Molecular epidemiology of nosocomial invasive aspergillosis

Moderately repeated DNA sequences were used to fingerprint strains ofAspergillusfumigatus isolated from patients with invasive aspergillosis and their hospital environment. Most strains sampled from the environ-ment displayed different Southern blot hybridization patterns. A temporal survey of air contaminants showed that some strains can persist in the same environment for at least 6 months. Patients with invasive aspergillosis were infected by a single strain. In two patients, a nosocomial origin of infection was suggested. Invasive aspergillosis is a very severe nosocomial human disease associated with heavy immunosuppressive treatments (6, 25). Aspergillus fumigatus is the species of Aspergillus most frequently responsible for this life-threatening disease. High concentrations of the conidia of A. fumigatus associated with contaminated ventilation systems or hospital building works have been correlated with aspergillosis outbreaks (2, 3, 14, 16, 21). Until now, airborne transmission suggested by this circum-stancial evidence has not been demonstrated in the absence of an efficient typing system for A. fumigatus (25)