Molecular characterisation of Mycobacterium tuberculosis isolates in the First National Survey of Anti-tuberculosis Drug Resistance from Venezuela

Background

Molecular typing of Mycobacterium tuberculosis strains has become a valuable tool in the epidemiology of tuberculosis (TB) by allowing detection of outbreaks, tracking of epidemics, identification of genotypes and transmission events among patients who would have remained undetected by conventional contact investigation. This is the first genetic biodiversity study of M. tuberculosis in Venezuela. Thus, we investigated the genetic patterns of strains isolated in the first survey of anti-tuberculosis drug-resistance realised as part of the Global Project of Anti-tuberculosis Drug Resistance Surveillance (WHO/IUATLD).

Results

Clinical isolates (670/873) were genotyped by spoligotyping. The results were compared with the international spoligotyping database (SpolDB4). Multidrug resistant (MDR) strains (14/18) were also analysed by IS6110-RFLP assays, and resistance to isoniazid and rifampicin was characterised. Spoligotyping grouped 82% (548/670) of the strains into 59 clusters. Twenty new spoligotypes (SITs) specific to Venezuela were identified. Eight new inter-regional clusters were created. The Beijing genotype was not found. The genetic network shows that the Latin American and Mediterranean family constitutes the backbone of the genetic TB population-structure in Venezuela, responsible of >60% of total TB cases studied. MDR was 0.5% in never treated patients and 13.5% in previously treated patients. Mutations in rpoB gene and katG genes were detected in 64% and 43% of the MDR strains, respectively. Two clusters were found to be identical by the four different analysis methods, presumably representing cases of recent transmission of MDR tuberculosis.

Conclusion

This study gives a first overview of the M. tuberculosis strains circulating in Venezuela during the first survey of anti-tuberculosis drug-resistance. It may aid in the creation of a national database that will be a valuable support for further studies.     

Analysis of the Optical Properties of Chiral Au Nanorod Stacks

Plasmonics - We analyze the optical and chirooptical response of two Au nanorods vertically separated and with arbitrary relative in-plane orientation. The use of a simple model of Lorentzian...     

Surface Enhanced Infrared Characterization Using Disordered Slit-Antenna Arrays for the Detection of Electrodeposited Cytochrome C

Plasmonics - An approach which allows both electrochemical studies and surface enhanced infrared characterization of electrodeposited Cytochrome C is presented. This approach is based on in-plane...     

Syncytial giant cell component. Review of 55 renal cell carcinomas

Different types of multinucleated giant cells (MGC) have been documented in tumors with osteoclast-like appearance, with trophoblastic differentiation or as tumoral malignant giant cells. A new variety of MGC has been described in renal cell carcinoma. In order to study the frequency, nature and significance of this cellular type, we have reviewed our files. To assess the presence, nature and significance of these MGC in renal cell carcinomas and associated histologic subtype. To review all malignant renal tumors diagnosed in the last 5 years in our hospital and to carry out a morphologic and immunohistochemical study in renal cell carcinomas with syncytial type MGC. 55 renal cell carcinomas were reviewed. Clear cell (conventional) renal cell carcinoma was the most common type encountered (40 cases); two of these cases showed syncytial type MGC and low grade malignancy. Microscopically the MGC contained from 5 to 40 nuclei. Immunohistochemically, mononucleated and multinucleated cells were positive for cytokeratin CAM 5.2, cytokeratin AE1/AE3 and weakly positive for vimentin. Histiocytic, muscular, neural markers, beta-HCG and alpha-fetoprotein were negative. The presence of syncytial type MGC in renal cell carcinomas is an exceptional event. Among 55 renal cell carcinomas we found two cases, both of which were of clear cell subtype and low grade malignancy. The MGC proved positive for epithelial markers and probably are the result of mononucleated tumoral cell fusion. We are unaware of the impact of this MGC in the outcome of patients; such cells appear in low grade carcinomas and do not seem to be of dismal prognosis.     

Specific interactions of sticholysin I with model membranes: An NMR study

Sticholysin I (StnI) is an actinoporin produced by the sea anemone Stichodactyla helianthus that binds biological and model membranes forming oligomeric pores. Both a surface cluster of aromatic rings and the N‐terminal region are involved in pore formation. To characterize the membrane binding by StnI, we have studied by ¹H‐NMR the environment of these regions in water and in the presence of membrane‐mimicking micelles. Unlike other peptides from homologous actinoporins, the synthetic peptide corresponding to residues 1–30 tends to form helix in water and is more helical in either trifluoroethanol or dodecylphosphocholine (DPC) micelles. In these environments, it forms a helix‐turn‐helix motif with the last α‐helical segment matching the native helix‐α₁ (residues 14–24) present in the complete protein. The first helix (residues 4–9) is less populated and is not present in the water‐soluble protein structure. The characterization of wild‐type StnI structure in micelles shows that the helix‐α₁ is maintained in its native structure and that this micellar environment does not provoke its detachment from the protein core. Finally, the study of the aromatic resonances has shown that the motional flexibility of specific rings is perturbed in the presence of micelles. On these bases, the implication of the aromatic rings of Trp‐111, Tyr‐112, Trp‐115, Tyr‐132, Tyr‐136, and Tyr‐137, in the interaction between StnI and the micelle is discussed. Based on all the findings, a revised model for StnI interaction with membranes is proposed, which accounts for differences in its behavior as compared with other highly homologous sticholysins. Proteins 2010. © 2010 Wiley‐Liss, Inc.