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Characterization of aerosols containing Legionella generated upon nebulization

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ABSTRACT

Legionella pneumophila is, by far, the species most frequently associated with Legionnaires’ disease (LD). Human infection occurs almost exclusively by aerosol inhalation which places the bacteria in juxtaposition with alveolar macrophages. LD risk management is based on controlling water quality by applying standardized procedures. However, to gain a better understanding of the real risk of exposure, there is a need (i) to investigate under which conditions Legionella may be aerosolized and (ii) to quantify bacterial deposition into the respiratory tract upon nebulization. In this study, we used an original experimental set-up that enables the generation of aerosol particles containing L. pneumophila under various conditions. Using flow cytometry in combination with qPCR and culture, we determined (i) the size of the aerosols and (ii) the concentration of viable Legionella forms that may reach the thoracic region. We determined that the 0.26–2.5 μm aerosol size range represents 7% of initial bacterial suspension. Among the viable forms, 0.7% of initial viable bacterial suspension may reach the pulmonary alveoli. In conclusion, these deposition profiles can be used to standardize the size of inoculum injected in any type of respiratory tract model to obtain new insights into the dose response for LD.

No MeSH data available.


Typical cumulative distribution of airborne droplets characterized by a low-pressure impactor (DLPI).NaF quantification by an electrochemical method (expressed in % of mass reaching each stage of the DLPI, i.e., in % of total mass of NaF aerosolized). Legionella quantification by qPCR (expressed in % of genetic units reaching each stage of the DLPI, i.e., in % of total airborne Legionella). Particles larger than 10 μm were not plotted.
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f4: Typical cumulative distribution of airborne droplets characterized by a low-pressure impactor (DLPI).NaF quantification by an electrochemical method (expressed in % of mass reaching each stage of the DLPI, i.e., in % of total mass of NaF aerosolized). Legionella quantification by qPCR (expressed in % of genetic units reaching each stage of the DLPI, i.e., in % of total airborne Legionella). Particles larger than 10 μm were not plotted.

Mentions: To determine whether sodium fluoride (NaF) and Legionella nebulization generate distinctive aerosols, they were compared with respect to cumulative distribution (NaF cumulative mass distribution versus Legionella cumulative distribution in % of genomic units). Figure 4 shows aerodynamic diameters, which, for unit density spheres such as water droplets, are the same as physical diameters.


Characterization of aerosols containing Legionella generated upon nebulization
Typical cumulative distribution of airborne droplets characterized by a low-pressure impactor (DLPI).NaF quantification by an electrochemical method (expressed in % of mass reaching each stage of the DLPI, i.e., in % of total mass of NaF aerosolized). Legionella quantification by qPCR (expressed in % of genetic units reaching each stage of the DLPI, i.e., in % of total airborne Legionella). Particles larger than 10 μm were not plotted.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037422&req=5

f4: Typical cumulative distribution of airborne droplets characterized by a low-pressure impactor (DLPI).NaF quantification by an electrochemical method (expressed in % of mass reaching each stage of the DLPI, i.e., in % of total mass of NaF aerosolized). Legionella quantification by qPCR (expressed in % of genetic units reaching each stage of the DLPI, i.e., in % of total airborne Legionella). Particles larger than 10 μm were not plotted.
Mentions: To determine whether sodium fluoride (NaF) and Legionella nebulization generate distinctive aerosols, they were compared with respect to cumulative distribution (NaF cumulative mass distribution versus Legionella cumulative distribution in % of genomic units). Figure 4 shows aerodynamic diameters, which, for unit density spheres such as water droplets, are the same as physical diameters.

View Article: PubMed Central - PubMed

ABSTRACT

Legionella pneumophila is, by far, the species most frequently associated with Legionnaires’ disease (LD). Human infection occurs almost exclusively by aerosol inhalation which places the bacteria in juxtaposition with alveolar macrophages. LD risk management is based on controlling water quality by applying standardized procedures. However, to gain a better understanding of the real risk of exposure, there is a need (i) to investigate under which conditions Legionella may be aerosolized and (ii) to quantify bacterial deposition into the respiratory tract upon nebulization. In this study, we used an original experimental set-up that enables the generation of aerosol particles containing L. pneumophila under various conditions. Using flow cytometry in combination with qPCR and culture, we determined (i) the size of the aerosols and (ii) the concentration of viable Legionella forms that may reach the thoracic region. We determined that the 0.26–2.5 μm aerosol size range represents 7% of initial bacterial suspension. Among the viable forms, 0.7% of initial viable bacterial suspension may reach the pulmonary alveoli. In conclusion, these deposition profiles can be used to standardize the size of inoculum injected in any type of respiratory tract model to obtain new insights into the dose response for LD.

No MeSH data available.