Walsh & Hoyt: Gram-Positive Bacilli

Several species of gram-positive bacilli are capable of producing CNS infection in humans. The most common of these are bacteria that replicate extracellularly: Arcanobacterium haemolyticum (previously considered a species of Corynebacterium), Bacillus species, Clostridium species, Corynebacterium species, Erysipelothrix rhusiopathiae, Lactobacillus species, and Propionibacterium species. Intracellular gram-positive bacilli that commonly produce infection in the CNS include Listeria monocytogenes, Mycobacterium tuberculosis, and Mycobacterium leprae. M. tuberculosis, M. leprae, and other atypical mycobacteria belong to the order Actinomycetales, a group of fungus-like ""higher bacteria"" that also includes the filamentous, branching Nocardia and Actinomyces species, as well as Tropheryma whippelii, the bacterium that causes Whipple disease. Like other gram-positive bacilli, these organisms are rod-shaped, stain-positive with Gram stain, and are important causes of CNS infection.