Incidence and molecular epidemiology of Pseudomonas aeruginosa bacteremias in patients with acute leukemia: analysis by pulsed-field gel electrophoresis.

The incidence and molecular epidemiology of P. aeruginosa bacteremias, were monitored in patients with acute leukemia to define mechanisms of possible nosocomial transmission. From September 1997 to March 2001 febrile episodes were examined and blood isolates of P. aeruginosa were studied employing Pulsed-Field gel Electrophoresis (PFGE). Evaluation of DNA correlation was performed according to Tenover criteria. A total of 309 febrile episodes occurred in 187 patients. Of 139 organisms isolated in 116 bacteremias, 48% were gram negative bacilli (GNB); P. aeruginosa bacteremias were recorded in 34 (51%) of GNB sepsis. Evaluation of DNA correlation showed 2 related in 1997, 7 related in 1998, 10 related in 1999, 6 related in 2000-2001 (mainly closely and possibly related); therefore isolates closely related among themselves were also possibly related with other strains. About 60% of patients with related strains were hospitalized in the same room or in different rooms but became infected in the same period. Our data suggest a horizontal spread among the patients even if other sources were possible. The study assessed the usefulness of PFGE in bacteriological epidemiology.