ABSTRACT
Microbiology The Corynebacterium species are Gram-positive bacilli. Groups of bacterial cells form angles with each other, looking like Chinese characters under the microscope. There are many Corynebacterium species. Most are harmless, causing disease only in the immunocompromised host, or are detected when they contaminate laboratory cultures. However, C. diphtheriae is a most important human pathogen. Three subspecies of C. diphtheriae are known, gravis, intermedius and mitis.
