Prevention of bloodstream infections by photodynamic inactivation of multi-resistant Pseudomonas aeruginosa in burn wounds

摘要

Bloodstream infections are potentially life-threatening diseases. They can cause serious secondary infections, and may result in endocarditis, severe sepsis or toxic-shock syndrome. Pseudomonas aeruginosa is an opportunistic pathogen and one of the most important etiological factors responsible for nosocomial infections, mainly in immuno-compromissed hosts, characteristic of patients with severe burns. Its multiresistance to antibiotics produces many therapeutic problems, and for this reason, the development of an alternative method to antibiotic therapy is needed. Photodynamic inactivation (PDI) may be an effective and alternative therapeutic option to prevent bloodstream infections in patients with severe burns. In this study we report the use of PDI to prevent bloodstream infections in mice with third-degree burns. Burns were produced on the back of the animals and they were infected with 10~9 cfu/mL of multi-resistant (MR) P. aeruginosa. Fifteen animals were divided into 3 groups: control, PDT blue and PDT red. PDT was performed thirty minutes after bacterial inoculation using lOuM HB:La~+3 and a light-emitting diode (LED) emitting at λ=460nm±20nm and a LED emitting at λ=645 nm±10nm for 120s. Blood of mice were colected at 7h, lOh, 15h, 18h and 22h pos-infection (p.I.) for bacterial counting. Control group presented lxl0~4 cfu/mL in bloodstream at 7h p.I. Increasing to lxl0~ 6 at 22h, while mice PDT-treated did not present any bacteria at 7h; only at 22h p.I. They presented lxl0~4cfu/mL. These results suggest that HB:La~+3 associated to blue LED or red LED is effective to delay and diminish MR P.aeruginosa bloodstream invasion in third-degree-burned mice.