Risk factors for Streptococcus suis infection: A systematic review and meta-analysis

Abstract Streptococcus suis (S. suis) is a gram-positive bacterial pathogen in pigs which can cause serious infections in human including meningitis, and septicaemia resulting in serious complications. There were discrepancies between different data and little is known concerning associated risk factors of S. suis. A systematic review and meta-analysis was conducted to investigate on S. suis infection risk factors in human. We searched eight relevant databases using the MeSH terms “Streptococcus suis” OR “Streptococcus suis AND infection” limited in human with no time nor language restriction. Out of 4,999 articles identified, 32 and 3 studies were included for systematic review and meta-analysis respectively with a total of 1,454 Streptococcus suis cases reported. S. suis patients were generally adult males and the elderly. The mean age ranged between 37 to 63 years. Meningitis was the most common clinical manifestation, and deafness was the most common sequelae found among survivors followed by vestibular dysfunction. Infective endocarditis was also noted as among the most common clinical presentations associated with high mortality rate in a few studies. Meta-analyses categorized by type of control groups (community control, and non-S. suis sepsis) were done among 850 participants in 3 studies. The combined odd ratios for studies using community control groups and non-S. Suis sepsis as controls respectively were 4.63 (95% CI 2.94–7.29) and 78.00 (95% CI 10.38–585.87) for raw pork consumption, 4.01 (95% CI 2.61–6.15) and 3.03 (95% CI 1.61–5.68) for exposure to pigs or pork, 11.47, (95% CI 5.68–23.14) and 3.07 (95% CI 1.81–5.18) for pig-related occupation and 3.56 (95% CI 2.18–5.80) and 5.84 (95% CI 2.76–12.36) for male sex. The results were found to be significantly associated with S. suis infection and there was non-significant heterogeneity. History of skin injury and underlying diseases were noted only a small percentage in most studies. Setting up an effective screening protocol and public health interventions would be effective to enhance understanding about the disease

Streptococcus suis

Streptococcus suis is an important pathogen causing economic problems in the pig industry. Moreover, it is a zoonotic agent causing severe infections to people in close contact with infected pigs or pork-derived products. Although considered sporadic in the past, human S. suis infections have been reported during the last 45 years, with two large outbreaks recorded in China. In fact, the number of reported human cases has significantly increased in recent years. In this review, we present the worldwide distribution of serotypes and sequence types (STs), as determined by multilocus sequence typing, for pigs (between 2002 and 2013) and humans (between 1968 and 2013). The methods employed for S. suis identification and typing, the current epidemiological knowledge regarding serotypes and STs and the zoonotic potential of S. suis are discussed. Increased awareness of S. suis in both human and veterinary diagnostic laboratories and further establishment of typing methods will contribute to our knowledge of this pathogen, especially in regions where complete and/or recent data is lacking. More research is required to understand differences in virulence that occur among S. suis strains and if these differences can be associated with specific serotypes or STs