The crucial role of antibiotics in modern medicine, in curing infections and enabling advanced medical procedures, is being threatened by the increasing frequency of resistant bacteria. Better understanding of the forces selecting resistance mutations could help develop strategies to optimize the use of antibiotics and slow the spread of resistance. Resistance to ciprofloxacin, a clinically important antibiotic, almost always involves target mutations in DNA gyrase and Topoisomerase IV. Because ciprofloxacin is a substrate of the AcrAB-TolC efflux pump, mutations causing pump up-regulation are also common. Studying the role of efflux pump-regulatory mutations in the development of ciprofloxacin resistance, we found a strong bias against gene-inactivating mutations in marR and acrR in clinical isolates. MIC and fitness measurements revealed that amino acid substitutions conferred smaller susceptibility reductions and smaller fitness costs than gene-inactivating mutations, suggesting that resistance mutations in clinical isolates are selected for high fitness rather than high resistance (Paper I and II). We asked whether the high fitness costs of marR-inactivating mutations could be ameliorated without affecting the resistance phenotype. Multiple independent lineages were experimentally evolved to select for improved growth fitness. Whole genome sequencing revealed mutations affecting marA, lon and arcA as potential compensatory pathways. For the marA and lon mutations the improved growth rate was associated with an increased susceptibility (arcA is being investigated). (Paper III). An evolution experiment selecting for ciprofloxacin resistance revealed upon whole genome sequencing the expected mutations in drug target and efflux-regulatory genes, but also in genes encoding aminoacyl-tRNA synthetases. We investigated two independently selected leuS mutations, and concluded that they contributed to ciprofloxacin resistance by activating the stringent response that in turn caused up-regulation of genes involved in efflux. However, these leuS mutations incur a high fitness cost (Paper IV). To summarize, the research findings in this thesis suggest that the potential ciprofloxacin resistome may include more genes than previously thought, but a strong selection for high fitness selectively purifies many resistance mutations from clinical isolates. In conclusion, selection for high relative fitness constrains the spectrum of mutations that survive and get fixed in clinical populations of bacteria.

UA Open Access Publishing Fund / Molecular diagnostics offers quick access to information but fails to operate at a speed required for clinical decision-making. Our novel methodology, droplet-on-thermocouple silhouette real-time polymerase chain reaction (DOTS qPCR), uses interfacial effects for droplet actuation, inhibition relief, and amplification sensing. DOTS qPCR has sample-to-answer times as short as 3 min 30 s. In infective endocarditis diagnosis, DOTS qPCR demonstrates reproducibility, differentiation of antibiotic susceptibility, subpicogram limit of detection, and thermocycling speeds of up to 28 s/cycle in the presence of tissue contaminants. Langmuir and Gibbs adsorption isotherms are used to describe the decreasing interfacial tension upon amplification. Moreover, a log-linear relationship with low threshold cycles is presented for real-time quantification by imaging the droplet-on-thermocouple silhouette with a smartphone. DOTS qPCR resolves several limitations of commercially available real-time PCR systems, which rely on fluorescence detection, have substantially higher threshold cycles, and require expensive optical components and extensive sample preparation. Due to the advantages of low threshold cycle detection, we anticipate extending this technology to biological research applications such as single cell, single nucleus, and single DNA molecule analyses. Our work is the first demonstrated use of interfacial effects for sensing reaction progress, and it will enable point-of-care molecular diagnosis of infections.

O reconhecimento da resistência antimicrobiana como um fenômeno emergente em saúde pública, tem constituído um problema em nível mundial. O abuso na utilização de antibióticos na medicina humana e veterinária, e na agricultura, tem originado incremento na diversidade de micro-organismos resistentes, refletindo em falha terapêutica. Os mecanismos de resistência a antibióticos em micro-organismos são mediados principalmente por genes adquiridos de DNA exógeno. A dinâmica da transferência horizontal é realizada por meio de elementos genéticos móveis que carregam genes de resistência. A ampla distribuição deste tipo de estruturas, como o elemento SXT, isolado inicialmente em V. cholerae, tem contribuído para a disseminação de complexos específicos clonais em determinadas áreas geográficas. Este estudo pioneiro no Brasil pesquisou a presença de elementos SXT, em espécies bacterianas do grupo das gama proteobactérias em espécies ambientais, determinou suas características estruturais e funcionais, incluindo genes de resistência a antibióticos, bem como a sensibilidade aos antibióticos dentre os isolados bacterianos que os abrigam. O resultado foi a classificação de 43 elementos SXT obtidos no Brasil, através da comparação com aqueles descritos na literatura. Dentre os elementos SXT obtidos, quatro são albergados por Morganella morganii, fato inédito na literatura. O conhecimento da evolução bacteriana constitui importante ferramenta para estabelecer estratégias eficazes de controle e tratamento de infecções, sem aumentar a pressão seletiva sobre os micro-organismos, bem como instrumento preciso e de grande importância para subsidiar estudos epidemiológicos. / Recognition of antimicrobial resistance as an emerging phenomenon in public health has been a problem worldwide. The abuse in the use of antibiotics in human and veterinary medicine, and agriculture, has caused an increase in the diversity of resistant microorganisms, reflecting in treatment failure. The mechanisms of antibiotic resistance in microorganisms are primarily mediated by genes acquired from exogenous DNA. The dynamics of the horizontal transfer is performed by mobile genetic elements which carry resistance genes. The wide distribution of these structures, such as the SXT element originally isolated from V. cholerae, has contributed to the spread of specific clonal complexes in certain geographical areas. This pioneering study in Brazil researched the presence of SXT elements in the group of bacterial species in environmental gamma-proteobacteria species, determined their structural and functional characteristics, including genes for resistance to antibiotics and the antibiotic susceptibility among bacterial isolates that harbor them. The result was the classification of 43 SXT elements found in Brazil, by comparison with those found in the literature. Among the SXT elements found, four are sheltered by Morganella morganii, unprecedented in the literature. Knowledge of bacterial evolution is an important to establish effective strategies to control and treat infections without increasing the selective pressure on microorganisms, as well as a precise instrument and very important tool to support epidemiological studies.

O objetivo deste estudo foi caracterizar bactérias multirresistentes (MDR) isoladas de cavalos saudáveis (fezes) e doentes no Brasil e na França. De março de 2012 a dezembro de 2014, amostras clínicas coletadas de cavalos saudáveis e doentes no Brasil foram selecionadas para pesquisa da presença de bactérias MDR. A investigação sobre as amostras franceses foi restria a isolados de Escherichia coli (EC) recuperados a partir de amostras clínicas coletadas entre 2014 e 2015. Nos cavalos brasileiros, a análise de amostras de fezes de animais saudáveis revelou a presença de clones de EC não relacionados pertencentes aos filogrupos A, D ou B2 que carreavam genes como: blaCTX-M-1, blaCMY-2, qnr- e genes add-tipo (amino-transferases); enquanto que nos cavalos doentes foram encontradas EC, Proteus mirabilis, Klebsiella pneumoniae, Pseudomonas aeruginosa e Serratia marcescens carreando genes blaCTX-M-15, blaCTX-M-1, rmtD 16S rRNA metilase, qnr-tipo, aac(6´)-Ib-cr e aad-tipo. Nos cavalos doentes franceses de EC MDR foram positivas para CTX-M-1, seguido de M-2- e M-9. Estes resultados destacam a importância de cavalos como um novo reservatório de bactérias MDR. / The aim of this study was to characterize multidrug-resistant (MDR) bacteria isolated from healthy and infected horses in Brazil and France. From March 2012 to December 2014, clinical samples collected from healthy and infected horses, in Brazil, were screened for the presence of MDR bacteria. Investigation on French isolates was restricted to E. coli strains recovered from clinical samples collected between 2014 and 2015. In Brazilian horses, the analysis of fecal samples from healthy animals revealed the presence of clonally unrelated A, D or B2 phylogroups of E. coli strains carrying blaCTX-M-1, blaCMY-2, qnr- and aminoglycoside adenyl transferase (aad)-type genes, whereas in infected horses, E. coli, Proteus mirabilis, Klebsiella pneumoniae, Pseudomonas aeruginosa and Serratia marcescens isolates carrying blaCTX-M-15, blaCTX-M-1, rmtD 16S rRNA methylase, qnr-type, aac(6´)-Ib-cr and aad-type genes. In French infected horses, most MDR E. coli isolates were positive for CTX-M-1-, followed by CTX-M-2- and CTX-M-9-type extended-spectrum beta-lactamases. These results highlight the importance of horses as a new reservoir of MDR bacteria.

Clostridium difficile is the most common antibiotic related diarrhéa disease in Sweden. New recommendations from the Swedish public health authority and European Society of Clinical Microbiology and Infectious Diseases (ESCMID) had led to that a more advanced diagnostic algorithm is of priority. Hence this study, whose purpose was to investigate whether the performance of the rapid test C. diff Quik Chek Complete® could enable the introduction of a new diagnostic algorithm for detection of toxin-forming C. difficile in laboratory medicine in Sundsvall, according to these new recommendations. In the study 119 patient stool-samples were analysed with both GeneXpert and C. diff Quik Chek Complete® and these two combined fulfils these new recommendations of detecting toxin A and B from toxigenic C. difficile together with the enzyme Glutamate Dehydrogenase (GDH) which is produced by all C. difficile stems. The results shows that C. diff Quik Chek Complete® is well matched with GeneXpert and that most of the samples would come to be answered immediately after analysis with C. diff Quik Chek Complete®. The laboratory will save both time and money to establish C. diff Quik Chek Complete® in their algorithm for diagnosing C. difficile infection.

D’après un rapport de l’OMS, la tuberculose reste en 2015 l’une des 10 premières causes de décès à l’échelle mondiale. De ce fait, en matière de santé, éradiquer la maladie à l’horizon 2030 est un des objectifs majeurs fixés par les Nations Unies. La bactérie responsable de cette infection, Mycobacterium tuberculosis, est un pathogène obligatoire dont l’origine et l’évolution sont intrinsèquement liées à celles de son hôte principal, Homo sapiens. En effet, les souches actuelles de tuberculose présentent, tout comme l’homme, une forte structure phylogénétique, trace de leur origine géographique. Les pays pauvres et en développement sont les plus touchés par l’épidémie globale, favorisée par des systèmes de santé défaillants et une haute prévalence du VIH. Les pays occidentaux ne sont pas épargnés, menacés par l’émergence de souches de plus en plus résistantes aux antibiotiques provenant en grande partie de l’ex URSS. Au cours de cette thèse, j’analyse l’histoire évolutive, la propagation et l’acquisition de résistances aux antibiotiques de plusieurs épidémies de tuberculose en me basant sur des données génétiques et génomiques. Dans un premier temps je m’intéresse aux effets d’une campagne nationale de traitements en Asie Centrale sur le développement de souches multi-résistantes et met également en lumière le rôle clef de certaines mutations dans le succès des clones présentés. Ainsi cette campagne a été partiellement mise en échec par la présence de souches pré-résistantes, grâce à la survenue de mutations avant même la mise en place des traitements antibiotiques. Par la suite je me suis focalisé sur un clade particulier de souches multi-résistantes, le clone Russe W148. Je présente sa dispersion géographique et temporelle à travers l’Eurasie et démontre l’importance des mutations compensatoires dans son succès épidémique. De plus, la tuberculose ne touche pas seulement les hommes mais infecte également plusieurs autres mammifères. Afin d’appréhender les contraintes adaptatives accompagnants ces changements d’hôtes, j’ai effectué divers tests de sélection dans le but d’identifier les gènes impliqués. Pour finir, nous avons développé un indice souche spécifique, permettant de mesurer le succès épidémique de celles-ci à un niveau individuel. Dans le cadre d’études épidémiologiques, cette mesure peut être croisée avec des informations sur le patient, la souche ou même socio-économiques. / According to a 2015 WHO report, tuberculosis remains one of the top 10 causes of death worldwide. Despite considerable efforts by the United Nations to eradicate the disease by 2030, a global TB epidemic still persists. Its causative agent, the bacterium Mycobacterium tuberculosis, an obligate pathogen, has been plaguing humanity since it originated, and has coevolved with its main host, Homo sapiens, over thousands of years. Contemporary tuberculosis strains exhibit a structured phylogeographic pattern, carrying the genetic print of their geographic origin. The Koch bacillus infects and kills in large numbers, in poor and developing countries, where fragile health care systems, combined with high HIV prevalence, facilitate epidemic spread. In western countries, the major current threats are the multiplication and propagation of antibiotic resistant strains (MDR/XDR) coming predominantly from former Soviet republics. In this thesis, I unravel the evolutionary history, propagation, and acquisition of drug resistance-conferring mutations in different settings, by implementing multiple genetic and genomic data sets. First, focusing on Central Asia, using whole genome sequencing and Bayesian statistics, I assess the effects of a treatment campaign on the development of MDR strains and highlight key mutations in successful strains. More importantly, the success of DOTs campaigns was compromised by the genetic make-up of these outbreak clades (pre-treatment low frequency resistance SNPs). Special attention was also given to a particular outbreak of MDR strains, i.e. the Russian W148 clone. I present its westward spatial and temporal propagation at a continental scale during the last century, and underline the key contribution of compensatory mutations in its epidemic success. However, tuberculosis does not only infect humans, but also has experienced successive mammalian host jumps. To decipher the adaptive constraints accompanying such secondary events, a systemic gene screen with selection signature-detecting algorithms was implemented to identify putative targets during diversifying selection. Finally, novel mathematical tools and indices that reflect the epidemicity of a strain were developed, jumping from a population-driven approach to a strain specific one, with broader epidemiological applications. This allows us to correlate strain fitness with patient, lineage, and socio-economic information.

Les polluants atmosphériques de type oxydes d’azote (NOx), principalement constitués du NO, NO2 et leurs dérivés, représentent une énorme menace d’un point de vue environnemental et sanitaire. Leurs propriétés chimiques sont largement exploitées à l’échelle du vivant pour leur rôle dans divers processus de signalisation (systèmes nerveux et cardiovasculaire) ou l’élimination de pathogènes (système immunitaire). Néanmoins, des dérégulations dans la production cellulaire ou l’apport exogène de ces composés est à l’origine de nombreuses pathologies humaines (e.g. pulmonaires), généralement attribuées à la pollution. Toutefois, un grand nombre de microorganismes aéroportés sont continuellement exposés à ces composés délétères, intimement connectés aux espèces réactives de l’oxygène (ROS). Ainsi l’hypothèse de l’ensemble de ce travail a porté sur l’impact du NO2, NOx majoritairement retrouvés dans l’atmosphère, sur une souche aéroportée de P. fluorescens, espèce désormais associée aux voies aériennes et potentiellement pathogène. A l’issue d’une exposition à 45 ppm de NO2, la survie de P. fluorescens MFAF76a est significativement impactée suggérant un effet bactériostatique, conforté par l’impact observé sur le métabolisme énergétique. De plus, le NO2 induit un stress d’enveloppe via la perte d’un glycérophospholipide (UGP) et le remaniement de divers composants membranaires (LPS, peptidoglycane, acides gras). La pompe à efflux MexEF-OprN semblent participer à la stabilisation de la membrane et pourraient être également impliquée dans l’efflux des oxydes d’azotes, mécanismes confortés par l’étude d’un mutant MFAF76a-oprN. La porine majoritaire OprF semble également contribuer à la stabilisation de la membrane externe, néanmoins son implication reste à confirmer. De plus, une interconnexion entre ROS et NOx dans la signalisation (OxyR, IscR), et les mécanismes de détoxification, a été observée. La flavohémoprotéine Hmp semble être un élément crucial dans la détoxification des NOx chez P. fluorescens comme l’illustre un mutant MFAF76a-hmp. Les similitudes importantes entre les effets connus du NO et ceux observés lors d’une exposition au NO2 suggèrent une conversion non enzymatique du NO2, une fois pénétré dans la cellule, en NO. Désormais, une étude plus approfondie est nécessaire afin de décrypter (i) les mécanismes impliqués dans la régulation de la pompe à efflux RND MexEF-OprN et de la flavohémoprotéine Hmp, (ii) d’autres acteurs intervenant dans la réponse au stress d’enveloppe et la détoxification ainsi que (iii) le devenir de NO2 dans la cellule. / Nitrogen oxides (NOx) atmospheric pollutants, mainly constituted of NO, NO2 and derived compounds, are a big threat to the environment and health. Their chemical properties are largely exploited at the cellular scale for their role in diverse physiological processes such as signalisation (nervous and cardiovascular systems) or in pathogens eradication (immunity system).However, dysregulation in production pathways or exogenous input of these compounds lead to several pathologies (e.g. respiratory diseases), usually attributed to atmospheric pollution. However, a wide range of airborne microorganisms are constantly exposed to these deleterious compounds, intimately connected to reactive oxygen species (ROS). Thus, the hypothesis of this work deals with the impact of NO2, the main atmospheric NOx, on an airborne P. fluorescens, a strain usually neglected but yet associated with human airways, and potentially pathogenic. Following an exposure to 45 ppm of NO2, the survival of P. fluorescens MFAF76a is severely impaired, suggesting a bacteriostatic effect, as comforted by NO2 impact on energetic metabolism. Moreover, an exposure to NO2 induces an envelope stress through the loss of an Unknown Glycerophospholipid (UGP) and the reorganisation of membrane constituents (LPS, peptidoglycan, fatty acids). The efflux pump MexEF-OprN is involved in membrane stabilization and could also efflux NOx, as highlighted by a MFAF76a-oprN mutant. The major porin OprF could also contribute in external membrane stabilisation, however its implication is still under investigation. Moreover, ROS and NOx are interconnected as illustrated by their shared signalisation (OxyR, IscR) and detoxification pathways. The flavohemoprotein Hmp is a crucial element in the detoxification of NOx in P. fluorescens as illustrated in an MFAF76a-hmp mutant. The similarities between the known effects of NO and those observed in the case of an exposure to NO2, suggest a non-enzymatic conversion of NO2, following cell penetration, into NO. Henceforth, deeper studies are required to decode (i) the mechanisms involved in the regulation of the RND efflux pump MexEF-OprN and the flavohemoprotein Hmp, (ii) other relevant actor implicated in the envelope stress response and in detoxification pathways as well as (iii) the fate of NO2 within the cell.

O reconhecimento da resistência antimicrobiana como um fenômeno emergente em saúde pública, tem constituído um problema em nível mundial. O abuso na utilização de antibióticos na medicina humana e veterinária, e na agricultura, tem originado incremento na diversidade de micro-organismos resistentes, refletindo em falha terapêutica. Os mecanismos de resistência a antibióticos em micro-organismos são mediados principalmente por genes adquiridos de DNA exógeno. A dinâmica da transferência horizontal é realizada por meio de elementos genéticos móveis que carregam genes de resistência. A ampla distribuição deste tipo de estruturas, como o elemento SXT, isolado inicialmente em V. cholerae, tem contribuído para a disseminação de complexos específicos clonais em determinadas áreas geográficas. Este estudo pioneiro no Brasil pesquisou a presença de elementos SXT, em espécies bacterianas do grupo das gama proteobactérias em espécies ambientais, determinou suas características estruturais e funcionais, incluindo genes de resistência a antibióticos, bem como a sensibilidade aos antibióticos dentre os isolados bacterianos que os abrigam. O resultado foi a classificação de 43 elementos SXT obtidos no Brasil, através da comparação com aqueles descritos na literatura. Dentre os elementos SXT obtidos, quatro são albergados por Morganella morganii, fato inédito na literatura. O conhecimento da evolução bacteriana constitui importante ferramenta para estabelecer estratégias eficazes de controle e tratamento de infecções, sem aumentar a pressão seletiva sobre os micro-organismos, bem como instrumento preciso e de grande importância para subsidiar estudos epidemiológicos. / Recognition of antimicrobial resistance as an emerging phenomenon in public health has been a problem worldwide. The abuse in the use of antibiotics in human and veterinary medicine, and agriculture, has caused an increase in the diversity of resistant microorganisms, reflecting in treatment failure. The mechanisms of antibiotic resistance in microorganisms are primarily mediated by genes acquired from exogenous DNA. The dynamics of the horizontal transfer is performed by mobile genetic elements which carry resistance genes. The wide distribution of these structures, such as the SXT element originally isolated from V. cholerae, has contributed to the spread of specific clonal complexes in certain geographical areas. This pioneering study in Brazil researched the presence of SXT elements in the group of bacterial species in environmental gamma-proteobacteria species, determined their structural and functional characteristics, including genes for resistance to antibiotics and the antibiotic susceptibility among bacterial isolates that harbor them. The result was the classification of 43 SXT elements found in Brazil, by comparison with those found in the literature. Among the SXT elements found, four are sheltered by Morganella morganii, unprecedented in the literature. Knowledge of bacterial evolution is an important to establish effective strategies to control and treat infections without increasing the selective pressure on microorganisms, as well as a precise instrument and very important tool to support epidemiological studies.

Our research aim was to design, synthesize, and study the competitive enzyme inhibition kinetics of pyrrolo[2,1-c][1,4]benzodiazepine (PBD) derivatives as potential non-²-lactam ²-lactamase inhibitors. All compounds (1-13) passed the Lipinski’s rule of 5 test and were docked into the active site of TEM-1 ²-lactamase. PBD derivatives 1-7 were synthesized in high yields and tested for their potency against TEM-1 and P99 ²-lactamases. Kinetic data showed that compounds 1, 4, 5, and 7 possessed inhibitory activity against TEM-1 ranging from 4-34 %. Docking results revealed significant interactive spanning of the active site of TEM-1 by PBDs. The limited inhibitory activity of the compounds, 1-7 could be attributed to the lack of solubility and bulky nature of the molecules, thus limiting the optimal ligand-enzyme interactions. 1,2,4- Oxadiazolinones (8-13) were further synthesized to reduce the steric hindrance of the PBD scaffolds while promoting the electrophilicity of the potentially active lactam and also evaluated for potency.

Le monoxyde d'azote NO• est impliqué dans de nombreux processus biologiques. Il intervient, entre autres, dans la vasodilatation, la neurotransmission, il peut impliquer le développement ou l'apoptose des cellules et possède également des propriétés bactéricides. Le contrôle de la libération de ce radical est donc de grand intérêt pour des applications biomédicales en chimiothérapie photo-activée (PACT) ainsi qu'en inactivation photo-dynamique (PDI). La stratégie ici est de synthétiser des complexes de ruthénium à ligand nitrosyle photoréactifs, qui sont capables de libérer NO• sous irradiation mono ou biphotonique. L'excitation à deux photons permet une irradiation dans la fenêtre thérapeutique, très focalisée et une pénétration du faisceau plus profonde qu'en monophotonique. Ces travaux de thèse sont consacrés à la synthèse et l'étude des propriétés photochimiques de complexes [RuNO] et à leurs applications en biologie. Le premier chapitre de cette thèse développe l'état de l'art dans le domaine des complexes de ruthénium à ligand nitrosyle et présente les enjeux biologiques. Le second chapitre présente les propriétés de photolibération de NO• de complexes possédant le ligand 4'-(2-fluorényl)-2,2':6',2''-terpyridine, sous excitation à un et à deux photons par des études spectroscopiques. Les photoproduits obtenus sont caractérisés par diffraction des rayons X. Dans un troisième chapitre, l'étude des complexes cis (Cl,Cl)- et trans (Cl,Cl)-[RuII(fluorène-terpyridine)Cl2NO]PF6 est menée dans l'eau. Les capacités de photolibération du trans (NO,OH)-[RuII(fluorène-terpyridine)(Cl)(OH)(NO)]PF6 dans les conditions biologiques sont étudiées. Le quatrième chapitre s'intéresse à la synthèse de nouveaux complexes constitués de ligands dérivés du 4'-(2-fluorényl)-2,2':6',2''-terpyridine et à leurs propriétés de photolibération de NO•. Le cinquième chapitre s'intéresse aux propriétés phototoxiques de ces complexes envers des cellules cancéreuses (HCT 116 et FaDu). Enfin, dans le sixième chapitre, les propriétés remarquables de ces systèmes dans la levée de la résistance de Staphylococcus epidermidis aux antibiotiques sont exposées. / Nitric oxide NO• is involved in numerous biological processes. It takes part to vasodilatation, neurotransmission, it can trigger cell proliferation or apoptosis and it also has bactericidal properties. Thus, NO• release control is of high interest for biomedical applications such as photo-activated chemotherapy (PACT) or photodynamic inactivation (PDI). The strategy here is to synthesize photoreactive ruthenium complexes with nitrosyl ligand which can release NO• under one and two-photon absorption. Compared with one-photon excitation, two-photon excitation allows high focalization and deep penetration of the beam, while exciting in the therapeutic window. This thesis is dedicated to the synthesis of [RuNO] complexes and their biological applications. The first chapter develops the state of the art in the field of ruthenium nitrosyl complexes and presents the biological issues. The second chapter presents the NO• photorelease properties of complexes with 4'-(2-fluorenyl)-2,2':6',2''-terpyridine ligand under one and two-photon excitation by spectroscopic studies. Photoproducts are characterized by X-ray diffraction. In a third chapter, cis (Cl,Cl)- and trans (Cl,Cl)-[RuII(2-fluorene-terpyridine)Cl2NO]PF6 are studied in water. The photorelease capacities of trans (NO,OH)-[RuII(fluorene-terpyridine)(Cl)(OH)(NO)]PF6 are studied in biological conditions. The fourth chapter presents the synthesis of new complexes with 4'-(2-fluorenyl)-2,2':6',2''-terpyridine ligand derivatives and their photorelease properties. The fifth chapter describes the phototoxic studies of these complexes on cancer cells (HCT 116 and FaDu). Finally, in the sixth chapter, the outstanding properties of these systems in the falling of antibiotic resistance in Staphylococcus epidermidis are exposed.