Gram-positive aerobic and facultative rods

Bacillus, Corynebacterium, Lactobacillus and others

Arcanobacterium haemolyticum Small Gram-positive rods in a culture from a throat

smear (Gram stain).

Bacillus anthracis The anthrax bacillus is a large Gram-positive rod. It forms chains and spores in culture. The spores do not stain by Gram’s

method and are seen as clear spots. The chains ressemble bamboo stems (Gram stain).

Bacillus subtilis Gram-positive rods in culture. A frequent contaminant

in the laboratory (Gram stain).

Corynebacterium diphteriae A culture of C. diphteriae shows fine rods with irregularly swollen ends. The metachromatic granules are better shown by

specific staining methods (Gram stain).

Corynebacterium diphteriae Fine rods of C. diphteriae with several

polymorphonuclear white blood cells in a throat smear (Gram stain).

Corynebacterium hofmanii Also called the pseudo-diphteria bacillus, seen here in

sputum. This bacterium is shorter and stouter than C. diphteriae (Gram stain).

Corynebacterium jeikeium Small Gram-positive rods in culture. These multi-resistant rods are frequently involved in opportunistic

infections (Gram stain).

Corynebacterium striatum Small Gram-positive rods in culture isolated from

sputum (Gram stain).

Corynebacterium urealyticum Small Gram-positive rods in culture. These multi-resistant rods are sometimes associated with struvite

stones (Gram stain).

Erysipelothrix rhusiopathiae In culture. Gram-positive rods, sometimes with long

non-branching filaments (Gram-stain).

Lactobacillus acidophilus Döderlein bacillus in vaginal smear. Long, slender rods on a background of large vaginal epithelial cells

and polymorphonuclear leukocytes (Gram stain).

Lactobacillus acidophilus Döderlein bacillus in vaginal smear. Slender rods and

large vaginal epithelial cells (Gram stain).

Lactobacillus acidophilus Slender rods of the Döderlein bacillus in a vaginal

smear (Gram stain).

Listeria monocytogenes In blood culture. Short, fine Gram-positive rods, easily

confused with the pseudo-diphteria bacillus (Gram stain).

Listeria monocytogenes Short Gram-positive rods in culture

(Gram stain).

Rhodococcus equi A young culture (at the left) of Rhodococcus (previously

Corynebacterium) equi consists of coccobacilli, an older culture (at the right) of cocci (Gram stain).

Rothia dentocariosa In culture. Aerobic Gram-positive rods forming

filaments (Gram-stain).

Rothia dentocariosa White, raised, and rough colonies with a “spoke

wheel” form.