Investigation of in vivo antimicrobial effects of beard lichen aqueous methanolic extract in rainbow trout (Onchorhynchus mykiss) against lactococcus garviae infection

In this study, therapeutical effects of aqueous methanolic extracts of beard lichen (Usnea barbat) against Lactococcus garvieae in rainbow trout (Onchorhynchus mykiss) were investigated. Four different concentration of extract (0 mg/100 µl (Control), 4 mg/100 µl, 8 mg/100 µl, 12 mg/100 µl) and also to compare results two different type of antibiotic such as florfenicol and eritromycine were given orally using feeding needle to the each individual in all experimental group twice in a day after intramuscular inoculation of L. garvieae. The study was maintained during 10 days and every 0, 3rd, 7th and 10th day of the study, blood was collected and immune responses were determined. In the study, superoxide radical realizing was increased in 12 mg beard lichen, florfenicol and eritromycine compared to control (P<0.05). Lysozyme activity was generally decreased (P<0.05) or not differences observed in all experimental group compared to control (P>0.05). Myeloperoxidase was generally significantly increased in all antibiotic groups. Florfenicol group at the 7th day of the sampling time (P<0.05). Generally myeloperoxidase was increased in almost all experimental groups compared to control. Some hematological parameters in experimental groups were increased. However this increase was not significant. However, 7th day of the study almost all blood parameters were significantly increased in 4 mg beard lichen group. Survival rate of the groups was found in control group as 46.15 %. There were no significant differences between control and 12 mg beard lichen groups (P>0.05). All the other groups' survival rate was significantly increased compared to control. The highest survival rate was found in florcenicol group (82.69 %). 4 mg beard lichen group, 8 mg beard lichen group and eritromycine group survival rate was investigated as 73.08 %, 65.38% and 80.77% respectively. According to our results, beard lichen methanolic extract is an effective therapeutic against L. garvieae infection in rainbow trout at the dose of 4 mg/32,34g body weight/day.