Genetic polymorphism of Aspergillus fumigatus in clinical samples from patients with invasive aspergillosis: Investigation using multiple typing methods

The genotypes of 52 strains of Aspergillus fumigatus isolated from 12 patie nts with invasive aspergillosis were investigated using three typing method s (random amplified polymorphic DNA, sequence-specific DNA polymorphism, an d microsatellite polymorphism) combined with multilocus enzyme electrophore sis. Isolates were from patients hospitalized in three different geographic areas (Lyon, France; Grenoble, France; and Milan, Italy). In each case, th e genetic polymorphism of several colonies (two to five) within the first r espiratory clinical sample was studied. For the 52 isolates tested, random amplified polymorphic DNA identified 8 different genotypes, sequence-specif ic DNA polymorphism identified 9 different types, and microsatellite polymo rphism identified 14 types. A combination of these results with multilocus enzyme electrophoresis study identified 25 different types within the sampl e studied. We identified 3 patients (of the 12 studied) who carried a singl e genotype; 6 patients were infected by two genotypes, 1 patient had four g enotypes, while the last patient had five. A combination of typing methods provided better discrimination than the use of a single method. Typing meth ods revealed a population structure within each geographical site, suggesti ng that the epidemiology of A. fumigatus should be considered separately fo r each of these geographic areas. This study demonstrates the usefulness of combining several typing methods in reaching an understanding of the epide miology of A. fumigatus and clarifies whether it is sufficient to type one isolate from each specimen to determine the strain involved in invasive asp ergillosis.