FIG. 1.
LD50 and quantification of lung bacterial load of B. bronchiseptica strains RB50 and 253. Groups of three to four C57BL/6 mice were inoculated intranasally with the indicated doses of strains RB50 (A) or 253 (B). Survival curves were generated by inoculating mice with the indicated dose and determining the percent survival over a 28-day period. (C) Groups of three mice were inoculated intranasally with 105.7 CFU of strain RB50 (filled squares) or strain 253 (open squares). The bacterial load in the lungs was quantified 3, 7, 14, 28, and 56 days postinoculation. The dashed line indicates the lower limit of detection. Bacterial numbers are expressed as the log10 mean ± the standard error (error bars).