Evaluation of sampling techniques for detection and quantification of airborne legionellae at biological aeration basins and shower rooms

Inhalation of legionellae aerosolized from biological aeration basins (AB) and shower rooms (SR) has been linked to severe pneumonia and Pontiac fever. However, comprehensive evaluations at these facilities using various bioaerosol sampling techniques are lacking. This study assessed two agar-based (Andersen one-stage sampler and MAS-100/A), three liquid-based (BioSampler, AGI-30 and MAS-100/L) and two filter-based sampling methods (cassette/polycarbonate filter and IOM/gelatin filter) at AB. The BioSampler obtained the highest positive rate of culturable legionellae (8–50%) (P<0.05). As for collecting total and viable legionellae, the IOM consistently showed the highest efficiencies regardless of sampling time (30–270 min). When assessing the cassette, BioSampler and AGI-30 at SR, the cassette was more efficient in collecting total and viable legionellae (P<0.05), whereas only the BioSampler and AGI-30 recovered culturable legionellae. The viability percentages (calculated as viable cell counts to total cell counts, 12–77%) were not significantly different between the samplers regardless of sampling location and sampling time (P>0.05). Overall, the IOM and cassette performed better for collecting total and viable legionellae, and culturable legionellae may be detected more frequently by the BioSampler at AB and SR.