Identification of Aspergillus species using internal transcribed spacer regions 1 and 2

Aspergillus species are the most frequent cause of invasive mold infections in immunocompromised patients, Although over 180 species are found within the genus, 3 species, Aspergillus flavus, A. fumigatus, and A. terreus, acc ount for most cases of invasive aspergillosis (ZA), with A. nidulans, A. ni ger, and A. ustus being rare causes of IA. The ability to distinguish betwe en the various clinically relevant Aspergillus species may have diagnostic value, as certain species are associated with higher mortality and increase d virulence and vary in their resistance to antifungal therapy, A method to identify Aspergillus at the species level and differentiate it from other true pathogenic and opportunistic molds was developed using the 18S and 28S rRNA genes for primer binding sites. The contiguous internal transcribed s pacer (ITS) region, ITS 1-5.8S-ITS 2, from referenced strains and clinical isolates of aspergilli and other fungi were amplified, sequenced, and compa red with non-reference strain sequences in GenBank. ITS amplicons from Aspe rgillus species ranged in size from 565 to 613 bp. Comparison of reference strains and GenBank sequences demonstrated that both ITS I and ITS 2 region s were needed for accurate identification of Aspergillus at the species lev el. Intraspecies variation among clinical isolates and reference strains wa s minimal. Sixteen other pathogenic molds demonstrated less than 89% simila rity with Aspergillus ITS 1 and 2 sequences, A blind study of 11 clinical i solates was performed, and each was correctly identified. Clinical applicat ion of this approach may allow for earlier diagnosis and selection of effec tive antifungal agents for patients with IA.