Effects of Thymus vulgaris, Allium sativum, Cinnamomum verum and Cuminum cyminum on infectious bacterium (Streptococcus iniae), an in vitro experiment

The importance of aquatic animal diseases, as well as a large amount of reports on economic losses in the rainbow trout industry due to infectious disorders is not obscure todays. As a result, the emergence of antibiotic-resistance of bacteria led to higher demand for identifying the effective concentration of essences as an alternative antimicrobial agent. The aim of this study was to evaluate the effects of Thymus vulgaris, Allium sativum, Cinnamomum verum and Cuminum cyminum essences on Streptococcus iniae growth rate, an in vitro experiment. To address that, the completely randomized design was performed with 3 replicates. Following bacterial culturing on plates, several wells were created and then four different concentrations (50, 100, 150,200 ppm) of each essence were injected into the wells. The plated were incubated for 24, 48, 72 and 120 h and the maximum inhibitory zone was measured by using a Caliper. Obtained results showed significant (P<0.001) combined effects of type of essence, essence concentration and time of incubation on bacterial growth. The maximum inhibition for S. iniae was observed in A. sativum, T. vulgaris and to some degree in C. cyminum and finally C. verum, which were significantly different (P<0.05). At the beginning of incubation (24 h), the most inhibition zone for S. iniae was found in A. sativum and T. vulgaris (P<0.05). In conclusion, the herbal essence applied here, had significant antibacterial effects but with different degrees.