Short Communication
Communication brève
Clonal distribution of Streptococcus suis isolated from diseased pigs in the central region of Chile Bárbara Morales, Álvaro Ruiz, Sonia Lacouture, Marcelo Gottschalk
Abstract The characteristics of 29 Chilean field strains of Streptococcus suis recovered between 2007 and 2011 from pigs with clinical signs at different farms were studied. Serotyping with use of the coagglutination test revealed that all but 1 strain belonged to serotype 6; the remaining strain was serotype 22. All the serotype-6 strains were suilysin (hemolysin)-negative; in addition, they were found to be genotypically homogeneous by enterobacterial repetitive intergenic consensus sequence-based polymerase chain reaction (ERIC-PCR) and sensitive to ampicillin, ceftiofur, penicillin, and trimethoprim/sulfamethoxazole. The results indicate that, in contrast to what is generally observed in other countries, a single clone of S. suis was isolated from diseased pigs in the central region of Chile.
Résumé Les caractéristiques de 29 souches de Streptococcus suis d’origine chilienne provenant de porcs malades, dont la plupart d’entre elles n’ont aucun lien épidémiologique, ont été étudiées. Toutes les souches ont montré appartenir au sérotype 6 sauf 1, qui a été caractérisée comme étant un sérotype 22. De plus, toutes les souches du sérotype 6 se sont révélées négatives pour la production de suilysine (hémolysine). Avec l’utilisation d’un test PCR ciblant des séquences consensus intergéniques répétées d’entérobactéries (ERIC-PCR), toutes les souches de sérotype 6 testées se sont avérées être génétiquement homogènes. Finalement, ces souches se sont montrées sensibles à l’ampicilline, au ceftiofur, à la pénicilline ainsi qu’à l’association triméthoprime-sulfaméthoxazole. Les résultats indiquent que, contrairement à ce qui a déjà été observé dans d’autres pays, un seul clone de S. suis est majoritairement isolé chez des porcs malades dans la région centrale du Chili. (Traduit par les auteurs)
Streptococcus suis is a bacterial pathogen of global importance, able to induce meningitis, sepsis, and arthritis in piglets and grower– finisher pigs (1). Furthermore, S. suis is a zoonotic agent, causing meningitis in humans that are in direct contact with infected pigs or pork-derived products (2). There are currently 35 serotypes, of which serotypes 2, 3, and 9 are the most frequently isolated from diseased pigs in different parts of the world (3). Some previously described serotypes have recently been classified as a new species (4). Virulence factors and pathogenesis of S. suis infection have been studied mainly for serotype 2, which is also an important zoonotic agent (5). Very few data are available concerning serotype distribution of S. suis isolated from diseased pigs in South America. In fact, they are available only from Brazil (2). Interestingly, cases of S. suis infection in humans have recently been described in Chile (6); however, there is no information about how this pathogen affects the pig farms in this country. In addition to Chile, 2 other South American countries, Argentina and French Guiana, have reported cases of S. suis infection in humans (2). In the present study, and for the first time, we phenotypically and genotypically analyzed strains isolated from diseased pigs at nonrelated farms in central Chile. Included in this study were 29 field strains isolated from clinically affected pigs at 7 nonrelated intensive-production farms in the
central region of Chile between 2007 and 2011 (Table I). Some strains from the same farm were recovered during different years. Strains were recovered from various tissues (Table II), but predominantly from cases of meningitis, and were kept in storage beads (Cryobank; Copan Diagnostics, Murrieta, California, USA) at −80°C. Bacteria were plated on 5% sheep blood agar (bioMérieux, Marcy l’Étoile, France), incubated aerobically at 37°C, and evaluated for growth after 24 and 48 h until a-hemolytic colonies were observed. Capsular serotyping of the field strains was carried out by means of the coagglutination test with 34 reference antisera as previously described (7). The hemolysin test was done on all the field strains as well as negative (serotype-2 strain TD10) and positive (serotype-2 strain P1/7) controls; the supernatant and erythrocytes were prepared and the hemolytic activity was assessed as previously described (7). All the analyzed strains were 100% serotypeable: all but 1 strain belonged to serotype 6; the remaining strain was serotype 22. Enterobacterial repetitive intergenic consensus sequencebased polymerase chain reaction (ERIC-PCR) was carried out with 22 of the serotype-6 strains (6 strains were no longer viable) and, for comparison purposes, the Danish serotype-6 reference strain to compare the strains genotypically. DNA extraction was done with the QIAamp DNA minikit (Qiagen, Valencia, California, USA), and
Departamento de Patología y Medicina Preventiva, Universidad de Concepción, Concepción, Chile (Morales, Ruiz); Faculté de médecine vétérinaire, Université de Montréal, 3200, rue Sicotte, Saint-Hyacinthe, Québec J2S 2M2 (Lacouture, Gottschalk). Address all correspondence to Dr. Marcelo Gottschalk; telephone: 450-773-8521, ext. 8374; fax: 450-778-8108; e-mail: [email protected] Received January 8, 2015. Accepted March 26, 2015. 2015;79:343–346
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Table I. Field strains of Streptococcus suis used in this study as distributed by Chilean farm and year of isolation
Table II. Distribution of the 28 serotype-6 S. suis field isolates according to the tissue from which they were recovered
Number of strains Farm 2007 2008 2009 2010 2011 Total A 1 2 2 5 B 1 2 1 3 7 C 2 2 D 9 9 E 3 3 F 1 1 G 2 2 Total 2 16 4 5 2 29
Tissue Number of isolates Brain or cerebrospinal fluid 15 Joint or synovial fluid 6 Heart 2 Lymph node 1 Lung 4
the PCR technique was applied as previously described (8). Band patterns were analyzed with the use of Bionumerics software, version 6.5 (Applied Maths, Austin, Texas, USA). Five randomly chosen representative isolates of S. suis were plated on Müeller–Hinton agar supplemented with 5% sheep blood (Oxoid, Ottawa, Ontario) and tested for susceptibility to the antibiotics ampicillin, ceftiofur, penicillin, and trimethoprim/sulfamethoxazole (TMP/SMX) before being incubated at 37°C for 18 h (9). Finally, to evaluate virulence, we used a mouse model of infection as previously described for serotype-2 strains (10). One representative Chilean isolate of serotype 6 was chosen and compared with the serotype-6 reference strain. A well-known virulent strain of S. suis serotype 2 (strain 31533) was used as a positive control. This study was conducted according to the policies and principles of the Canadian Council on Animal Care (11). Of 30 CD1 female mice (Charles Rivers Laboratories, Wilmington, Massachusetts, USA) 10 were inoculated with a Chilean strain, 10 with the Danish serotype-6 reference strain, and 6 with the serotype-2 positive control, each mouse receiving 2 3 108 colony-forming units by the intraperitoneal route; the other 4 mice served as negative noninfected controls. The mice were monitored 3 times a day for 10 d for the presence of clinical signs associated with septicemia and/or meningitis or death (10). Of the 29 strains, 28 belonged to a single serotype, serotype 6. It is quite unusual to find a common serotype among so many strains recovered from different herds of a region or country. In fact, this has not been previously described for S. suis. Almost half of the strains were isolated from cases of meningitis (Table II). The ERICPCR results showed that the 22 tested strains of serotype 6 had an identical genetic pattern (Figure 1), a pattern clearly different from that of the Danish reference serotype-6 strain. The molecular weights of the bands were between the ranks of 1700 and 800 bp for the reference strain but between the ranks of 4000 and 300 bp for the 22 Chilean strains. The dendrogram confirmed that the Chilean strains presented a genetic profile with a high homology index that was different from the profile of the reference strain, with which the Chilean profile had low homology (< 50%). Similarity among the field strains analyzed was further confirmed by the fact that all the serotype-6 strains tested presented the same antibiotic-sensitivity profile: they were 100% susceptible to the 4 antibiotics used (ampicillin, ceftiofur, penicillin, and TMP/SMX), which have been reported to be highly effective against this patho-
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gen (12). The serotype-22 strain presented a similar profile, except that it was resistant to TMP/SMX. Our results clearly showed low variation among the field strains recovered from diseased pigs at different farms and from those at the same farm over time. One possible explanation is that Chile works with a relatively small number of genetic companies that provide pigs, which may reduce the origin diversity of strains. No studies of the virulence of serotype-6 strains have been described in the literature. In fact, this serotype is seldom isolated from diseased animals. For example, less than 1% of more than 1000 strains isolated from diseased pigs in Canada between 2008 and 2011 belonged to this serotype (13). Results from the present study indicate that the serotype-6 field strains from Chile (as well as the Danish serotype-6 reference strain) do not secrete suilysin, a virulence factor previously described for S. suis serotype 2 (5). When we experimentally infected 26 mice, using a well-standardized model, to evaluate the potential virulence of a representative Chilean strain, we found that all 6 animals in the positive-control group (those inoculated with a serotype-2 strain) showed, as expected (10), clinical signs of depression at 4 h, and all died during the 2nd day after infection. The 10 mice inoculated with the Danish serotype-6 reference strain and the 10 mice inoculated with a serotype-6 Chilean strain from the current study, however, showed no clinical signs of septicemia or meningitis during 10 d of observation after inoculation. Although the murine model has been successfully used to study serotypes 2 (10), 14 (14), and 9 (M. Gottschalk, 2015, unpublished observations), whether it is appropriate for studying serotype-6 strains, or at least the strains tested in this study, is not known. Clinical problems due to S. suis in the studied herds could not be associated with the presence of concomitant infections or underlying problems. In fact, the country was free of porcine respiratory and reproductive syndrome virus at the time the isolates were recovered. These facts suggest that the isolated strains of serotype 6 possess, in fact, enhanced virulence capacity. Finally, only 1 strain, isolated from a case of arthritis, was different from all the other strains recovered from the 29 studied pigs. It was confirmed to be of serotype 22. Interesting, this serotype has recently been described as a new species: S. parasuis (4). More studies about the virulence of this serotype are to come. In conclusion, this is the first report of S. suis at Chilean swine farms studied by means of serotyping, hemolysin production, genotyping, antibiotic resistance, and virulence capacity. Further studies with a higher number of strains and farms, as well as farms from different production regions of Chile, are necessary to confirm whether the distribution of virulent S. suis recovered from diseased
2000;64:0–00
100
80
60
270 271 284 285 286 287 289 296 297 298 398 423 424 425 510 511 526 54 743 763 772 800
Figure 1. Dendrogram obtained from the results of enterobacterial repetitive intergenic consensus sequence-based polymerase chain reaction of DNA from 22 field strains of Streptococcus suis serotype 6 recovered from pigs with clinical signs at different farms in central Chile.
pigs is mostly clonal. It is important to remember that serotype 2 is also present in Chile, since human cases due to this serotype have been reported.
4.
Acknowledgments Dr. Morales was awarded a scholarship from the Emerging Leaders in the Americas Program (http://www.scholarshipsbourses.gc.ca/scholarships-bourses/can/institutions/elap-pfla. aspx?lang=eng). This work was supported by the Natural Sciences and Engineering Research Council of Canada through grant 154280 to Dr. Gottschalk.
References 1. Gottschalk M. Streptococcosis. In: Zimmerman J, Karriker L, Ramirez A, Schwartz K, Stevenson G, eds. Diseases of Swine. 10th ed. Ames, Iowa: Wiley-Blackwell, 2012:841–855. 2. Benga L, Fulde M, Neis C, Goethe R, Valentin-Weigand P. Polysaccharide capsule and suilysin contribute to extracellular survival of Streptococcus suis co-cultivated with primary porcine phagocytes. Vet Microbiol 2008;132:211–219. 3. Goyette-Desjardins G, Auger JP, Xu J, Segura M, Gottschalk M. Streptococcus suis, an important pig pathogen and emerging zoonotic agent — An update on the worldwide distribution
2000;64:0–00
5.
6.
7.
8.
9.
based on serotyping and sequence typing. Emerg Microbes Infect 2014;3:1–20. Epub 2014 Jun 18. Nomoto R, Maruyama F, Ishida S, Tohya M, Sekizaki T, Osawa R. Reappraisal of the taxonomy of Streptococcus suis serotypes 20, 22, and 26: Streptococcus parasuis sp. nov. Int J Syst Evol Microbiol 2015;65:438–443. Epub 2014 Nov 10. Fittipaldi N, Segura M, Grenier D, Gottschalk M. Virulence factors involved in the pathogenesis of the infection caused by the swine pathogen and zoonotic agent Streptococcus suis. Future Microbiol 2012;7:259–279. Koch E, Fuentes G, Carvajal R, et al. Meningitis bacteriana aguda por Streptococcus suis en criadores de cerdos: Comunicación de los primeros dos casos en Chile. Rev Chilena Infectol 2013;30:557–561. Gottschalk M, Higgins R, Boudreau M. Use of polyvalent coagglutination reagents for serotyping of Streptococcus suis. J Clin Microbiol 1993;31:2192–2194. Versalovic J, Koeuth T, Lupski JR. Distribution of repetitive DNA sequences in eubacteria and application to fingerprinting of bacterial genomes. Nucleic Acids Res 1991;19:6823–6831. Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Disk and Dilution Susceptibility Tests for Bacteria Isolated from Animals; Approved Standard. 3rd ed. CLSI doc M31-A3. Wayne, Pennsylvania: CLSI, 2008: 19–20.
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10. Dominguez-Purano MC, Segura M, Plante MM, Lacouture S, Rivest S, Gottshalk M. Streptococcus suis serotype 2, an important swine and human pathogen, induces strong systemic and cerebral inflammatory responses in a mouse model of infection. J Immunol 2007;179:1842–1854. 11. Olfert ED, Cross BM, McWilliam AA, eds. Guide to the Care and Use of Experimental Animals. 2nd ed. Vol. 1. Ottawa, Ontario: Canadian Council on Animal Care, 1993. Available from: www.ccac.ca/Documents/Standards/Guidelines/Experimental_ Animals_Vol1.pdf Last accessed June 21, 2015. 12. Baez M, Espinosa I, Vichi J, Martínez S. Estudio de la sensibilidad in vitro frente a diferentes antimicrobianos en cepas
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de S. suis asociados a neumonía porcina. Rev Salud Anim 2012;34:57–62. 13. Gottschalk M, Lacouture S, Bonifait L, Roy D, Fittipaldi N, Grenier D. Characterization of Streptococcus suis isolates recovered between 2008 and 2011 from diseased pigs in Québec, Canada. Vet Microbiol 2013;162:819–825. 14. Roy D, Auger JP, Segura M, et al. Role of the capsular polysaccharide as a virulence factor for Streptococcus suis serotype 14. Can J Vet Res 2015;79:141–146.
2000;64:0–00
Communication brève
Clonal distribution of Streptococcus suis isolated from diseased pigs in the central region of Chile Bárbara Morales, Álvaro Ruiz, Sonia Lacouture, Marcelo Gottschalk
Abstract The characteristics of 29 Chilean field strains of Streptococcus suis recovered between 2007 and 2011 from pigs with clinical signs at different farms were studied. Serotyping with use of the coagglutination test revealed that all but 1 strain belonged to serotype 6; the remaining strain was serotype 22. All the serotype-6 strains were suilysin (hemolysin)-negative; in addition, they were found to be genotypically homogeneous by enterobacterial repetitive intergenic consensus sequence-based polymerase chain reaction (ERIC-PCR) and sensitive to ampicillin, ceftiofur, penicillin, and trimethoprim/sulfamethoxazole. The results indicate that, in contrast to what is generally observed in other countries, a single clone of S. suis was isolated from diseased pigs in the central region of Chile.
Résumé Les caractéristiques de 29 souches de Streptococcus suis d’origine chilienne provenant de porcs malades, dont la plupart d’entre elles n’ont aucun lien épidémiologique, ont été étudiées. Toutes les souches ont montré appartenir au sérotype 6 sauf 1, qui a été caractérisée comme étant un sérotype 22. De plus, toutes les souches du sérotype 6 se sont révélées négatives pour la production de suilysine (hémolysine). Avec l’utilisation d’un test PCR ciblant des séquences consensus intergéniques répétées d’entérobactéries (ERIC-PCR), toutes les souches de sérotype 6 testées se sont avérées être génétiquement homogènes. Finalement, ces souches se sont montrées sensibles à l’ampicilline, au ceftiofur, à la pénicilline ainsi qu’à l’association triméthoprime-sulfaméthoxazole. Les résultats indiquent que, contrairement à ce qui a déjà été observé dans d’autres pays, un seul clone de S. suis est majoritairement isolé chez des porcs malades dans la région centrale du Chili. (Traduit par les auteurs)
Streptococcus suis is a bacterial pathogen of global importance, able to induce meningitis, sepsis, and arthritis in piglets and grower– finisher pigs (1). Furthermore, S. suis is a zoonotic agent, causing meningitis in humans that are in direct contact with infected pigs or pork-derived products (2). There are currently 35 serotypes, of which serotypes 2, 3, and 9 are the most frequently isolated from diseased pigs in different parts of the world (3). Some previously described serotypes have recently been classified as a new species (4). Virulence factors and pathogenesis of S. suis infection have been studied mainly for serotype 2, which is also an important zoonotic agent (5). Very few data are available concerning serotype distribution of S. suis isolated from diseased pigs in South America. In fact, they are available only from Brazil (2). Interestingly, cases of S. suis infection in humans have recently been described in Chile (6); however, there is no information about how this pathogen affects the pig farms in this country. In addition to Chile, 2 other South American countries, Argentina and French Guiana, have reported cases of S. suis infection in humans (2). In the present study, and for the first time, we phenotypically and genotypically analyzed strains isolated from diseased pigs at nonrelated farms in central Chile. Included in this study were 29 field strains isolated from clinically affected pigs at 7 nonrelated intensive-production farms in the
central region of Chile between 2007 and 2011 (Table I). Some strains from the same farm were recovered during different years. Strains were recovered from various tissues (Table II), but predominantly from cases of meningitis, and were kept in storage beads (Cryobank; Copan Diagnostics, Murrieta, California, USA) at −80°C. Bacteria were plated on 5% sheep blood agar (bioMérieux, Marcy l’Étoile, France), incubated aerobically at 37°C, and evaluated for growth after 24 and 48 h until a-hemolytic colonies were observed. Capsular serotyping of the field strains was carried out by means of the coagglutination test with 34 reference antisera as previously described (7). The hemolysin test was done on all the field strains as well as negative (serotype-2 strain TD10) and positive (serotype-2 strain P1/7) controls; the supernatant and erythrocytes were prepared and the hemolytic activity was assessed as previously described (7). All the analyzed strains were 100% serotypeable: all but 1 strain belonged to serotype 6; the remaining strain was serotype 22. Enterobacterial repetitive intergenic consensus sequencebased polymerase chain reaction (ERIC-PCR) was carried out with 22 of the serotype-6 strains (6 strains were no longer viable) and, for comparison purposes, the Danish serotype-6 reference strain to compare the strains genotypically. DNA extraction was done with the QIAamp DNA minikit (Qiagen, Valencia, California, USA), and
Departamento de Patología y Medicina Preventiva, Universidad de Concepción, Concepción, Chile (Morales, Ruiz); Faculté de médecine vétérinaire, Université de Montréal, 3200, rue Sicotte, Saint-Hyacinthe, Québec J2S 2M2 (Lacouture, Gottschalk). Address all correspondence to Dr. Marcelo Gottschalk; telephone: 450-773-8521, ext. 8374; fax: 450-778-8108; e-mail: [email protected] Received January 8, 2015. Accepted March 26, 2015. 2015;79:343–346
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343
Table I. Field strains of Streptococcus suis used in this study as distributed by Chilean farm and year of isolation
Table II. Distribution of the 28 serotype-6 S. suis field isolates according to the tissue from which they were recovered
Number of strains Farm 2007 2008 2009 2010 2011 Total A 1 2 2 5 B 1 2 1 3 7 C 2 2 D 9 9 E 3 3 F 1 1 G 2 2 Total 2 16 4 5 2 29
Tissue Number of isolates Brain or cerebrospinal fluid 15 Joint or synovial fluid 6 Heart 2 Lymph node 1 Lung 4
the PCR technique was applied as previously described (8). Band patterns were analyzed with the use of Bionumerics software, version 6.5 (Applied Maths, Austin, Texas, USA). Five randomly chosen representative isolates of S. suis were plated on Müeller–Hinton agar supplemented with 5% sheep blood (Oxoid, Ottawa, Ontario) and tested for susceptibility to the antibiotics ampicillin, ceftiofur, penicillin, and trimethoprim/sulfamethoxazole (TMP/SMX) before being incubated at 37°C for 18 h (9). Finally, to evaluate virulence, we used a mouse model of infection as previously described for serotype-2 strains (10). One representative Chilean isolate of serotype 6 was chosen and compared with the serotype-6 reference strain. A well-known virulent strain of S. suis serotype 2 (strain 31533) was used as a positive control. This study was conducted according to the policies and principles of the Canadian Council on Animal Care (11). Of 30 CD1 female mice (Charles Rivers Laboratories, Wilmington, Massachusetts, USA) 10 were inoculated with a Chilean strain, 10 with the Danish serotype-6 reference strain, and 6 with the serotype-2 positive control, each mouse receiving 2 3 108 colony-forming units by the intraperitoneal route; the other 4 mice served as negative noninfected controls. The mice were monitored 3 times a day for 10 d for the presence of clinical signs associated with septicemia and/or meningitis or death (10). Of the 29 strains, 28 belonged to a single serotype, serotype 6. It is quite unusual to find a common serotype among so many strains recovered from different herds of a region or country. In fact, this has not been previously described for S. suis. Almost half of the strains were isolated from cases of meningitis (Table II). The ERICPCR results showed that the 22 tested strains of serotype 6 had an identical genetic pattern (Figure 1), a pattern clearly different from that of the Danish reference serotype-6 strain. The molecular weights of the bands were between the ranks of 1700 and 800 bp for the reference strain but between the ranks of 4000 and 300 bp for the 22 Chilean strains. The dendrogram confirmed that the Chilean strains presented a genetic profile with a high homology index that was different from the profile of the reference strain, with which the Chilean profile had low homology (< 50%). Similarity among the field strains analyzed was further confirmed by the fact that all the serotype-6 strains tested presented the same antibiotic-sensitivity profile: they were 100% susceptible to the 4 antibiotics used (ampicillin, ceftiofur, penicillin, and TMP/SMX), which have been reported to be highly effective against this patho-
344
The Canadian Journal of Veterinary Research
gen (12). The serotype-22 strain presented a similar profile, except that it was resistant to TMP/SMX. Our results clearly showed low variation among the field strains recovered from diseased pigs at different farms and from those at the same farm over time. One possible explanation is that Chile works with a relatively small number of genetic companies that provide pigs, which may reduce the origin diversity of strains. No studies of the virulence of serotype-6 strains have been described in the literature. In fact, this serotype is seldom isolated from diseased animals. For example, less than 1% of more than 1000 strains isolated from diseased pigs in Canada between 2008 and 2011 belonged to this serotype (13). Results from the present study indicate that the serotype-6 field strains from Chile (as well as the Danish serotype-6 reference strain) do not secrete suilysin, a virulence factor previously described for S. suis serotype 2 (5). When we experimentally infected 26 mice, using a well-standardized model, to evaluate the potential virulence of a representative Chilean strain, we found that all 6 animals in the positive-control group (those inoculated with a serotype-2 strain) showed, as expected (10), clinical signs of depression at 4 h, and all died during the 2nd day after infection. The 10 mice inoculated with the Danish serotype-6 reference strain and the 10 mice inoculated with a serotype-6 Chilean strain from the current study, however, showed no clinical signs of septicemia or meningitis during 10 d of observation after inoculation. Although the murine model has been successfully used to study serotypes 2 (10), 14 (14), and 9 (M. Gottschalk, 2015, unpublished observations), whether it is appropriate for studying serotype-6 strains, or at least the strains tested in this study, is not known. Clinical problems due to S. suis in the studied herds could not be associated with the presence of concomitant infections or underlying problems. In fact, the country was free of porcine respiratory and reproductive syndrome virus at the time the isolates were recovered. These facts suggest that the isolated strains of serotype 6 possess, in fact, enhanced virulence capacity. Finally, only 1 strain, isolated from a case of arthritis, was different from all the other strains recovered from the 29 studied pigs. It was confirmed to be of serotype 22. Interesting, this serotype has recently been described as a new species: S. parasuis (4). More studies about the virulence of this serotype are to come. In conclusion, this is the first report of S. suis at Chilean swine farms studied by means of serotyping, hemolysin production, genotyping, antibiotic resistance, and virulence capacity. Further studies with a higher number of strains and farms, as well as farms from different production regions of Chile, are necessary to confirm whether the distribution of virulent S. suis recovered from diseased
2000;64:0–00
100
80
60
270 271 284 285 286 287 289 296 297 298 398 423 424 425 510 511 526 54 743 763 772 800
Figure 1. Dendrogram obtained from the results of enterobacterial repetitive intergenic consensus sequence-based polymerase chain reaction of DNA from 22 field strains of Streptococcus suis serotype 6 recovered from pigs with clinical signs at different farms in central Chile.
pigs is mostly clonal. It is important to remember that serotype 2 is also present in Chile, since human cases due to this serotype have been reported.
4.
Acknowledgments Dr. Morales was awarded a scholarship from the Emerging Leaders in the Americas Program (http://www.scholarshipsbourses.gc.ca/scholarships-bourses/can/institutions/elap-pfla. aspx?lang=eng). This work was supported by the Natural Sciences and Engineering Research Council of Canada through grant 154280 to Dr. Gottschalk.
References 1. Gottschalk M. Streptococcosis. In: Zimmerman J, Karriker L, Ramirez A, Schwartz K, Stevenson G, eds. Diseases of Swine. 10th ed. Ames, Iowa: Wiley-Blackwell, 2012:841–855. 2. Benga L, Fulde M, Neis C, Goethe R, Valentin-Weigand P. Polysaccharide capsule and suilysin contribute to extracellular survival of Streptococcus suis co-cultivated with primary porcine phagocytes. Vet Microbiol 2008;132:211–219. 3. Goyette-Desjardins G, Auger JP, Xu J, Segura M, Gottschalk M. Streptococcus suis, an important pig pathogen and emerging zoonotic agent — An update on the worldwide distribution
2000;64:0–00
5.
6.
7.
8.
9.
based on serotyping and sequence typing. Emerg Microbes Infect 2014;3:1–20. Epub 2014 Jun 18. Nomoto R, Maruyama F, Ishida S, Tohya M, Sekizaki T, Osawa R. Reappraisal of the taxonomy of Streptococcus suis serotypes 20, 22, and 26: Streptococcus parasuis sp. nov. Int J Syst Evol Microbiol 2015;65:438–443. Epub 2014 Nov 10. Fittipaldi N, Segura M, Grenier D, Gottschalk M. Virulence factors involved in the pathogenesis of the infection caused by the swine pathogen and zoonotic agent Streptococcus suis. Future Microbiol 2012;7:259–279. Koch E, Fuentes G, Carvajal R, et al. Meningitis bacteriana aguda por Streptococcus suis en criadores de cerdos: Comunicación de los primeros dos casos en Chile. Rev Chilena Infectol 2013;30:557–561. Gottschalk M, Higgins R, Boudreau M. Use of polyvalent coagglutination reagents for serotyping of Streptococcus suis. J Clin Microbiol 1993;31:2192–2194. Versalovic J, Koeuth T, Lupski JR. Distribution of repetitive DNA sequences in eubacteria and application to fingerprinting of bacterial genomes. Nucleic Acids Res 1991;19:6823–6831. Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Disk and Dilution Susceptibility Tests for Bacteria Isolated from Animals; Approved Standard. 3rd ed. CLSI doc M31-A3. Wayne, Pennsylvania: CLSI, 2008: 19–20.
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10. Dominguez-Purano MC, Segura M, Plante MM, Lacouture S, Rivest S, Gottshalk M. Streptococcus suis serotype 2, an important swine and human pathogen, induces strong systemic and cerebral inflammatory responses in a mouse model of infection. J Immunol 2007;179:1842–1854. 11. Olfert ED, Cross BM, McWilliam AA, eds. Guide to the Care and Use of Experimental Animals. 2nd ed. Vol. 1. Ottawa, Ontario: Canadian Council on Animal Care, 1993. Available from: www.ccac.ca/Documents/Standards/Guidelines/Experimental_ Animals_Vol1.pdf Last accessed June 21, 2015. 12. Baez M, Espinosa I, Vichi J, Martínez S. Estudio de la sensibilidad in vitro frente a diferentes antimicrobianos en cepas
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de S. suis asociados a neumonía porcina. Rev Salud Anim 2012;34:57–62. 13. Gottschalk M, Lacouture S, Bonifait L, Roy D, Fittipaldi N, Grenier D. Characterization of Streptococcus suis isolates recovered between 2008 and 2011 from diseased pigs in Québec, Canada. Vet Microbiol 2013;162:819–825. 14. Roy D, Auger JP, Segura M, et al. Role of the capsular polysaccharide as a virulence factor for Streptococcus suis serotype 14. Can J Vet Res 2015;79:141–146.
2000;64:0–00
