring, thus preventing possible fresh outbreaks.

RESUMEN El peligro de la ocurrencia de endemia por la COVID-19 es una preocupación del gobierno y epidemiólogos cubanos, pero conocer alguna métrica que influya en su surgimiento es de gran utilidad para evitarla. El objetivo de este trabajo es demostrar mediante modelos dinámicos y teoría cualitaiva de ecuaciones diferenciales, cómo el número reproductivo básico Ro constituye una métrica que incide en la ocurrencia de estos eventos. Se empleó un modelo de tipo SIR con demografía adaptado a las condiciones de Cuba. Los resultados demostraron que se consigue dar respuesta, desde el punto de vista matemático, a las condiciones que pueden causar un rebrote de la enfermedad. Recomendamos mantener activadas las medidas epidemiológicas que se relacionan en este trabajo y que ayudan a mantener controlados los casos confirmados que aparezcan y evitar de esta manera posibles rebrotes.

ABSTRACT The application of data mining techniques using supervised techniques provide knowledge to arrange the choices that make the academic managers. This paper discusses the results of the KEEL software algorithms, that are used 14 extracted, including rules that predict high school applicants in the success or failure of the levelling course.

RESUMEN El uso de datos que extraen técnicas que usan supervisado proporciona el conocimiento para arreglar las opciones que ellos hacen sus directores (gerentes) académicos. Este papel (periódico) habla de los resultados de los algoritmos de software de QUILLA, los algoritmos son usados 14 extraído incluyendo las reglas que predicen a aspirantes de instituto en el éxito o el fracaso del curso de nivelación.

‘LPD-5 F1’, is the first hybrid of pepper for the System of Protected Cultivation (SCP), type Lamuyo, of big fruits, with good adaptation, productivity and resistant to potyvirus. This hybrid has been validated in the Institute and also with great acceptance in all the areas of the SCP of Cuba since 2001 positively, but it didn’t go up to 2011 that was introduced completely, after beginning the production of their seed in IIHLD (horticulture research institute "Liliana Dimitrova")

‘LPD-5 F1’, primer híbrido de pimiento para el Sistema de Cultivo Protegido (SCP), tipo Lamuyo, de frutos grandes, con buena adaptación, productividad y resistente a potyvirus. Ha sido validado en el Instituto y también con gran aceptación en todas las áreas del SCP desde 2001 positivamente, pero no fue hasta 2011 que se introdujo completamente, después de comenzar la producción de su semilla en IIHLD (Instituto de investigaciones Hortícolas "Liliana Dimitrova")

ABSTRACT INTRODUCTION Systematic surveillance of antituberculosis drug resistance allows identification of multidrug-resistant and extensively drug-resistant isolates of Mycobacterium tuberculosis. Surveillance studies of antituberculosis drug resistance systematically conducted in Cuba for over 15 years have revealed low circulation of multidrug-resistant tuberculosis, under 1% in new cases. OBJECTIVE Characterize antituberculosis drug resistance in isolates of M. tuberculosis recovered from patients with pulmonary tuberculosis in Cuba in 2012–2014. METHODS The nitrate reductase assay was used to test 997 isolates of M. tuberculosis for sensitivity to isoniazid and rifampicin. Isolates identified as multidrug resistant were tested for sensitivity to isoniazid, rifampicin, streptomycin, ethambutol, ofloxacin, amikacin, kanamycin and capreomycin by the proportion method, as well as genetic resistance mutations in rpoB, katG, inhA, gyrA, rrs and embB genes, using GenoType MTBDRplus and MTBDRsl commercial kits. RESULTS Some 95.6% of isolates from new cases and 89.6% of isolates from previously treated patients were sensitive to isoniazid and rifampicin. Multidrug resistance was found in 0.8% of new and 5.2% of previously treated patients, a statistically significant difference. One extensively drug-resistant isolate was detected among previously treated cases. All isolates examined with the molecular method had mutations in the rpoB gene, which is associated with resistance to rifampicin; only seven showed mutations in the katG gene and one in the inhA gene associated with isoniazid resistance. In one isolate, we found mutations in both gyrA and rrs genes, which are associated with resistance to fluoroquinolones and second-line injectable drugs and therefore, extensive resistance. CONCLUSIONS Results corroborate the low frequency of multidrug-resistant and extensively resistant M. tuberculosis strains in Cuba and highlight the need for continuous improvement of surveillance of antituberculosis drug resistance in Cuba.

Background: Baciloscopy is the primary tool for pulmonary tuberculosis diagnosis, being this technique the most used internationally in the search for infectious cases. Quality control is the process of the rechecking smears by a highly qualified observer. Aim: To evaluate and highlight the importance of quality control of smear microscopy in the Provincial Laboratories diagnosticians of Tuberculosis in Cuba. Methods: This study was conducted at the National Reference Laboratory and Research in Tuberculosis, Leprosy and Mycobacteria in the Institute of Tropical Medicine "Pedro Kouri", Havana, Cuba, Were evaluated 2676 smears received from January 2013 to December 2014, from Provincial Centers of Hygiene, Epidemiology and Microbiology of Cuba, including the special municipality Isla de la Juventud. Results: 2,664 (99.5%) were concordant smears, the correlation obtained for the positive smears were 96.5% and 99.8% for negative. Were identified12 reading errors: 7 (3.5%) false positive and 5 (0.2%) false negatives. Slides were classified with adequate quality of smears in 2039 (76.2%), showed difficulties in realizing the extension in 1464 (54.7%) and staining were adequate in 2343 (87.6%). The kappa index was 0.9674. Conclusion: Although there was good agreement between observations it is recommended to improve the quality of extended, maintain staff training program that performs this activity, like regular supervision by specialists, to further improve the quality of diagnosis.

Introducción: La baciloscopia es la herramienta primaria en el diagnóstico de la tuberculosis (TBC) pulmonar activa, siendo esta la técnica más utilizada internacionalmente en la búsqueda de casos infecciosos. El control de calidad consiste en la relectura de las láminas por un observador altamente calificado. Objetivo: Evaluar y destacar la importancia del control de la calidad de la baciloscopia en los laboratorios provinciales encargados del diagnóstico de TBC en Cuba. Material y Métodos: Este estudio fue realizado en el Laboratorio Nacional de Referencia e Investigaciones de Tuberculosis, Lepra y Micobacterias del Instituto de Medicina Tropical "Pedro Kourí", La Habana, Cuba. Fueron evaluadas 2.676 láminas recibidas en el período de enero de 2013-diciembre de 2014, procedentes de los diferentes Centros Provinciales de Higiene, Epidemiología y Microbiología de Cuba, incluido el Municipio Especial Isla de la Juventud. Resultados: Hubo 2.664 (99,5%) láminas concordantes, la concordancia obtenida para las láminas positivas fue 96,5% y las negativas 99,8%. Se identificaron 12 errores de lectura: 7 (3,5%) falsos positivos, 5 (0,2%) falsos negativos. Se calificaron láminas con calidad de la muestra adecuada en 2.039 (76,2%), presentaron deficiencias en la realización de la extensión 1.464 (54,7%), y la tinción fue adecuada en 2.343 (87,6%). El índice de kappa fue de 0.9674. Conclusión: Aunque hubo una adecuada concordancia entre las observaciones realizadas, se recomienda mejorar la calidad del extendido, mantener programa de entrenamiento al personal que realiza esta actividad, al igual que las supervisiones periódicas por parte de especialistas, para continuar mejorando la calidad del diagnóstico.

Kidney infections caused by Mycobacterium genus are torpid and chronic evolution. In this study were analyzed 177 urine samples (included 110 from HIV patients) received between January 2006 and July 2014 in the National Reference Laboratory of Tuberculosis at Tropical Medicine Institute "Pedro Kourí" (IPK). The results were 17 isolates Mycobacterium tuberculosis, and 30 isolates of nontuberculous mycobacteria were detected. This study confirms the diagnostic importance of these infections especially in HIV/AIDS patients.

Introducción. La vigilancia de la resistencia a medicamentos antituberculosos permite alertar sobre el hallazgo de aislamientos de Mycobacterium tuberculosis multirresistentes y extremadamente resistentes . Objetivo. Determinar los patrones de resistencia de los aislamientos de M. tuberculosis recuperados en Cuba entre los años 2010 y 2011 y demostrar el desempeño del Laboratorio Nacional de Referencia en la ejecución de las pruebas de sensibilidad. Materiales y métodos. Se realizó un estudio prospectivo longitudinal en el que se incluyeron 657 aislamientos de M. tuberculosis recibidos de todo el país. Se empleó el método de la nitrato reductasa para detectar resistencia a isoniacida y rifampicina, y el método de las proporciones para corroborar la resistencia a dichos medicamentos e investigar la sensibilidad a estreptomicina, etambutol, ofloxacina, kanamicina y capreomicina en aislamientos multirresistentes. Como parte del control de calidad externo de las pruebas de sensibilidad, se evaluaron dos paneles de cepas de M. tuberculosis . Resultados. En 95,69 % de los aislamientos recuperados de casos nuevos de tuberculosis y en 72,64 % de los recuperados de casos previamente tratados, se encontró sensibilidad a isoniacida y rifampicina, siendo la multirresistencia de 1,03 y 10,38 %, respectivamente. Se encontraron dos aislamientos extremadamente resistentes. Con la excepción del etambutol y la capreomicina, para todos los medicamentos la eficiencia fue de 100% en el control de calidad externo. Conclusiones. Se confirmó la baja prevalencia de aislamientos de M. tuberculosis multirresistentes en Cuba, resultado avalado por el excelente desempeño demostrado en el control de calidad externo de las pruebas de sensibilidad.

Introduction: Antituberculosis-drug resistance surveillance is very important to identify multidrug-resistant and extensively drug-resistant Mycobacterium tuberculosis isolates. Objective: To determine the prevalence of resistance in M. tuberculosis strains isolated between 2010 and 2011, and to demonstrate the laboratory performance in the external quality control of drug susceptibility testing. Materials and methods: A prospective longitudinal study was carried out to determine antituberculosis-drug resistance in 657 M. tuberculosis isolates obtained throughout the country. The nitrate reductase assay was used to detect resistance to isoniazid and rifampin. The proportion method was performed to confirm resistance to these drugs and to further investigate in multidrug-resistant isolates their susceptibility to streptomycin, ethambutol, ofloxacin, kanamycin and capreomycin. Additionally, as part of external quality control, susceptibility was evaluated in two M. tuberculosis strain panels. Results: In 95.69% of the isolates recovered from new tuberculosis cases, and in 72.64 % of isolates from previously treated patients we found susceptibility to isoniazid and rifampicin; multidrug resistance was 1,03 and 10.38%, respectively. We found two extensively resistant isolates. Except for ethambutol and capreomycin, the efficiency of all other drugs was 100% in the external quality control. Conclusion: The study confirmed the low prevalence of M. tuberculosis multidrug-resistant isolates in Cuba. This result was confirmed by the external quality control of drug susceptibility testing.

The direct detection of pyrazinamide resistance in Mycobacterium tuberculosis is not routinely performed in many laboratories in the world because the drug is active only at acid pH, which also affects the growth of M. tuberculosis. The pyrazinamidase enzyme, encoded by pncA gene, is necessary to convert prodrug pyrazinamide to its active form. Taking into account that nicotinamide, a structural analogue of pyrazinamide, converted in its active forms by the pyrazinamidase enzyme at a physiological pH does not affect bacterial growth, the aim of this research was to evaluate two colorimetric methods: Nitrate reductase and malachite green microtube assays, using nicotinamide to perform susceptibility testing in 102 M. tuberculosis strains. The results were compared with those obtained by the classic Wayne assay. Mutations in the pncA gene were identified by sequencing the pncA gene from all isolates in which pyrazinamide resistance was detected by any of the three methods. Both the nitrate reductase and malachite green microtube assays showed sensitivities of 93.75% and specificities of 97.67%. Mutations in the pncA gene were found in 14 of 16 strains (87.5%) that were pyrazinamide resistant.

Los estudios de susceptibilidad a PZA no se realizan de rutina debido a que el pH ácido requerido para lograr la actividad de la droga, afecta el crecimiento de Mycobacterium tuberculosis. La PZA es convertida en su forma activa por acción de la enzima pirazinamidasa (PZAasa) que es codificada por el gen pncA. Tomando en consideración que la enzima PZAasa es la responsable de convertir la nicotinamida (NIC), droga análoga de la PZA, en su forma activa sin requerir de un pH ácido, nos propusimos evaluar dos métodos colorimétricos: Método de la Nitrato Reductasa (MNR) y Microensayo Verde Malaquita (MVM) para conocer la susceptibilidad de 102 cepas de M. tuberculosis a la PZA empleando la NIC. Los resultados se compararon con el Ensayo Enzimático de Wayne (método de referencia). A las cepas resistentes y las que mostraron resultados discordantes, se les secuenció el gen pncA. Se alcanzó una sensibilidad del 93.75% y una especificidad del 97.67% para el MNR y el MVM. El 87.5% de las cepas resistentes (14/16) mostraron mutaciones en el gen pncA.

El uso prolongado de insecticidas ha conducido al desarrollo de resistencia en diferentes especies de mosquitos y al incremento de la degradación del ambiente. El control biológico de insectos ha devenido como una alternativa útil y de bajo impacto ambiental. En nuestro estudio fueron identificados, caracterizados tres aislamientos de suelos procedentes de diferentes regiones del archipiélago cubano y comparados con cepas de referencia: aisladas de los biolarvicidas Bactivec y Bactoculicida, además de IPS82. La diferenciación de los mismos se llevó a cabo mediante métodos morfológicos, bioquímicos y moleculares (SDSPAGE, perfil plasmídico, RAPD). Los aislamientos fueron identificados como Bacillus thuringiensis; A21, A51 y C17 mostraron una mayor actividad contra larvas de Aedes aegypti and Culex quinquefasciatus que la cepa aislada del biolarvicida Bactivec, utilizada como referencia en este estudio. Dos de los aislamientos poseían perfiles proteicos y plasmídicos similares al de la cepa control IPS82, pero el restante difería de ellos. Los tres mostraron patrones de RAPD diferentes lo que nos permitió su diferenciación. Estos patrones de RAPD también diferían del observado para las cepas utilizadas comúnmente en el control biológico en nuestro país.

Chemical insecticides may be toxic and cause environmental degradation. Consequently, biological control for insects represents an alternative with low ecological impact. In this work, three soil isolates (A21, A51 and C17) from different regions of the Cuban archipelago were identified, characterized and evaluated against Aedes aegypti and Culex quinquefasciatus. The new isolates were compared with reference IPS82 strain and two strains isolated from biolarvicides Bactivec and Bactoculicida, respectively. The differentiation was done by morphological, biochemical, bioassays activity and molecular methods (SDS-PAGE, plasmid profile and random amplified polymorphic analysis). All isolates were identified as Bacillus thuringiensis. The A21, A51 and C17 isolates showed higher larvicide activity than Bactivec’s isolated reference strain, against both A. aegypti and C. quinquefasciatus. A21 isolate had a protein profile similar to IPS82 and Bactivec strain. A51 and C17 isolates produced a characteristic proteins pattern. A21 and A51 isolates had plasmid patterns similar to IPS82 standard strain, while C17 isolate had different both plasmid profile and protein bands. All the studied isolates showed a diverse RAPD patterns and were different from the strains previously used in biological control in Cuba. Rev. Biol. Trop. 59 (3): 1007-1016. Epub 2011 September 01.

O objetivo do estudo foi avaliar a influência da substituição parcial de nitrito de sódio por quitosana na qualidade do presunto Visking, (um tipo de embutido de carne de porco). Elaboraram-se cinco formulações do produto, modificando-se apenas as concentrações de nitrito de sódio (0,011% e 0,016%) e quitosana (0,25% e 0,5%). Para determinar o tempo de prateleira dos embutidos, as amostras foram armazenadas em temperaturas a 4 ºC , e realizaram-se análises físico-químicas, microbiológicas e sensoriais. A quitosana pode ser utilizada em embutidos suínos sem afetar atributos sensoriais como cor, apesar do fato dos provadores terem reportado diferenças na textura entre amostras com quitosana, possivelmente essas diferenças de textura sejam influenciadas pelo grau de desacetilação da quitosana. Entretanto, esses resultados ainda precisam ser esclarecidos para se poder ter uma aplicação eficiente da quitosana em embutidos. A redução do nitrito de sódio residual não afetou a cor nem o sabor destes produtos. Entretanto, quando se adicionou quitosana, foi observado um aumento no tempo de prateleira do embutido.

The aim of the study was to evaluate the influence of partial nitrite replacement by chitosan on the quality of Ham Visking (a type of pork sausages). Five Ham Visking formulations were elaborated modifying the sodium nitrite (0.011; 0.016 or 0.0212%) and chitosan concentrations (0.25 or 0.5%) in the products. Sausages were stored at 4 ºC and physicochemical, microbiological, and sensorial evaluations were performed in order to estimate their shelf life. Chitosan can be used in pork sausages without affecting ensory attributes such as color although the panelists detected textural differences among the samples with chitosan, which suggests that there is some influence of deacetylation degree of chitosan on the textural behavior of sausages which still needed to be explained for a successful application of chitosan in meat products. The reduction of residual sodium nitrite did not affect the color and flavor of such products, but the use of chitosan increasedsignificantly the shelf life of sausages.

DNA extraction from paraffin-embedded tissue (PET) is a critical step for many molecular techniques. Several protocols have been carried out for this objective according to the literature. In the present study, the performances of three DNA extraction methods from PET were compared to establish the optimal protocol for our laboratory. Ten lymph nodes from ten patients dying of AIDS were investigated. Histological and bacteriological studies were performed in lymph nodes samples. DNA was extracted using three methods: boiling for 20 minutes in distilled water (Method A); boiling for 30 minutes in 5% Chelex-100 resin solution (Method B) and a 4-hours lasting proteinase K digestion (Method C). PCR with specific sequence (IS 6110) were evaluated for the identification of Mycobacterium tuberculosis in PET. The DNA extract by the three methods was degraded. Statistical differences were observed when three DNA extraction methods were compared according to the purity of extracted DNA. Only with Methods B and C successful amplification was obtained. The last method (C) was the more time consuming of all. These results demonstrated that the Chelex-100 DNA extraction method (Method B), which uses a quelating resin, is useful as a routine method to achieve DNA extraction with good enough quality and quantity in a short period of time from PET. Method B is a good option in molecular pathology research.

La extracción de ADN de tejidos embebidos en parafina (TEP) es crucial en muchos estudios moleculares. Varios han sido los protocolos utilizados para conseguir tal propósito. En esta investigación se compararon tres métodos de extracción de ADN con la finalidad de seleccionar uno para el trabajo en nuestro laboratorio. Se tomaron diez ganglios linfáticos de diez fallecidos por sida, para su estudio histológico y bacteriológico. El ADN se extrajo por calentamiento a 100 °C (método A); con el empleo de resina quelante Chelex-100 (método B) y por digestión con proteinasa K (método C). Para la identificación de Mycobacterium tuberculosis se amplificó una región de la secuencia específica de inserción IS 6110, mediante la reacción en cadena de la polimerasa. El ADN de los TEP se obtuvo degradado, con diferencias significativas de pureza. Solo se logró amplificación con los métodos B y C; este último fue el más laborioso. El método que requirió resina quelante Chelex-100 (método B) fue el más útil: se obtuvo ADN con calidad y cantidad suficiente en un menor tiempo. Por tanto, este método puede ser considerado como una buena opción en patología molecular.