Streptococcus suis infection is a severe zoonotic disease commonly found in Northern Thailand where people often consume raw pork and/or pig’s blood. The most frequent clinical presentations are meningitis, sepsis, and endocarditis with higher rate of mortality and hearing loss sequelae. To clarify the correlation between pulsed-field gel electrophoresis (PFGE) groups and mrp/epf/sly genotypes of S. suis serotype 2, 62 patient and 4 healthy pig isolates from Northern Thailand were studied. By PFGE analysis, at 66% homology, most human isolates (69.4%) and 1 pig isolate were in group A, whereas 14.5% of human isolates and 3 out of 4 pig isolates were in group D. According to mrp/epf/sly genotypes, 80.6% of human isolates were identified in mrp+epf？sly？ and only 12.9% were in mrp？epf？sly+ genotypes; in contrast, 1 and 3 pig isolates were detected in these two genotypes, respectively. Interestingly, all isolates of S. suis serotype 2 classified in PFGE groups A, B, and E were set in mrp+epf？sly？ genotypes. These data show a close correlation between PFGE groups and mrp/epf/sly genotypes of human S. suis serotype 2. 1. Introduction Streptococcus suis, recognized as a significant swine and human pathogen, mainly causes meningitis, sepsis, endocarditis, and septic shock [1]. It can be transmitted to humans by contact with sick or carrier pigs, pig-derived products [2], or eating undercooked pork [3, 4]. Capsular polysaccharide (CPS) is the most important proven critical virulence factor, due to its antiphagocytosis activity [5]. Of 35 serotypes, serotype 2 is the most frequently isolated and associated with disease in both animals and humans [6]. In addition, virulence-related proteins, such as muramidase-released protein (MRP), extracellular factor (EF), and hemolysin (suilysin, SLY), are expressed by some strains of S. sui “as discussed by Gottschalk and Segura [1].” These proteins are encoded by the genes mrp, epf, and sly, respectively. MRP/EF/SLY phenotypes or mrp/epf/sly genotypes of S. suis serotype 2 have been studied mostly in pig isolates with very little data for human isolates [1, 7], especially in Northern Thailand. Pulsed-field gel electrophoresis (PFGE) of DNA restricted with SmaI has been confirmed to be valuable for evaluating the genetic diversity of S. suis [8]. The present study aims to clarify the correlation between PFGE and mrp/epf/sly genotypes of S. suis serotype 2 isolated from patients in Northern Thailand. 2. Materials and Methods 2.1. S. suis Serotype 2 Strains from Humans and Healthy Pigs A total of 66 S. suis serotype 2 (SS2)
References
[1]
M. Gottschalk and M. Segura, “The pathogenesis of the meningitis caused by Streptococcus suis: the unresolved questions,” Veterinary Microbiology, vol. 76, no. 3, pp. 259–272, 2000.
[2]
M. Gottschalk, M. Segura, and J. Xu, “Streptococcus suis infections in humans: the Chinese experience and the situation in North America,” Animal Health Research Reviews, vol. 8, no. 1, pp. 29–45, 2007.
[3]
A. Fongcom, R. Mongkol, N. Yoonim, S. Pruksakorn, and P. Tharavichitkul, “Streptococcus suis infection in Northern Thailand,” Journal of the Medical Association of Thailand, vol. 84, no. 10, pp. 1502–1508, 2001.
[4]
W. Wangsomboonsiri, T. Luksananun, S. Saksornchai, K. Ketwong, and S. Sungkanuparph, “Streptococcus suis infection and risk factors for mortality,” Journal of Infection, vol. 57, no. 5, pp. 392–396, 2008.
[5]
M. Segura, M. Gottschalk, and M. Olivier, “Encapsulated Streptococcus suis inhibits activation of signaling pathways involved in phagocytosis,” Infection and Immunity, vol. 72, no. 9, pp. 5322–5330, 2004.
[6]
M. Gottschalk, A. Lebrun, H. Wisselink, J. D. Dubreuil, H. Smith, and U. Vecht, “Production of virulence-related proteins by Canadian strains of Streptococcus suis capsular type 2,” Canadian Journal of Veterinary Research, vol. 62, no. 1, pp. 75–79, 1998.
[7]
D. Takamatsu, K. Wongsawan, M. Osaki et al., “Streptococcus suis in humans, Thailand,” Emerging Infectious Diseases, vol. 14, no. 1, pp. 181–183, 2008.
[8]
F. Berthelot-Hérault, C. Marois, M. Gottschalk, and M. Kobisch, “Genetic diversity of Streptococcus suis strains isolated from pigs and humans as revealed by pulsed-field gel electrophoresis,” Journal of Clinical Microbiology, vol. 40, no. 2, pp. 615–619, 2002.
[9]
Y. Kataoka, C. Sugimoto, M. Nakazawa, and M. Kashiwazaki, “Detection of Streptococcus suis type 2 in tonsils of slaughtered pigs using improved selective and differential media,” Veterinary Microbiology, vol. 28, no. 4, pp. 335–342, 1991.
[10]
W.-G. Son, D.-S. Lee, N. Yamatoda et al., “Molecular typing of vapA-positive Rhodococcus equi isolates from Jeju native horses, Korea,” Journal of Veterinary Medical Science, vol. 68, no. 3, pp. 249–253, 2006.
[11]
S. Pruksakorn, N. Sittisombut, C. Phornphutkul, C. Pruksachatkunakorn, M. F. Good, and E. Brandt, “Epidemiological analysis of non-M-typeable group A Streptococcus isolates from a Thai population in Northern Thailand,” Journal of Clinical Microbiology, vol. 38, no. 3, pp. 1250–1254, 2000.
[12]
H. J. Wisselink, F. H. Reek, U. Vecht, N. Stockhofe-Zurwieden, M. A. Smits, and H. E. Smith, “Detection of virulent strains of Streptococcus suis type 2 and highly virulent strains of Streptococcus suis type 1 in tonsillar specimens of pigs by PCR,” Veterinary Microbiology, vol. 67, no. 2, pp. 143–157, 1999.
[13]
O. Okwumabua, O. Abdelmagid, and M. M. Chengappa, “Hybridization analysis of the gene encoding a hemolysin (suilysin) of Streptococcus suis type 2: evidence for the absence of the gene in some isolates,” FEMS Microbiology Letters, vol. 181, no. 1, pp. 113–121, 1999.
[14]
A. Allgaier, R. Goethe, H. J. Wisselink, H. E. Smith, and P. Valentin-Weigand, “Relatedness of Streptococcus suis isolates of various serotypes and clinical backgrounds as evaluated by macrorestriction analysis and expression of potential virulence traits,” Journal of Clinical Microbiology, vol. 39, no. 2, pp. 445–453, 2001.
[15]
L. M. G. Silva, C. G. Baums, T. Rehm, H. J. Wisselink, R. Goethe, and P. Valentin-Weigand, “Virulence-associated gene profiling of Streptococcus suis isolates by PCR,” Veterinary Microbiology, vol. 115, no. 1–3, pp. 117–127, 2006.
[16]
N. T. Hoa, T. T. B. Chieu, T. T. T. Nga, et al., “Slaughterhouse pigs are a major reservoir of Streptococcus suis serotype 2 capable of causing human infection in southern Vietnam,” PloS ONE, vol. 6, no. 3, Article ID e17943, 2011.
[17]
Z. Wei, R. Li, A. Zhang et al., “Characterization of Streptococcus suis isolates from the diseased pigs in China between 2003 and 2007,” Veterinary Microbiology, vol. 137, no. 1-2, pp. 196–201, 2009.
[18]
N. Fittipaldi, T. E. Fuller, J. F. Teel et al., “Serotype distribution and production of muramidase-released protein, extracellular factor and suilysin by field strains of Streptococcus suis isolated in the United States,” Veterinary Microbiology, vol. 139, no. 3-4, pp. 310–317, 2009.
[19]
K. Wongsawan, N. Takenami, S. Pruksakorn et al., “Genetic diversity of Streptococcus suis isolated from pigs and humans in Chiang Mai and Lamphun province, Thailand,” International Congress Series, vol. 1289, pp. 151–154, 2006.
[20]
A. Kerdsin, S. Dejsirilert, P. Puangpatra et al., “Genotypic profile of Streptococcus suis serotype 2 and clinical features of infection in humans, Thailand,” Emerging Infectious Diseases, vol. 17, no. 5, pp. 835–842, 2011.
