Prevalence of Aspergillus Section Nigri Complex Species Isolated from Clinical Specimens in Kuwait and Their Susceptibility to Antifungal Drugs

Aspergillus spp. are common environmental molds worldwide and mostly cause infections in immunocompromised individuals. We have previously shown that black aspergilli (Aspergillus section Nigri) isolates are the most common aspergilli in indoor and outdoor hospital environments in Kuwait. This study reports on the relative prevalence of different Aspergillus section Nigri complex species among clinical isolates and their susceptibility to antifungal drugs. Black aspergilli isolated from clinical (n = 34) and environmental (n = 2) sources were studied. The isolates were initially identified as Aspergillus section Nigri complex members based on morphological characteristics. Species-specific identification was carried out by PCR-sequencing of the β-tubulin gene fragment and sequence comparisons with the GenBank database. The phylogenetic analysis was performed by using the Maximum Likelihood method in MEGA (version 11) software. Antifungal susceptibility testing was performed by Etest. The phylogenetic analysis based on β-tubulin gene sequences identified only three species: A. niger sensu stricto (A. niger) (n = 26), A. tubingensis (n = 7), and A. luchuensis (n = 1) among 34 clinical Aspergillus section Nigri isolates in Kuwait. All seven otomycoses cases were due to A. niger. The two environmental isolates were identified as A. niger and A. tubingensis. All isolates appeared susceptible to all five (amphotericin B, itraconazole, voriconazole, posaconazole, and caspofungin) antifungal drugs tested. In conclusion, our study shows that A. niger predominates among phenotypically identified clinical isolates of the Aspergillus section Nigri complex, and that A. niger is also the main agent in otomycosis cases in Kuwait. The detection of only three species within the Aspergillus section Nigri complex in Kuwait could be due to the limited number (n = 34) of clinical isolates analyzed in this study.