الملخص

Pigment production is considered an important virulence factor among many virulence factors that are produced by pseudomonas aeruginosa. A strong relationship between pigment production and both virulence and pathogenicity of Pseudomonas isolates has been revealed in this study. Among the important results considered in the present study, 80% of Pseudomonas isolates produce pigments. Culture media and broth that contain cetrimide were the most inducible media for pigment production within 24 hrs compared with modified MaConkey agar and broth in which pigmentation occurred within 4- 5 days . To determine the virulence of pigmented and non- pigmented Pseudomonas aeruginosa isolates, 0.1 ml of each broth cultured bacteria and filtrate were injected in an intentionally inscised wound (1 cm) on dorsal side of mice. Pyocyanin (blue- green) pigment producer strains were highly virulent, since they caused death of mice within 24 hrs. On the other hand, pyoveridin (yellowish - green) producer strains caused death of animals after 48hrs. On the contrary, injection of mice with extracts of non pigmented strains caused local inflammatory reactions rather than death. However, culture filtrates of isolates also showed inflammations upon injection of mice. It is evident from the results of this study that the pigment production is considered an important virulence factor in Pseudomonas aeruginosa.