CLINICAL AND VACCINE IMMUNOLOGY, Oct. 2010, p. 1605–1611
Copyright © 2010, American Society for Microbiology. All Rights Reserved.
Vol. 17, No. 10
Characterization of Erysipelothrix Species Isolates from Clinically
Affected Pigs, Environmental Samples, and Vaccine
Strains from Six Recent Swine Erysipelas
Outbreaks in the United States?
J. S. Bender, H. G. Shen, C. K. Irwin, K. J. Schwartz, and T. Opriessnig*
Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa
Received 18 May 2010/Returned for modification 15 July 2010/Accepted 7 August 2010
The aim of this study was to characterize Erysipelothrix sp. isolates from clinically affected pigs and their
environment and compare them to the Erysipelothrix sp. vaccines used at the sites. Samples were collected
during swine erysipelas outbreaks in vaccinated pigs in six Midwest United States swine operations from 2007
to 2009. Pig tissue samples were collected from 1 to 3 pigs from each site. Environmental samples (manure,
feed, central-line water, oral fluids, and swabs collected from walls, feed lines, air inlets, exhaust fans, and
nipple drinkers) and live vaccine samples were collected following the isolation of Erysipelothrix spp. from
clinically affected pigs. All Erysipelothrix sp. isolates obtained were further characterized by serotyping.
Selected isolates were further characterized by PCR assays for genotype (E. rhusiopathiae, E. tonsillarum,
Erysipelothrix sp. strain 1, and Erysipelothrix sp. strain 2) and surface protective antigen (spa) type (A, B1, B2,
and C). All 26 isolates obtained from affected pigs were E. rhusiopathiae, specifically, serotypes 1a, 1b, 2, and
21. From environmental samples, 56 isolates were obtained and 52/56 were E. rhusiopathiae (serotypes 1a, 1b,
2, 6, 9, 12, and 21), 3/56 were Erysipelothrix sp. strain 1 (serotypes 13 and untypeable), and one was a novel
species designated Erysipelothrix sp. strain 3 (serotype untypeable). Four of six vaccines used at the sites were
commercially available products and contained live E. rhusiopathiae serotype 1a. Of the remaining two
vaccines, one was an autogenous live vaccine and contained live E. rhusiopathiae serotype 2 and one was a
commercially produced inactivated vaccine and was described by the manufacturer to contain serotype 2
antigen. All E. rhusiopathiae isolates were positive for spaA. All Erysipelothrix sp. strain 1 isolates and the novel
Erysipelothrix sp. strain 3 isolate were negative for all currently known spa types (A, B1, B2, and C). These
results indicate that Erysipelothrix spp. can be isolated from the environment of clinically affected pigs;
however, the identified serotypes in pigs differ from those in the environment at the selected sites. At one of the
six affected sites, the vaccine strain and the isolates from clinically affected pigs were of homologous serotype;
however, vaccinal and clinical isolates were of heterologous serotype at the remaining five sites, suggesting that
reevaluation of vaccine efficacy using recent field strains may be warranted.
Organisms of the genus Erysipelothrix are facultative anaer-
obic small, slender, Gram-positive rods and are distributed
worldwide. Erysipelothrix spp. have been isolated from domes-
tic and wild species of both birds and mammals and have been
identified as the causative agent of the clinical disease known
as “erysipelas” in animals and “erysipeloid” in humans (2). The
genus Erysipelothrix consists of four species and 25 associated
serotypes: E. rhusiopathiae (serotypes 1a, 1b, 2, 4, 5, 6, 8, 9, 11,
12, 15, 16, 17, 19, 21, N), E. tonsillarum (serotypes 3, 7, 10, 14,
20, 22, 23), Erysipelothrix sp. strain 1 (serotype 13), and Erysipe-
lothrix sp. strain 2 (serotype 18) (27, 28). Among the four
species, E. rhusiopathiae causes the greatest economic loss,
primarily to the swine and turkey industries (34, 36).
Three clinical presentations of swine erysipelas are recog-
nized, i.e., acute, subacute, and chronic, and serotypes 1a, 1b,
and 2 are frequently isolated from all disease stages (36). The
additional serotypes (3 to 23 and N) have little clinical signif-
icance in swine. It is estimated that 30 to 50% of healthy pigs
harbor E. rhusiopathiae in tonsils and lymphatic tissue. Sub-
clinically affected pigs are thought to be the source for acute
erysipelas outbreaks due to shedding of the organism in urine,
feces, saliva, and nasal secretions (36).
Economic losses due to swine erysipelas continue to occur
worldwide. For this reason, accurate, reliable, and timely di-
agnostic strategies are important (4). Immunohistochemistry
techniques have been shown to be highly sensitive and specific,
especially when diagnostic specimens include lesions from an-
timicrobial-treated pigs or chronically affected pigs (16). Our
previous studies confirmed that an Erysipelothrix species-selec-
tive broth technique is more sensitive than traditional direct
plating of regular and contaminated specimens (1). Although
the enrichment technique has been used by other countries for
a number of years, it has only recently been adopted by diag-
nostic laboratories within the Midwestern United States (1).
PCR technology is also being employed to complement tradi-
tional detection methods (10, 19, 28, 39). In addition to im-
proved diagnostic assays, methods to further characterize and
differentiate Erysipelothrix spp. through the use of randomly
amplified DNA, pulsed-field gel electrophoresis, and ribotyp-
ing have been shown to be useful and credible (13–15, 17).
* Corresponding author. Mailing address: Veterinary Diagnostic
and Production Animal Medicine, College of Veterinary Medicine,
Iowa State University, Ames, IA 50011. Phone: (515) 294-1137. Fax:
(515) 294-3564. E-mail: firstname.lastname@example.org.
?Published ahead of print on 18 August 2010.
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VOL. 17, 2010 CHARACTERIZATION OF SWINE ERYSIPELAS OUTBREAKS1611