In immunodeficient patients, for example with cystic fibrosis (CF), the opportunistic pathogen Staphylococcus aureus causes chronic infections of respiratory tract that are treated with antibiotics (ATB) in the long term. However, exposure to antibiotics can lead to persistence, thereby result a recurrence of infection. The aim of this work was to examine in selected pairs of S. aureus chronological isolates from the respiratory tract of CF patients how their ability to form persisters is changing in time. I have found that the ability to persist within the clonal pair does not change significantly after two years of survival in the host, and that the ability to persist depends on the adaptative mutations of the isolates. Persister formation may depend on mutations in operon of the alternative sigma B factor (sigB) and the major virulence gene regulator (agr). By dual staining with DioC2(3) and To-pro-3, I was able to determine the changes in membrane potential and membrane permeability during the killing curve with ATBs. The distribution into subpopulations according to these parameters depends primarily on the antibiotic used. I conclude that various antibiotics can induce different mechanisms causing a persistent state. Futhermore, I have constructed plasmids with a labeled promoter to determine...

In immunodeficient patients, for example with cystic fibrosis (CF), the opportunistic pathogen Staphylococcus aureus causes chronic infections of respiratory tract that are treated with antibiotics (ATB) in the long term. However, exposure to antibiotics can lead to persistence, thereby result a recurrence of infection. The aim of this work was to examine in selected pairs of S. aureus chronological isolates from the respiratory tract of CF patients how their ability to form persisters is changing in time. I have found that the ability to persist within the clonal pair does not change significantly after two years of survival in the host, and that the ability to persist depends on the adaptative mutations of the isolates. Persister formation may depend on mutations in operon of the alternative sigma B factor (sigB) and the major virulence gene regulator (agr). By dual staining with DioC2(3) and To-pro-3, I was able to determine the changes in membrane potential and membrane permeability during the killing curve with ATBs. The distribution into subpopulations according to these parameters depends primarily on the antibiotic used. I conclude that various antibiotics can induce different mechanisms causing a persistent state. Futhermore, I have constructed plasmids with a labeled promoter to determine...

Institutions of higher education invest a significant amount of resources in recruiting, processing, and advising new students. When students leave the institution prior to graduation, the university loses considerable revenues. Therefore, it is important for colleges and universities to refine their student recruitment and retention strategies to avoid forgone revenues by predicting which students are likely to need particular types of support services (DeBerard et al, 2004). Current models of prediction utilize extensive surveys that are impractical to administer each term, and they do not adequately identify the broad range of student persistence categories needed in order to gain a greater understanding of persistence behavior (Davidson, 2005; Porter, 2000; Tinto, 1975). This study created a linear discriminant function to predict a broad range of persistence levels of first-time freshmen students at California State University, Bakersfield (CSUB), by identifying pre-enrollment and early enrollment student variables that existed within the database of the University. This information may be used to develop support service strategies to better assist incoming students predicted to have a greater probability of not persisting.

[ES] Las biopelículas bacterianas y fúngicas contribuyen enormemente a la persistencia de muchas infecciones graves y potencialmente mortales, las cuales anualmente provocan millones de defunciones. Además, estas bacterias y hongos que crecen adheridas formando biopelículas son hasta 1.000 veces más resistentes a los tratamientos antimicrobianos convencionales, generando una carga económica significativa y dificultando su diagnóstico y tratamiento. Por tanto, es necesario buscar nuevas herramientas fiables para estudiar la dinámica de formación de biopelículas con el fin de mejorar las estrategias de tratamiento.El objetivo general de la tesis doctoral es la puesta a punto de un sistema basado en medidas de impedancia eléctrica para el estudio de la formación y dinámica de crecimiento de las biopelículas bacterianas (gram-positivas y gram-negativas) y fúngicas, así como de biopelículas complejas multi-especie como las de la placa dental subgingival de muestras periodontales humanas. Tras la puesta a punto del sistema, los objetivos específicos de la tesis doctoral son su aplicación como herramienta en la identificación de tratamientos efectivos contra biopelículas persistentes, la búsqueda de nuevos compuestos antimicrobianos con actividad anti-biofilm, así como la evaluación de novedosas nanopartículas autopropulsadas para la erradicación de biofilms multirresistentes. Finalmente, se ha evaluado su aplicación clínica directa en la selección de la terapia antibiótica para el tratamiento personalizado de pacientes con enfermedad periodontal. / [CA] Les biopelícules bacterianes i fúngiques contribueixen en gran manera a la persistència de moltes infecciones greus i potencialment mortals les quals provoquen anualment milions de morts. A més, estes bactèries i fongs que creixen adherides en forma de biopelícules son fins a 1000 vegades més resistents als tractaments antimicrobians convencionals, generant una càrrega econòmica significativa i dificultant el diagnòstic i tractament. Per això, es necessari trobar noves eines fiables per a estudiar la dinàmica de formació de biopelícules amb l'objectiu de millorar les estratègies de tractament. El objectiu general de la tesis doctoral es la posta a punt de un sistema basat en mesures d'impedància elèctrica per al estudi de la formació i dinàmica de creixement de les biopelícules bacterianes (gram-positives i gram-negatives) i fúngiques, així com de biopelícules complexes mutiespècie com les de la placa dental subgingival de mostres periodontals humanes. Una vegada posat a punt el sistema, els objectius específics de la tesis doctoral son la aplicació com a eina de la identificació de tractaments efectius contra biopelícules persistents, la recerca de nous compostos antimicrobians amb activitat antibiopelícula, així com la avaluació de noves nanopartícules autopropulsades per a l'eliminació de biofilms multiresistents. Finalment, s'ha avaluat l'aplicació clínica directa en la selecció de la teràpia antibiòtica per al tractament personalitzat de pacients amb periodontitis. / [EN] Bacterial and fungal biofilms contribute enormously to the persistence of many life-threatening infections, causing millions of deaths annually. In addition, bacteria and fungi growing as biofilms are up to 1.000 times more resistant to conventional antimicrobial treatments, resulting in a significant economic burden and challenging diagnosis and treatment. Therefore, there is a need to search for new reliable tools to study biofilm formation dynamics to improve treatment strategies. This doctoral thesis aims to set up an impedance-based system to study biofilm formation and dynamics of bacterial (gram-positive and gram-negative) and fungal species, as well as complex multi-species biofilms such as subgingival plaque collected from patients with chronic periodontitis. After the impedance system is set up, the specific objectives of the doctoral thesis are its application as a tool in the identification of effective treatment against persistent biofilms, testing new antimicrobial and anti-biofilm compounds, and the evaluation of novel self-propelled nanoparticles on the eradication of multi-resistant S. aureus biofilms. Finally, a clinical application of the impedance system is proposed, aiming at determining the best individual antibiotic therapy in dental clinics (personalized use of antibiotics). / Work performed at Genomics & Health Department at FISABIO Foundation and described in this doctoral thesis was supported by the Spanish Ministry of Science, Innovation and Universities scholarship FPU17/01302 to Miglė Žiemytė and a grant RTI2018-102032-B-I00 to Alex Mira Obrador. / Ziemyte, M. (2023). Towards Personalized Medicine in Antibiotic Treatment: Development of a Real-Time Cell Analysis System for Biofilm Studies [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/195434