Changes in the incidence and etiological patterns of bacteremia associatedwith acute leukemia over a 25-year period

During the 25-year period from 1972-1996, 360 episodes of bacteremia occurr ed in 248 (45 %) of a total of 548 patients with acute leukemia on our hema tology ward, with the rate of occurrence remaining almost unchanged. Patien ts with acute nonlymphocytic leukemia, however, had a significant decrease in the incidence of bacteremia during the last 5-year period. Grant-negativ e bacilli decreased in relative frequency from 64% for the first 15-year pe riod to 40 % for the last 5-year period, whereas gram-positive cocci increa sed from 24% to 51%. Escherichia coli and Enterobacter cloacae somewhat dec reased in frequency, whereas coagulase-negative staphylococci and streptoco cci had considerable increases. In contrast, Pseudomonas aeruginosa was Iso lated at a relatively constant frequency, forming one of the top two pathog ens throughout the study period. Despite the shift toward gram-positive coc ci, therefore, P. aeruginosa remains a key organism in considering the init ial empiric antibiotic regimen and infection prevention during neutropenia.