Use of CSP typing for genotyping of azole-resistant and -susceptible Aspergillus fumigatus isolates in Iran

Summary

Aspergillus fumigatus is the leading cause of mortality in severely immunocompromised individuals. Understanding pathogen dispersion and relatedness is essential for determining the epidemiology of nosocomial infections. Therefore, the aim of this study was to investigate the diversity and putative origins of clinical and environmental azole-susceptible and -resistant A. fumigatus isolates from Iran. Seventy-nine isolates, including 64 azole-susceptible and 15 azole-resistant isolates, were genotyped using the cell surface protein (CSP) gene. Seven distinct repeat types (r01, r02, r03, r04, r05, r06 and r07) and 11 different CSP variants (t01, t02, t03, t04A, t06A, t06B, t08, t10, t18A, t18B and t22) were observed. Interestingly t06B, t18A and t18B were exclusively present in azole-resistant isolates. The Simpson's index of diversity (D) was calculated at 0.78. Resistant isolates were genetically less diverse than azole-susceptible isolates. However, azole-resistant A. fumigatus without TR₃₄/L98H were more diverse than with TR₃₄/L98H. The limited CSP type diversity of the TR₃₄/L98H isolates versus azole- susceptible isolates suggests that repeated independent emergence of the TR₃₄/L98H mechanism is unlikely. It has been suggested that CSP types might have a common ancestor that developed locally and subsequently migrated worldwide.

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