FIG 2 .

B. pseudomallei penetrates degraded olfactory and intact respiratory epithelium (RE). All sections were immunolabeled with anti-B. pseudomallei antibodies (green) and DAPI (blue); some were also labeled with anti-OMP antibodies and UEA1 lectin as indicated. (A) A coronal section of the nasal cavity (NC) shows that one side has extensive infection (arrow) while the other side has little evidence of infection. Boxed areas are shown in panels F to H as indicated. (B) A higher-magnification view of uninfected olfactory epithelium (OE) shows a uniform structure. (C) OE in an inoculated mouse shows an extensive presence of B. pseudomallei (arrow; green) in the NC at 24 h. The OE is crenellated (arrow with tail); the thin respiratory epithelium (RE) in the ventral NC was not visually affected. The asterisk indicates nonspecific autofluorescence. (D) Bacteria (green) occasionally penetrated relatively intact epithelium, but only in patches where neurons (immunolabeled with OMP; red) were absent (arrow). (E) In the olfactory epithelium, bacteria (green; arrow) were not associated with Bowman’s glands (labeled with UEA1 lectin; white; arrow with tail); olfactory neurons (red) are labeled with anti-OMP antibodies. (F to H) Higher-magnification views of the boxed areas indicated in panel A. (F) B. pseudomallei (arrow) was present on the surface of the OE, but no morphological reaction was apparent. (G) Ulceration of the OE (dashed line) was seen, although the presence of bacteria was limited (arrow). (H) The OE showed extensive destruction and loss of integrity, and bacteria were present (arrows) within the epithelium. Bacteria were not detected in the lamina propria (LP) underlying the OE (G and H). (I) In patches of respiratory epithelium, there was widespread infection with B. pseudomallei (arrow), but bacteria did not penetrate the deeper layers. (J and K) OMP immunolabeling (red) demonstrates that healthy epithelium was not penetrated by bacteria (arrow) despite their presence in the adjacent nasal cavity, but that epithelium was penetrated as the neurons partially degraded; panel K shows the same section as that in panel J but with the red channel (OMP) turned off. (L to O) OMP immunolabeling became patchy with some areas showing low levels of OMP reactivity (arrow with tail). Bacteria penetrated the outer layers and were present in nerve bundles in the lamina propria (arrows in panels N and O); panels M and O show the same sections as those in panels L and N, respectively, but with the red channel (OMP) turned off. (P and Q) Complete loss of the neuronal layer led to colonization of the remaining layer by bacteria (arrows); arrows with tails point to neurons in the nasal cavity and remaining epithelium. (R to T) Schematics summarizing the infection of the epithelium. (R) Sagittal view of the nasal cavity, olfactory bulbs (OB), and cortex (Cx). (S) In uninfected mice, the olfactory epithelium is uniform and neurons (red) are distributed throughout the epithelium. (T) When B. pseudomallei (green) is present, the majority of epithelium becomes crenellated but neurons remain within the epithelium and bacteria cannot penetrate. In some regions, the neurons are lost (arrow) and bacteria penetrate the remaining layers. Bar sizes are in μm.