Antibacterial Activity of Chrysanthemum indicum, Centella asiatica and Andrographis paniculata against Bacillus cereus and Listeria monocytogenes under Osmotic Stress

Abstract

Bacillus cereus and Listeria monocytogenes have an ability to survive in high osmotic stress. Three Thai herbs; Chrysanthemum indicum, Centella asiatica and Andrographis paniculata, are chosen to study their antibacterial activity on B. cereus and L. monocytogenes 10403S under normal and osmotic stress (5% NaCl) condition by agar disc diffusion method. The in vitro antibacterial screening results of crude 95% ethanolic extracted under normal stress showed A. paniculata, the highest antibacterial activity, C. asiatica and C. indicum crude 3.33 ± 0.47, 1.67 ± 0.94, and 1.17 ± 0.85 mm, respectively, against B. cereus. Only C. asiatica and A. paniculata crude showed antibacterial activity against L. monocytogenes; 1.67 ± 0.24, and 1.83 ± 0.24 mm, respectively. Under osmotic stress, the antibacterial activity of all crude 95% ethanolic extracted was increased two-fold. The MICs of A. paniculata, C. asiatica and C. indicum showed 4, 16, and 16 µl /ml against B. cereus while A. paniculata and C. asiatica showed 16 and 8 µl /ml, respectively, against L. monocytogenes, respectively. The MCBs of A. paniculata, C. asiatica and C. indicum showed 4, 16, and 32 µl /ml against B. cereus while A. paniculata and C. asiatica showed 16 and 32 µl /ml, respectively, against L. monocytogenes.