Relationship Between Airborne Particulate Counts and Fungal Aerobiocontamination in a Tertiary-Care Pediatric Hospital


Author address: 

CHU Sainte-Justine, Montreal, QC, Canada


Background: Air quality is of the utmost importance in hospital settings to prevent the acquisition of infection by inhalation of fungal conidia, especially in units where immunocompromised or critically ill patients are treated. Many outbreaks of nosocomial aspergillosis were linked to contaminated ventilation systems. However, there is no well established correlation between particulate counts and the presence of fungal conidia in air samples. This study aims to determine the relationship between particulate count and the presence of fungal spores. Methods: We conducted a single-center retrospective study comparing particulate counts with air fungal cultures (per m3) obtained from air sampling in HEPA-filtered patient rooms on selected units of our institution. Three thresholds were selected to evaluate correlation with a positive culture: 3 000, 10 000 and 20 000. Results: Between March 2009 and August 2010, 254 air samples were obtained. Among those, 159 (62.6%) samples were positive by fungal culture. The most frequently isolated organisms were Penicillium sp. (25%) and Aspergillus sp. (17%). Aspergillus sp. was isolated from two rooms harboring less than 100 particulates/m3. Median particulate count was 3 787 (IQR=7 256). A particulate count greater than 20 000 was associated with a positive air culture (OR=6.7; 95%CI 1.5-29.3; p=0.012). However, of the 232 samples with a particulate count under 20 000, 152 (65.5%) were found to have positive cultures. A one log increase in particulate count was associated with a 55% increase in the odds of finding a positive fungal culture. ROC analysis of particulate count log resulted in AUC of 0.58. Conclusion: A particulate count greater than 20 000 is significantly associated with an increased risk of fungal aerobiocontamination. However, a particulate count under 20 000 does not exclude fungal aerobiocontamination. Particulate count does not accurately predict presence of fungal conidia. Therefore, air culture should be considered in areas where immunocompromised patients are hospitalized.

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ID Week 2012
    • IDWeek 2012