Aerobiocontamination of moulds: epidemiology and influence of on invasive fungal infection in a tertiary care hospital

A. Imhof, M. Spiess Pangrazzi, C. Ruef (Zurich, CH)

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Objectives: Nosocomial aspergillosis, is thought to be caused primarily by Aspergillus organisms in the air. We conducted this study to asses the role of mold concentrations of ambient air and the impact of various weather conditions on mold concentration inside the hospital. Methods: Air sampling was conducted in 18 areas (6 outdoors) of our hospital (1000 beds, tertiary care) two times a week. The weather conditions were monitored at the day of sampling. Surveillance of Nosocomial Aspergillus infection was conducted by reviewing the records of all hospitalised neutropenic patients from 4/2004 to 10/2004. Results: During the study period a total of 614 air samples were available of which 514 (84%) revealed at least one fungal colony. Aspergillus sp. (AS) were isolated most frequently (mean 12 cfu/ m3 of air), followed by Zygomycetes (zyg) (0.6 cfu/m3) and other molds (3 cfu/m3). A. niger (mean 3 vs. 2 cfu/m3), A. flavus (1.5 vs. 0.3 cfu/m3) and A. terreus (0.2 vs. 0.01 cfu/m3) were found more frequently inside the hospital, whereas A. fumigatus was more common outdoors (10 vs. 7 cfu/m3). During a short time of renovation activity, colony counts of AS (OR: 2.93, 95% CI 1.585.43) and zyg (OR: 4.08, 95% CI 2.297.29) increased significantly. Fungal growth was highest at 1922C (42% of isolates), in particular AS (OR: 1.62, CI 1.042.54) and zyg (OR: 3.53, CI 1.548.09). On rainy days, there were significantly higher chances of growth of AS (17 vs. 8 cfu/m3, p = 0.003) and zyg (0.5 vs. 1, p = 0.024) than during other weather conditions. High risk patient with leukemia or bone marrow transplantation were hospitalized during the study period. The number of neutropenic days was 635 with a mean of 31.6 days. Invasive mold infection was diagnosed In 10 patients (53%), and one of them died due to this infection. Conclusion: Our observations show relatively high concentrations of A. fumigatus in all environments, with a significantly increased amount of AS spores on rainy days. Our investigation suggests that exposure of high risk patients to high concentration of spores is a continuous risk for invasive fungal infections.

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    • ECCMID 15th (2005)