Publicação
Polymicrobial interactions in infections: the case Pseudomonas aeruginosa and Candida albicans in ventilator-associated pneumonia
| Resumo: | Ventilator-associated pneumonia (VAP) is one of the most common nosocomial pneumonia among intensive care units contributing to high rates of morbidity and mortality. Polymicrobial biofilm infections with Pseudomonas aeruginosa and Candida albicans have being recently reported in VAP. Their antimicrobial resistance profiles represent a serious impact on the treatment of the disease by reducing the effective therapies and affecting the state of health of patients. As such, the present work aimed to provide novel insights concerning the characterization of single- and dual-species biofilms phenotype involving P. aeruginosa and C. albicans under the presence of different antimicrobials agents. Planktonic and biofilm assays were performed using P. aeruginosa PAO1, C. albicans SC5314 and four clinically important antimicrobials: amphotericin B (AmB), tobramycin (ToB), colistin (CoL) and polymyxin B (PolyB) as single or in combination. The quantitative methods (CFUs enumeration and biomass quantification) and qualitative methods (SEM, PNA FISH analysis and LIVE/DEAD staining) were used to study the single- and dual-species biofilms. The results showed that the incubation time did not influence biofilm formed by both pathogens in the overall consortia. Concerning single antimicrobials use, P. aeruginosa was the pathogen more sensitive to most tested antimicrobials and their effect showed to be concentration and time dependent. For antimicrobial combinations it was demonstrated that most formulations presented synergistic effect in P. aeruginosa, both in single and in mixed planktonic cultures. Specially, when applied to biofilms only AmB/PolyB and ToB/PolyB combinations (particularly with PolyB at high concentrations: 256 mg/L), promoted a significant reduction in the number of cultivable cells of both strains entrapped in single- and in dual-species biofilms. However, PNA FISH analysis and LIVE/DEAD staining showed that both strains are still existent and viable in presence of these antimicrobial combinations. In conclusion, different antimicrobial therapies used in this work did not display any effectiveness in the treatment of polymicrobial infections associated to VAP. Nevertheless, certain antimicrobial combinations tested in this work are essentials to future studies in order to better clarify the clinical dosage concentrations. Despite of the aforementioned concentrations being toxicity for humans they present strong potency to be used in future novel methodologies for VAP therapy. |
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| Autores principais: | Pereira, Cláudia Ribeiro |
| Assunto: | Engenharia e Tecnologia::Biotecnologia Industrial |
| Ano: | 2015 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | português |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Ventilator-associated pneumonia (VAP) is one of the most common nosocomial pneumonia among intensive care units contributing to high rates of morbidity and mortality. Polymicrobial biofilm infections with Pseudomonas aeruginosa and Candida albicans have being recently reported in VAP. Their antimicrobial resistance profiles represent a serious impact on the treatment of the disease by reducing the effective therapies and affecting the state of health of patients. As such, the present work aimed to provide novel insights concerning the characterization of single- and dual-species biofilms phenotype involving P. aeruginosa and C. albicans under the presence of different antimicrobials agents. Planktonic and biofilm assays were performed using P. aeruginosa PAO1, C. albicans SC5314 and four clinically important antimicrobials: amphotericin B (AmB), tobramycin (ToB), colistin (CoL) and polymyxin B (PolyB) as single or in combination. The quantitative methods (CFUs enumeration and biomass quantification) and qualitative methods (SEM, PNA FISH analysis and LIVE/DEAD staining) were used to study the single- and dual-species biofilms. The results showed that the incubation time did not influence biofilm formed by both pathogens in the overall consortia. Concerning single antimicrobials use, P. aeruginosa was the pathogen more sensitive to most tested antimicrobials and their effect showed to be concentration and time dependent. For antimicrobial combinations it was demonstrated that most formulations presented synergistic effect in P. aeruginosa, both in single and in mixed planktonic cultures. Specially, when applied to biofilms only AmB/PolyB and ToB/PolyB combinations (particularly with PolyB at high concentrations: 256 mg/L), promoted a significant reduction in the number of cultivable cells of both strains entrapped in single- and in dual-species biofilms. However, PNA FISH analysis and LIVE/DEAD staining showed that both strains are still existent and viable in presence of these antimicrobial combinations. In conclusion, different antimicrobial therapies used in this work did not display any effectiveness in the treatment of polymicrobial infections associated to VAP. Nevertheless, certain antimicrobial combinations tested in this work are essentials to future studies in order to better clarify the clinical dosage concentrations. Despite of the aforementioned concentrations being toxicity for humans they present strong potency to be used in future novel methodologies for VAP therapy. |
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