Streptococcus suis (S. suis) is a major swine pathogen and an emerging zoonotic agent and is an increasing public health problem across Asia. The present study was undertaken to estimate the antibacterial effect of GR extract and therapeutic effect of GR extract against S. suis infection in mice. At the concentration of GR extract 2.5 mg/ml, the antibacterial effect was not shown on S. suis. However, the antibacterial effect against S. suis was observed at the concentration of GR extract 5.0 mg/ml. Oral administration of GR extract at the dose of 10 mg/kg showed a therapeutic effect for S. suis infected BALB/c mice. The mortality of GR extract-treated mice at the concentration of 5, 10 and 20 mg/kg was 80%, 70%, and 50% at 12 days, respectively, while that of untreated mice was 100% at 8 days after a lethal dose of S. suis infection. The results of our study strongly indicate that GR extract has potential as an effective for S. suis infection in mice.

ABSTRACT
 Introduction
 Materials and Methods
  Bacteria and culture
  Preparation of GR extracts
  Determination of antibacterial activity
  Animal challenge test
  Statistical analyses
 Results and Discussion
  Determination of antibacterial activity
  Animal challenge test
 References

• Chun-Nam Cha(Engineering Research Institute, Department of Industrial Systems Engineering, Gyeongsang National University)
• Eun-Ah Yu(Tongyeong National Quarantine Station, Ministry of Health & Welfare)
• Eun-Kee Park(Medical Humanities and Social Medicine, College of Medicine, Kosin University)
• Hyunju Choi(Elderly Life Redesign Institute, Department of Biomedical Laboratory Science, Inje University)
• Suk Kim(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University)
• Hu Jang Lee(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University) Correspondence to