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Monday, 07/29/2013
Laia Fernández Barat successfully defended her doctoral thesis: “Biofilm study in a porcine model of ventilator associated pneumonia: role of systemic antibiotherapy in its microbiology and microscopic morphology”
The public event was held last July 5th in the University of Barcelona, Faculty of Medicine
Laia Fernández Barat has been working as doctoral researcher at the Applied Research in Respiratory Diseases group led by Prof. Antoni Torres at the IDIBAPS. She obtained her degree in Biology from the University of Barcelona. During her doctoral thesis her research was aimed to determine the effects of systemic treatment on endotracheal tube biofilm development. Results were published on 2012 in the journals Critical Care Medicine and FEMS Immunology and Medical Microbiology. The public event took place on July 5th in the University of Barcelona, Faculty of Medicine, and the thesis tribunal comprised Dr. Josep Maria Miró, of the Department Infectious Diseases and internal medicine of the Hospital Clínic, Dr. Ernesto García, from the Centro de Investigaciones Biológicas del Consejo Superior de Investiciones Científicas (CIB-CSIC), and Dra. Paula Ramírez, from the Hospital La Fe de Valencia.
For her thesis Dr. Laia Fernández Barat prospectively analyzed 70 ETT samples. ETTs were obtained from pigs either untreated (controls, n=20), or treated with vancomycin (n=32) or linezolid (n=18). Main results indicated a variation almost significant in biofilm MRSA burden (Log CFU•mL-1) among groups (p=0.057), and the lowest bacterial burden was found in ETTs treated with linezolid (1.98±1.68) in comparison with untreated ETTs (3.72±2.20, p=0.045) or treated with vancomycin (2.97±2.43, p=0.286). More importantly, biofilm linezolid concentration was 19-fold above the linezolid minimum inhibitory concentration (MIC); while biofilm vancomycin concentration (1.60±0.91µg•mL-1) was consistently below or close to the vancomycin MIC. Biofilm was thicker in the vancomycin group (p=0.077).
The article published in Critical Care Medicine (2012; 40: 2385–2389) concluded that systemic treatment with linezolid limits ETT biofilm development and MRSA burden. The second article included the analysis of 127 confocal microscopy images of ETT biofilm to perform a direct analysis of bacterial viability and biofilm structure. The median ratio of live/dead bacteria was 0.51, 0.74 and 1 for the linezolid, vancomycin and control groups, respectively (p=0.002 for the 3 groups); this ratio was significantly lower for the linezolid group, compared with the control group (p=0.001). Images showed bacterial biofilm attached and non attached to the ETT surface but growing within secretions accumulated inside ETT.
This second article published in FEMS Immunology and Medical Microbiology (2012;65:309–317) concluded that systemic treatment with linezolid is associated with a higher proportion of dead bacteria in the ETT biofilm of animals with MRSA pneumonia. Biofilm clusters not necessarily attach to the ETT surface.
Dr. Laia Fernández Barat brilliantly defended her doctoral thesis and obtained the best qualification, Excellent Cum Laude. The thesis was presented in spanish and raised interest among the thesis tribunal for its clinical implications. The tribunal members also acknowledged the leadership of the thesis directors, Prof. Antoni Torres, Dr. Miquel Ferrer.