Clinical utility of antifungal susceptibility testing in patients with fungal rhinosinusitis.

Purpose: To determine the association between antifungal susceptibility test (AFST) results and in vivo therapeutic response in Indian patients with fungal rhinosinusitis.

Methods: The clinicoradiological, fungal culture, AFST, histopathology results and outcomes of 48 patients with fungal rhinosinusitis seen between 20132015 were analysed. Minimum inhibitory concentration (MIC) determination was performed for amphotericin B, itraconazole, voriconazole and posaconazole.

Results: Forty patients had invasive and 8 had non-invasive fungal sinusitis. Rhizopus and Aspergillus species which comprised 46.9% each of isolates were mostly associated with acute invasive fungal rhinosinusitis and chronic granulomatous fungal rhinosinusitis respectively. All patients with non-invasive fungal rhinosinusitis had Aspergillus isolates. The Geometric Mean (GM) MIC for R. arrhizus of amphotericin B and posaconazole was 0.51 mcg/mL and 3.08 mcg/mL respectively and for A. flavus species for amphotericin B and voriconazole values were 1.41mcg/mL and 0.35 mcg/mL respectively. In patients with Aspergillus infections, while there was no association of MICs for azoles and outcome (p = 1), a strong association was noted between azole therapy and a good outcome (p = 0.003). In patients with Rhizopus infections, no association was found between MICs for amphotericin B and outcome (p = 1) and because of therapeutic complications, no association was found between amphotericin B therapy and outcome (p = 1).

Conclusion: No significant association exists between in vitro (AFST) and in vivo responses despite low GM MICs for the drugs used in Aspergillus and Rhizopus infections. Therapeutic complications following conventional amphotericin B therapy confounds analysis. Clinical responses suggest that azoles are the drug of choice for Aspergillus infections.