Nelson E. Arenas

Molecular modeling and in silico characterization of Mycobacterium tuberculosis TlyA: Possible misannotation of this tubercle bacilli-hemolysin

BackgroundThe TlyA protein has a controversial function as a virulence factor in Mycobacterium tuberculosis (M. tuberculosis). At present, its dual activity as hemolysin and RNA methyltransferase in M. tuberculosis has been indirectly proposed based on in vitro results. There is no evidence however for TlyA relevance in the survival of tubercle bacilli inside host cells or whether both activities are functionally linked. A thorough analysis of structure prediction for this mycobacterial protein in this study shows the need for reevaluating TlyAs function in virulence.ResultsBioinformatics analysis of TlyA identified a ribosomal protein binding domain (S4 domain), located between residues 5 and 68 as well as an FtsJ-like methyltranferase domain encompassing residues 62 and 247, all of which have been previously described in translation machinery-associated proteins. Subcellular localization prediction showed that TlyA lacks a signal peptide and its hydrophobicity profile showed no evidence of transmembrane helices. These findings suggested that it may not be attached to the membrane, which is consistent with a cytoplasmic localization. Three-dimensional modeling of TlyA showed a consensus structure, having a common core formed by a six-stranded β-sheet between two α-helix layers, which is consistent with an RNA methyltransferase structure. Phylogenetic analyses showed high conservation of the tlyA gene among Mycobacterium species. Additionally, the nucleotide substitution rates suggested purifying selection during tlyA gene evolution and the absence of a common ancestor between TlyA proteins and bacterial pore-forming proteins.ConclusionAltogether, our manual in silico curation suggested that TlyA is involved in ribosomal biogenesis and that there is a functional annotation error regarding this protein family in several microbial and plant genomes, including the M. tuberculosis genome.

Búsqueda Activa de Individuos con Tuberculosis Pulmonar y Extrapulmonar en Calarcá-Quindío, Colombia-2005

OBJECTIVE Describing socio-demographic characteristics in a population of 195 respiratory symptomatic and 18 tuberculosis patients from Calarcá-Quindío, Colombia during 2005. METHODS An active search for individuals having symptomatic tuberculosis was carried out in three urban areas, Calarcas municipal prison and the San Juan de Dios teaching hospital. Prior to entering the study, the patients were required to fill out an application form and sign an informed consent form. Sputum samples were taken from each patient for bacilloscopy and culture in Ogawa-Kudoh medium. Phenotypic and genotypic identification were made when growth was observed by using conventional and molecular methods. RESULTS 18 (9 ,2 %) out of 195 individuals having respiratory symptoms were diagnosed as having tuberculosis. 78 % were male and 22 % female; the average age was 40 for both genders. 174 sputum, 21 bronchial lavage, one urine, one cervical ganglia and pleural liquid sample were analysed; 77 % proved positive by direct smear test and culture, 16,7 % by culture and only 5,5 % by direct smear test. Bacilloscopy average per patient was 2 ,3 . The presence of H1, T1, H3 and LAM9 genotypes was demonstrated by using the spoligotyping test. CONCLUSIONS The results confirmed the importance of using both direct smear test and/or culture for improving the early detection of pulmonary tuberculosis, its follow-up and control. The existence of four different Mycobacterium tuberculosis genotypes in Calarcá was established .

Screening food-borne and zoonotic pathogens associated with livestock practices in the Sumapaz region, Cundinamarca, Colombia

Hazardous practices regarding antibiotics misuse, unsanitary milking procedures, and the commercial sales of raw milk and unpasteurized dairy products are currently being practiced by livestock farmers in the Sumapaz region (Colombia). The purpose of this study was to screen for food-borne and zoonotic pathogens associated with local livestock practices. We evaluated 1098 cows from 46 livestock farms in the Sumapaz region that were selected by random. Of the total population of cattle, 962 animals (88%) were tested for bovine TB using a caudal-fold tuberculin test and 546 (50%) for brucellosis by a competitive ELISA. In the population tested, 23 cows were positive for Brucella sp. representing a 4.2% seroprevalence and no cases of bovine tuberculosis were found. In addition, food-borne contamination with Escherichia coli and Staphylococcus aureus was assessed together with antibiotic susceptibility for ten different antibiotics in milk samples from 16 livestock farms. We found that 12 of the farms (75%) were contaminated with these food-borne pathogens. Noteworthy, all of the isolated pathogenic strains were resistant to multiple antibiotics, primarily to oxytetracycline and erythromycin. Our findings suggest that livestock products could be a source of exposure to Brucella and multidrug-resistant E. coli and S. aureus strains as a result of unhygienic livestock practices in the Sumapaz region. Training in good farming practices is the key to improving safety in food production.

Complete Genome Sequence of Escherichia coli AS19, an Antibiotic-Sensitive Variant of E. coli Strain B REL606

ABSTRACT The chemically mutagenized Escherichia coli strain AS19 was isolated on the basis of its enhanced sensitivity to different antibiotics, in particular to actinomycin. The strain was later modified to study rRNA modifications that confer antibiotic resistance. Here, we present the genome sequence of the variant E. coli AS19-RrmA-.

Características clínicas y sociodemográficas de los casos con tuberculosis resistente en el municipio de Armenia, Quindío (Colombia)

Analizar los factores sociodemograficos y clinicos de los pacientes con diagnostico de tuberculosis resistente en el municipio de Armenia durante el periodo 2006-2009. Metodos: Se realizo un estudio descriptivo y retrospectivo con base en la notificacion de pacientes con tuberculosis resistentes durante el periodo de estudio. Los datos fueron tomados de los registros consignados en las fichas de notificacion y las tarjetas individuales de tratamiento categoria IV.