Browsing by Autor "Rafaela Sierra"

Now showing 1 - 3 of 3

Distribution of Open Reading Frames of Plasticity Region of Strain J99 in <i>Helicobacter pylori</i> Strains Isolated from Gastric Carcinoma and Gastritis Patients in Costa Rica
(American Society for Microbiology, 2000) Alessandra Occhialini; Armelle Marais; Richard A. Alm; Fernando Tuffi García; Rafaela Sierra; Françis Mégraud
The plasticity region of Helicobacter pylori strain J99 is a large chromosomal segment containing 33 strain-specific open reading frames (ORFs) with characteristics of a pathogenicity island. To study the diversity of the plasticity region, 22 probes corresponding to 20 ORFs inside the plasticity region and two ORFs on its boundaries were hybridized to genomic DNA isolated from clinical strains of H. pylori from patients with gastritis or gastric adenocarcinoma. Highly variable hybridization patterns were observed. The majority of the clinical strains presented a hybridization profile similar to that of J99; thus, these ORFs are not J99 strain specific. No association was found between a particular hybridization pattern and the clinical origin of the strain. Nevertheless, two single ORFs (JHP940 and JHP947) were more likely to be found in gastric cancer strains. They may be new pathogenicity markers. An in vitro expression study of these ORFs was also performed for the J99 strain, under different conditions. Thirteen ORFs were consistently expressed, six were consistently shut off, and three were expressed differentially. Most of the constitutionally expressed genes were located on the 3' part of the plasticity region. Our results show that the plasticity region, rather than being considered a pathogenicity island per se, should be considered a genomic island, which represents a large fragment of foreign DNA integrated into the genome and not necessarily implicated in the pathogenic capacity of the strain.
Distribution of Open Reading Frames of Plasticity Region of Strain J99 in Helicobacter pylori Strains Isolated from Gastric Carcinoma and Gastritis Patients in Costa Rica
(American Society for Microbiology, 2000) Alessandra Occhialini; Armelle Marais; Richard A. Alm; Fernando Tuffi García; Rafaela Sierra; Françis Mégraud
The plasticity region of Helicobacter pylori strain J99 is a large chromosomal segment containing 33 strain-specific open reading frames (ORFs) with characteristics of a pathogenicity island. To study the diversity of the plasticity region, 22 probes corresponding to 20 ORFs inside the plasticity region and two ORFs on its boundaries were hybridized to genomic DNA isolated from clinical strains of H. pylori from patients with gastritis or gastric adenocarcinoma. Highly variable hybridization patterns were observed. The majority of the clinical strains presented a hybridization profile similar to that of J99; thus, these ORFs are not J99 strain specific. No association was found between a particular hybridization pattern and the clinical origin of the strain. Nevertheless, two single ORFs (JHP940 and JHP947) were more likely to be found in gastric cancer strains. They may be new pathogenicity markers. An in vitro expression study of these ORFs was also performed for the J99 strain, under different conditions. Thirteen ORFs were consistently expressed, six were consistently shut off, and three were expressed differentially. Most of the constitutionally expressed genes were located on the 3′ part of the plasticity region. Our results show that the plasticity region, rather than being considered a pathogenicity island per se, should be considered a genomic island, which represents a large fragment of foreign DNA integrated into the genome and not necessarily implicated in the pathogenic capacity of the strain.
Erradicación de Helicobacter pylori mediante triple teerapia (amoxicilina, claritromicina, omeprazole), en pacientes del Hospital Dr. Rafael A. Calderón Guardia
(2009) Rigoberto Salas Aguilar; Rolando Páez Sáenz; Gerardo Avendaño Alvarado; Alessia Ávalos Giugliarelli; Ricardo Barahona García; Lore Lang; Vanessa Ramírez; Rafaela Sierra; Fernando Tuffi García
Justificación y objetivo: H. pylori es un factor importante en el desarrollo de diversos tipos de patologías gástricas como: gastritis crónica, úlcera péptica, adenocarcinoma tipo intestinal y linfoma. Erradicar la infección es una importante posibilidad en la terapia de los pacientes con esas patologías. En el estudio se analizó la utilidad de la triple terapia para erradicar de la infección por H. pylori en pacientes con gastritis crónica y úlcera péptica.Métodos: Se incluyeron 267 pacientes que atendieron el Servicio de Gastroenterología del HCG, entre enero y mayo de 2000. La presencia de H. pylori fue determinada por ureasa rápida, cultivo y antígenos fecales específicos. Se determinó la CIM de algunos aislamientos mediante la prueba de E-test. Los pacientes recibieron triple terapia con amoxicilina (1000 mg bid vo), claritromicina (500 mg bid vo - Claritrobac‚) y omeprazole (20 mg bid vo - Proton‚), por 10 días. La erradicación de la infección se definió como presencia de H. pylori al principio del tratamiento y un resultado negativo en la prueba de antígenos fecales específicos, entre 30 y 45 días después de finalizado el tratamiento.Resultados: De los 267 pacientes que recibieron la triple terapia, 189 (70,8%) la completaron. La erradicación de la bacteria se confirmó en 127 (84,7%) de los pacientes que completaron el tratamiento. Treinta y siete (94,9%) de los 39 pacientes con diagnóstico endoscópico de úlcera péptica erradicaron la bacteria. La erradicación fue exitosa incluso en pacientes portadores de cepas que mostraron resistencia in vitro a amoxicilina o a claritromicina, aunque en este estudio la presencia de cepas sensibles no predice el éxito del tratamiento en todos los casos.Conclusión: La triple terapia basada en amoxicilina (1000 mg bid vo), claritromicina (500 mg bid vo - Claritrobac‚) y omeprazole (20 mg bid vo - Proton‚), por 10 días, erradicó la infección por H. pylori en el 84,7% de los pacientes que cumplieron el tratamiento, incluyendo a 37 de 39 pacientes (94,9%) con enfermedad úlcero-péptica. La triple terapia por 10 días constituye una opción exitosa para erradicar de la infección por H. pylori.