An investigation of the expression and adhesin function of H7 flagella in the interaction of Escherichia coli O157: H7 with bovine intestinal epithelium

Enterohaemorrhagic Escherichia coli O157 : H7 is a bacterial pathogen that can cause haemorrhagic colitis and haemolytic uremic syndrome. In the primary reservoir host, cattle, the terminal rectum is the principal site of E. coli O157 colonization. In this study, bovine terminal rectal primary epithelial cells were used to examine the role of H7 flagella in epithelial adherence. Binding of a fliC(H7) mutant O157 strain to rectal epithelium was significantly reduced as was binding of the flagellated wild-type strain following incubation with H7-specific antibodies. Complementation of fliC(H7) mutant O157 strain with fliC(H7) restored the adherence to wild-type levels; however, complementation with fliC(H6) did not restore it. High-resolution ultrastructural and imunofluorescence studies demonstrated the presence of abundant flagella forming physical contact points with the rectal epithelium. Binding to terminal rectal epithelium was specific to H7 by comparison with other flagellin types tested. In-cell Western assays confirmed temporal expression of flagella during O157 interaction with epithelium, early expression was suppressed during the later stages of microcolony and attaching and effacing lesion formation. H7 flagella are expressed in vivo by individual bacteria in contact with rectal mucosa. Our data demonstrate that the H7 flagellum acts as an adhesin to bovine intestinal epithelium and its involvement in this crucial initiating step for colonization indicates that H7 flagella could be an important target in intervention strategies.

Triclosan resistance in Salmonella enterica serovar Typhimurium

Objectives: The aim of this study was to characterize the mechanisms of resistance to triclosan in Salmonella enterica serovar Typhimurium. Methods: Mutants resistant to triclosan were selected from nine S. enterica serovar Typhimurium strains. Mutants were characterized by genotyping, mutagenesis and complementation of fabI and analysis of efflux activity. Fitness of triclosan-resistant mutants was determined in vitro and in vivo. Results: Three distinct resistance phenotypes were observed: low- (LoT), medium- (MeT) and high-level (HiT) with MICs of 4-8, 16-32 and > 32 mg/L of triclosan, respectively, for inhibition. The genotype of fabI did not correlate with triclosan MIC. Artificial overexpression and mutagenesis of fabI in SL1344 each resulted in low-level triclosan resistance, indicating that FabI alone does not mediate high-level triclosan resistance in Salmonella Typhimurium. Active efflux of triclosan via AcrAB-TolC confers intrinsic resistance to triclosan as inactivation of acrB and tolC in wild-type strains and the triclosan-resistant mutants led to large decreases in triclosan resistance, which were reversed by complementation. Exemplars of each phenotype were evaluated for fitness in vivo; no fitness cost was seen and mutants colonized and persisted in chickens throughout a 28 day competitive index experiment. Conclusions: These data show that triclosan resistance can occur via distinct pathways in salmonella and that mutants selected after single exposure to triclosan are fit enough to compete with wild-type strains.

Multiple antibiotic resistance (mar) locus in Salmonella enterica serovar typhimurium DT104

In order to understand the role of the mar locus in Salmonella with regard to multiple antibiotic resistance, cyclohexane resistance, and outer membrane protein F (OmpF) regulation, a marA::gfp reporter mutant was constructed in an antibiotic-sensitive salmonella enterica serovar Typhimurium DT104 background. Salicylate induced marA, whereas a number of antibiotics, disinfect ants, and various growth conditions did not. Increased antibiotic resistance was observed upon salicylate induction, although this was shown to be by both mar-dependent and mar-independent pathways. Cyclohexane resistance, however, was induced by salicylate by a mar-dependent pathway. Complementation studies with a plasmid that constitutively expressed marA confirmed the involvement of map in Salmonella with low-level antibiotic resistance and cyclohexane resistance, although the involvement of mar in down regulation of OmpF was unclear. However, marA overexpression did increase the expression of a ca. 50-kDa protein, but its identity remains to be elucidated Passage of the marA::gfp reporter mutant with increasing levels of tetracycline, a method reported to select for mar mutants in Escherichia coli, led to both multiple-antibiotic and cyclohexane resistance. Collectively, these data indicate that low-level antibiotic resistance, cyclohexane resistance, and modulation of OMPs in Salmonella, as in E. coli, can occur in both a mar-dependent and mar-independent manner.

Membrane ruffling and invasion of human and avian cell lines is reduced for aflagellate mutants of Salmonella enterica serotype Enteritidis

Independent studies have demonstrated that flagella are associated with the invasive process of Salmonella enterica serotypes, and aflagellate derivatives of Salmonella enterica serotype Enteritidis are attenuated in murine and avian models of infection. One widely held view is that the motility afforded by flagella, probably aided by chemotactic responses, mediates the initial interaction between bacterium and host cell. The adherence and invasion properties of two S. Enteritidis wild-type strains and isogenic aflagellate mutants were assessed on HEp-2 and Div-1 cells that are of human and avian epithelial origin, respectively. Both aflagellate derivatives showed a significant reduction of invasion compared with wild type over the three hours of the assays. Complementation of the defective fliC allele recovered partially the wild-type phenotype. Examination of the bacterium-host cell interaction by electron and confocal microscopy approaches showed that wild-type bacteria induced ruffle formation and significant cytoskeletal rearrangements on HEp-2 cells within 5 minutes of contact. The aflagellate derivatives induced fewer ruffles than wild type. Ruffle formation on the Div-1 cell line was less pronounced than for HEp-2 cells for wild-type S. Enteritidis. Collectively, these data support the hypothesis that flagella play an active role in the early events of the invasive process.

Binding properties and adhesion-mediating regions of the major sheath protein of Treponema denticola ATCC 35405

There is growing evidence that a number of oral Treponema species, in particular Treponema denticola, are associated with the progression of human periodontal disease. The major sheath (or surface) protein (Msp) of T. denticola is implicated in adhesion of bacteria to host cells and tissue proteins and is likely to be an important virulence factor. However, the binding regions of the Msp are not known. We have purified from Escherichia coli recombinant Msp (rMsp) polypeptides corresponding to the following: full-length Msp (rMsp) minus 13 N-terminal amino acid (aa) residues, an amino-terminal fragment (rN-Msp, 189 aa residues), a 57-aa residue segment from the central region (rV-Msp), and a C-terminal fragment (rC-Msp, 272 aa residues). rMsp (530 aa residues) bound to immobilized fibronectin, keratin, laminin, collagen type 1, fibrinogen, hyaluronic acid, and heparin. The N- and V-region polypeptides, but not rC-Msp, also bound to these substrates. Binding of rMsp to fibronectin was targeted to the N-terminal heparin I/fibrin I domain. Antibodies to the N-region or V-region polypeptides, but not antibodies to the rC-Msp fragment, blocked adhesion of T. denticola ATCC 35405 cells to a range of host protein molecules. These results suggest that the N-terminal half of Msp carries epitopes that are surface exposed and that are involved in mediating adhesion. Binding of rMsp onto the cell surface of low-level fibronectin-binding Treponema isolates conferred a 10-fold increase in fibronectin binding. This confirms that Msp functions autonomously as an adhesin and raises the possibility that phenotypic complementation of virulence functions might occur within mixed populations of Treponema species.

The AcrAB-TolC efflux system of Salmonella enterica serovar Typhimurium plays a role in pathogenesis

The ability of an isogenic set of mutants of Salmonella enterica serovar Typhimurium L354 (SL1344) with defined deletions in genes encoding components of tripartite efflux pumps, including acrB, acrD, acrF and tolC, to colonize chickens was determined in competition with L354. In addition, the ability of L354 and each mutant to adhere to, and invade, human embryonic intestine cells and mouse monocyte macrophages was determined in vitro. The tolC and acrB knockout mutants were hyper-susceptible to a range of antibiotics, dyes and detergents; the tolC mutant was also more susceptible to acid pH and bile and grew more slowly than L354. Complementation of either gene ablated the phenotype. The tolC mutant poorly adhered to both cell types in vitro and was unable to invade macrophages. The acrB mutant adhered, but did not invade macrophages. In vivo, both the acrB mutant and the tolC mutant colonized poorly and did not persist in the avian gut, whereas the acrD and acrF mutant colonized and persisted as well as L354. These data indicate that the AcrAB-TolC system is important for the colonization of chickens by S. Typhimurium and that this system has a role in mediating adherence and uptake into target host cells.

Effect of the anti-neoplastic drug doxorubicin on XPD-mutated DNA repair-deficient human cells

Doxorubicin (DOX), a member of the anthracycline group, is a widely used drug in cancer therapy. The mechanisms of DOX action include topoisomerase II-poisoning, free radical release, DNA adducts and interstrand cross-link (ICL) formation. Nucleotide excision repair(NER) is involved in the removal of helix-distorting lesions and chemical adducts, however, little is known about the response of NER-deficient cell lines to anti-tumoral drugs like DOX. Wild type and XPD-mutated cells, harbouring mutations in different regions of this gene and leading to XP-D, XP/CS or TTD diseases, were treated with this drug and analyzed for cell cycle arrest and DNA damage by comet assay. The formation of DSBs was also investigated by determination of gamma H2AX foci. Our results indicate that all three NER-deficient cell lines tested are more sensitive to DOX treatment, when compared to wild type cells or XP cells complemented by the wild type XPD cDNA, suggesting that NER is involved in the removal of DOX-induced lesions. The cell cycle analysis showed the characteristic G2 arrest in repair-proficient MRC5 cell line after DOX treatment, whereas the repair-deficient cell lines presented significant increase in sub-G1 fraction. The NER-deficient cell lines do not show different patterns of DNA damage formation as assayed by comet assay and phosphorylated H2AX foci formation. Knock-down of topoisomerase II alpha with siRNA leads to increased survival in both MRC5 and XP cells, however, XP cell line still remained significantly more sensitive to the treatment by DOX. Our study suggests that the enhanced sensitivity is due to DOX-induced DNA damage that is subject to NER, as we observed decreased unscheduled DNA synthesis in XP-deficient cells upon DOX treatment. Furthermore, the complementation of the XPD-function abolished the observed sensitivity at lower DOX concentrations, suggesting that the XPD helicase activity is involved in the repair of DOX-induced lesions. (C) 2009 Elsevier B.V. All rights reserved.

The Trypanosoma cruzi proteins TcCox10 and TcCox15 catalyze the formation of heme A in the yeast Saccharomyces cerevisiae

Trypanosoma cruzi, the etiologic agent for Chagas` disease, has requirements for several cofactors, one of which is heme. Because this organism is unable to synthesize heme, which serves as a prosthetic group for several heme proteins (including the respiratory chain complexes), it therefore must be acquired from the environment. Considering this deficiency, it is an open question as to how heme A, the essential cofactor for eukaryotic CcO enzymes, is acquired by this parasite. In the present work, we provide evidence for the presence and functionality of genes coding for heme O and heme A synthases, which catalyze the synthesis of heme O and its conversion into heme A, respectively. The functions of these T. cruzi proteins were evaluated using yeast complementation assays, and the mRNA levels of their respective genes were analyzed at the different T. cruzi life stages. It was observed that the amount of mRNA coding for these proteins changes during the parasite life cycle, suggesting that this variation could reflect different respiratory requirements in the different parasite life stages.

Trypanosome Prereplication Machinery Contains a Single Functional Orc1/Cdc6 Protein, Which Is Typical of Archaea

In unicellular eukaryotes, such as Saccharomyces cerevisiae, and in multicellular organisms, the replication origin is recognized by the heterohexamer origin recognition complex (ORC) containing six proteins, Orc1 to Orc6, while in members of the domain Archaea, the replication origin is recognized by just one protein, Orc1/Cdc6; the sequence of Orc1/Cdc6 is highly related to those of Orc1 and Cdc6. Similar to Archaea, trypanosomatid genomes contain only one gene encoding a protein named Orc1. Since trypanosome Orc1 is also homologous to Cdc6, in this study we named the Orc1 protein from trypanosomes Orc1/Cdc6. Here we show that the recombinant Orc1/Cdc6 from Trypanosoma cruzi (TcOrc1/Cdc6) and from Trypanosoma brucei (TbOrc1/Cdc6) present ATPase activity, typical of prereplication machinery components. Also, TcOrc1/Cdc6 and TbOrc1/Cdc6 replaced yeast Cdc6 but not Orc1 in a phenotypic complementation assay. The induction of Orc1/Cdc6 silencing by RNA interference in T. brucei resulted in enucleated cells, strongly suggesting the involvement of Orc1/Cdc6 in DNA replication. Orc1/Cdc6 is expressed during the entire cell cycle in the nuclei of trypanosomes, remaining associated with chromatin in all stages of the cell cycle. These results allowed us to conclude that Orc1/Cdc6 is indeed a member of the trypanosome prereplication machinery and point out that trypanosomes carry a prereplication machinery that is less complex than other eukaryotes and closer to archaea.

Characterization of Paracoccidioides brasiliensis COX9, COX12, and COX16 respiratory genes

Paracoccidioides brasiliensis is a thermo-dimorphic fungus that is the causative agent of paracoccidioidomyicosis (PCM), a human systemic granulomatous mycosis found in Latin America. Dimorphic transition from mycelium to yeast is required for establishing pathogenicity. Dimorphism is marked by changes in mitochondrial physiology, including modulation of respiration rate. In this work, we present the identification of three P. brasiliensis nuclear genes PbCOX9, PbCOX12, and PbCOX16 that code for structural sub-units and a putative assembly facilitator (PbCOX16) of the mitochondrial cytochrome c oxidase (COX), the terminal enzyme complex of the respiratory chain. We measured their expression pattern during the dimorphic transition from mycelium to yeast and back by real-time reverse transcription quantitative polymerase chain reaction (real-time RT-qPCR). Our results show that messages from these genes increase during the mycelium to yeast transition and decrease during the opposite conversion. This result supports active mitochondrial participation in the transition. Heterologous complementation of the corresponding Saccharomyces cerevisiae null mutant with the PbCOX9 gene was successfully obtained. (C) 2008 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.

Alianças estratégicas e suas implicações para a configuração de capacidades tecnológicas: evidências da indústria farmacêutica multinacional

Esta dissertação examina as capacidades tecnológicas (sistema técnico-organizacional, molécula e medicamento) disponibilizadas em alianças estratégicas pela indústria farmacêutica multinacional, assim como as principais implicações das alianças estratégicas para a indústria farmacêutica em termos de configuração de suas capacidades tecnológicas . Essas questões são examinadas à base de evidências empíricas secundárias sobre alianças estratégicas em uma amostra de 25 companhias multinacionais da indústria farmacêutica, pertencentes a três grupos: companhia farmacêutica de grande porte (big pharma); companhia biofarmacêutica de grande porte (biofarma) e companhia pequena de pesquisa . A literatura relacionada oferece uma grande quantidade de estudos sobre alianças estratégicas e capacidades tecnológicas na indústria farmacêutica multinacional. Porém, o tema das implicações de tais alianças estratégicas para mudanças na configuração de capacidades tecnológicas ainda carece de mais fundamentação empírica, pela perspectiva de gestão de empresa e, mais precisamente, pela perspectiva de estratégia empresarial baseada em competências dinâmicas. Essa dissertação baseia-se em extensiva e sistemática coleta de evidências empíricas relativas às alianças estratégicas implementadas por 25 companhias da indústria farmacêutica e, publicadas durante o período de 1993 a 2003. Tais evidências empíricas foram coletadas a partir de três bancos de dados: Business & Industry; Galé e Dialog . Com relação aos resultados, foi encontrado que: Em termos de participações com capacidades tecnológicas ingressantes em alianças estratégicas: (i) as 'big pharmas' ingressaram com 11 % das 169 capacidades tecnológicas; (ii) as biofarmas ingressaram com 44% das 143 capacidades tecnológicas; (iii) as companhias pequenas de pesquisa ingressaram com 72% das 95 capacidades tecnológicas . 2 Em termos de implicações das alianças estratégicas para a mudança na configuração de capacidades tecnológicas que ingressaram em alianças estratégicas, foi encontrado que: (i) as 'big pharmas' aumentaram a proporção em moléculas (16% para 55%); (ii) as biofarmas aumentaram a participação em moléculas (22% para 32%) e sistema técnico-organizacional para pesquisa de molécula (49% para 55%); (iii) as companhias pequenas de pesquisa inseriram-se a uma nova atividade (comercialização de medicamento no mercado farmacêutico) a partir do aumento da participação em medicamentos (3% para 29%). Adicionalmente, atualizaram sistemas técnico-organizacionais para pesquisa de molécula . As evidências sugerem que o critério de escolha por companhia parceira e por mecanismo de aliança estratégica foi condicionado aos objetivos e às necessidades de cada grupo de companhia da indústria farmacêutica. Por fim, enquanto as companhias integradas, 'big pharmas' e biofarmas, principalmente, as primeiras, têm adaptado o modelo de negócio "Fully Integrated Pharmaceutical Company" com a adoção de alianças estratégicas para complementação de capacidades tecnológicas, as companhias pequenas de pesquisa capitalizam as suas capacidades tecnológicas através das alianças estratégicas e ingressam no mercado farmacêutico com a comercialização de medicamentos adquiridos por meio de alianças estratégicas. Portanto, as evidências sugerem que a busca por complementação de base de conhecimento para competir no mercado globalizado, tem implicado ainda que, informalmente, uma alteração na organização das atividades tecnológicas inovadoras, especialmente, em termos de produtos (medicamentos) .

Fusões, aquisições estratégicas, e capacidades tecnológicas inovadoras: evidências da indústria de telecomunicações multinacional

This dissertation studies the innovative technological capabilities available in the merger and acquisitions processes and the relationship between these processes with the technological capabilities accumulation to get convergence of technology and services. This study was examined in fourteen companies of the telecommunications industry during 2002 to 2007. Starting on 1990 there were from one end a profusion of studies on the technological capabilities as source of competitive advantages; from another end there are studies on merger and acquisitions with the objective to evaluate the motivations derived from technological factors and stimulation to the competition and the opening of the market. However few of the empirical studies of long stated period that examine the correlation of these events in the industry of telecommunications under the optics of the technological qualification in the level of the companies and for the strategic perspective of enterprise based on the dynamics abilities. An analytical framework already available in the literature was used to describe the contribution of the merger and acquisitions processes for the accumulation of innovative technological capabilities in the studied companies. However the framework was adapted specifically for the industry of Telecommunications. This dissertation also studies the importance of the strategic merger and acquisitions as organizational form in the complementation of technological capability for external sources. Such empirical evidences had been collected from information and data bases published for the own companies who had been examined in this dissertation. Regarding the results, it was found that: 1. In terms of participation with ingress technological capabilities in strategic merger and acquisitions the equipment manufacturers had entered with 71% to 55 of the technological capabilities and the service operator company had entered with 61% to 71 technological capabilities. 2. In terms of implications of the merger and acquisitions for the configuration of resultant technologic capabilities, it was found that the equipment manufacturers had increased 31% the ratio of convergence of technology and the operators of services had increased 4% the ratio for the change in the organizational structure. 3. Regarding the accumulation technological capability to obtain convergence of technology and services was verified the increase these technological capabilities after the merger and acquisitions process in the companies studied. Considering the limitation of this study, the evidences found in this dissertation suggest that the companies use the processes of strategic merger and acquisitions to search for external complementation of their knowledge base to compete in the globalization market. The result demonstrates that this movement has implied in an alteration and accumulation of capability from organization on innovative technological activities regarding the convergence of technology and services.

Estratégias de internacionalização: investimentos diretos externos de multinacionais brasileiras

With the improvement of the international trade on the last decades, the Brazilian firms are searching to operate beyond the national borders in order to guarantee its presence on the key markets. The dissertation aimed to analyze the motivations and the strategies of internationalization implemented by the firms: Petrobras, Vale, Embraer, Gerdau and Marcopolo as well as determine the existence of a dominant strategy. In order to do that, Dunning¿s eclectic paradigm and the strategies of internationalization supported by him were revised along with the main literature from Brazilian authors on the internationalization process of the selected firms. The comparative analysis between the strategies of internationalization selected and the industrial sector, origin of capital and the preferred mode of entrance on the markets were done through an exploratory research, with a qualitative character and collection of secondary data from the internationalization process of the firms. At the end of this research, it was possible to identify that each firm had adopted a predominant strategy however it was also possible to observe that new strategies were aggregated in complementation of the previous one. Besides that, no evidence was found between the predominant strategy of internationalization and the origin of the capital neither with the preferred mode of entrance.

Programas e políticas públicas para o desenvolvimento de vínculos de negócios entre grandes empresas compradoras e pequenos fornecedores locais

Vínculos de negócios são caracterizados como relacionamentos entre grandes empresas e pequenos fornecedores locais, com beneficios que incluem o aumento de negócios entre as empresas, diminuição de custos e dinamização da economia local, com implicações diretas para o desenvolvimento. Isso faz com que o Estado possa ter interesse na promoção destes vínculos, sendo as políticas públicas seu instrumento de promoção. Esta dissertação tem como objetivo identificar as condições para que o Estado estabeleça políticas públicas para a promoção de tais vínculos. Na revisão bibliográfica faz-se a análise de temas ligados ao relacionamento entre empresas, bem como do ambiente de investimento no Brasil. Também é realizada uma análise dos conceitos de vínculos de negócios e de políticas públicas. Para se chegar ao objetivo da pesquisa, foram analisados dois programas, ambos com o objetivo de fortalecer a relação entre grandes empresas compradoras e pequenos fornecedores: Projeto Vínculos e Programa de Desenvolvimento de Fornecedores (dos estados de Maranhão, Espírito Santo e Pará). Utilizou-se como técnica de coleta de dados a entrevista em profundidade, com um total de quatorze entrevistados, que autorizaram a transcrição para posterior análise. A conclusão é que o Estado pode estimular vínculos de negócios por meio de políticas públicas nas seguintes condições: ao complemento de políticas de Estado, como política de qualificação profissional, complemento à política de atração de investimentos, como incentivo à transferência de tecnologia e para o desenvolvimento do ambiente de negócios.

A política pública para resposta às ameaças químicas, biológicas, radiológicas, nucleares e explosivas

Esta pesquisa objetiva verificar de que forma, no Brasil, as políticas públicas relacionadas às ameaças químicas, biológicas, radiológicas, nucleares e explosivas (QBRNE) contribuem para o preparo de resposta a um incidente de tal natureza. No mundo contemporâneo há uma concentração das populações nos centros urbanos, tornando-as vulneráveis a desastres químicos, biológicos, radiológicos e nucleares, os quais podem ser desencadeados por eventos adversos, intencionais ou não, resultando em grandes impactos humanos, ambientais, materiais, sociais e econômicos à nação. O terrorismo é uma das possibilidades de ocorrência de um grande desastre, utilizando-se principalmente de atentados com explosivos e podendo se valer dos efeitos dos agentes contaminantes. Então, foram pesquisadas e apresentadas políticas públicas e ações do governo federal norte-americano para o trato de ameaças QBRNE, as quais são comparadas à situação prospectada no território brasileiro, por meio da legislação, políticas públicas, orçamento, documentos e bibliografia. Diversas instituições foram avaliadas quanto ao papel a ser desempenhado em uma situação emergencial, sendo os dados tratados por análise de conteúdo e historiografia. A literatura sobre política pública é ampla, com rica discussão sobre as boas práticas de gestão pública, a evolução do papel dos servidores públicos para um ser técnico e político simultaneamente e de que maneira é influenciada a concepção de uma política pública. O Modelo de Fluxos Múltiplos e a Teoria de Equilíbrio Pontuado são usados para compreender o processo dinâmico de construção da agenda decisória no governo federal para o tema estudado. Concluiu-se que as políticas públicas de resposta para ameaças QBRNE surgem dispersas em diversas instituições, promovidas pelas equipes técnicas, de maneira descentralizada e sem uma orientação do governo central, o que acarreta sobreposição de atividades, havendo casos de problemas não tratados, desprezando-se a complementação de recursos e efetivos.