Pseudoepidemic of aspergillosis after development of pulmonary infiltrates in a group of bone marrow transplant patients

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Abstract
During February and March 1985, seven patients in the pediatric bone marrow transplant unit (PBMTU) of a 350-bed cancer hospital developed pulmonary infiltrates. Five of the patients had Aspergillus spp. isolated from the respiratory tract, and two of these patients had histologic evidence of aspergillosis. Between 26 February and 22 April, Aspergillus spp. were isolated in a total of 70 cultures from 39 hospitalized patients. Of the 70 cultures, 14 (group 1) were from respiratory specimens of PBMTU patients with pulmonary infiltrates and were submitted to the laboratory intermittently over the 56-day period. However, of the other 56 Aspergillus-positive cultures (group 2), 41 (73%) were submitted on six days during this period (P < 0.001, chi-square goodness of fit), including 8 blood cultures submitted on one day. When Aspergillus sp. was recovered from group 1 cultures early during this period, the isolates were stored in the culture-processing room. Aspergillus isolates were not handled in a biological safety cabinet, and blood cultures were done by using a system which requires opening of an evacuated bottle to room air. The presence of stored Aspergillus isolates was associated with a markedly elevated concentration of airborne fungi in the culture-processing room. After removal of the stored Aspergillus isolates from the culture-processing room, the concentration of airborne fungi returned to background level and there were no further Aspergillus-positive cultures. These findings suggested that group 2 cultures had been contaminated by stored Aspergillus isolates. No evidence for a common source of infection was found in the PBMTU with pulmonary infiltrates.