Bacillus anthracis Portal of entry 1D50 Skin 10-50 endospores Inhalation 10,000-20,000 endospores Ingestion 250,000-1,000,000 endospores Bacillus anthracis Portal of entry ID50 Skin 10-50 endospores Inhalation 10,000-20,000 endospores Ingestion 250,000-1,000,000 endospores