http://hdl.handle.net/10362/4551 2013-06-19T16:24:05Z 2013-06-19T16:24:05Z Gaspar, Frédéric Bustos http://hdl.handle.net/10362/8590 2013-01-22T15:37:37Z 2012-06-01T00:00:00Z

Title: Non-clinical isolates bring new findings on enterococcal virulence Authors: Gaspar, Frédéric Bustos Abstract: Enterococci are Gram-positive lactic acid bacteria, widespread in the environment, present in water, soil, plants and animals, including humans. They typically colonize the skin and mucous membranes, namely the gastrointestinal tract. However, enterococci, and most notably Enterococcus faecalis and Enterococcus faecium, have become problematic causative agents of several nosocomial infections, including urinary tract infections, bacteraemia, surgical sight infections, and endocarditis. Besides being opportunistic pathogens, the resilient bacteria of the genus Enterococcus are key factors contributing to the ripening, flavour, and the organoleptic properties of fermented food products. The ubiquitous nature of enterococci derives from a number of features, which can be intrinsic to the genus or specific to some species or even strains. These traits allow probing the environment in order to adapt, enabling a survival and fitness advantage. They are encoded in numerous genes that can be easily transferable due to the high genomic promiscuity of enterococci. These genes have been ascribed a role in virulence as they are relevant to different stages of the bacterial infection process, including adhesion, colonization, invasion, evasion of the immune system and spread through the hostʼs tissues. Enterococcal virulence factors can be either secreted (cytolysin, proteases, hyaluronidase, superoxide), surface associated (enterococcal surface protein, aggregation substance, extracellular polymeric substances, pilin gene clusters, enterococcal microbial surface component recognizing adhesive matrix molecules), or intracellular. At the time this thesis work began, researchers were starting to realize that virulence factors in enterococcal clinical isolates were also present in isolates from other environments, in particular, where enterococci play beneficial roles, namely food. Since dissemination of virulence factors among food isolates was no longer crucial, other issues started to become relevant in the still debated enterococcal virulence.(...) Description: Dissertation presented to obtain the PhD degree in Biology

2012-06-01T00:00:00Z Abrantes, Marta Coelho http://hdl.handle.net/10362/8575 2013-01-18T16:48:35Z 2012-07-01T00:00:00Z

Title: Precious transition metals: the importance of Zn2+, Mn2+ and Cu2+ in the human pathogen Enterococcus faecalis Authors: Abrantes, Marta Coelho Abstract: Enterococcus faecalis is a commensal bacterium able to colonize different sites in the human host, such as the gastrointestinal tract, the genito-urinary tract and the oral cavity. It can also be found in numerous other environments, including soil, sand, water, food products and plants. These bacteria show a dual behavior: they can behave quite harmlessly as commensals, but are able to become opportunistic pathogens and cause serious infections, such as urinary tract infections and endocarditis, in hospital settings. The question as to how these bacteria are able to change from commensalism to pathogenicity has directed many recent studies to focus on the environmental host conditions that may trigger this transition as well as on the underlying molecular mechanisms. Metals are very important elements in the host environment, as they are key components of many proteins and are involved in numerous cell processes in both the host and the invading pathogen. The maintenance of metal homeostasis is fundamental to both to ensure that metabolism and cell functions are functioning properly. Variations in this homeostasis must be tightly regulated. In several Gram positive pathogens, metal homeostasis and regulation has been linked to their pathogenicity. The lack of knowledge on this subject in E. faecalis motivated the work presented in this thesis.(...) Description: Dissertation presented to obtain the Ph.D degree in Biology

2012-07-01T00:00:00Z Braga, Teresa http://hdl.handle.net/10362/6183 2011-10-27T16:45:01Z 2011-06-01T00:00:00Z

Title: Enterococcus and biocides: mechanisms of tolerance and selection for vancomycin resistance Authors: Braga, Teresa Abstract: Biocides are chemical agents, generally with a broad-spectrum of activity, used to destroy, render harmless, prevent the action of, or otherwise exert a controlling effect on any harmful organism. Biocidal products comprise several chemical groups. Among the most commonly used are alcohols, aldehydes, biguanidines (e.g. chlorhexidine), phenols (e.g. triclosan) and quaternary ammonium compounds (e.g. benzalkonium chloride). Although some of the biocides were discovered many years ago, their generalised use began only some decades ago. They are used for cleaning and/or disinfecting in many different environments, such as in hospital facilities, veterinary facilities, food and pharmaceutical industry sites and in our homes. Biocides are also incorporated in several products as preservatives, such as deodorants, body creams and soaps. Some of the environments where biocides are applied are shared with enterococci.(...) Description: Dissertation presented to obtain a Doctoral degree in Biology, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa.

2011-06-01T00:00:00Z Ribeiro, Tânia Catarino http://hdl.handle.net/10362/5762 2011-06-09T15:01:46Z 2011-01-01T00:00:00Z

Title: Studies on resistance and response to vancomycin in Enterococcus faecalis: a last resort antibiotic Authors: Ribeiro, Tânia Catarino Abstract: Enterococci are part of the normal human and animal gut microbiota and hardly cause infections in healthy individuals. In the last 20 years enterococci have emerged as common causes of hospital-acquired infections. One of the major reasons why these microorganisms easily survive in the hospital environment is their intrinsic resistance to several commonly used antibiotics, and more importantly, their ability to acquire resistance to many currently used antibiotics, including glycopeptides. Development of resistance to the glycopeptide vancomycin in the Enterococcus genus presents a worldwide major problem. Infections with vancomycin resistant enterococci are not only difficult to treat but the organisms show a strong propensity to disseminate and spread from patient to patient in the hospital setting. Accurate knowledge of the real scenario of vancomycin resistance is essential to design national and global strategies and prevent community and nosocomial transmission of vancomycin resistant organisms.(...) Description: Dissertation presented to obtain a Ph.D. degree in Biochemistry by Instituto de Tecnologia Química e Biológica Universidade Nova de Lisboa.

2011-01-01T00:00:00Z