Assessing Bioaerosol Contamination in HEPA-Filtered Rooms Housing Patients with Hematologic Malignancy

Background: Nosocomial invasive aspergillosis is associated with high morbidity/mortality in patients with hematologic malignancy. HEPA-filtered rooms under positive air flow are known to decrease risk/concentration of bioaerosol contamination with Aspergillus (Asp) species. Various methods are available for evaluating patient room air contamination. Hand-held particle counters and spore traps were used to evaluate bioaerosol levels. Objective: To evaluate particle counters as effective screening tools for air quality investigations involving Asp/Penicillium (Pen) spp. in immunocompromised patient rooms. Methods: From April–October 2004, 209 concurrent spore trap and particle count measurements were taken from 72 HEPA-filtered rooms housing patients with hematologic malignancy in a tertiary cancer center. Samples were obtained from 104 and 105 events within 30 minutes of and prior to terminal decontamination of rooms, respectively. Particle counters differentiated between 0.3, 0.5, 1.0, 2.0 and 5.0 µm sized particles. Results: Seventy-five indoor trap samples were contaminated with Asp/Pen-like spores. Asp/Pen spores were detected in 38% of cleaned and 34% of uncleaned room samples. Spore median density from cleaned rooms was 20 spores/m3 of air, compared with 23.5 from uncleaned rooms (P = .74). Spearman correlation test showed a significant link between total spores and all particle sizes (P < .0001). Analyses showed spore trap-contaminated density significantly correlated with the particle sizes tested. Conclusion: Based on statistical analysis comparing particle count and trap results collected concurrently, the particle counter does not provide enough differential data to determine risk of Asp exposure. Particle counter results do provide enough information to merit additional sampling.