Impact of a Food Safety Campaign on Streptococcus suis Infection in Humans in Thailand.

AbstractStreptococcus suis is an important zoonotic pathogen in swine and humans that causes sepsis and meningitis. Our previous study in Thailand showed that the prevalence of S. suis infection in humans, especially in northern areas of Thailand, and the transmission of the pathogen occurred mainly through the consumption of traditional raw pork products. Considering the high incidence proportion and mortality rate of the disease as an important public health problem, we implemented a food safety campaign in the Phayao Province in northern Thailand in 2011. We evaluated the effects of a food safety campaign by comparing the sociodemographic, clinical, and bacteriological characteristics of cases before and after the campaign. The follow-up study showed a marked decrease of the incidence proportion in the first 2 years, indicating the effectiveness of the campaign. In the third year, however, the incidence proportion slightly increased again, indicating the existence of deep-rooted cultural behaviors and the necessity of continuous public health intervention. Furthermore, epidemiological analysis of the cases made it possible to estimate the infectivity of the pathogen via the oral route of infection. In the present study, we showed the effectiveness of the food safety campaign for controlling the S. suis infection, and we present a role model public health intervention for prevalent areas affected by S. suis infection in humans.

Colloidal gold-based immunochromatographic strip test compromising optimised combinations of anti-S. suis capsular polysaccharide polyclonal antibodies for detection of Streptococcus suis.

A rapid diagnosis kit that detects Streptococcus suis (S. suis) antigens from urine with an immunochromatographic stripe (ICS) test was developed in this study. The ICS test was produced using colloidal gold coated with polyclonal antibodies (pAbs) against S. suis. The pAbs were developed from rabbits immunised with S. suis serotype 2 capsular polysaccharides (CPS). Development of the pAbs was investigated to establish their binding to CPS and to determine the maximum sensitivity of two combination antibodies for the ICS test. The results of the ICS optimisation revealed that the combinations of pAb C-N1 and pAb C-N2 had the highest sensitivity to CPS. The minimum limitation of ICS sensitivity indicated 1.0 × 10(4) colony forming units (CFU) and a CPS concentration of 0.05 µg. The assay time for detection of S. suis antigens is less than 15 min, which is suitable for rapid detection. A cross-reactive test was also conducted, and it detected no other bacteria (Streptococcus pneumoniae, Streptococcus agalactiae, Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae). The cross-reactivity of other serotypes in S. suis was also investigated, and tests for serotypes of 1, 1/2, 3, 4, 5, 6, 7, 8, 9, 14, and 16 were positive. This study presents the first report of a development of an ICS that enables the quantitative detection of streptococcal antigens. The S. suis ICS provides several advantages over other methods, including the speed and simplicity of use.

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

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.