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Corynebacterium spp. have been identified in a variety of indoor environments, e.g., office building, homes, air planes, day care centers, schools and automobile air conditioning systems. These organisms are associated with illnesses in both animals and humans. These will be briefly reviewed below with respect to species and the pathology associated with a particular species. 

Corynebacterium are found in the oral cavity and skin of humans and animals.

Corynebacteria belong to the Corynebacteriaceae Actinobacteria group. The genus attained notoriety from the diphtheria species (C. diphtheriae) that caused upper respiratory infections in children often leading to death caused by a choking mucous and the diphtheria toxin released by this organism. The toxin is absorbed and disseminated throughout the body--affecting the heart, peripheral nerves, adrenal glands, kidneys, liver and spleen.

The Corynebacteria are small, generally non-motile, non-sporulating gram positive bacteria. They are pleomorphic bacillus due to their particular type of cell division (snapping configuration). They often lie in clusters referred to as Chinese letters. They are identified by culture on Blood Agar and their morphology. However, current technology using Real Time PCR analytical methods have been developed for species identification.

Human Diseases

C. diphtheriae: This organism caused upper respiratory infections in children resulting in death from choking and the adverse affects of its toxin. Plagues occurred in Europe in the 17th, 18th and 19th centuries. The disease was eventually treated with sera obtained from horses inoculated with the organisms. Diphtheria vaccinations are available as a deterrent.
C. jeikeium: Generally, this species has caused systemic infections in neutropenic individuals. However, other species include pseudodiphtheriticum, amycolatum, propinquum, xerosis and minutissimum.

C. pseudodiphtheriticum: This species has been isolated from a variety of conditions including endocarditis, nosocomial pneumonia, idiopathic mastitis, sarcoidosis, and systemic infections in cancer patients.

C. xerosis: This species has been identified in bacteremia, skin infections and pneumonia in immune-compromised individuals, patients with blood disorders, bone marrow transplants, intravenous catheters and pharyngitis.

C. urealyticum: Known to cause rare urinary tract infections. The bacterium is often overlooked in these conditions.

C. ulcerans: Causes pharyngitis.

C. pseudotuberculosis: subacute relapsing lymphadenitis

Species of Corynebacterium cause infections in animals which are the source of human infections. 

You have seen here that the same species of Corynebacterium are causally connected to infections in immune-compromised patients. What about immune-competent individuals? 

Individuals who have inflammatory sinus and lung conditions resulting from exposure to damp indoor spaces are placed on corticosteroid therapy. Corticosteroid use of two weeks or more has been associated with the onset of aspergillosis in immune-competent individuals. 

The species of Corynebacterium are overlooked as a general rule as causative in infections. The rational for this is derived from the fact that these bacteria can be isolated from the skin and oral cavity of humans. Therefore, the cultures must have been contaminated during collection of specimens. 

Below are additional reading materials on this topic. 

University of Maryland. Corynebacteria Summary.

Coryneform Bacteria in Infectious Diseases: Clinical and Laboratory Aspects. CLINICAL MICROBIOLOGY REVIEWS, July 1990, p. 227-246. 

A clinicopathological review of 34 cases of inflammatory breast disease showing an association between corynebacteria infection and granulomatous mastitis. Pathology. 2003 Apr 35(2):109-19. 

Corynebacterium accolens Isolated from Breast Abscess: Possible Association with Granulomatous Mastitis. JOURNAL OF CLINICAL MICROBIOLOGY, May 2007, p. 1666–1668. 
Corynebacterium diphtheriae

Corynebacterium diphtheriae

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