An Innovative Method for Determining Amphotericin B Susceptibility in Leishmania infantum Isolates: A Modified Disk...

Due to the potential development of resistance to amphotericin B (AmpB), a widely used drug in leishmaniasis treatment, monitoring drug susceptibility has become increasingly important. This study aimed to evaluate the applicability of a modified version of the disk elution method-originally developed for detecting colistin resistance in bacteria-for the first time in determining AmpB susceptibility in Leishmania infantum (L. infantum) isolates.

The minimum parasiticidal concentration (MPC) of AmpB against L. infantum was determined using the broth microdilution method. Additionally, the disk elution method was modified for use with Leishmania. Disks impregnated with AmpB were placed into indicator-containing culture tubes, and parasite viability was visually assessed based on a color shift from purple to yellow. The MPC was recorded as the lowest concentration at which complete parasite death occurred.

In both methods, AmpB exhibited complete parasiticidal activity at concentrations of ≥0.5 μg/mL. Statistical comparison using the Mann-Whitney U test revealed no significant difference between the two methods at 48 and 72 hours (p>0.05).

The findings indicate that the modified disk elution method provides comparable reliability to the standard broth microdilution technique. Its low cost, ease of implementation, and visual interpretability make it a promising alternative for drug susceptibility testing, especially in resource-limited laboratories or field settings. Moreover, the use of commercially prepared AmpB disks could facilitate standardization and broader adoption. This study introduces an innovative approach that may simplify routine drug susceptibility screening in Leishmania isolates and support wider surveillance of anti-leishmanial resistance.