An endotracheal tube (ETT) is required for the management of critically ill, mechanically ventilated patients. Ventilatorassociated pneumonia (VAP) affects patients hospitalized in intensive care units; its risk of occurrence is 1% to up 3% for each day of mechanical ventilation. The polymicrobial nature of VAP is established with mixed bacterial-fungal biofilms colonizing the ETT. The microbial interaction enhances the microbial pathogenesis contributing to high indexes of morbidity/mortality. Antimicrobial Photodynamic Therapy (aPDT) could be a suitable therapy for decontamination of oral cavity and ETT at the same time, but the use of a fiber optics inside the ETT seems to not be appropriated since a cannula for secretion aspiration has to be introduced into the ETT to keep it´s lumen. The aim of this study is to proof the concept that an external light source from a LED is capable of reach all areas of the ETT. We use a commercial ETT, 60μM methylene blue (MB), and a 660nm diode laser and calculated the transmission coefficient of light in different situations as only tube, tube with biofilm and biofilm+MB. The results prove that is possible to transmit light through the tube even in the presence of MB and biofilm although a high attenuation of about 60% was measured depending on the tested condition.
Photodynamic antimicrobial therapy (PAT) may become a useful clinical tool to treat microbial infections, overcoming
microbial resistance that is a major problem nowadays. The aim of our work was to verify the damage caused by
photosensitization over a Escherichia col) via atomic force microscopy (AFM), looking for structural changes that might
occur in cells after PAT. Cells culture were grown until a stationary phase to reach a concentration of approximately 108
cells/mL allowing the production of extracellular slime in a
biofilm-like structure. The cells including the extracellular
matrix were put in a slide and its structure was observed using AFM; subsequently a water solution of methylene blue at
60μM was applied over the cells and a pre-irradiation time of 3 minutes was waited and followed by illumination with a
diode laser (λ=660nm, power 40mW, 3min, fluence 180J/cm2, beam diameter 0.04cm2). The same cells were observed
and the images stored. A second set of experiments was performed with a smaller number of cells/area and without
extracellular slime, using the parameters abovementioned. The results showed alterations on cellular scaffold markedly
dependent on the number of cells and the presence of extracellular slime. The slime is targeted by the photosensitizer,
and after irradiation a destruction of the matrix was observed; when fewer cells were evaluated the destruction is much
more evident. The images suggested rupture of the cellular membrane and cellular fragments were observed. Our
findings indicate that AFM seems is a useful tool to investigate parameters linked with photodestruction of
microorganisms.
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