Ubiquitous gram-positive, rod-shaped bacteria that can be obligate aerobes or facultative anaerobes, and test positive for the enzyme catalase.
Bacillus are known to form intracellular inclusions of polyhydroxyalkanoates under certain environmental conditions.
Two Bacillus species are considered medically significant: B. anthracis, which causes anthrax, and B. cereus, which causes a foodborne illness similar to that of Staphylococcus.
B. subtilis: notable food spoiler, causing ropiness in bread and related food.
Microscopic examination: Bacillus cells appear as rods, and a substantial portion usually contain an oval endospore at one end, making it bulge.
Important considerations: The choice of an agent should be based on local antimicrobial sensitivities, site of infection, cost, and comorbid conditions. Generally, the most common agents/regimens are listed first. Listed dosages may need to be adjusted for renal dysfunction.
Bacillus cereus and Bacillus subtilis:
Clindamycin 600mg IV every 6 or 8 hours or 300mg orally four times daily