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. 2012;7(2):e31265.
doi: 10.1371/journal.pone.0031265. Epub 2012 Feb 21.

Population-based study of Streptococcus suis infection in humans in Phayao Province in northern Thailand

Dan Takeuchi  1 , Anusak Kerdsin, Anupong Pienpringam, Phacharaphan Loetthong, Sutit Samerchea, Pakkinee Luangsuk, Kasean Khamisara, Nithita Wongwan, Prasanee Areeratana, Piphat Chiranairadul, Suwat Lertchayanti, Sininat Petcharat, Amara Yowang, Phanupong Chaiwongsaen, Tatsuya Nakayama, Yukihiro Akeda, Shigeyuki Hamada, Pathom Sawanpanyalert, Surang Dejsirilert, Kazunori Oishi
Affiliations

Population-based study of Streptococcus suis infection in humans in Phayao Province in northern Thailand

Dan Takeuchi et al. PLoS One. 2012.

Abstract

Background: Streptococcus suis infection in humans has received increasing worldwide recognition.

Methods and findings: A prospective study of S. suis infection in humans was conducted in Phayao Province in northern Thailand to determine the incidence and the risk behaviors of the disease in this region in 2010. Thirty-one cases were confirmed. The case fatality rate was 16.1%, and the estimated incidence rate was 6.2 per 100,000 in the general population. The peak incidence occurred in May. The median age of the patients was 53 years and 64.5% were men. Consumption of raw pork products was confirmed in 22 cases and the median incubation period (range) was 2 days (0-11) after consumption of raw pork products. Isolates from 31 patients were confirmed as serotype 2 in 23 patients (74.2%) and serotype 14 in eight patients (25.8%). The major sequence types (STs) were ST1 (n = 20) for serotype 2 and ST105 (n = 8) for serotype 14. The epidemiological analysis suggested three possible clusters, which included 17 cases. In the largest possible cluster of 10 cases in Chiang Kham and its neighboring districts in May, the source of infection in four cases was identified as a raw pork dish served at the same restaurant in this district. Microbiological analysis confirmed that three of four cases associated with consumption of raw pork at this restaurant were attributable to an identical strain of serotype 2 with ST1 and pulsotype A2.

Conclusions: Our data suggest a high incidence rate of S. suis infection in the general population in Phayao Province in 2010 and confirm a cluster of three cases in 31 human cases. Food safety control should be strengthened especially for raw pork products in northern Thailand.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Location of the study site and distribution of human isolates.
(A) Location of Phayao Province in northern Thailand. (B) Distribution and sequence typing of 31 human isolates of Streptococcus suis in Phayao Province in 2010 (B). One symbol is one case. Closed symbols denote fatal cases, and open symbols denote nonfatal cases.
Figure 2
Figure 2. Monthly distribution of human cases of Streptococcus suis infection in each district in Phayao Province in 2010.
See this image and copyright information in PMC

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