[The use of molecular biology in the modeling of Pseudomonas aeruginosa strains recovered from nosocomial infections].

Different methods of molecular typing (ribotyping, genomic DNA RFLP and RAPD) were tested on Pseudomonas aeruginosa strains isolated in Polish hospitals in order to elaborate a reliable typing scheme for epidemiological investigations. The combined RAPD analysis with the use of two different primers, RAPD-4 and RAPD-7, was found to have the highest discriminatory power which considering also the easiness and low time-consumption has suggested its high usefulness in studies of outbreaks caused by P. aeruginosa. Ribotyping was shown to be the least discriminatory, however, especially with the use of the PvuII restriction enzyme, this method can be very useful in revealing the genetic structure of P. aeruginosa populations persisting in hospital environments over longer periods. Clonal relations within populations of strains isolated in four different hospitals were revealed. In two of the hospitals P. aeruginosa populations demonstrated a very high diversity which suggested that infections had been caused by strains of different origins, probably introduced from other environments. P. aeruginosa strains from two remaining hospitals were found to form some clonally related clusters what revealed that in these hospitals epidemic strains of this microorganism have been circulating for prolonged periods and infecting predisposed patients.