Browsing by Author "García, Patricia"

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    A Novel Gemcitabine-Resistant Gallbladder Cancer Model Provides Insights into Molecular Changes Occurring during Acquired Resistance
    (2023) Vergara-Gómez, Luis; Bizama, Carolina; Zhong, Jun; Buchegger, Kurt; Suárez Vega, Felipe Ignacio; Rosa, Lorena; Ili, Carmen; Weber, Helga; Obreque, Javiera; Espinoza, Karena; Repetto, Gabriela; Roa, Juan C.; Leal, Pamela; García, PatriciaVergara-Gómez, Luis; Bizama, Carolina; Zhong, Jun; Buchegger, Kurt; Suárez Vega, Felipe Ignacio; Rosa, Lorena; Ili, Carmen; Weber, Helga; Obreque, Javiera; Espinoza, Karena; Repetto, Gabriela; Roa, Juan C.; Leal, Pamela; García, Patricia
    Treatment options for advanced gallbladder cancer (GBC) are scarce and usually rely on cytotoxic chemotherapy, but the effectiveness of any regimen is limited and recurrence rates are high. Here, we investigated the molecular mechanisms of acquired resistance in GBC through the development and characterization of two gemcitabine-resistant GBC cell sublines (NOZ GemR and TGBC1 GemR). Morphological changes, cross-resistance, and migratory/invasive capabilities were evaluated. Then, microarray-based transcriptome profiling and quantitative SILAC-based phosphotyrosine proteomic analyses were performed to identify biological processes and signaling pathways dysregulated in gemcitabine-resistant GBC cells. The transcriptome profiling of parental and gemcitabine-resistant cells revealed the dysregulation of protein-coding genes that promote the enrichment of biological processes such as epithelial-to-mesenchymal transition and drug metabolism. On the other hand, the phosphoproteomics analysis of NOZ GemR identified aberrantly dysregulated signaling pathways in resistant cells as well as active kinases, such as ABL1, PDGFRA, and LYN, which could be novel therapeutic targets in GBC. Accordingly, NOZ GemR showed increased sensitivity toward the multikinase inhibitor dasatinib compared to parental cells. Our study describes transcriptome changes and altered signaling pathways occurring in gemcitabine-resistant GBC cells, which greatly expands our understanding of the underlying mechanisms of acquired drug resistance in GBC.
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    Análisis de los fenotipos y genotipos de resistencia a eritromicina y clindamicina en cepas de Streptococcus pyogenes aisladas en Chile en un período de 10 años
    (2011) Rodríguez, Carlos; Rojas, Pablo; Wozniak, Aniela; Kalergis, Alexis M.; Cerón, Inés; Riedel, Ingrid; Román, Juan C.; Villarroel, Luis A.; Berríos, Ximena; Bavestrello, Luis; García, Patricia
    Background: Macrolide and lincosamide resistance in Streptococcus pyogenes is due to the acquisition of mef, ermB and ermA genes, which confer different resistance phenotypes, namely M, MLSBconstitutive and MLSBinducible respectively. The last report of resistance in Chile was done in the period 1990-1998, in which resistance to macrolides was 5.4%, with M phenotype as the predominant one. Aim: To characterize the evolution of erythromycin and clindamycin resistance and their associated genes in S. pyogenes strains isolated from patients with invasive and noninvasive infections in the period 1996 to 2005. Material and Methods: Resistance to erythromycin and clindamycin was determined in 1,282 clinical isolates using the disk diffusion test. Resistant isolates were analyzed by polymerase chain reaction (PCR) for the presence of the above mentioned resistance genes. Results: Global resistance to erythromycin and clindamycin was 3.5 and 0.7% respectively. Eighty percent of the resistant strains possessed the M. phenotype. Conclusions: Resistance levels of S. pyogenes have decreased in Chile in the last years. Most resistant strains have M phenotype in contrast to many countries in which the MLSB constitutive phenotype is the predominant one.
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    Chromosome-Mediated Colistin Resistance in Clinical Isolates of Klebsiella pneumoniae and Escherichia coli: Mutation Analysis in the Light of Genetic Background
    (Dove Medical Press Ltd, 2023) Riquelme, María Paz; Martínez, Rodrigo W.; Brito, Bárbara; García, Patricia; Wozniak Banchero, Aniela; Legarraga, Paulette
    © 2023 Riquelme et al.Purpose: Colistin resistance mechanisms involving mutations in chromosomal genes associated with LPS modification are not completely understood. Mutations in genes coding for the MgrB regulator frequently account for colistin resistance in Klebsiella pneumoniae, whereas mutations in genes coding for PhoPQ and PmrAB are frequent in E. coli. Our aim was to perform a genetic analysis of chromosomal mutations in colistin-resistant (MIC ≥4 µg/mL) clinical isolates of K. pneumoniae (n = 8) and E. coli (n = 7) of different STs. Methods: Isolates were obtained in a 3-year period in a university hospital in Santiago, Chile. Susceptibility to colistin, aminoglyco-sides, cephalosporins, carbapenems and ciprofloxacin was determined through broth microdilution. Whole genome sequencing was performed for all isolates and chromosomal gene sequences were compared with sequences of colistin-susceptible isolates of the same sequence types. Results: None of the isolates carried mcr genes. Most of the isolates were susceptible to all the antibiotics analyzed. E. coli isolates were ST69, ST127, ST59, ST131 and ST14, and K. pneumoniae isolates were ST454, ST45, ST6293, ST380 and ST25. All the isolates had mutations in chromosomal genes analyzed. K. pneumoniae had mutations mainly in mgrB gene, whereas E. coli had mutations in pmrA, pmrB and pmrE genes. Most of the amino acid changes in LPS-modifying enzymes of colistin-resistant isolates were found in colistin-susceptible isolates of the same and/or different ST. Eleven of them were found only in colistin-resistant isolates. Conclusion: Colistin resistance mechanisms depend on genetic background, and are due to chromosomal mutations, which implies a lower risk of transmission than plasmid-mediated genes. Colistin resistance is not associated with multidrug-resistance, nor to high-risk sequence types.
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    Development of an implantable three-dimensional model of a functional pathogenic multispecies biofilm to study infected wounds
    (2022) Cárdenas Calderón, Camila Valentina; Veloso Giménez, Valentina del Carmen; González, Tamara; Wozniak Banchero, Aniela; García, Patricia; San Martín, Sebastián; Varas, Juan F.; Carrasco-Wong, Ivo; Vera, Mario; Egaña, José T.
    Chronic wounds cannot heal due to impairment of regeneration, mainly caused by the persistent infection of multispecies biofilms. Still, the effects of biofilm wound infection and its interaction with the host are not fully described. We aimed to study functional biofilms in physiological conditions in vitro, and their potential effects in health and regeneration in vivo. Therefore, Pseudomonas aeruginosa, Staphylococcus aureus and Enterococcus faecalis were seeded in collagen-based scaffolds for dermal regeneration. After 24 h, scaffolds had bacterial loads depending on the initial inoculum, containing viable biofilms with antibiotic tolerance. Afterwards, scaffolds were implanted onto full skin wounds in mice, together with daily supervision and antibiotic treatment. Although all mice survived their health was affected, displaying fever and weight loss. After ten days, histomorphology of scaffolds showed high heterogeneity in samples and within groups. Wounds were strongly, mildly, or not infected according to colony forming units, and P. aeruginosa had higher identification frequency. Biofilm infection induced leucocyte infiltration and elevated interferon-γ and interleukin-10 in scaffolds, increase of size and weight of spleen and high systemic pro-calcitonin concentrations. This functional and implantable 3D biofilm model allows to study host response during infection, providing a useful tool for infected wounds therapy development.
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    Estrategia de pesquisa sistemática y seguimiento prolongado revela alto número de nuevas infecciones tuberculosas en contactos adultos en la Región Metropolitana, Chile
    (2020) Balcells Marty, María Elvira; Carvajal, Camila; Fernández, Paula; Ruiz-Tagle, Cinthya; Pizarro, Alejandra; García, Patricia; Peña, Carlos; Cuevas, Gerardo; Naves, Rodrigo
    Background: Contact investigation is cardinal in the control of tuberculosis (TB) since it helps to stop its transmission. In Chile, the National TB Program strategy does not include latent TB infection testing, regular chemoprophylaxis or follow-up in adults. Active TB was found in only 1.2% of contacts at country-level during 2018. Aim: To evaluate the performance of a systematic screening ofadult household contacts with targeted chemoprophylaxis and prolonged active follow-up. Material and Methods: Prospective cohort of household contacts in Santiago. Two face-to-face visits (at 0 and 12 weeks) that included QuantiFERON TB-Gold plus tests (QFT), chest radiography (CXR) at 0 and 24 weeks and, periodic text messaging or phone call follow-up for up to 48 weeks were implemented. Contacts with positive QFT were referred for TB chemoprophylaxis. Results: A total of 200 contacts were enrolled, 69% were migrants. At baseline evaluation, 45% had a positive QFT result and 1.6% had co-prevalent active TB. At follow-up, 13% contacts further converted to QFT (+), and 5.1% more were diagnosed with active TB (mean follow-up time 32 weeks). Of these 10 further active TB cases, 6 (60%) had a negative QFT and all (100%) had normal CXR at baseline; while three cases occurred in QFT converters. Conclusions: In this cohort of household contacts, 6.7 % were diagnosed with active TB (more than 2/3 at follow-up) and 13% had a late QFT (+) conversion. Active and prolonged contacts’ follow-up are essential to detect new infections and tackle the TB epidemic in Chile.