Made available in DSpace on 2016-01-26T12:51:29Z (GMT). No. of bitstreams: 1 vivianedeciceracolombooliveira_dissert.pdf: 908582 bytes, checksum: 3c95ae4a3fb33fb357397cfbcc4f9bdf (MD5) Previous issue date: 2011-05-02 / Hospital bacterial resistance to multiple antibiotics is a great concern worldwide. This study objective was to know the multidrug-resistantance (MDR) agents, clinical materials, origin, trends, and to correlate them with the bacterial sensitivity and antimicrobial consumption. A total of 53,316 nosocomial bacteria were assessed in a tertiary hospital during the period from 1999 to 2008. MDR was defined for gram negative bacteria (GNB) when it presented resistance to two or more classes/groups of antibiotics. GNB were predominant (66.1%). GNB MDR had a global increase of 3.7 times in the end of the period. Acinetobacter baumannii was the most prevalent (36.2%). The most frequent materials were urinary and respiratory. A significant increase occurred during the period of 4.8 and 14.6 times of the A. baumannii and K. pneumoniae, respectively. Sixty-seven percent of GNB MDR was from the Intensive Care Units. A. baumannii resistance to carbapenemics increased from 7.4% to 57.5% during the period, concomitant to the consumption increase. The resistance of K. pneumoniae to the cephalosporins had a high increase during the decade. P. aeruginosa decreased in these last two years with a recovery of the sensitivity. / A resistência bacteriana hospitalar a múltiplos antibióticos é uma grande preocupação mundial. O objetivo deste estudo foi conhecer os agentes multidroga-resistentes (MDR), materiais clínicos, origem, evolução e correlacionar com a sensibilidade bacteriana e consumo de antimicrobianos. Foram avaliadas 53.316 bactérias de origem nosocomial, num hospital terciário, durante o período de 1999 a 2008. Foi definida a MDR para as bactérias gram negativas (BGN) quando apresentava resistência a duas ou mais classes/grupos de antibióticos. As BGN foram predominantes (66,1%). As BGN MDR tiveram um aumento global de 3,7 vezes no final do período. O Acinetobacter baumannii foi o mais prevalente (36,2%). Os materiais mais freqüentes foram urinário e respiratório. Ocorreu um aumento significativo durante o período de 4,8 e 14,6 vezes do A. baumannii e K. pneumoniae, respectivamente. Sessenta e sete por cento das BGN MDR foram das UTIs. A resistência do A. baumannii aos carbapenêmicos aumentou de 7,4% para 57,5% durante o período, concomitante ao aumento do consumo. A resistência da K. pneumoniae às cefalosporinas teve um grande aumento durante a década. Houve diminuição da P. aeruginosa nos últimos dois anos com uma recuperação da sensibilidade.

A reemergência de algumas bactérias Gram-positivas, em particular, do gênero Staphylococcus, como principal foco causador de infecções hospitalares, tem se intensificado nas últimas décadas, e, apesar da existência de potentes fármacos voltados para o tratamento de infecções causadas por este gênero de bactéria, as taxas de morbidade e mortalidade prevalecem com perfil crescente. Além disso, um grande problema associado a cepas de MRSA (Methicillin-Resistant Staphylococcus aureus) é o fenótipo de multi-resistência, característica que confere a este microrganismo resistência não apenas à meticilina como também a uma série de outros fármacos, exceto frente à vancomicina e à teicoplanina. Muito tem se feito, mas ainda são poucos os resultados efetivamente aplicáveis no tratamento de infecções com caráter de multi-resistência, justificando, desta forma, a necessidade de desenvolvimento de sucedâneos que sejam consideravelmente mais efetivos para a solução deste problema. Baseado nestes fatos, a proposta deste estudo envolveu o planejamento, síntese, identificação e estudos de QSAR (Quantitative Structure-Activity Relationships) em duas e três dimensões de derivados 5-nitro-2-tiofilidênicos com atividade antimicrobiana frente a cepas padrão e multi-resistente de Staphylococcus aureus. A escolha dos grupos substituintes foi realizada em duas etapas. Na primeira delas seguiu-se metodologia de substituição em anéis aromáticos proposta por Topliss para a otimização da bioatividade de compostos. Em uma segunda etapa, predominantemente quantitativa, foram selecionados mais alguns derivados baseando-se em faixa de hidrofobicidade ótima pré-determinada experimentalmente e na variação de efeito estérico dos grupos substituintes. Quatorze derivados 5-nitro-2-tiofilidênicos foram sintetizados, estruturalmente identificados e avaliados quanto à atividade antimicrobiana frente às cepas padrão (ATCC 25923) e multi-resistente (3SP/R33) de Staphylococcus aureus por determinação da concentração inibitória mínima empregando-se método de macrodiluição sucessiva em tubos. Salienta-se que a cepa 3SP/R33 se mostra resistente a dezenove antibióticos empregados na prática médica e apresenta suscetibilidade apenas à vancomicina. As concentrações inibitória e bactericida mínimas apresentadas pelos compostos sintetizados mostraram sofrer influência significativa da hidrofobicidade sobre as referidas atividades de acordo com os estudos de QSAR-2D e QSAR-3D, sendo os resultados obtidos para a cepa multi-resistente absolutamente compatíveis com os anteriormente determinados para a cepa padrão. Os estudos de QSAR-2D indicaram que a atividade antimicrobiana das 5nitro-2-tiofilideno benzidrazidas substituídas sofre influência significativa de duas propriedades físico-químicas que são a hidrofobicidade e a distribuição eletrônica. A relevância dos descritores estruturais σ e efe na determinação da atividade antimicrobiana, sinalizam que a distribuição eletrônica influencia fortemente o aumento da potência antimicrobiana dos compostos em estudo tanto pela influência dos efeitos indutivo e de ressonância na estrutura química do ligante, como também pelos campos moleculares gerados ao redor de grupos substituintes, sugerindo uma possível interação dos mesmos com uma área específica do sítio receptor. Nos estudos de QSAR-3D, foi evidenciado, em concordância com o estudo clássico anteriormente realizado, que a hidrofobicidade prevalece como propriedade de fundamental importância no estabelecimento da atividade antimicrobiana. Foi observada a importância da presença de regiões hidrofílicas pontuais nos compostos de forma a propiciar processos de solvatação e dessolvatação que são críticos na difusão através de membranas biológicas. Pode-se afirmar que a análise de QSAR, considerando os aspectos tridimensionais ligantes, ressaltou a necessidade de um balanço lipofílico-hidrofílico para um bom desempenho das 5-nitro-2-tiofilideno benzidrazidas ρ-substituídas como agentes antimicrobianos. A partir dos resultados obtidos evidenciou-se, neste estudo, o forte potencial de derivados 5-nitro-2-tiofilidênicos como possível alternativa para o desenvolvimento racional, em nível molecular, de fármacos voltados para o tratamento de infecções causadas por cepas multi-resistentes de Staphylococcus aureus. / In the last decade, there has been a reemergence of Gram-positive bacteria, in particular Staphylococcus, which isconsidered one of the. most causing of nosocomial infections. Although potent antistaphylococcal drugs are available, this infection continues presenting increasing morbidity and mortality rates. Besides, a serious problem associated with MRSA (Methicillin-Resistant Staphylococcus aureus) is the phenotype of multidrug resistance, which is, resistance not only to methicillin but also to many other drugs, except to vancomycin and teicoplanin. Many efforts have been made in a tentative to reduce this problem, nevertheless there is only a few number of alternatives to combat Staphylococcus aureus multidrug-resistant strains, justifying the necessity of development of more effective compounds to the treatment of these infections. Based in these facts, the purpose of this study was the design, synthesis, structural identification and 2D-QSAR and 3D-QSAR (Quantitative Structure-Activity Relationships) studies of 5-nitro-2-thiophylidene derivatives with antimicrobial activity against multidrug-resistant strains of Staphylococcus aureus. The choice of substituent groups was made in two stages. The first stage comprises on application of Topliss operational scheme for aromatic substitution. In a second quantitative stage, more derivatives were selected according by hydrophobicity range previously determined. Other standard considered at the selection of substituent groups was the variation of steric effect. Fourteen 5-nitro-2-thiophylidene derivatives were synthesized, structural identified and tested against standard (A TCC 25923) and multidrug-resistant (3SP/R33) strains of Staphylococcus aureus. The Minimal Inhibitory Concentration, MIC, was determined using the serial dilution tests in two sequential stages. The 3SP/R33 strain is resistant to nineteen antimicrobial agents in use, except to vancomycin. The minimal inhibitory and bactericidal concentrations of synthesized compounds showed, according by 2D-QSAR and 3D-QSAR studies, a significant influence of hydrophobic properties on antimicrobial activity determination and the results obtained for multidrug-resistant strain were consistent with those determined for A TCC 25923 strain. 2D-QSAR studies showed that antimicrobial activity are mainly influenced by two physico-chemical properties: hydrophobicity and electronic distribution. The relevance of σ e ephe parameters on antimicrobial activity determination, denotes the contribution of inductive and resonance effects for the polar performed by the substituent groups, probably suggesting an interaction between them and specific receptor site. 3D-QSAR studies showed that hydrophobicity is a essential property to antimicrobial activity determination, sustained the same conclusions previously obtained by Hansch Analysis. It was observed a great concern of small hydrophilic regions distributed on derivatives in order to promote solvation and desolvation process, that have critical importance on diffusion process through the biological membranes. QSAR studies considering three-dimensional properties of ligands indicated the necessity of accurate hydrophilic-hydrophobic balance on nitrothiophene derivatives for their good performance as antimicrobial agents. The results obtained in this preliminary study have shown the potential of synthesized compounds as alternatives to the treatment of infections caused by multidrug-resistant strains of Staphylococcus aureus.

INTRODUÇÃO: A incidência de tuberculose (TB) em Santos (SP) situa-se em 73/100.000 habitantes-ano. A prevalência média de coinfecção TB/HIV é de 16%, taxas de cura e abandono de tratamento, entre casos novos são, respectivamente, 71% e 12%. Tais indicadores sugerem elevado risco para TB multidroga resistente (TBMR) no município, com incidência estimada em 1,9/100.000 habitantes-ano. OBJETIVO: Descrever e analisar o perfil de sensibilidade às drogas (TS) de primeira e segunda linha de tratamento entre pacientes com TB pulmonar (TBP), estimar a incidência de TBMR e a proporção de TB extensivamente resistente (TBXR); analisar aspectos moleculares, epidemiológicos e institucionais dos casos de TBP resistentes em Santos (SP). MÉTODOS: Estudo descritivo de uma coorte de pacientes de TBP, com início de tratamento ou retratamento entre 01 de janeiro de 2011 a 31 de dezembro de 2012. Definiu-se como caso de TBP, indivíduos com 15 anos ou mais, de ambos os sexos, residentes no município de Santos, com manifestações clínicas compatíveis com TBP e confirmação por cultura com isolamento de Mycobacterium tuberculosis. As variáveis de interesse para o estudo foram as características sociodemográficas, história atual e pregressa de TB, aspectos relativos ao tratamento, co-morbidades, ao diagnóstico e resistência a drogas. Para as análises comparativas entre proporções foram usados os testes qui-quadrado de Pearson e o Exato de Fisher e para variáveis contínuas o teste T de Student ou o de Kruskal - Wallis. Os perfis genéticos dos isoladas resistentes a ao menos uma droga foram obtidos pela técnica RLFP e analisados pelo programa Bionumerics versão 5.0 (Applied Maths - Bélgica). A descrição da distribuição espacial da TB resistentes e clusters foram feitas mediante a inserção dos casos no mapa de Santos, por endereço de residência, segundo o índice de vulnerabilidade social. RESULTADOS: Dos 263 casos de TBP selecionados, 68,4% (180/263) eram do sexo masculino, a mediana da idade foi de 38 anos, 8,7% (23/263) eram diabéticos; 20,4% (42/206) dos casos novos apresentavam ao menos um fator de risco para TBMR; destacando-se entre estes casos 10,7% (22/206) de confecção HIV/TB; 47,3% (123/260) tiveram tratamento supervisionado, 14,7% (91/617) dos contatos foram examinados, 18,6% (49/263) foram hospitalizados durante o tratamento, perfazendo uma média de 145,4 dias por paciente. Entre os casos resistentes a ao menos uma droga, a resistência à isoniazida foi 8,4% (22/263) e à rifampicina 3,8% (10/263) dos casos. A TBMR primária foi encontrada em 1,9% (4/206) dos casos e destes 25,0% (1/4) eram TBXR. A incidência média anual de TBMR foi de 0,57/100,000 habitantes. Dos 25 isolados resistentes ao menos uma droga, submetidos à RFLP, 12 (48,0%) foram agrupados em seis grupos genéticos, com dois pacientes em cada grupo. CONCLUSÕES: A elevada proporção TBMR primária, com um caso de TBXR enfatizam a necessidade de universalizar a cultura e TS, ampliar a cobertura do tratamento supervisionado, a investigação rotineira dos contatos e o monitoramento da resistência a drogas. O fortalecimento da vigilância da resistência às drogas é indispensável para o contínuo aperfeiçoamento do Programa de Controle da TB, especialmente em regiões de elevada carga da doença / INTRODUCTION: The incidence of tuberculosis (TB) in Santos (SP) is located around 73 / 100,000-year, approximately double that found on average in the country. The average prevalence of TB / HIV is 16% cure rates and treatment dropout among new cases are, respectively, 71% and 12%. Such indicators suggest high risk for multidrug-resistant TB (MR-TB) in the city, with the incidence estimated at 1.9 / 100,000-year. OBJECTIVE: To describe and analyze the sensitivity to drugs of first and second line treatment of patients with pulmonary TB (PTB) to estimate the incidence of MR-TB and extensively drugresistant TB (TBXR), describe molecular and institutional aspects, spatial distribution, epidemiological PTB resistant cases in the city of Santos (SP). METHODS: A descriptive study of a cohort of patients with PTB residing in the city who started treatment or retreatment in the period January 2011 to December 31, 2012. The case definition PTB individuals 15 years or more, both sexes, living in the city of Santos (SP), who present clinical manifestations compatible with PTB and whose confirmation was made by culture with isolation of M. tuberculosis. The variables of interest for the study were: bacteriological / laboratory socio-demographic characteristics, current and previous history of TB, aspects related to treatment, and comorbidities. For comparative analyzes of proportions the chi-squared tests and Fisher\'s exact were used for continuous variables and the Student t test or the Kruskal - Wallis. The genetic profiles of isolates resistant to at least one drug were obtained by RFLP (length polymorphism restriction fragment) and analyzed using version BioNumerics 5.0 (Applied Maths - Belgium) software. The description of the spatial distribution of resistant TB and the clusters was made by inserting the cases in Santos map, by address of residence, which was according to the index of social vulnerability. RESULTS: Of the 263 cases of PTB selected, 68.4% (180/263) were male, th median age was 38 years, 8.7% (23/263) were diabetes; 20.4% (42/206) of new cases had at least one risk factor for MR-TB, especially 10.7% (22/206) of making HIV / TB; 47.3% (123/260) underwent supervised treatment, 14.7% (91/617) of the contacts were examined, 18.6% (49/263) were hospitalized during treatment, totaling 7127 days of hospitalization with a mean 145.4 days per patient. Among the cases resistant to at least one drug resistance to isoniazid 8.4% (22/263) and rifampin 3.8% (10/263) of the cases was found. The primary MR-TB was found in 1.9% (4/206) of MR-TB cases and of these 25.0% (1/4) were TBXR. The average annual incidence of MDR-TB was 0.57/100,000 inhabitants. Of the 25 isolates resistant least one drug, subjected to molecular characterization of IS6110, 12 (48.0%) were grouped in six clusters, with each group including two isolates. CONCLUSIONS: A high proportion of primary MR-TB, including a case of TBXR emphasizes the need to universalize culture and TS, expand the coverage of supervised treatment, routine investigation of contacts and monitoring of drug resistance. The strengthening of the surveillance of drug resistance is essential for continuous improvement of the TB Control Program, especially in regions of high disease burden

Fosfoetanolamina sintética (Pho-s) é um monoéster análogo à fosfoetanolamina da membrana celular fosforilada artificialmente, com propriedades antiinflamatórias e apoptóticas para vários tipos de células tumorais humanas e murinas. Neste projeto foram avaliados os efeitos antitumorais in vitro da Pho-s e da formulação lipossomal DODAC/Pho-s na linhagem tumoral de leucemia mielóide crônica humana (K-562), em comparação ao modelo resistente a múltiplas drogas K-562 Lucena (MDR+). Os efeitos de citotoxicidade da Pho-s na linhagem tumoral K-562 e K-562 Lucena (MDR+) foram avaliados pela viabilidade celular utilizando o teste da Sulforodamina B, e os valores da IC50% obtidos foram de 43.1 mM e 145.9 mM, respectivamente após 24 horas de tratamento. O tratamento com o carreador DODAC vazio nas células K-562 e K-562 Lucena (MDR+) a IC50% foi de 0,0003mM e 0,008mM respectivamente, e com o tratamento com a formulação lipossomal DODAC/Pho-s a IC50% obtida respectivamente de, 0,56 mM e 0,31 mM. A viabilidade celular foi determinada a exclusão pelo azul de tripan 0,2%, em sistema automatizado Vi-Cell e foram significativas as diminuições da viabilidade celular em comparação ao grupo controle não tratado nas diversas concentrações e em diferentes períodos de tempo de tratamento. As alterações nas distribuições nas populações celulares nas fases do ciclo celular determinadas por citometria de fluxo mostraram aumento do DNA fragmentado (Sub/G1) em 12 e 24 horas de tratamento. Atividade apoptótica das células tumorais pela expressão da Anexina V/PI, no estágio de apoptose inicial, apoptose tardia e necrose foram quantificadas em citometria de fluxo, o tratamento com Pho-s, quando comparado ao grupo controle K-562 (40 e 80 mM) e K-562 Lucena (MDR+) (146 e 292 mM) ocorreu aumento significativo do número de células apoptóticas e em menor percentual o número de células necróticas. O tratamento com a Pho-s em célula leucêmica K-562 e K-562 Lucena (MDR+) tratadas, respectivamente com 40 e 80 mM e 146 e 292 mM mostraram que independente da expressão do fenótipo de resistência há uma redução significativa no potencial elétrico mitocondrial, analisado pelo o ensaio da rodamina-123. Os marcadores de controle e progressão do ciclo celular e da apoptose, mostraram efeitos moduladores da Pho-s dependentes da p53 na expressão da moléculas pró-apoptóticas. Esse conjunto de informações demonstrou os efeitos apoptóticos da Pho-s e da formulação lipossomal nas células tumorais independentemente do perfil molecular de resistência (MDR+), o que possibilita dizer que esse composto possui significativo potencial terapêutico nesse grupo de leucemias / Synthetic phosphoethanolamine (Pho-s) is a monoester analogous to the phosphoethanolamine which composes the membrane of an artificially phosphorylated cell, with anti-inflammatory and apoptotic properties for various types of human and murine tumor cells. In this project, we evaluated in vitro antitumor effects of Pho-s and the DODAC/Pho-s liposomal formulation in the human chronic myeloid leukemia (K-562) tumor line in comparison with the K-562 Lucena (MDR+). The effects of cytotoxicity of Pho-s on K-562 and K-562 Lucena (MDR +) tumor cells lines were evaluated by cell viability using the Sulforhodamine B test, and the IC50% values obtained were 43.1 mM and 145.9 mM after 24 hours of treatment, respectively. Treatment with the empty DODAC carrier on the K-562 and K-562 Lucena (MDR+) at IC50% cells was 0.0003 mM and 0.008 mM, and the treatment with the DODAC/Pho-s liposomal formulation obtained results of 0.56 mM and 0.31 mM, respectively. Cell viability was determined by 0.2% trypan blue exclusion in automated Vi-Cell system and the decreases in cell viability were significant in comparison to the untreated control group at various concentrations and different treatment time periods. Alterations in the distributions of cell populations in the cell cycle phases determined by flow cytometry showed increment of fragmented DNA (Sub/G1) in 12 and 24 hours of treatment. Apoptotic activity of tumor cells by the expression of Annexin V/PI, in the early apoptosis, late apoptosis phase and necrosis stage were quantified in flow cytometry, the treatment with Pho-s, when compared to the control group K-562 (40 and 80 mM) and K-562 Lucena (MDR +) (146 and 292 mM) demonstrated that there was a significant increase in the number of apoptotic cells and, in a lower percentage, the number of necrotic cells. Treatments with Pho-s in leukemic cell K-56 with 40 and 80 mM and in K-562 Lucena (MDR+) with 146 and 292 mM showed that independent of the expression of the resistance phenotype there is a significant reduction in the electrical potential of the mitochondrial membrane, analyzed with the rhodamine-123 assay. Control and progression markers of cell cycle and apoptosis showed p53-dependent modulating effects on the expression of pro-apoptotic molecules. This set of information demonstrated the apoptotic effects of Pho-s and liposomal formulation on tumor cells independently of the molecular resistance profile (MDR+), which makes it possible to say that this compound has significant therapeutic potential in this group of leukemias

Infections arising from multidrug-resistant pathogenic bacteria are spreading rapidly throughout the world and threaten to become untreatable. The origins of resistance are numerous and complex, but one underlying factor is the capacity of bacteria to rapidly export drugs through the intrinsic activity of efflux pumps. In this work, a summary is provided of our current understanding of the structures and molecular mechanisms of multidrug efflux pumps in bacteria (Chapter 1). The emerging picture of the structure, function and regulation of efflux pumps suggests opportunities for countering their activities. Although this thesis primarily explores structure and function, it also elucidates the hidden regulatory mechanism (post-translational) behind the association of a small protein called AcrZ with the tripartite complex AcrAB/TolC, in connection with the lipid environment, and the resulting changes in the latter's functionality (Chapter 2). A regulatory role of the native membrane lipid environment as well as of small proteins for efflux pump activity have previously been hypothesised. I present the first example of a function-regulating role of the lipid cardiolipin in combination with a small protein binding partner (AcrZ) for the substrate selectivity and transport activity of an efflux pump protein (AcrB). This regulation happens through induced structural changes which have remained unseen so far. Alongside with these results, a nanodisc reconstitution method was experimentally adapted for a structure-function investigation of an efflux pump (complex) using cryo-EM (Chapter 2). Beyond some fundamental regulatory insights, hidden intrinsic transport mechanisms for some transporters have also remained to be explored and studied. The discovery of a mechanism for active influx by a prominent efflux pump model system (Chapter 3) provides hope that this phenomenon is more common amongst multidrug transporters and that it could be utilised for drug discovery purposes. This novel feature explains the contradictory findings on this transporter in the past and raises new questions about the little-known physiological role and evolution of efflux pumps. The development and evolution of antimicrobial resistance has frequently shown to be a multifactorial and fast-moving process. One of these factors is the evolution of pumps itself towards an altered functionality (e.g. towards a broader or altered substrate spectrum or higher efflux rates). Against this background, the role of key carboxylate residues for efflux-energising proton trafficking was investigated for a prominent study model of a secondary-active transporter (Chapter 4). The re-allocation and/or addition of acidic residues was demonstrated to result in the preservation of wild type activity or the generation of hyper-efflux activity, respectively. These findings suggest that rapid emergence of antimicrobial resistance could be enhanced by the 'plasticity' in the location of key carboxylate residues with a role in proton coupling. It also demonstrates the necessity of antimicrobial drug design programmes to anticipate possible trajectories of an adaptive evolution of efflux pump. The 'cryo-EM revolution' has boosted the pace at which new structural and functional insights into multidrug efflux pumps are gained. Nevertheless, in order to derive the structure of individual pump components or of a full assembly, it is sometimes necessary to identify and characterise homologues and mutants, which would allow the application of cryo-EM for obtaining near-atomic maps. Functional analyses presented in this work helped to characterise a homologue and mutants of the MacAB/TolC tripartite complex to justify the obtained protein structures and strategies for further functional characterisation (Chapter 5). Given (1) the unusual stoichiometry of a MacB dimer in complex with a hexameric membrane-fusion protein (MacA), which leads to a seeming leakiness of the assembly, and (2) the fact that substrate has to pass through a narrow aperture in the membrane-fusion protein for extrusion, it is rather surprising that MacB was previously shown to transport an entire toxin. An experimental approach was developed that could enable the structure determination of a toxin-bound full assembly of MacAB/TolC (Chapter 5). Finally, the role of multidrug efflux pumps for the evolution of multidrug resistance is yet to be studied and better explored. For instance, evolutionary trajectories of pump overexpression, as compared to those of regular expression or no expression, are unknown yet could have the potential to reveal useful insights for spread prevention and drug design. The outline of an experimental design with some preliminary validating data is presented in Chapter 6.

The MdfA is a 410 amino acid-long integral membrane protein, which belongs to the Major Facilitator superfamily of multidrug transporters. It is predicted to consist of 12 transmembrane helices. MdfA uses the energy of the transmembrane proton gradient to pump a variety of toxic compounds out of E. coli cells. No high resolution structure of MdfA is available. The goals of this research project were to develop a practical method for purification of MdfA, to evaluate the feasibility of structure determination by Nuclear Magnetic Resonance (NMR) and X-ray crystallography, and to develop an activity assay for purified MdfA. To this end, MdfA, with a hexa-histidine tag attached to facilitate protein purification, was successfully expressed and incorporated into the cell membrane using an E. coli expression system. MdfA was extracted from the cell membrane with the detergents 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC), n-dodecyl-B-D-maltoside (DDM), and 1-myristoyl-2-hydroxy-sn-glycero-3-[phospho-rac-(1-glycerol)] (LMPG) and purified by affinity chromatography on nickel-nitrilotriacetic acid agarose. Pure protein was found to be monodisperse in DHPC, DDM and LMPG micelles. To achieve simple amino acid selective isotope labeling for high-resolution NMR studies, MdfA was expressed in a cell-free translation system. To determine if the purified protein was properly folded, 19F NMR experiments were carried out on 5-fluoro-tryptophan-labeled MdfA while titrating the MdfA substrates ethidium bromide and chloramphenicol into the fluoro-tryptophan-labeled MdfA sample. An activity assay was developed for MdfA incorporated into liposomes using the fluorescent dye 9-amino-6-chloro-2-methoxyacridine (ACMA) to detect proton translocation coupled to substrate transport. Results from both the 19F NMR and the transport activity assay indicated that the purified MdfA was properly folded and functional. NMR experiments with pure MdfA yielded spectra of insufficient quality for high-resolution structure determination but did indicate that structural studies of MdfA by NMR are feasible. Crystallization trials yielded crystals that are likely to contain protein and will serve as a starting point for further optimization of crystallization conditions for X-ray structure determination.

The MdfA is a 410 amino acid-long integral membrane protein, which belongs to the Major Facilitator superfamily of multidrug transporters. It is predicted to consist of 12 transmembrane helices. MdfA uses the energy of the transmembrane proton gradient to pump a variety of toxic compounds out of E. coli cells. No high resolution structure of MdfA is available. The goals of this research project were to develop a practical method for purification of MdfA, to evaluate the feasibility of structure determination by Nuclear Magnetic Resonance (NMR) and X-ray crystallography, and to develop an activity assay for purified MdfA. To this end, MdfA, with a hexa-histidine tag attached to facilitate protein purification, was successfully expressed and incorporated into the cell membrane using an E. coli expression system. MdfA was extracted from the cell membrane with the detergents 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC), n-dodecyl-B-D-maltoside (DDM), and 1-myristoyl-2-hydroxy-sn-glycero-3-[phospho-rac-(1-glycerol)] (LMPG) and purified by affinity chromatography on nickel-nitrilotriacetic acid agarose. Pure protein was found to be monodisperse in DHPC, DDM and LMPG micelles. To achieve simple amino acid selective isotope labeling for high-resolution NMR studies, MdfA was expressed in a cell-free translation system. To determine if the purified protein was properly folded, 19F NMR experiments were carried out on 5-fluoro-tryptophan-labeled MdfA while titrating the MdfA substrates ethidium bromide and chloramphenicol into the fluoro-tryptophan-labeled MdfA sample. An activity assay was developed for MdfA incorporated into liposomes using the fluorescent dye 9-amino-6-chloro-2-methoxyacridine (ACMA) to detect proton translocation coupled to substrate transport. Results from both the 19F NMR and the transport activity assay indicated that the purified MdfA was properly folded and functional. NMR experiments with pure MdfA yielded spectra of insufficient quality for high-resolution structure determination but did indicate that structural studies of MdfA by NMR are feasible. Crystallization trials yielded crystals that are likely to contain protein and will serve as a starting point for further optimization of crystallization conditions for X-ray structure determination.

No description available.

The study arose out of a need to investigate and control a nosocomial outbreak caused by multidrug resistant Acinetobacter spp in the fifteen-bed intensive care unit of King Edward VIII Hospital. Following the discovery of the index case, four other patients were found to have a similar strain of Acinetobacter spp. All fifteen patients in the ward were subsequently screened for the organism. Forty-seven isolates were obtained from 12 patients. Eight of the patients were infected with the organism and six of these eight patients subsequently died. Swabs from the ward environment were also screened for the organism, which was found in patients' baths, suction water and urine collection jars. The outbreak was aborted by the use of strict infection control techniques. Minimum inhibitory concentrations (MICs) of 20 of the 47 isolates were determined for the following antimicrobials: imipenem, ciprofloxacin, gentamicin, amikacin, netilmycin,cefotaxime, ceftazidime and tetracycline. The same 20 isolates were further typed using ribotyping. Seven different antibiogram patterns were obtained using the MIC data. The majority of isolates (11) fit into a Single type, and showed resistance to all drugs tested, except for susceptibility to tetracycline and netilmycin only. Ribotyping revealed 5 different types. There were 9 isolates of ribotype a, 2 of ribotype b, 3 of ribotype c, 5 of ribotype d and 1 of ribotype e. In conclusion, this study describes a nosocomial outbreak with a multidrug resistant Acinetobacter spp. in an intensive care unit. The results showed that there was no correlation between the two typing methods used, ribotyping was more discriminatory than antibiogram types, with the majority of strains belonging to two different ribotypes. / Thesis (M.Med.)-University of Natal, Durban, 2000.

La pollution croissante des milieux aquatiques nécessite la mise au point de nouvelles technologies permettant d'optimiser la surveillance de la qualité de l'eau. Dans ce contexte, nous avons développé un biomarqueur de susceptibilité du degré de la pollution globale des milieux aquatiques intitulé " Sentinelle ". Le principe du biomarqueur Sentinelle est basé sur le niveau de coexpression de deux protéines " Multidrug Resistance " (MDR), la protéine ABCG2-like et la P-gp, dans les érythrocytes de la truite Salmo trutta fario. Le biomarqueur sentinelle a été validé en conditions in vitro grâce au développement des cultures primaires d'érythrocytes de truite. Après l'exposition des globules rouges de truites à des concentrations croissantes d'un polluant modèle, le Benzo-a-pyrène, l'expression de la protéine ABCG2-like et de la P-gp augmente d'une manière dose dépendante. Le biomarqueur Sentinelle a ensuite été validé en milieu naturel sur des truites fario en provenance de différents cours d'eau d'Auvergne. En milieu naturel, les deux protéines MDR sont exprimées différemment dans les érythrocytes de truites fario selon le degré de contamination du cours d'eau. En effet, dans une rivière où la pollution est faible voire nulle, seule la protéine ABCG2-like est exprimée, alors que dans une rivière présentant une contamination plus importante, la P-gp et l'ABCG2-like sont toutes les deux coexprimées par une réponse de type relais. Les expériences menées en conditions in vitro et en milieu naturel, laissent supposer que la protéine ABCG2-like assure une fonction de garde alors que la P-gp assurerait une fonction de protection défensive. En conséquence, selon le niveau d'expression de la protéine de garde et de la protéine de défense, le degré de contamination de la rivière pourrait être évalué. L'intérêt de l'utilisation du biomarqueur Sentinelle a aussi été validé sur des Salmonidés en provenance de pisciculture. Ce nouvel outil biologique apporte des informations plus intégratives et plus précoces sur la qualité des milieux aquatiques, informations essentielles pour une meilleure gestion des ressources en eau.