Susceptibility testing of filamentous fungi to amphotericin B by a rapid radiometric method

A rapid, radiometric method was developed to determine the susceptibility of filamentous fungi to amphotericin B. The rapid, radiometric method depended on measurement of the inhibition of 14CO2 production in the presence of amphotericin B. Thirty isolates of filamentous fungi were tested by the rapid, radiometric method and a reference agar dilution method. There was 93% agreement between the two methods when an 80% or greater decrease in CO2 production was used to calculate the minimal inhibitory concentration with the rapid, radiometric method. Minimal inhibitory concentrations, based on 80% decrease of CO2 production, were achieved within 24 h of incubation with all of the fungi tested.