Corynebacterium

Corynebacterium includes many species of aerobic and facultative Gram-positive rods.
The cells tend to have clubbed ends, and often remain attached after division, forming
“Chinese letter” or palisade arrangements. Spores are not formed. Growth is generally
best under aerobic conditions on media enriched with blood or other animal products, but
many strains will grow anaerobically. Colonies on blood agar are typically small (1 to
2 mm), and most are nonhemolytic. Catalase is produced, and many strains form acid
(usually lactic acid) through carbohydrate fermentation.

This chapter includes a variety of highly pathogenic Gram-positive rods that are not
currently common causes of human disease. Their medical importance lies in the lessons
learned when they were more common, and the continued threat their existence poses.
Corynebacterium diphtheriae, the cause of diphtheria, is a prototype for toxigenic disease.
Listeria monocytogenes is a sporadic cause of meningitis and other infections in the
fetus, newborn, and immunocompromised host. Occurrences in 2001 have served as a
painful reminder that Bacillus anthracis, the cause of anthrax, is still the agent with the
most potential for use in bioterrorism