MOLECULAR EPIDEMIOLOGIC-STUDY OF ASPERGILLUS-FUMIGATUS IN A BONE-MARROW TRANSPLANTATION UNIT BY PCR AMPLIFICATION OF RIBOSOMAL INTERGENIC SPACER SEQUENCES

We have developed a PCR-based method for the subspecific discriminatio n of Aspergillus fumigatus types by using two primers designed to ampl ify the intergenic spacer regions between ribosomal DNA transcription units. The method permitted the reproducible discrimination of 11 dist inct DNA types among a total of 119 isolates of A. fumigatus collected from patients and from the environment of a bone marrow transplantati on (BMT) unit over a three-year period. Ten DNA types of A. fumigatus were isolated from patients in the BMT unit; eight of these types were also found in the hospital environment, and six of these were present in the unit itself. Thirteen BMT patients developed infection with on e of three DNA types some months after these had first been found in t he environment of the unit. In other instances, the same DNA types of A. fumigatus were isolated from BMT patients that were later recovered from the environment of the unit. Several DNA types of A. fumigatus w ere found in the hospital environment over an 18-month period. Molecul ar typing of multiple isolates of A. fumigatus, obtained from postmort em tissue samples, shelved that one patient was infected with a single DNA type, but two others had up to three different DNA types. Our fin dings suggest that A. fumigatus infection in BMT recipients may be nos ocomial in origin and underline the need for careful environmental mon itoring of units in which high-risk patients are housed.