Erysipelothrix rhusiopathiae
Suzy Dawson
Erysipelothrix rhusiopathiae was first isolated by Koch in 1876.  E. rhusiopathiae is the only named species in the genus Erysipelothrix.  In the history of this organism there have been as many as three species distinguished, but in 1966 it was decided that all these strains belonged to one species.  The official name the organism was given was Erysipelothrix rhusiopathiae, which literally means "erysipelas thread of red disease."  There is more variation in the rhusiopathiae strains than is usually found within a single species therefore more tests need to be completed to determine if the genus Erysipelothrix should indeed contain more than one species.

Erysipelothrix rhusiopathiae is a slender gram positive nonsporulating rod that is a facultative anaerobe.  Growth of this organism is improved by 5-10% CO2.  This organism can be found in a variety of configurations such as in short chains, in pairs, in a "V" configuration or even grouped randomly.  These gram positive organisms can appear gram negative because of their tendency to decolorize rapidly.

Erysipelothrix  rhusiopathiae colonies have two distinct forms the smooth form and the rough form.  The smooth form are approximately 0.1 mm in diameter, convex and circular. (Fig 1) The rough form are slightly larger at 0.2-0.4 mm in diameter. (Fig 2)  They are flatter colonies and have a matte surface.  The rough form prefers slightly acidic conditions at a temperature of 37oC whereas the smooth form prefers slightly Alkaline pH's at a temperature of 30oC.

Erysipelothrix rhusiopathiae is a pathogen that causes infections in the hosts it infects.   This organism infects a large variety of animals  from a house fly to a wild bear.  Infections have been  reported world wide in as many as 50 different types of animals.  The highest occurrence is found in domestic swine.  Erysipelothrix rhusiopathiae  is unable to survive for an indefinite amount of time within the external environment.  External environments where this organism would be most likely to be found is in sewage or on ground contaminated with animal feces.  Pathogenic strains of Erysipelothrix rhusiopathiae have been isolated from the feces of apparently healthy swine indicating that infection may not always induce a disease. Four forms of the clinical effects of this organism have been identified in swine  an acute, subacute uriticarial, joint arthritic ,and chronic cardiac form.

Erysipelothrix rhusiopathiae causes infections within humans as well.  There are three clinical categories for the human disease caused by this organism.  A localized cutaneous form (most common), a generalized cutaneous form, and a septicemic form (associated with the heart disease endocarditis). Human infections are primarily found as a result of occupational hazards such as those who handle fish.  This organism has never been reported as causing a disease in fish but grows and persists for long periods of times in the exterior of these animals. This fact puts those who handle fish at high risk of contracting this organism.  Erysipelothrix rhusiopathiae primarily enters its host via scratches or puncture wounds on the surface of the skin.  A patient infected by this organism with the localized cutaneous form commonly exhibit symptoms of a throbbing itching pain and swelling on the finger or part of hand infected.  Infections can be easily treated by antibiotic therapy.

This organism has several very interesting characteristics such as its ability to infect such a large variety of vertebrate and invertebrate animals.  The extreme diversity found within this single species is also of interest because further studies are still required to determine if one species is really a sufficient means to catagorize this organism.

References:

Prokaryotes volume II Chapter 73 pps 1629-1638

 

*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.

 

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