Control By Herbal Extract Of Serratia Marcescens From Cultured Siberian Sturgeon Acipenser Baerii Brandt

A virulent strain of Serratia marcescens, provisionally named SFY, was isolated from farmed Siberian sturgeon Acipenser baerii Brandt suffering from mouth-swelling disease and identified using the ATB 32GN system. Its taxonomic position was determined by phylogenetic analysis. A phylogenetic tree constructed using the neighbor-joining method showed that the SFY isolate was the S. marcescens strain (GenBank accession no. FJ530951). The strain was resistant to chloramphenicol, erythromycin, furazolidone, sulfamethoxydiazine, tetracycline, and trimethoprim-sulfamethoxazole, and susceptible to ciprofloxacin, enrofloxacin, gentamicin, neomycin, norfloxacin, ofloxacin, and streptomycin. Extracts from 30 Chinese herbs were screened as possible agents for control of the disease. Fructus mume extract was the most efficacious agent against the SFY isolate and control bacteria, indicated by its low minimum inhibitory concentration = 21 mg/ml. At concentrations of 10 and 15 g/kg feed, protective efficacy was 42.68% and 64.64%.