Avaliação do impacto biótico dos antimicrobianos em isolados clínicos obtidos em infecões polimicrobianas

  • Joana Manuela Machado Freitas da Silva (Student)

Student thesis: Master's Thesis


Even though polymicrobial infections are very common, their study is still at an early stage. In these infections, particularly when biofilms are formed, microorganisms establish a complex network of interactions that can change between antagonism and synergism. These interactions play an important role in the severity and progression of disease, with consequences in virulence, in the the immune response and in the effectiveness of antimicrobial therapy. In an era in which resistance to antimicrobials is an alarming and rapidly expanding scenario, the choice of appropriate treatment is paramount, with consequences in preventing the development and spreading of resistances.The aim of this work was to study the biotic interactions between bacterial strains isolated from veterinary clinical samples, both in the planktonic state and in biofilms. The studies were conducted for single-species or dual-species combinations. The viability of cells in the planktonic phase was determined by culture-dependent methods, whilst total cell counts and cell morphology were assessed with FISH. The biofilm-forming capacity of the tested strains was quantified, as well as their matrix production. Cellular viability was evaluated through metabolic activity quantification and Live/Dead staining. All these methods were used progressively, in order to identify changes in morphology and cell viability, and thus focusing our work in co-isolated strains and inhibitory concentrations in which the most significant changes were detected.In this study, we showed that co-culturing two strains in the presence of a cephalosporin benefits the most sensitive one rather than the resistant one. The viability of the most sensitive strain at concentrations higher than its minimum inhibitory concentration increased in comparison to its response alone.
Date of Award29 Jan 2018
Original languagePortuguese
Awarding Institution
  • Universidade Católica Portuguesa
SupervisorPaulo Manuel Rodrigues Martins da Costa (Supervisor) & Ângela Rosalina Sanches Inácio (Co-Supervisor)


  • Polymicrobial infections
  • Biofilms
  • Antimicrobial drugs
  • Cephalosporins


  • Mestrado em Microbiologia Aplicada

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