Evaluation of antibacterial effect of annatto (norbixin) against several pathogenic bacteria

Using well method and Macrodilution technique، the effect of annatto extract (norbixin 1%) on growth ability and spore germination of several pathogenic bacteria (Staphylococcus aureus، Bacillus sereus، Clostridium perfringens and Escherchia coli) was investigated. According to the results emerged from inhibition zone diameter evaluation، the annatto extract showed inhibitory effect on S. aureus، B. sereus and C. perfringens (with 13، 12 and 10 mm inhibition zone diameter، respectively)، but it was inactive against Ecoli. The outcome of Macrodilution technique indicated that the minimum inhibitory concentrations in 106، 104 and 102 cfu/ml of S. aureus and B. sereus are 1. 2، 0. 6 and 0. 3 g/l of the annatto extract. The concentration values، however، are 2. 4، 1. 2 and 0. 6 g/l at the same cfu/ml of C. perfringens. In addition، the abovementioned concentration values of annatto were capable of inhibiting spore germination of B. sereus and C. perfringens. As an overall result، annatto can be used as a natural antibacterial food additive in many food products.