Association between embB mutations and ethambutol resistance in Mycobacterium tuberculosis isolates from Cuba and the Dominican Republic: reproducible patterns and problems.

The relation of ethambutol resistance to embB mutations remains unclear, and there are no reports on ethambutol resistance from the caribbean. We examined the sequence of embB in 57 distinct Multi-Drug Resistant (MDR) and non-MDR strains of Mycobacterium tuberculosis, mostly from Cuba and the Dominican Republic. embB306 codon mutations were found exclusively in MDR-TB, but in both ethambutol sensitive and resistant strains. Valine substitutions predominated in ethambutol resistant strains, while isoleucine replacements were more common in sensitive strains. Three ethambutol resistant MDR strains without embB306 substitutions had replacements in embB406 or embB497, but these were also found in ethambutol sensitive MDR strains. The results confirm previous findings that amino acid substitutions in EmbB306, EmbB406 and EmbB497 are found only in MDR-TB strains but in both phenotypically resistant and sensitive strains. One ethambutol resistant non-MDR strain did not have any embB mutation suggesting that other undefined mutations can also confer ethambutol resistance.

Association between embB mutations and ethambutol resistance in Mycobacterium tuberculosis isolates from Cuba and the Dominican Republic: reproducible patterns and problems / Association between embB mutations and ethambutol resistance in Mycobacterium tuberculosis isolates from Cuba and the Dominican Republic: reproducible patterns and problems.

The relation of ethambutol resistance to embB mutations remains unclear, and there are no reports on ethambutol resistance from the caribbean. We examined the sequence of embB in 57 distinct Multi-Drug Resistant (MDR) and non-MDR strains of Mycobacterium tuberculosis, mostly from Cuba and the Dominican Republic. embB306 codon mutations were found exclusively in MDR-TB, but in both ethambutol sensitive and resistant strains. Valine substitutions predominated in ethambutol resistant strains, while isoleucine replacements were more common in sensitive strains. Three ethambutol resistant MDR strains without embB306 substitutions had replacements in embB406 or embB497, but these were also found in ethambutol sensitive MDR strains. The results confirm previous findings that amino acid substitutions in EmbB306, EmbB406 and EmbB497 are found only in MDR-TB strains but in both phenotypically resistant and sensitive strains. One ethambutol resistant non-MDR strain did not have any embB mutation suggesting that other undefined mutations can also confer ethambutol resistance.

Entorno virtual de enseñanza-aprendizaje para la construcción del conocimiento en bioquímica médica / Virtual teaching and learning for the construction of knowledge in medical biochemistry

Se presenta la experiencia de diseño, implementación y evaluación formativa de un entorno virtual de enseñanza aprendizaje basado en Moodle como apoyo al curso de bioquímica durante los períodos 2005-2006, 2006-2007 y 2007-2008. Los resultados indican que los estudiantes tuvieron una buena disposición y una percepción positiva del entorno virtual de enseñanza aprendizaje. Se encontró una correlación positiva entre la frecuencia del uso del entorno virtual de enseñanza aprendizaje y la calificación previa de los estudiantes (r= 0,297 P= 0,000). La frecuencia del uso de los materiales interactivos fue mayor en los estudiantes con calificación previa igual o mayor que 10 puntos en comparación con los de calificación previa inferior a 10 puntos (21,3 ± 2,5 vs. 9,5 ± 1,6; P= 0,007). Como resultado de la aplicación de una estrategia didáctica denominada curso de recuperación se observó un aumento del número de aprobados (52 por ciento) con respecto a los estudiantes que no realizó el curso (21 por ciento), encontrándose una correlación positiva estadísticamente significativa entre la calificación obtenida por los estudiantes en el examen de reparación tanto con el total de entradas al entorno virtual de enseñanza aprendizaje (r= 0,543, P= 0,001) como con el total de las tareas cumplidas por cada uno (r= 0,621, P= 0,000). La experiencia indica que el entorno virtual de enseñanza aprendizaje puede ser utilizado como herramienta para favorecer la construcción del conocimiento bioquímico

The experience of the design, implementation, and formative evaluation of a virtual teaching and learning environment based on Moodle as support to the Biochemistry course during the periods 2005-2006, 2006-2007 and 2007-2008 is presented. The results indicate that the students showed a good disposition and positive perception of the virtual teaching and learning environment. A positive correlation between virtual teaching and learning environment use and grades of the students (r= 0.297 P= 0.000) was found. The frequency of the use of the interactive materials was higher by students with previous grades equal or higher than 10 points compared to those with previous grades lower than 10 points (21.3 ± 2.5 vs. 9.5 ± 1.6; P= 0.007). As a result of the application of a didactic strategy called recovery course, an increase on the number of students who passed (52 percent), with respect to those who didn’t take the course (21 percent), was observed, finding a statistically significant positive correlation between the grades obtained by the students in the recovery exam, both with the total number of hits to thevirtual teaching and learning environment (r= 0.543, P= 0.001), as well as with the total number of assignments completed by each student (r= 0.621, P= 0.000). The experience indicates that virtual teaching and learning environment can be used as a tool to favor the construction of biochemical knowledge

Alcances y limitaciones de los métodos de epidemiología molecular basados en el análisis de ácidos nucleicos / Scope and limitations of molecular methods applied to epidemiological studies

La Epidemiología es la rama de la ciencia que se dedica al estudio del origen, la distribución y el control de las enfermedades que afectan a las poblaciones. La Epidemiología Molecular es una nueva rama de la ciencia en la cual se implementan técnicas moleculares en los estudios epidemiológicos. Diversos métodos de genotipificación molecular pueden ser empleados para clasificar a los microorganismos en grupos estrechamente relacionados o divergentes. Entre los métodos de genotipificación más usados están: la electroforesis de campo pulsado, la prueba de PCR, la secuenciación del genoma y la hibridación con sondas de DNA. Cada técnica ha ofrecido una alternativa para la investigación epidemiológica; sin embargo, también tienen aplicabilidades limitadas. El presente trabajo tiene como objetivo la revisión de las fortalezas y debilidades de éstas técnicas moleculares utilizadas para la genotipificación.

Epidemiology is a science dedicated to the study of the origin, distribution and control of diseases that affect populations. Molecular Epidemiology is a new branch of science that uses molecular techniques in epidemiological studies. Several molecular genotyping methods can be used to classify microorganisms in closely related or divergent groups. Pulsed-field gel electrophoresis, the PCR test, genomic sequencing, and DNA probe hybridization are the most used techniques in genotyping. Each technique offers an alternative for epidemiological investigation; nevertheless, they also have limited applications. The objective of this work was to review the strengths and weaknesses of these molecular techniques used for genotyping.

Characterization of plasmid MIP233 (IncHI3) of the H complex.

Plasmid MIP233, the unique member of the IncHI3 subgroup of the H incompatibility complex, is a large self-transferable plasmid encoding for sucrose utilization, the PacB character and resistance to tellurite. The current study examined whether pMIP233 conferred other putatively advantageous plasmid-encoded functions. Heavy metal studies revealed pMIP233 phenotypes of resistance to cadmium, cobalt, lead, zinc and nickel. Sequencing of random clones from a pMIP233 library revealed extensive homology with IS elements and genes involved in the metabolic processes demonstrated. Interestingly, pMIP233 did not appear to code for resistance to a wide range of antibiotics. pMIP233 is considered to be a metabolic plasmid.