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Hide, Keep Quiet, and Keep Low: Properties That Make Aspergillus fumigatus a Successful Lung Pathogen.

Escobar N, Ordonez SR, Wösten HA, Haas PJ, de Cock H, Haagsman HP - Front Microbiol (2016)

Bottom Line: Germination of A. fumigatus and A. niger conidia in the presence of epithelial cells was delayed when compared to conidia in the medium.Neutrophils reduced germination and hyphal growth of A. niger, but not of A fumigatus, in presence of epithelial cells.Taken together, efficient internalization, delayed germination, and hyphal growth parallel to the epithelium gives a new insight into what could be the causes for the success of A. fumigatus compared to A. niger as an opportunistic pathogen in the lung.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Institute of Biomembranes, Utrecht University Utrecht, Netherlands.

ABSTRACT
Representatives of the genus Aspergillus are opportunistic fungal pathogens. Their conidia can reach the alveoli by inhalation and can give rise to infections in immunocompromised individuals. Aspergillus fumigatus is the causal agent of invasive aspergillosis in nearly 90% of the cases. It is not yet well-established what makes this fungus more pathogenic than other aspergilli such as A. niger. Here, we show that A. fumigatus and A. niger conidia adhere with similar efficiency to lung epithelial A549 cells but A. fumigatus conidia internalized 17% more efficiently. Conidia of both aspergilli were taken up in phagolysosomes 8 h after the challenge. These organelles only acidified in the case of A. niger, which is probably due to the type of melanin coating of the conidia. Viability of both types of conidia was not affected after uptake in the phagolysosomes. Germination of A. fumigatus and A. niger conidia in the presence of epithelial cells was delayed when compared to conidia in the medium. However, germination of A. niger conidia was still higher than that of A. fumigatus 10 h after exposure to A549 cells. Remarkably, A. fumigatus hyphae grew mainly parallel to the epithelium, while growth direction of A. niger hyphae was predominantly perpendicular to the plane of the cells. Neutrophils reduced germination and hyphal growth of A. niger, but not of A fumigatus, in presence of epithelial cells. Taken together, efficient internalization, delayed germination, and hyphal growth parallel to the epithelium gives a new insight into what could be the causes for the success of A. fumigatus compared to A. niger as an opportunistic pathogen in the lung.

No MeSH data available.


Related in: MedlinePlus

Germination and hyphal length of A. fumigatus are more effectively decreased in the presence of A549 cells than that of A. niger. (A) Germination and (B) hyphal length. Bar represents standard error of the mean. ∗ Indicates significant difference. Data are obtained from three separate experiments; at least 100 conidia per condition were analyzed.
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Figure 4: Germination and hyphal length of A. fumigatus are more effectively decreased in the presence of A549 cells than that of A. niger. (A) Germination and (B) hyphal length. Bar represents standard error of the mean. ∗ Indicates significant difference. Data are obtained from three separate experiments; at least 100 conidia per condition were analyzed.

Mentions: Interestingly, by using a nystatin protection assay we observed that all internalized conidia from A. fumigatus and A. niger were viable after 20 h (Supplementary Figure S3). As part of the Aspergillus cycle of infection, internalized conidia need to escape from cellular endosomes. Germination mediates this step and is essential for dissemination, enabling the fungi to reach new organs. Therefore, the germination time in the absence or presence of epithelial cells was investigated. In cell culture medium, germ tubes appeared after 6 and 5 h for A. fumigatus and A. niger, respectively. Germination was delayed for 2 h in the presence of A549 cells (Supplementary Figure S4). At 10 h after infection as little as 6% of the conidia of A. fumigatus had germinated, while at 9 h, 24% of A. niger conidia had already germinated (Figure 4A). Germtubes also differed in length. A. fumigatus hyphae were significantly smaller compared to those of A. niger (Figure 4B). In addition, hyphae of A. fumigatus and A. niger showed a difference in growth direction. Hyphae of A. fumigatus grew mainly parallel to the A549 epithelial cell layer (reaching maximally 22 μm above the cell layer), while hyphae of A. niger grew perpendicular to the cell layer, reaching 70 μm above the epithelial cell monolayer (Figure 5; Figure 5G for quantification). These observations were not related to differences in growth since hyphae of both strains were grown until a comparable size prior to the analysis (Figures 5D,F). However, to prove that these differences are not due to growth, the ratio of hyphae perpendicular to the cells vs. the number of hyphae parallel to the cells was calculated. For A. fumigatus this ratio was 1:3 in contrast to A. niger which gave a ratio of 2:1.


Hide, Keep Quiet, and Keep Low: Properties That Make Aspergillus fumigatus a Successful Lung Pathogen.

Escobar N, Ordonez SR, Wösten HA, Haas PJ, de Cock H, Haagsman HP - Front Microbiol (2016)

Germination and hyphal length of A. fumigatus are more effectively decreased in the presence of A549 cells than that of A. niger. (A) Germination and (B) hyphal length. Bar represents standard error of the mean. ∗ Indicates significant difference. Data are obtained from three separate experiments; at least 100 conidia per condition were analyzed.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4821987&req=5

Figure 4: Germination and hyphal length of A. fumigatus are more effectively decreased in the presence of A549 cells than that of A. niger. (A) Germination and (B) hyphal length. Bar represents standard error of the mean. ∗ Indicates significant difference. Data are obtained from three separate experiments; at least 100 conidia per condition were analyzed.
Mentions: Interestingly, by using a nystatin protection assay we observed that all internalized conidia from A. fumigatus and A. niger were viable after 20 h (Supplementary Figure S3). As part of the Aspergillus cycle of infection, internalized conidia need to escape from cellular endosomes. Germination mediates this step and is essential for dissemination, enabling the fungi to reach new organs. Therefore, the germination time in the absence or presence of epithelial cells was investigated. In cell culture medium, germ tubes appeared after 6 and 5 h for A. fumigatus and A. niger, respectively. Germination was delayed for 2 h in the presence of A549 cells (Supplementary Figure S4). At 10 h after infection as little as 6% of the conidia of A. fumigatus had germinated, while at 9 h, 24% of A. niger conidia had already germinated (Figure 4A). Germtubes also differed in length. A. fumigatus hyphae were significantly smaller compared to those of A. niger (Figure 4B). In addition, hyphae of A. fumigatus and A. niger showed a difference in growth direction. Hyphae of A. fumigatus grew mainly parallel to the A549 epithelial cell layer (reaching maximally 22 μm above the cell layer), while hyphae of A. niger grew perpendicular to the cell layer, reaching 70 μm above the epithelial cell monolayer (Figure 5; Figure 5G for quantification). These observations were not related to differences in growth since hyphae of both strains were grown until a comparable size prior to the analysis (Figures 5D,F). However, to prove that these differences are not due to growth, the ratio of hyphae perpendicular to the cells vs. the number of hyphae parallel to the cells was calculated. For A. fumigatus this ratio was 1:3 in contrast to A. niger which gave a ratio of 2:1.

Bottom Line: Germination of A. fumigatus and A. niger conidia in the presence of epithelial cells was delayed when compared to conidia in the medium.Neutrophils reduced germination and hyphal growth of A. niger, but not of A fumigatus, in presence of epithelial cells.Taken together, efficient internalization, delayed germination, and hyphal growth parallel to the epithelium gives a new insight into what could be the causes for the success of A. fumigatus compared to A. niger as an opportunistic pathogen in the lung.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Institute of Biomembranes, Utrecht University Utrecht, Netherlands.

ABSTRACT
Representatives of the genus Aspergillus are opportunistic fungal pathogens. Their conidia can reach the alveoli by inhalation and can give rise to infections in immunocompromised individuals. Aspergillus fumigatus is the causal agent of invasive aspergillosis in nearly 90% of the cases. It is not yet well-established what makes this fungus more pathogenic than other aspergilli such as A. niger. Here, we show that A. fumigatus and A. niger conidia adhere with similar efficiency to lung epithelial A549 cells but A. fumigatus conidia internalized 17% more efficiently. Conidia of both aspergilli were taken up in phagolysosomes 8 h after the challenge. These organelles only acidified in the case of A. niger, which is probably due to the type of melanin coating of the conidia. Viability of both types of conidia was not affected after uptake in the phagolysosomes. Germination of A. fumigatus and A. niger conidia in the presence of epithelial cells was delayed when compared to conidia in the medium. However, germination of A. niger conidia was still higher than that of A. fumigatus 10 h after exposure to A549 cells. Remarkably, A. fumigatus hyphae grew mainly parallel to the epithelium, while growth direction of A. niger hyphae was predominantly perpendicular to the plane of the cells. Neutrophils reduced germination and hyphal growth of A. niger, but not of A fumigatus, in presence of epithelial cells. Taken together, efficient internalization, delayed germination, and hyphal growth parallel to the epithelium gives a new insight into what could be the causes for the success of A. fumigatus compared to A. niger as an opportunistic pathogen in the lung.

No MeSH data available.


Related in: MedlinePlus