EFFECT OF FERRIOXAMINE ON THE GROWTH OF RHIZOPUS

Zygomycosis, caused by Rhizopus spp., has recently been reported to oc cur in dialysis patients treated with desferrioxamine, suggesting a ro le of this drug in the pathogenesis of this infection. The hypothesis that ferrioxamine, the iron chelate of desferrioxamine, stimulates the growth of Rhizopus spp. has been brought forward. The growth rate of 2 x 10(5) spores of R. rhizopodiformis (isolated from a dialysis patie nt who died of zygomycosis while on desferrioxamine therapy) was studi ed in an iron-deficient medium (1) with human serum at increasing conc entrations and (2) with 40% human serum in the presence of ferrioxamin e at different concentrations. After grinding the mycelium, growth was measured by absorbance density at 450 nm. The results show that a con centration of 40% human serum inhibits the growth of R. rhizopodiformi s >50% and that, in the presence of serum, ferrioxamine causes a signi ficant growth stimulation at 24 h that persists at 48 h. In conclusion , ferrioxamine stimulates the growth of R. rhizopodiformis in vitro. T his probably plays a key role in the pathogenesis of desferrioxamine-r elated zygomycosis.