(A) Line drawing of transverse section of olfactory bulbs and mucosa shows the locations from which micrographs (B-E) were obtained. At 6 h post-inoculation, FITC-conjugated bacteria (arrows) are present in the olfactory epithelium (OE) and olfactory nerve bundles (NB) in the lamina propria (LP; B) and in the olfactory nerve layer (ONL) and glomerular layer (GmL) of the olfactory bulb (C). Inset in c shows aggregates of bacteria. At 24 h post-inoculation, there appear to be more FITC-conjugated bacteria in the ONL and GmL of the treated side with the corresponding layers of the untreated side (ONL/NT, GmL/NT) showing the presence of a small number of bacteria (D). Numerous FITC-conjugated S. aureus were located near the nares (E). At 5 days post-inoculation, FITC-conjugated bacteria are restricted largely to the ONL (F). NC = nasal cavity; EPL = external plexiform layer. Scale bar = 200 μm (B,C,D,F), 500 μm (E), 100 μm (inset in C).