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Characterization of aerosols containing Legionella generated upon nebulization

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.


Microscopic epifluorescent image (Gx400) of aerosolized Legionella suspension.(A) Lp1 008 EPF cells. (B) Lp1 008 SPF cells.
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f3: Microscopic epifluorescent image (Gx400) of aerosolized Legionella suspension.(A) Lp1 008 EPF cells. (B) Lp1 008 SPF cells.

Mentions: Figure 3 shows that Lp1 008 EPF cells were composed mostly of cells approximately 1 μm long whereas Lp1 008 SPF cells consisted of polymorphic bacilli ranging from 1 μm to >5 μm. It is known that Legionella become highly polymorphic with age27. Because the size of the contaminating bacteria may be a critical factor with respect to both bioaerosol infection and access to the respiratory tract and small bacilli 1 μm long are often encountered within environmental samples as planktonic cells2829, the use of Lp1 008 EPF cell suspensions seemed more pertinent for further testing.


Characterization of aerosols containing Legionella generated upon nebulization
Microscopic epifluorescent image (Gx400) of aerosolized Legionella suspension.(A) Lp1 008 EPF cells. (B) Lp1 008 SPF cells.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: Microscopic epifluorescent image (Gx400) of aerosolized Legionella suspension.(A) Lp1 008 EPF cells. (B) Lp1 008 SPF cells.
Mentions: Figure 3 shows that Lp1 008 EPF cells were composed mostly of cells approximately 1 μm long whereas Lp1 008 SPF cells consisted of polymorphic bacilli ranging from 1 μm to >5 μm. It is known that Legionella become highly polymorphic with age27. Because the size of the contaminating bacteria may be a critical factor with respect to both bioaerosol infection and access to the respiratory tract and small bacilli 1 μm long are often encountered within environmental samples as planktonic cells2829, the use of Lp1 008 EPF cell suspensions seemed more pertinent for further testing.

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.