The treatment of patients after mechanical ventilation of lungs, suffering from a multi-species infection of the tracheobronchial tree became complicated rapidly in recent years. The situation is aggravated in patients with post intubation tracheal stenosis, where infection plays a leading pathogenetic role in damage to the tracheal wall resulting in infected tracheal stenosis (ITS). The aim of this work was to study in vitro the possibility of photodynamic inactivation of pathogenic microbiota, typical for patients with ITS, using methylene blue (MB) as a photosensitizer (PS). Gram-positive (Staphylococcus aureus, Corynebacterium propinquum, Corynebacterium striatum, Enterococcus faecalis) and Gram-negative (Pseudomonas aeruginosa, Proteus mirabilis, Klebsiella pneumoniae, Stenotrophomonas maltofila) bacteria, multi- and pan-resistant to antibacterial drugs, in combinations of up to 4 microorganisms in one patient, were found. Minimal bactericidal concentration of MB was evaluated for 13 isolates of 8 species of bacteria from 9 patients. Incubation of bacteria with 30 μM MB for 15 min and irradiation with LED at a dose of 25 J/cm2 allow to completely inactivate bacteria found in the tracheobronchial secretions of patients with ITS, including Pseudomonas aeruginosa, the most resistant to photodynamic inactivation. Analysis of absorption and fluorescence spectra revealed, that in these ranges, aggregation and photo-bleaching of methylene blue is neglizible and PS retains its optic-physical properties and provides effective inactivation of isolated Gram-positive and Gram-negative bacteria, including multi- and pan-resistant to antibacterial drugs. MB can be delivered via nebulizing and medical lasers with fiber-optic means for delivering light radiation, with specially shaped diffusers, can provide the irradiation, required for photodynamic therapy inside the tracheobronchial area for treatment and disinfection.
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