The Use of Molecular, Immunological and Microbiological Methods to Evaluate Similarities and Differences Between ATCC Reference Strains of Erysipelothrix rhusiopathiae and Erysipelothrix tonsillarum and Environmental Isolates of Erysipelothrix rhusiopathiae Implicated in the Death of Marine Mammals
Robert C. Osgood; Bobby L. Middlebrooks; Rhonda A. Patterson
The University of Southern Mississippi, Department of Biological Sciences, Hattiesburg, MS
Erysipelothrix rhusiopathiae is a ubiquitous gram-positive rod. It
is able to cause disease in a wide range of animals. In humans the organism is known to cause
erysipeloid and endocarditis. Although Erysipelothrix rhusiopathiae has never been known
to cause disease in fish, it can persist for long periods of time in their external mucus.
Consequently, this organism presents an occupational risk to fishermen as well as to those who
handle fish because of the opportunities to acquire the organism through small cuts on the hands
and arms. In marine mammals, however, Erysipelothrix rhusiopathiae is often the cause of
a fatal form of septicemia.
In this study, six recent isolates from the Shedd aquarium, isolates from
Sea World of Texas and Sea World of California, as well as several other previously acquired
environmental isolates from various marine mammal institutions, were compared to several ATCC
reference isolates of Erysipelothrbc rhusiopathiae and Erysipelothrix tonsillarum
using various immunological, microbiological and molecular biology techniques. All isolates and
reference strains were tested for their ability to ferment twelve different carbohydrates and
for their ability to produce caseinase, DNAase, amylase, tryptophanase and urease. In addition,
miscellaneous tests including nitrate reduction and citrate utilization were performed.
Extracted surface proteins from all of the isolates and reference strains were western blotted
and immunostained with antisera preparations raised against extracted surface proteins or
against heat-killed bacterial suspensions representing several Erysipelothrix
rhusiopathiae serotypes. Additionally, all of the environmental isolates and ATCC reference
strains were analyzed by the polymerase chain reaction using species specific primers that
amplify base pair products that are specific for Erysipelothrix rhusiopathiae, and
Erysipelothrix tonsillarum. Furthermore, all of the isolates were analyzed for the
presence of plasmids. Microbiological and immunological testing revealed some differences among
the isolates and between the isolates and the reference strains. All of the environmental
isolates were confirmed as Erysipelothrix rhusiopathiae, however, the polymerase chain
reaction proved to be more discriminatory in its ability to distinguish between
Erysipelothrix rhusiopathiae and Erysipelothrix tonsillarum.