Figure 3

Kinetics and localization of MG infection in chicken tracheae. (A) Kinetic analysis of TOC exposure to MG was performed. Differences in the bacterial load at 3 dpi, 5 dpi, and 7 dpi are shown, and the fold change was determined via RT‒qPCR. Each point represents a chicken, and the horizontal line represents the average value. (B) Quantitative analysis of the intensity of the red fluorescence signal in TOCs infected with MG was performed. (C) The specific distribution of MG in tracheal tissue was evaluated by FISH. Fluorescence microscopy was applied to determine the specific distribution of MG in tracheal tissues after infection. The number of bacteria increased significantly with the duration of infection. Nuclei stained with DAPI were blue under UV excitation, positive signals were red for the corresponding fluorescein (CY3) labelling, and mRNA in situ hybridization confirmed that the cytoplasm was theoretically positive, with a few nuclear positives being normal. Micrographs were taken at 400 × magnification (n = 8), and the fluorescence brightness was strong or weak depending on the amount of expression.