Value of environmental sampling and molecular typing of aspergilli to assess nosocomial sources of aspergillosis.

In order to investigate the risk of hospital-acquired infections due to environmental Aspergillus, air sampling outside and inside the bone marrow transplantation (BMT) clinic of the University Hospital, Essen, Germany, was performed prospectively for one year. The spore concentration in the air was matched with meteorological data. Two BMT-patients, who were hospitalized during the sampling period, suffered from aspergillosis after discharge. The patients' isolates obtained at re-admission were compared with environmental isolates obtained during the first hospitalization. Analysis by randomly amplified polymorphic DNA showed that the two BMT-patients were infected with Aspergillus strains that were different from the environmental strains. It is concluded that it is not possible to predict the environmental Aspergillus spore concentration by analysis of meteorological data. Since the concentration of specific strains may fluctuate rapidly, a hospital-acquired Aspergillus infection cannot be excluded even if the infecting strain is not found in the hospital environment.