P047 Comparative evaluation of disc diffusion and E-test with broth micro-dilution in susceptibility testing of amphotericin B, posaconazole, isuvuconazole, itraconazole against Rhizopus isolates of post COVID mucormycosis

Abstract

Poster session 1, September 21, 2022, 12:30 PM - 1:30 PMObjectivesTo investigate and compare susceptibility pattern of Rhizopus isolates in post-COVID mucormycosis by disc diffusion (DD), E-test, and broth micro-dilution for amphotericin B, posaconazole. DD and BMD for isavuconazole and itraconazole.MethodsAll the isolates were identified by MALDI-ToF (Vitek MS). A total of 72 isolates of R. oryzae complex and 48 isolates of R. microsporus complex were selected. AFS by DD and E-test was done on non-supplemented Mueller Hinton Agar (MHA) and was compared with the Clinical Laboratory Standard Institute (CLSI M 38 A2) broth micro-dilution (BMD) method of AFS.ResultsThe disk diffusion method for amphotericin B showed 91.6% agreement while E-test showed 97.2% agreement with broth micro-dilution. Disk diffusion method for posaconazole showed 93% agreement while E-test showed 97.2% agreement with broth micro-dilution. Disk diffusion method for ITZ and ISC showed 94.4% and 100% agreement respectively with broth micro-dilution.ConclusionCLSI method of DD promises to be an easier, reproducible, and cost-effective method of susceptibility testing, but this method must be interpreted with caution in the case of amphotericin B susceptibility testing. E-test correlates better than DD with BMD.