Raúl Díaz

Determination of elemental concentrations in atmospheric aerosols in mexico city using proton induced x-ray emission, proton elastic scattering, and laser absorption

Abstract A study of the concentrations of elements present in atmospheric aerosols at two different sites in Mexico City was done with samples taken during September 1990 and February 1991. The samples were taken daily during 6 h periods (from 6:00 to 12:00 hr), using a Stacking Filter Unit (SFU) of the Davis design. This allowed the separation of particles with sizes ranging from 2.5 to 15 μm (coarse mass), and smaller than 2.5 μm (fine mass). Analyses of the samples with Proton Induced X-ray Emission (PIXE) gave information on elements heavier than Ne, Proton Elastic Scattering Analysis (PESA) on hydrogen contents, and the Laser Integrating Plate Method (LIPM) was used on the fine fraction to determine soot contents. Cluster Analysis is applied to the sample set in order to identify the emission sources of the elements. Additionally, the relationship to several meteorological variables is presented. Comparisons with previous studies are also provided.

Conspicuous multidrug-resistant Mycobacterium tuberculosis cluster strains do not trespass country borders in Latin America and Spain.

Multidrug-resistant Mycobacterium tuberculosis strain diversity in Ibero-America was examined by comparing extant genotype collections in national or state tuberculosis networks. To this end, genotypes from over 1000 patients with multidrug-resistant tuberculosis diagnosed from 2004 through 2008 in Argentina, Brazil, Chile, Colombia, Venezuela and Spain were compared in a database constructed ad hoc. Most of the 116 clusters identified by IS6110 restriction fragment length polymorphism were small and restricted to individual countries. The three largest clusters, of 116, 49 and 25 patients, were found in Argentina and corresponded to previously documented locally-epidemic strains. Only 13 small clusters involved more than one country, altogether accounting for 41 patients, of whom 13 were, in turn, immigrants from Latin American countries different from those participating in the study (Peru, Ecuador and Bolivia). Most of these international clusters belonged either to the emerging RD(Rio) LAM lineage or to the Haarlem family of M. tuberculosis and four were further split by country when analyzed with spoligotyping and rifampin resistance-conferring mutations, suggesting that they did not represent ongoing transnational transmission events. The Beijing genotype accounted for 1.3% and 10.2% of patients with multidrug-resistant tuberculosis in Latin America and Spain, respectively, including one international cluster of two cases. In brief, Euro-American genotypes were widely predominant among multidrug-resistant M. tuberculosis strains in Ibero-America, reflecting closely their predominance in the general M. tuberculosis population in the region, and no evidence was found of acknowledged outbreak strains trespassing country borders.

Prevalence and Genotype Distribution of Pneumocystis jirovecii in Cuban Infants and Toddlers with Whooping Cough

ABSTRACT This study describes the prevalence and genotype distribution of Pneumocystis jirovecii obtained from nasopharyngeal (NP) swabs from immunocompetent Cuban infants and toddlers with whooping cough (WC). A total of 163 NP swabs from 163 young Cuban children with WC who were admitted to the respiratory care units at two pediatric centers were studied. The prevalence of the organism was determined by a quantitative PCR (qPCR) assay targeting the P. jirovecii mitochondrial large subunit (mtLSU) rRNA gene. Genotypes were identified by direct sequencing of mtLSU ribosomal DNA (rDNA) and restriction fragment length polymorphism (RFLP) analysis of the dihydropteroate synthase (DHPS) gene amplicons. qPCR detected P. jirovecii DNA in 48/163 (29.4%) samples. mtLSU rDNA sequence analysis revealed the presence of three different genotypes in the population. Genotype 2 was most common (48%), followed in prevalence by genotypes 1 (23%) and 3 (19%); mixed-genotype infections were seen in 10% of the cases. RFLP analysis of DHPS PCR products revealed four genotypes, 18% of which were associated with resistance to sulfa drugs. Only contact with coughers (prevalence ratio [PR], 3.51 [95% confidence interval {CI}, 1.79 to 6.87]; P = 0.000) and exposure to tobacco smoke (PR, 1.82 [95% CI, 1.14 to 2.92]; P = 0.009) were statistically associated with being colonized by P. jirovecii. The prevalence of P. jirovecii in infants and toddlers with WC and the genotyping results provide evidence that this population represents a potential reservoir and transmission source of P. jirovecii.

Genetic diversity of Pneumocystis jirovecii in colonized Cuban infants and toddlers

Pneumocystis jirovecii is a leading cause of opportunistic infections among immunocompromised patients. The aim of this study was to determine the genetic diversity of P. jirovecii from colonized Cuban infants and toddlers by analysis of four genetic loci: mitochondrial large subunit (mtLSU) rRNA, cytochrome b (CYB), superoxide dismutase (SOD) and β-tubulin (β-tub). We determined the multilocus profiles based on concatenated genotype data (multilocus genotype; MLG) and nucleotide sequences (multilocus sequence analysis; MLSA) respectively, calculated the discriminatory power of each analysis, and investigated possible associations with demographic and clinical data. Sixteen of 51 PCR-positive nasopharyngeal swab specimens (years 2010-2013) with high P. jirovecii load were selected for downstream analysis. In mixed allelic profiles all genotypes/nucleotide sequence patterns were considered separately. All samples could be genotyped based on mtLSU, CYB and β-tub locus. However, the SOD locus could be successfully amplified in only 7/16 (44%) specimens. Eight different P. jirovecii MLGs were identified among the 16 cases and eight samples presented identical MLG (MLG 1). Seventeen MLSA profiles were distinguished. No statistical association between genotypes or MLGs and demographic or clinical data could be identified. For MLSA the higher discriminatory power (S=0.976) was observed. The combination of mtLSU, CYB and β-tub loci proved to be useful for molecular epidemiology studies of P. jirovecii. A total of 17 different MLSA profiles observed in 16 specimens indicated high genetic variability of P. jirovecii circulating in colonized Cuban infants and toddlers.

Vigilancia de la resistencia a los fármacos antituberculosos en Cuba, 2000-2009

OBJETIVO: Determinar la prevalencia de la resistencia a los farmacos antituberculosos en Cuba en el decenio 2000-2009. METODOS: Se realizo un estudio prospectivo longitudinal. El universo de trabajo estuvo constituido por un total de 2 285 aislamientos de Mycobacterium tuberculosis obtenidos de todo el pais en el periodo comprendido entre el 1 de enero de 2000 y el 31 de diciembre de 2009. Se empleo el metodo de las proporciones en medio Lowenstein-Jensen con los farmacos de primera linea: isoniazida, estreptomicina, etambutol y rifampicina. RESULTADOS: La resistencia entre los casos nuevos y los pacientes con antecedente de tratamiento previo fue de 8,5% y 37,0%, respectivamente; para estas mismas categorias de caso, la multirresistencia fue de 0,4% y 8,8%, respectivamente. CONCLUSIONES: El presente estudio muestra baja prevalencia de cepas multirresistentes en Cuba. Estos resultados reflejan los avances logrados por el programa nacional de control, que trabaja en la actualidad hacia la eliminacion de la tuberculosis como problema de salud publica en el pais.

Extracción de ADN de tejidos embebidos en parafina por Chelex-100. ADN de tejidos en parafina por resina quelante

SUMMARY Introduction: Paraffin-embedded tissue (PET) is an invaluable resource for retrospective molecular studies. Chelex-100 method has been used to DNA extraction from PET. The DNA obtained is used in Polymerase Chain Reac- tion (PCR) technique. In this work, the utility of Chelex-100 method for the detection of Mycobacterium tuberculosis is showed. Methods: The Hematoxilyn-Eosin and Ziehl-Neel- sen techniques were performed in PET samples from three patients dying of AIDS. Additionally, Chelex-100 method was used for DNA extraction from these tissues and two PCR with different primers were evaluated for identifica- tion of M tuberculosis. Results: Genetic material with a good quality and in enough quantity was obtained the Che- lex-100 method. M tuberculosis was identified in the sam- ples by PCR, using a specific sequence (IS 6110). We sho- wed the utility of Chelex-100 method in PCR from short DNA fragments. Conclusions: The Chelex-100 method is a rapid, easy, safe and inexpensive option in molecular Patho- logy research.

Concomitant Mycobacterium avium Infection and Hodgkin’s Disease in a Lymph Node from an HIV-negative Child

We report a case of an immunocompetent child with simultaneously an infection with Mycobacterium avium and Hodgkin’s disease in a cervical lymph node. A positive PCR result for M. avium on a biopsy of the lymph node directed the definitive diagnosis for both etiologies and avoided a possible dissemination of this infection after chemotherapy was started.

Importancia del control de la calidad de la baciloscopia en los laboratorios de diagnóstico de tuberculosis

Resumen Introduccion: La baciloscopia es la herramienta primaria en el diagnostico de la tuberculosis (TBC)pulmonar activa, siendo esta la tecnica mas utilizada internacionalmente en la busqueda de casos infecciosos. El control de calidad consiste en la relectura de las laminas 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 diagnostico de TBC en Cuba. Material y Metodos : Este estudio fue realizado en el Laboratorio Nacional de Referencia e Investigaciones de Tuberculosis, Lepra y Micobacterias del Instituto de Medicina Tropical “Pedro Kouri”, La Habana, Cuba. Fueron evaluadas 2.676 laminas recibidas en el periodo de enero de 2013-diciembre de 2014, procedentes de los diferentes Centros Provinciales de Higiene, Epidemiologia y Microbiologia de Cuba, incluido el Municipio Especial Isla de la Juventud. Resultados: Hubo 2.664 (99,5%) laminas concordantes, la concor-dancia obtenida para las laminas 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 laminas con calidad de la muestra adecuada en 2.039 (76,2%), presentaron deficiencias en la realizacion de la extension 1.464 (54,7%), y la tincion fue adecuada en 2.343 (87,6%). El indice de kappa fue de 0.9674. Conclusion: Aunque hubo una adecuada concordancia entre las observaciones realizadas, se recomienda mejorar la calidad del extendido, mantener programa de entrena-miento al personal que realiza esta actividad, al igual que las supervisiones periodicas por parte de especialistas, para continuar mejorando la calidad del diagnostico.