[Pseudomonas aeruginosa and cystic fibrosis: first colonization to chronic infection].

Pseudomonas aeruginosa (Pa) is the most common virulent respiratory pathogen in cystic fibrosis and is characterized by an important capacity of adaptation, adherence and communication. The factors of virulence of Pa play a major part in adherence with the respiratory epithelial cells and in occurrence of infectious episodes. The factors responsible for the transition of first Pa acquisition to the chronic infection are not elucidated yet. The system of secretion of type III and the quorum sensing (QS) play an important role. The QS would intervene in the maturation of the biofilm of Pa, responsible for the "mucoid" phenotype of Pa, associated to a degradation of the respiratory function. We made a retrospective study on the period 1984-2005 within the Center of Cystic fibrosis of Caen allow to determine the percentage of firstly-colonized and chronic infected patients with Pa according to age. At 6 months of life, 11% of the infants were colonized with Pa reaching 48% to 7 years and 85% at the 18 years age. The percentage of chronic children carrying Pa was 0% at 1 year, 11% at 4 years, 44% at 12 years and 74% at 18 years according to the method of Kaplan-Meier. Comparing the period 1984-1994 with that of 1995-2005, the firstly-colonization and the chronic carrying of Pa occurred earlier and significantly during the second period. The current objective, beside the respiratory care, comprises the maintenance of an optimal nutritional statute and, waiting for an effective vaccine, the development of new therapeutic targets in order to attenuate the virulence of the stocks of Pa and as much as possible to delay the age of firstly-colonization and the age of chronic colonization with mucoid Pa.