FIG. 5.
Bacilli and spore load in lungs and distal organs of moribund mice after aerosol challenge with B. anthracis. Groups of A/J mice were exposed to aerosols of spores with an average pulmonary retained dose of 3 × 106 spores per mouse. Upon daily examination, regardless of the day postchallenge, any mouse that appeared moribund (i.e., ruffled fur, hunched over, or shallow breathing) was euthanized and the numbers of CFU in the lung, liver, and spleen (A) and the percentages of moribund mice CFU positive in lung, lymph node (LN), liver, and spleen (B) were determined. To determine CFU resulting from spores or spores plus bacilli (germination gives rise to heat-sensitive bacilli), a fraction of each homogenate was heat treated (HT) prior to diluting and plating. Untreated (UnT) CFU values are for spores and bacilli whereas HT CFU values are for spores only.