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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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Bacterial and spore burden in various organs at 2 and 4 weeks post-inoculation.Mice were inoculated i.n. with ∼1.3×107 spores/mouse. Bacterial burden in the lung, spleen, kidney, trachea, and nasopharynx (NP) at 2 (A) and 4 (B) weeks was determined as described in the Materials and Methods section. The results were combined from at least 2 independent experiments. Closed circles represent total viable bacteria and open circles heat-resistant dormant spores. **, p<0.01; ***, p<0.001; compared to respective total bacteria and spore titers in the lung.
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pone-0066177-g002: Bacterial and spore burden in various organs at 2 and 4 weeks post-inoculation.Mice were inoculated i.n. with ∼1.3×107 spores/mouse. Bacterial burden in the lung, spleen, kidney, trachea, and nasopharynx (NP) at 2 (A) and 4 (B) weeks was determined as described in the Materials and Methods section. The results were combined from at least 2 independent experiments. Closed circles represent total viable bacteria and open circles heat-resistant dormant spores. **, p<0.01; ***, p<0.001; compared to respective total bacteria and spore titers in the lung.

Mentions: To investigate if the lung was the major organ for spore persistence we examined the bacterial burden in other tissues. The bacterial titers in the spleen and kidney at 2 and 4 weeks were significantly lower (approximately 103–104 fold) than those in the lung (Fig. 2, A and B). Intranasal inoculation exposes the nasopharynx associated lymphoid tissue (NALT) to the spores. A previous report indicated that the NALT was among the first organs in which vegetative growth was observed following pulmonary exposure to spores [19]. We examined the bacterial burden in the nasopharynx as well as the trachea at 2 and 4 weeks post-inoculation. The results showed that both the total bacteria and spore titers in the trachea and the nasopharynx were significantly lower than those in the lung at both time points (Fig. 2, A and B). These results indicate that the lung is the primary site for spore persistence.


Characterization of Bacillus anthracis persistence in vivo.

Jenkins SA, Xu Y - PLoS ONE (2013)

Bacterial and spore burden in various organs at 2 and 4 weeks post-inoculation.Mice were inoculated i.n. with ∼1.3×107 spores/mouse. Bacterial burden in the lung, spleen, kidney, trachea, and nasopharynx (NP) at 2 (A) and 4 (B) weeks was determined as described in the Materials and Methods section. The results were combined from at least 2 independent experiments. Closed circles represent total viable bacteria and open circles heat-resistant dormant spores. **, p<0.01; ***, p<0.001; compared to respective total bacteria and spore titers in the lung.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0066177-g002: Bacterial and spore burden in various organs at 2 and 4 weeks post-inoculation.Mice were inoculated i.n. with ∼1.3×107 spores/mouse. Bacterial burden in the lung, spleen, kidney, trachea, and nasopharynx (NP) at 2 (A) and 4 (B) weeks was determined as described in the Materials and Methods section. The results were combined from at least 2 independent experiments. Closed circles represent total viable bacteria and open circles heat-resistant dormant spores. **, p<0.01; ***, p<0.001; compared to respective total bacteria and spore titers in the lung.
Mentions: To investigate if the lung was the major organ for spore persistence we examined the bacterial burden in other tissues. The bacterial titers in the spleen and kidney at 2 and 4 weeks were significantly lower (approximately 103–104 fold) than those in the lung (Fig. 2, A and B). Intranasal inoculation exposes the nasopharynx associated lymphoid tissue (NALT) to the spores. A previous report indicated that the NALT was among the first organs in which vegetative growth was observed following pulmonary exposure to spores [19]. We examined the bacterial burden in the nasopharynx as well as the trachea at 2 and 4 weeks post-inoculation. The results showed that both the total bacteria and spore titers in the trachea and the nasopharynx were significantly lower than those in the lung at both time points (Fig. 2, A and B). These results indicate that the lung is the primary site for spore persistence.

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