https://repositorio.ufu.br/handle/123456789/5488 Sun, 20 Sep 2026 15:21:39 GMT 2026-09-20T15:21:39Z https://repositorio.ufu.br/handle/123456789/49418 Title: Pesquisa do agente da Febre Maculosa Rickettsia parkeri cepa Mata Atlântica no Estado de Minas Gerais Abstract: Ticks are hematophagous ectoparasites responsible for transmitting diseases to humans and an-imals. Among these diseases, Brazilian Spotted Fever, caused by Rickettsia rickettsii, stands out due to its high lethality when diagnosed late. Confirmed cases of this disease are closely associated with ticks of the genus Amblyomma, which represents the greatest diversity of ixodid species in Brazil. On the other hand, other species of the genus Rickettsia, such as Rickettsia parkeri Atlantic rainforest strain (ARF), may cause milder and frequently underdiagnosed clin-ical manifestations, although they still hold epidemiological importance. Minas Gerais is a state of large geographic proportions, with areas that favor the circulation of both bacteria, as well as their vectors. However, R. parkeri ARF , associated with its main vector Amblyomma ovale, had never been reported in this state. In this study, divided into two articles, we evaluated in the state of Minas Gerais the exposure of dogs, important sentinels of this disease, to the rick-ettsial antigens, as well as the presence of genetic material in ticks, in addition to assessing the seasonality of A. ovale, the main vector of R. parkeri ARF. These observations allowed us to conclude that the vector A. ovale shows higher frequency and abundance in spring, with greater intensity in November. Furthermore, the results provided evidence of exposure to rickettsial antigens in dogs from rural properties in the state of Minas Gerais, Brazil. Furthermore, the presence of R. parkeri ARF DNA was detected in two A. ovale ticks, constituting the first report of this bacterium associated with this tick in Minas Gerais. Thu, 26 Mar 2026 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/49418 2026-03-26T00:00:00Z https://repositorio.ufu.br/handle/123456789/48402 Title: Infecções relacionadas à assistência à saúde em unidades de terapia intensiva de adultos no Brasil: Uma abordagem multicêntrica Abstract: Healthcare-associated infections (HAIs) remain one of the major global health challenges, particularly in low- and middle-income countries such as Brazil, where the clinical and economic impact is exacerbated by the high prevalence of multidrug-resistant microorganisms. This thesis, composed of three interrelated articles, integrates different aspects of the epidemiology and dissemination of Klebsiella pneumoniae and Acinetobacter baumannii resistant to carbapenems, as well as a discussion of the clinical impact of HAIs in Brazilian intensive care units (ICUs). The first article aimed to determine the point prevalence of HAIs and identify factors associated with microbiologically confirmed infections in adult ICUs across Brazil. This multicenter study, conducted in 57 ICUs from different regions of the country, included 664 patients, of whom 47.7% had HAIs, with 68.1% acquired in the ICU. Only 47.2% of these infections were microbiologically confirmed. Mechanical ventilation and the use of polymyxins were identified as independent risk factors. The etiology of pneumonia, urinary tract infections, and bloodstream infections (BSIs) was predominantly associated with Pseudomonas aeruginosa and Acinetobacter baumannii; Candida spp.; and coagulase-negative Staphylococcus, respectively. The second article investigated the dissemination of resistance genes (by polymerase chain reaction – PCR) and pulsotypes (by pulsed-field gel electrophoresis – PFGE) in Klebsiella pneumoniae carbapenemase- producing (KPC) and Acinetobacter baumannii oxacillinase-producing (OXA-23) isolates from hospitals located in the North, Northeast, Southeast, and Central-West regions of Brazil. The blaOXA-23 and blaKPC genes were detected in 88.1% and 83.3% of A. baumannii and K. pneumoniae isolates, respectively, and all displayed multidrug- resistant profiles. Eleven distinct genotypes of A. baumannii were identified, with clone E detected in the Southeast (2016) and Central-West (2019) regions. No inter-regional dissemination of identical K. pneumoniae pulsotypes was observed. The third article, presented as a letter complementing a previous international study, expanded the discussion on the clinical impact of carbapenem-resistant Klebsiella pneumoniae infections. As part of this thesis, a letter was written discussing the study by Shao et al. (2024), which analyzed bloodstream infections in pediatric intensive care units in China. Our contribution compared those findings with data from our multicenter cohort of adult ICU patients with multidrug-resistant K. pneumoniae infections, emphasizing the high mortality associated with carbapenem-resistant strains. The letter highlighted similarities between pediatric and adult populations regarding risk factors and clinical outcomes, particularly in severe infections such as BSIs and pneumonia, and reinforced the urgent need for targeted strategies to combat antimicrobial resistance in both patient groups. Taken together, the three studies provide a comprehensive overview of HAIs in Brazilian ICUs, revealing their high prevalence, regional dissemination, and clinical impact, particularly regarding infections caused by multidrug-resistant K. pneumoniae. The findings underscore the importance of strengthening epidemiological surveillance policies, microbiological diagnosis, and rational antimicrobial use, as well as promoting the integration of national and international data to address the global challenge of bacterial resistance. Tue, 10 Feb 2026 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/48402 2026-02-10T00:00:00Z https://repositorio.ufu.br/handle/123456789/48017 Title: A ausência da proteína P21 em Trypanosoma cruzi impacta a invasão celular por tripomastigotas e modula a multiplicação e a expressão gênica de amastigotas intracelular de cepas filogeneticamente distintas Abstract: Trypanosoma cruzi is a protozoan parasite and the causative agent of Chagas disease, a neglected tropical disease with wide distribution in the Americas. This parasite displays high genetic variability, classified into Discrete Typing Units (DTUs), which are associated with biological, clinical, and molecular differences. Among the various factors involved in T. cruzi pathogenicity, the P21 protein stands out as a secreted glycoprotein implicated in modulating the inflammatory response, promoting host cell adhesion and invasion, and potentially regulating the parasite cell cycle. This study aimed to investigate the functional role of the P21 protein through targeted gene knockout in different T. cruzi strains using the CRISPR/Cas9 genome editing system, with a special focus on transcriptomic changes resulting from its absence. Knockout lines were generated in Y (TcII) and G (TcI) strains, representing distinct DTUs. The phenotypic impact of the knockout was evaluated in different developmental forms of the parasite, followed by global gene expression analysis using RNA-seq. Transcriptomic profiling revealed distinct expression patterns between knockout strains, with differentially expressed genes related to key processes such as cell adhesion, signal transduction, stress response, post-translational modifications, and the expression of surface proteins involved in virulence. These findings suggest that P21 plays a modulatory role in T. cruzi biology, with strain-specific effects on host-parasite interactions. The results contribute to a better understanding of P21 function during the parasite life cycle and highlight the utility of genome editing as a powerful tool for functional studies in trypanosomatids. Fri, 28 Nov 2025 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/48017 2025-11-28T00:00:00Z https://repositorio.ufu.br/handle/123456789/47734 Title: Investigação de produtos naturais potenciais na modulação da infecção por Trypanosoma cruzi em modelos de interface materno-fetal humana Abstract: Congenital Chagas disease is a neglected public health issue with limited treatment options. This study evaluated the potential of oleoresins (ORs) from Copaifera spp. and the extract and isolated compounds from Brazilian red propolis (BRP) against Trypanosoma cruzi infection in trophoblastic cells (BeWo lineage) and human villous placental explants (HVPE). Toxicity was assessed through histological and MTT assays, while the anti-T. cruzi potential was evaluated by proliferation, invasion, egress, and reversibility assays. The ultrastructure of treated trypomastigotes and amastigotes was examined by scanning and transmission electron microscopy. Production of reactive oxygen species (ROS) and lipid bodies were quantified in BeWo cells, and cytokines were measured in both BeWo cells and HVPE. ORs and BRP significantly reduced T. cruzi proliferation in BeWo cells and the parasitic load in HVPE. ORs induced ultrastructural changes in the parasite, including body torsion, flagellar rupture, and cytoplasmic disorganization, whereas BRP did not cause such changes. Both exhibited antioxidant activity, reducing ROS in infected BeWo cells, and BRP modulated lipid metabolism by decreasing lipid bodies. T. cruzi infection altered the cytokine profile in BeWo cells and HVPE; ORs upregulated suppressed cytokines in BeWo cells and downregulated elevated cytokines in HVPE. In conclusion, ORs from Copaifera spp. and BRP, at noncytotoxic concentrations, demonstrated promising potential as candidates for new therapies against congenital Chagas disease, with antiparasitic, antioxidant, and immunomodulatory effects. Thu, 23 Oct 2025 00:00:00 GMT https://repositorio.ufu.br/handle/123456789/47734 2025-10-23T00:00:00Z