Examinando por Autor "Nieto, Pamela A."

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    Conjugal transfer of the pathogenicity island ROD21 in salmonella enterica serovar enteritidis depends on environmental conditions
    (Public Library of Science, 2014-04) Salazar-Echegarai, Francisco J.; Tobar, Hugo E.; Nieto, Pamela A.; Riedel, Claudia A.; Bueno, Susan M.
    Unstable pathogenicity islands are chromosomal elements that can be transferred from one bacterium to another. Salmonella enterica serovar Enteritidis (S. Enteritidis) is a pathogenic bacterium containing such unstable pathogenicity islands. One of them, denominated ROD21, is 26.5 kb in size and capable of excising from the chromosome in certain culture conditions, as well as during bacterial infection of phagocytic cells. In this study we have evaluated whether ROD21 can be effectively transferred from one bacterium to another. We generated a donor and several recipient strains of S. Enteritidis to carry out transfer assays in liquid LB medium. These assays showed that ROD21 is effectively transferred from donor to recipient strains of S. Enteritidis and S. Typhimurium. When Escherichia coli was used as the recipient strain, ROD21 transfer failed to be observed. Subsequently, we showed that a conjugative process was required for the transfer of the island and that changes in temperature and pH increased the transfer frequency between Salmonella strains. Our data indicate that ROD21 is an unstable pathogenicity island that can be transferred by conjugation in a species-specific manner between Salmonellae. Further, ROD21 transfer frequency increases in response to environmental changes, such as pH and temperature.
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    Ítem
    Gestational hypothyroidism improves the ability of the female offspring to clear streptococcus pneumoniae infection and to recover from pneumococcal pneumonia
    (Endocrine Society, 2016-06) Nieto, Pamela A.; Peñaloza, Hernán F.; Salazar-Echegarai, Francisco J.; Castellanos, Raquel M.; Opazo, Maria Cecilia; Venegas, Luis; Padilla, Oslando; Kalergis, Alexis M.; Riedel, Claudia A.; Bueno, Susan M.
    Maternal thyroid hormones are essential for proper fetal development. A deficit of these hormones during gestation has enduring consequences in the central nervous system of the offspring, including detrimental learning and impaired memory. Few studies have shown that thyroid hormone deficiency has a transient effect in the number of T and B cells in the offspring gestated under hypothyroidism; however, there are no studies showing whether maternal hypothyroidism during gestation impacts the response of the offspring to infections. In this study, we have evaluated whether adult mice gestated in hypothyroid mothers have an altered response to pneumococcal pneumonia. We observed that female mice gestated in hypothyroidism have increased survival rate and less bacterial dissemination to blood and brain after an intranasal challenge with Streptococcus pneumoniae. Further, these mice had higher amounts of inflammatory cells in the lungs and reduced production of cytokines characteristic of sepsis in spleen, blood, and brain at 48 hours after infection. Interestingly, mice gestated in hypothyroid mothers had basally increased vascular permeability in the lungs. These observations suggest that gestational hypothyroidism alters the immune response and the physiology of lungs in the offspring, increasing the resistance to respiratory bacterial infections.