Correlation between MIC of econazole nitrate and clinical response in otomycosis

Otomycosis is a common superficial fungal infection in otolaryngology, with an increasing incidence that severely affects patients' quality of life. There are regional variations in the distribution of dominant pathogenic fungi. This study was designed to determine the distribution of pathogenic fungi causing otomycosis in the local region, evaluate the in vitro susceptibility of predominant strains to econazole nitrate (a commonly used antifungal agent), and preliminarily investigate the correlation between drug susceptibility and clinical treatment duration, so as to fill the gap in regional research in this field.

Ear secretion specimens from 196 patients with otomycosis were collected at the Department of Otolaryngology of Zhejiang Provincial Hospital of Chinese Medicine from December 2022 to December 2024 for isolation, culture, and identification of pathogens, along with drug sensitivity testing. Clinical data from 149 patients with complete follow-up records were combined to analyze the correlation between MIC and treatment duration.

Among the 196 patients, Aspergillus was the predominant pathogen, accounting for 85.10% of which Aspergillus terreus (A. terreus) was the dominant species, accounting for 68.88%. Significant interspecies differences in MIC of econazole nitrate were observed among different Aspergillus strains (P < 0.05). The clinical course in patients infected with A. terreus (3-90 days) and Aspergillus niger (A. niger) (7-60 days) was significantly positively correlated with their corresponding MIC (0.2-12.5 μg/mL and 0.59-37.5 μg/mL, respectively).

The pathogenic spectrum of otomycosis in this region is unique, with A. terreus as the main pathogen. There are interspecies differences in the in vitro sensitivity of Aspergillus to econazole nitrate, and the elevated MIC values were significantly associated with prolonged time to clinical improvement in patients infected with A. terreus and A. niger.