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Journal of Clinical Microbiology, December 1999, p. 4202-4203, Vol. 37, No. 12
0095-1137/99/$04.00+0
LETTERS TO THE EDITOR
Dilemma of the Virulence of Streptococcus
suis Strains
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LETTER |
In a paper recently published (11), Rasmussen et al.
have reported an interesting association between ribotype profiles of
Streptococcus suis serotype 2 strains and clinical
pathological observations of pigs from which the strains had been
isolated. Their study provides further useful information on the use of molecular tools for epidemiological investigations. However, in their
study, the authors included among "five well-characterized avirulent
S. suis serotype 2 strains," the strain 89-1591. The paper
specifies that the information about the lack of virulence of this
strain was obtained from Dr. H. Smith, of the ID-LDO, Lelystad, The
Netherlands in a personnal communication. The experimental infection
model used by ID-LDO researchers is based on an intranasal inoculation
of 1-week-old colostrum-deprived piglets which had previously received
an intranasal infection with Bordetella bronchiseptica 2 days before the S. suis infection (14, 15).
The strain 89-1591 was originally isolated in our laboratory. As stated
in the paper published by Beaudoin et al. (1) which was
cited by Rasmussen et al. (11), this strain was recovered from a case of septicemia and was isolated from lungs, liver, heart, and spleen of the infected pig. This strain was originally used
as a virulent wild-type parent strain for the characterization of
spontaneous "low virulent" acapsulated mutants (6) and
was also considered to be a virulent strain after experimental
infection of conventional specific-pathogen-free piglets
(10). In addition, this strain was used to measure the in
vivo growth of S. suis using intraperitoneal chambers in
piglets (3). Moreover, we recall that in one of these
piglets, one of the intraperitoneal chambers was partially broken, and
the animal died from septicemia within 12 h. To our knowledge and
experience, this strain should be considered as virulent. In addition,
this strain is still being used in our laboratory for the study of
virulence factors in North American strains. Surprisingly, Staats et
al. (12) considered this strain as highly virulent for mice
but of low virulence for pigs.
Experimental infection models for S. suis can be misleading.
Different studies have designated field strains as being virulent or
avirulent based on the clinical condition of the animal from which the
strain was isolated (clinically diseased or healthy animals), the
presence of virulence-related proteins, the virulence in a mouse model,
and the virulence to pigs from high-health-status herds,
specific-pathogen-free pigs, and colostrum-deprived pigs (2, 7,
10, 12, 14, 15). In fact, several discrepencies exist in the
literature. For example, Okwumabua et al. (9) mentioned that
a field strain from Minnesota (DH5) was avirulent for pigs, whereas
Staats et al. (12) considered the same strain as highly
virulent for the same animal species. This strain was originally
isolated from the brain of a pig during an outbreak of S. suis meningitis in a closed farrow-to-finish herd and was considered as representative of the epidemic strain causing the problem
in that herd (8). Controversially, this strain was considered avirulent by Galina et al. 3 years later (5).
Similarly, the serotype 2 reference strain S735 was considered highly
virulent (2) or weakly virulent (14) after
experimental infections of pigs by two independent research groups.
Finally, the mouse model of the infection correlated well
(7) or not at all (13) with the pig model.
Since results from experimental infections of S. suis in
swine may rely, among other considerations, on the
immunological status of the animals, the route of infection, the
size of the inoculum, and the presence of S. suis as normal
inhabitants of the upper respiratory tract, caution should be taken
when the terms virulent and avirulent are used to reach definitive
conclusions. In the case of strain 89-1591 included in the study of
Rasmussen et al., the authors clearly stated that the atypical ribotype profile obtained with this strain is probably more related to its
geographical origin (it was the only North American strain) rather than
its lack of virulence. We found similar results in the past, as
reported by Beaudoin et al. (2) and, more recently, by
Chatellier et al. (4).
Ed. Note: The authors of the original
manuscript did not reply.
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FOOTNOTES |
*
Phone: (450) 773-8521, ext. 8374
Fax: (450) 778-8108
E-mail: gottschm{at}ere.umontreal.ca
| |
REFERENCES |
| 1.
|
Beaudoin, M.,
J. Harel,
R. Higgins,
M. Gottschalk,
M. Frenette, and J. McInnes.
1992.
Molecular analysis of isolates of Streptococcus suis capsular type 2 by restriction-endonuclease-digested DNA separated on SDS-PAGE and by hybridization with an rDNA probe.
J. Gen. Microbiol.
138:2639-2645[Abstract/Free Full Text].
|
| 2.
|
Charland, N.,
J. Harel,
M. Kobisch,
S. Lacasse, and M. Gottschalk.
1998.
Streptococcus suis serotype 2 mutants deficient in capsular expression.
Microbiology
144:325-332[Abstract/Free Full Text].
|
| 3.
|
Charland, N.,
M. Kobisch,
B. Martineau-Doizé,
M. Jacques, and M. Gottschalk.
1996.
Role of sialic acid in virulence and resistance to phagocytosis of Streptococcus suis capsular type 2.
FEMS Immun. Med. Microbiol.
14:195-203[Medline].
|
| 4.
|
Chatellier, S.,
M. Gottschalk,
R. Higgins,
R. Brousseau, and J. Harel.
1999.
Relatedness of Streptococcus suis serotype 2 isolates from different geographic origins as evaluated by molecular fingerprinting and phenotyping.
J. Clin. Microbiol.
37:362-366[Abstract/Free Full Text].
|
| 5.
|
Galina, L.,
C. Pijoan,
M. Sitjar,
W. T. Christianson,
K. Rossow, and J. E. Collins.
1994.
Interaction between Streptococcus suis serotype 2 and porcine reproductive and respiratory syndrome virus in specific pathogen-free piglets.
Vet. Rec.
134:60-64[Abstract].
|
| 6.
|
Gottschalk, M.,
R. Higgins,
M. Jacques, and D. Dubreuil.
1992.
Production and characterization of two Streptococcus suis capsular type 2 mutants.
Vet. Microbiol.
30:59-71[Medline].
|
| 7.
|
Kataoka, Y.,
M. Haritani,
M. Mori,
M. Kishima,
C. Sugimoto,
M. Nakazawa, and K. Yamamoto.
1991.
Experimental infections of mice and pigs with Streptococcus suis type 2.
J. Vet. Med. Sci.
53:1043-1049[Medline].
|
| 8.
|
Mogollon, J. D.,
C. Pijoan,
M. P. Murtaugh,
J. E. Collins, and P. P. Cleary.
1991.
Identification of epidemic strains of Streptococcus suis by genomic fingerprinting.
J. Clin. Microbiol.
29:782-787[Abstract/Free Full Text].
|
| 9.
|
Okwumabua, O.,
J. Staats, and M. M. Chengappa.
1995.
Detection of genomic heterogeneity in Streptococcus suis isolates by DNA restriction fragment lengh polymorphisms of rRNA genes (ribotyping).
J. Clin. Microbiol.
33:968-972[Abstract].
|
| 10.
|
Quessy, S.,
J. D. Dubreuil,
M. Caya, and R. Higgins.
1995.
Discrimination of virulent and avirulent Streptococcus suis capsular type 2 isolates from different geographical origins.
Infect. Immun.
63:1975-1979[Abstract].
|
| 11.
|
Rasmussen, S. R.,
F. M. Aarestrup,
N. E. Jensen, and S. E. Jorsal.
1999.
Associations of Streptococcus suis serotype 2 ribotype profiles with clinical disease and antimicrobial resistance.
J. Clin. Microbiol.
37:404-408[Abstract/Free Full Text].
|
| 12.
|
Staats, J.,
B. Plattner,
J. Nietfeld,
S. Dritz, and M. M. Chengappa.
1998.
Use of ribotyping and hemolysin activity to identify highly virulent Streptococcus suis type 2 isolates.
J. Clin. Microbiol.
36:15-19[Abstract/Free Full Text].
|
| 13.
|
Vecht, U.,
N. Stockhofe-Zurwieden,
B. Tetenburg,
H. J. Wisselin, and H. E. Smith.
1997.
Virulence of Streptococcus suis type 2 for mice and pigs appeared host-specific.
Vet. Microbiol.
58:53-60[Medline].
|
| 14.
|
Vecht, U.,
H. J. Wisselink,
N. Stockhofe-Zurwieden, and H. E. Smith.
1996.
Characterization of virulence of the Streptococcus suis serotype 2 strain Henrichsen S735 in newborn gnotobiotic pigs.
Vet. Microbiol.
51:125-136[Medline].
|
| 15.
|
Vecht, U.,
H. J. Wisselink,
J. Anakotta, and H. E. Smith.
1993.
Discrimination between virulent and nonvirulent Streptococcus suis type 2 strains by enzyme-linked immunosorbent assay.
Vet. Microbiol.
34:71-82[Medline].
|
| | | | |
M. Gottschalk*
R. Higgins
Groupe de Recherche sur les Maladies
Infectieuses
du Porc (GREMIP)
Département de pathologie et microbiologie
Faculté de médecine vétérinaire
Université de Montréal
C.P. 5000, St-Hyacinthe, Québec
Canada J2S 7C6
|
| | | | |
S. Quessy
Santé Canada
Laboratoire d'Hygiène Vétérinaire et
Alimentaire
3200 Casavant West
St-Hyacinthe, Québec
Canada J2S 8E3
|
Journal of Clinical Microbiology, December 1999, p. 4202-4203, Vol. 37, No. 12
0095-1137/99/$04.00+0
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