Colistin and trimethoprim-sulfamethoxazole for the prevention of infection in patients with acute non-lymphocytic leukaemia. Decrease in the emergence of resistant bacteria.

In a previous study we demonstrated that trimethoprim-sulfamethoxazole decreases the prevalence of infection in patients with severe granulocytopenia. However, treatment was accompanied by a relatively high incidence of multiresistant microorganisms. We therefore conducted this study to determine whether the addition of colistin to the trimethoprim-sulfamethoxazole regimen prevents the emergence of these resistant bacteria. Thirty consecutive adult patients with acute non-lymphocytic leukaemia received trimethoprim-sulfamethoxazole plus colistin p.o. prophylactically. The results of this study were compared with the results of our previously published controlled study. Trimethoprim-sulfamethoxazole plus colistin was as effective as trimethoprim-sulfamethoxazole in preventing infection. However, the addition of colistin significantly reduced the acquisition of and infection by gram-negative bacilli which were resistant to trimethoprim-sulfamethoxazole. Only two patients were colonized with resistant strains, and no infections with these strains were observed. We have concluded that patients with acute non-lymphocytic leukaemia should receive a combination of trimethoprim-sulfamethoxazole plus colistin prophylactically during remission induction treatment.