MICROSATELLITE MARKERS FOR TYPING ASPERGILLUS-FUMIGATUS ISOLATES

The use of microsatellites as highly polymorphic DMA markers for the t yping of isolates of Aspergillus fumigatus was investigated. Four CA r epeats were selected by screening an A. fumigatus DNA library,vith a ( CA),, oligonucleotide. Primers flanking these CA repeats were designed to amplify each locus. One primer of each pair was labeled with a flu orophore, and the PCR products were analyzed with an automatic sequenc er and the GeneScan software. For each primer set and for a given isol ate, one band was detected and was assigned to an allele because A. fu migatus is haploid, With 50 clinical isolates, 50 environmental isolat es, and 2 reference strains we obtained 12, 11, 10, and 23 different a lleles for the four CA microsatellites, respectively (discriminatory p ower, 0.994), The results were identical by whatever DNA extraction te chnique was used. Interestingly, no clustering between environmental a nd clinical isolates was observed, suggesting that every isolate is po tentially pathogenic. Microsatellite markers appear suitable for use i n large epidemiological studies of invasive aspergillosis.