Bacteremia complicating acute leukemia with special reference to its incidence and changing etiological patterns

Over the 15-yr period, 1972-1986, 194 episodes of bacteremia occurred in 132 patients with acute leukemia at the Third Department of Medicine, Kanazawa University Hospital, giving an incidence of 478 episodes per 1,000 hospital admissions. This incidence was at least twice as high as that in patients with chronic leukemia, malignant lymphoma, multiple myeloma or aplastic anemia, and about 40-fold higher than that in patients with all other internal diseases. The rate of occurrence of bacteremia, whether unimicrobial or polymicrobial, remained almost unchanged throughout the study period. The frequency of gram-negative bacilli decreased significantly, however, from 81% of the total isolates for the first 10-yr period to 50% for the second 5-yr period. Escherichia coli and Klebsiella pneumoniae were isolated in markedly decreasing frequency, but Pseudomonas aeruginosa and Enterobacter cloacae in relatively constant frequency. The majority of P. aeruginosa isolates belonged to a limited number of O-antigen groups, suggesting the possibility of nosocomial infection. On the other hand, the frequency of gram-positive cocci increased from 9 to 36%. Staphylococcus epidermidis, Enterococcus species, and Staphylococcus aureus emerged as important pathogens. Such a change in the spectrum of organisms was considered to coincide with the common use of the so-called second- and third-generation cephalosporins and central venous catheters. It is thus suggested that vancomycin be added to empiric antibiotic therapy, especially when gram-positive infections are clinically or microbiologically suspected, and that reducing the acquisition of P. aeruginosa from the hospital environment remains a priority in infection prevention.