Alterations in oral microflora and pathogenesis of acute oral infections during remission-induction therapy in patients with acute myeloid leukaemia.

To investigate changes in the aerobic and facultatively anaerobic oral microflora during remission-induction chemotherapy in patients with acute myeloid leukaemia, 10 consecutive patients were studied during a period of 28 days. During antineoplastic treatment, the concentration of microorganisms in saliva doubled from day 0 to day 2, presumably as a result of a concurrent 64% decrease in the salivary flow rate. No changes in the relative proportion of individual microorganisms or acquisition of new microorganisms occurred during antineoplastic treatment. During antibacterial treatment, which was subsequently initiated in all patients, a 100-fold decline occurred in the median salivary concentration of microorganisms within the first 7 days. During this period, members of the normal flora became undetectable in 5 patients, and Enterobacteriaceae, Enterococcus faecalis or Candida spp. became parts of the quantitatively predominant oral microflora in 7 patients. Apart from Candida spp., these potentially pathogenic microorganisms were acquired only after the initiation of the antibacterial treatment. After termination of the antibacterial treatment, the median concentration of microorganisms increased again to the original level and normal flora became reestablished within a period of 8 days. Clinically, 10/20 acute oral infections emerged before day 8, i.e. within the period with increased concentrations of microorganisms in saliva. Specifically, the clinical diagnosis of acute oral candidiasis was associated with a rise in the concentration of Candida spp. above a critical value of 1,000 CFU/ml. Herpes simplex virus (HSV) type 1 was detected in 4/9 HSV-seropositive patients on days 14 and 21, and HSV-1 was in all 4 cases isolated simultaneously with the emergence of an intraoral ulcer. The results suggest that chemotherapy-induced xerostomia plays a significant role in the pathogenesis of acute oral infections and transmission of potentially pathogenic microorganisms is of importance mainly after initiated antibiotic treatment in these patients.