Rapid quantification of bioaerosols containing L. pneumophila by Coriolis® μ air sampler and chemiluminescence antibody microarrays

Bioaerosols containing Legionella may cause Legionnairesʹ disease and Pontiac fever in humans. Legionella occur in natural and artificial water systems and are ubiquitous therein. Infection of humans is only caused by inhaling bioaerosols containing these bacteria. Those bioaerosols are, for example, generated by hot water systems, air-conditioning systems, while showering or by cooling towers and can be a threat for the health of people in surrounding areas. Rapid detection methods are essential to combine sampling of bioaerosols with multiplexed analysis for specification and quantification of Legionella species in air. The rapid quantification of bacteria with flow-through chemiluminescence microarrays was established in our laboratories and is applied for bioaerosol analysis in this work. Viable cells of E. coli and heat-inactivated L. pneumophila (serogroup 1) have been utilized as model organisms. The aerosol was generated by a nebulizer which is commonly used in the therapy of respiratory diseases. It was found that this nebulizer is suitable for the generation of bioaerosols with defined bacteria concentrations. The cyclone separator Coriolis® μ was applied for the collection of airborne microorganisms; a device specially designed for bioaerosol sampling with a high sampling rate. As reference, an impinger (type AGI-30) was used. Quantification was accomplished by flow cytometry and a flow-through microarray chip reader applying antibody microarrays for chemiluminescence sandwich immunoassays. The efficiency of bioaerosol sampling with Coriolis® μ was examined by nebulizing living E. coli in a chamber and quantifying them with flow cytometry after sampling. A recovery of 34±10% was found with a high reproducibility between 5×105 and 2×107 cells/mL. The impinger AGI-30 was compared to the cyclone separator Coriolis® μ by quantification of collected L. pneumophila with microarray sandwich immunoassay analysis. Similar recoveries were determined for both samplers. However, the detection limit with Coriolis® μ was lower by a factor of 100 due to the higher sampling rate. Different Legionella species might be rapidly quantified down to 4×103 cells/m3, which fulfills the requirements for bioaerosol measurements in the environment and in the interior.