title: Photodynamic therapy for pythiosis.
abstract: BACKGROUND
  Pythiosis is a life-threatening disease caused by Pythium insidiosum. Photodynamic therapy (PDT) is an alternative treatment to surgery that uses the interaction of a photosensitizer, light and molecular oxygen to cause cell death.
  
  
  OBJECTIVE
  To evaluate the effect of PDT on the in vitro growth of P. insidiosum and in an in vivo model of pythiosis.
  
  
  METHODS
  For in vitro studies, two photosensitizers were evaluated: a haematoporphyrin derivative (Photogem(®)) and a chlorine (Photodithazine(®)). Amphotericin B was also evaluated, and the control group was treated with sterile saline solution. All experiments (PDT, porphyrin, chlorine and light alone, amphotericin B and saline solution) were performed as five replicates. For in vivo studies, six rabbits were inoculated with 20,000 zoospores of P. insidiosum, and an area of 1 cm(3) was treated using the same sensitizers. The PDT irradiation was performed using a laser emitting at 660 nm and a fluence of 200 J/cm(2) . Rabbits were clinically evaluated daily and histopathological analysis was performed 72 h after PDT.
  
  
  RESULTS
  For in vitro assays, inhibition rates for PDT ranged from 60 to 100% and showed better results in comparison to amphotericin B. For the in vivo assays, after PDT, histological analysis of lesions showed a lack of infection up to 1 cm in depth.
  
  
  CONCLUSIONS
  In vitro and in vivo studies showed that PDT was effective in the inactivation of P. insidiosum and may represent a new approach to treating pythiosis.
authors: Physics Institute of São Carlos and Instituto de Biociências de Botucatu, Univ Estadual Paulista, Campus Botucatu, Departamento de Microbiologia e Imunologia, Distrito de Rubião Júnior, S/N, 18618-970, Botucatu-SP, Brazil. laylabtu@gmail.com
authors: Layla
authors: L
authors: Pires
authors: Sandra de M G
authors: Sde M
authors: Bosco
authors: Nelson F
authors: NF
authors: da Silva
authors: Cristina
authors: C
authors: Kurachi
mesh_terms: D000818:Animals; D002713:Chlorine / Q000627:therapeutic use*; D007239:Infections / Q000628:therapy*; D010778:Photochemotherapy / Q000662:veterinary*; D017319:Photosensitizing Agents / Q000627:therapeutic use; D011166:Porphyrins / Q000627:therapeutic use*; D011775:Pythium / Q000187:drug effects* / Q000528:radiation effects*; D011817:Rabbits; D012871:Skin Diseases / Q000382:microbiology / Q000628:therapy
chemical_list: D017319:Photosensitizing Agents; D011166:Porphyrins; D002713:Chlorine