Particle counting and microbiological air sampling: results of the simultaneous use of both procedures in different types of hospital rooms

Introduction In order to assess the relationship between the concentrations of airborne fungi and particles, particle counting was combined with fungal air sampling in several rooms of a hospital. Methods Concentrations of ≥0.5 μm particles (P05) and ≥1 μm particles (P1) were measured using a particle counter; fungal air sampling was performed with volumetric air samplers, which impacted air on Rodac plates with Sabouraud chloramphenicol agar. Particle counts were categorised according to ISO 14644-1 standard cut-off points; their association with fungal detection was assessed with Fisher's exact test. Results Forty-two simultaneous samplings were carried out: 24 in operating rooms, 13 in rooms for burns or haematology patients, 3 in pharmacy clean rooms, and two in other procedure rooms. Filamentous fungi were recovered in 5 samples, which also had higher particle counts. No fungi were detected in 12 samplings with both P05 and P1 concentrations below the maximum for class 6 clean rooms; 4 of 7 samplings with both concentrations within the range for class 8 clean rooms were positive for fungi. The association between fungal detection and higher particle counts was statistically significant, both for P05 (p = .004) and P1 (p = .003). There was a partial overlap between the concentrations of particles of samplings which were positive or negative for fungi. Conclusions There is a relationship between the concentrations of P05 and P1 and airborne fungi in hospital rooms. When both P05 and P1 concentrations are below the maximum for class 6 clean rooms, a negative fungal detection can be predicted.