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Characterization of Bacillus anthracis persistence in vivo.

Jenkins SA, Xu Y - PLoS ONE (2013)

Bottom Line: Immunofluorescence staining of lung sections showed that spores associated with the alveolar and airway epithelium.We also showed that the anthrax toxins did not play a role in persistence.Together, the results suggest that B. anthracis spores have special properties that promote their persistence in the lung, and that there may be multiple mechanisms contributing to spore persistence.

View Article: PubMed Central - PubMed

Affiliation: Center for Infectious and Inflammatory Diseases, Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, Texas, USA.

ABSTRACT
Pulmonary exposure to Bacillus anthracis spores initiates inhalational anthrax, a life-threatening infection. It is known that dormant spores can be recovered from the lungs of infected animals months after the initial spore exposure. Consequently, a 60-day course antibiotic treatment is recommended for exposed individuals. However, there has been little information regarding details or mechanisms of spore persistence in vivo. In this study, we investigated spore persistence in a mouse model. The results indicated that weeks after intranasal inoculation with B. anthracis spores, substantial amounts of spores could be recovered from the mouse lung. Moreover, spores of B. anthracis were significantly better at persisting in the lung than spores of a non-pathogenic Bacillus subtilis strain. The majority of B. anthracis spores in the lung were tightly associated with the lung tissue, as they could not be readily removed by lavage. Immunofluorescence staining of lung sections showed that spores associated with the alveolar and airway epithelium. Confocal analysis indicated that some of the spores were inside epithelial cells. This was further confirmed by differential immunofluorescence staining of lung cells harvested from the infected lungs, suggesting that association with lung epithelial cells may provide an advantage to spore persistence in the lung. There was no or very mild inflammation in the infected lungs. Furthermore, spores were present in the lung tissue as single spores rather than in clusters. We also showed that the anthrax toxins did not play a role in persistence. Together, the results suggest that B. anthracis spores have special properties that promote their persistence in the lung, and that there may be multiple mechanisms contributing to spore persistence.

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The majority of persisting spores associated tightly with the lung tissue.Mice were inoculated i.n. with ∼1.3×107 spores/mouse (A and B) and ∼1.1×108 spores/mouse (C and D). Lungs were lavaged with sterile PBS and collected. Total bacteria (closed circles) and spore (open circles) titers in the lung tissues and BAL fluids at 2 (A and C) and 4 (B and D) weeks were determined. The results were combined from at least two independent experiments. *, p<0.05; ***, p<0.001; compared to respective total bacteria and spore titers in the lung tissue.
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pone-0066177-g004: The majority of persisting spores associated tightly with the lung tissue.Mice were inoculated i.n. with ∼1.3×107 spores/mouse (A and B) and ∼1.1×108 spores/mouse (C and D). Lungs were lavaged with sterile PBS and collected. Total bacteria (closed circles) and spore (open circles) titers in the lung tissues and BAL fluids at 2 (A and C) and 4 (B and D) weeks were determined. The results were combined from at least two independent experiments. *, p<0.05; ***, p<0.001; compared to respective total bacteria and spore titers in the lung tissue.

Mentions: We next examined whether the persistent B. anthracis spores were tightly associated with the lung tissue or in the fluid lining the respiratory epithelium, the latter of which can be recovered in the bronchoaveolar lavage (BAL) fluid. The results showed that at both 2 and 4 weeks post-inoculation, there were significantly more total bacteria as well as spores in the lung tissues than in the BAL fluid, suggesting that spores preferentially associated with lung tissues (Fig. 4, A–D).


Characterization of Bacillus anthracis persistence in vivo.

Jenkins SA, Xu Y - PLoS ONE (2013)

The majority of persisting spores associated tightly with the lung tissue.Mice were inoculated i.n. with ∼1.3×107 spores/mouse (A and B) and ∼1.1×108 spores/mouse (C and D). Lungs were lavaged with sterile PBS and collected. Total bacteria (closed circles) and spore (open circles) titers in the lung tissues and BAL fluids at 2 (A and C) and 4 (B and D) weeks were determined. The results were combined from at least two independent experiments. *, p<0.05; ***, p<0.001; compared to respective total bacteria and spore titers in the lung tissue.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3672131&req=5

pone-0066177-g004: The majority of persisting spores associated tightly with the lung tissue.Mice were inoculated i.n. with ∼1.3×107 spores/mouse (A and B) and ∼1.1×108 spores/mouse (C and D). Lungs were lavaged with sterile PBS and collected. Total bacteria (closed circles) and spore (open circles) titers in the lung tissues and BAL fluids at 2 (A and C) and 4 (B and D) weeks were determined. The results were combined from at least two independent experiments. *, p<0.05; ***, p<0.001; compared to respective total bacteria and spore titers in the lung tissue.
Mentions: We next examined whether the persistent B. anthracis spores were tightly associated with the lung tissue or in the fluid lining the respiratory epithelium, the latter of which can be recovered in the bronchoaveolar lavage (BAL) fluid. The results showed that at both 2 and 4 weeks post-inoculation, there were significantly more total bacteria as well as spores in the lung tissues than in the BAL fluid, suggesting that spores preferentially associated with lung tissues (Fig. 4, A–D).

Bottom Line: Immunofluorescence staining of lung sections showed that spores associated with the alveolar and airway epithelium.We also showed that the anthrax toxins did not play a role in persistence.Together, the results suggest that B. anthracis spores have special properties that promote their persistence in the lung, and that there may be multiple mechanisms contributing to spore persistence.

View Article: PubMed Central - PubMed

Affiliation: Center for Infectious and Inflammatory Diseases, Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, Texas, USA.

ABSTRACT
Pulmonary exposure to Bacillus anthracis spores initiates inhalational anthrax, a life-threatening infection. It is known that dormant spores can be recovered from the lungs of infected animals months after the initial spore exposure. Consequently, a 60-day course antibiotic treatment is recommended for exposed individuals. However, there has been little information regarding details or mechanisms of spore persistence in vivo. In this study, we investigated spore persistence in a mouse model. The results indicated that weeks after intranasal inoculation with B. anthracis spores, substantial amounts of spores could be recovered from the mouse lung. Moreover, spores of B. anthracis were significantly better at persisting in the lung than spores of a non-pathogenic Bacillus subtilis strain. The majority of B. anthracis spores in the lung were tightly associated with the lung tissue, as they could not be readily removed by lavage. Immunofluorescence staining of lung sections showed that spores associated with the alveolar and airway epithelium. Confocal analysis indicated that some of the spores were inside epithelial cells. This was further confirmed by differential immunofluorescence staining of lung cells harvested from the infected lungs, suggesting that association with lung epithelial cells may provide an advantage to spore persistence in the lung. There was no or very mild inflammation in the infected lungs. Furthermore, spores were present in the lung tissue as single spores rather than in clusters. We also showed that the anthrax toxins did not play a role in persistence. Together, the results suggest that B. anthracis spores have special properties that promote their persistence in the lung, and that there may be multiple mechanisms contributing to spore persistence.

Show MeSH
Related in: MedlinePlus