Novel Assay Discriminates Several Aspergillus Species

Invasive aspergillosis (IA) is mainly caused by Aspergillus fumigatus and when diagnosis is made early and first line therapy with voriconazole is initiated promptly, a relatively low mortality is observed.

However, over the past decade, azole resistance has emerged worldwide and poses a threat as IA with azole-resistant A. fumigatus is associated with high mortality of 88%. As in vitro drug susceptibility testing is often not feasible, as cultures remain negative or sibling species fail to sporulate, molecular techniques are an option.

Scientists at the Erasmus University Medical Center used a multiplex real-time polymerase chain reaction (PCR) assay to detect Aspergillus species and mutations in the Cyp51A gene of A. fumigatus. They performed the assay on cultured sibling strains obtained from two clinical cases. In addition to assess the precision of the assay, a larger set of strains was tested: six A. lentulus strains and 12 A. felis species complex strains (five A. felis, four A. parafelis and three A. pseudofelis) were obtained and the three control A. fumigatus strains (one WT, one TR34/L98H mutant, one TR46/T289A/Y121F mutant).

The AsperGenius multiplex real-time PCR assay was performed on strains obtained from lung biopsy in one case and from pleural mass biopsy the second case. Both strains gave positive signals for the Aspergillus species and Aspergillus section Fumigati. The AsperGenius resistance PCR did not detect the TR34 target in A. lentulus and A. felis in contrast to A. fumigatus. Melting peaks for L98H and Y121F markers differed and those of the Y121F marker were particularly suitable to discriminate the three species. The authors concluded that the assay can be used to rapidly discriminate A. fumigatus, A. lentulus and A. felis. The study was published in the March 2017 issue of the journal Diagnostic Microbiology and Infectious Disease.