Arley Gómez

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.

Bacterial translocation in abdominal trauma and postoperative infections.

BACKGROUND Bacterial translocation (BT) describes the passage of bacteria residing into the gastrointestinal tract, through the intestinal mucosa barrier to sterile tissues such as mesenteric lymph nodes (MLN) and other organs. This phenomenon has not been thoroughly studied in patients with trauma to date, and an association between BT and postoperative infection has not been well established so far. METHODS MLNs from 36 patients with abdominal trauma were removed during laparotomy and cultured to detect BT. Postoperative infectious complications in these patients were registered, and both phenotypical and molecular typings (through multilocus sequencing) were carried out for microorganisms isolated from MLN and postoperative infection sites. Associations between clinical variables, BT presence, and postoperative infection development were established. RESULTS BT was detected in 33% of the patients (n = 12). Postoperative infections were present in 22.2% of the patients (n = 8). A significant statistical difference was found between postoperative infections in patients with BT evidence (41.6%), when compared with patients without BT (12.5%; p = 0.047). Bacteria isolated from infection sites were the same as those cultured in MLN in 40% of the cases (n = 2 of 5), allowing us to establish causality between BT and postoperative infection. CONCLUSIONS There is higher risk of BT in trauma patients, and it is associated with a significant increase of postoperative infections. An abdominal trauma index ≥10 was found to be associated with the development of BT. This is the first study describing BT among patients with abdominal trauma, where causality is confirmed at molecular level.

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 .