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.