Abstract:  In the artificial culture of Litopenaeus vannamei, we found yellow gill disease， resulting in great loss.In order to study the major pathogens causing the yellow gill disease in Litopenaeus vannamei, PCR and 16S rDNA sequencing techniques were used to identify the pathogens isolated from diseased Litopenaeus vannamei, and the pathogenicity of major pathogens was determined by artificial infection, paraffin section was used to observe histopathological lesions in gill tissues. Finally, the drug sensitivity of pathogenic bacteria was determined by drug sensitivity test. The results showed that the yellow gill disease in Litopenaeus vannamei caused by Vibrio shilonii and Exiguobacterium together. In addition, histopathological examination showed enlarged gill filament, diffussion and erosion of tissue in gill. The antibiotic susceptibility test indicated that the strain Vibrio shilonii was sensitive to pipemidic acid, ofloxacin, flumequine, etc., but resistant to sulfadimidine and ampicillin. While, the strain Exiguobacterium was sensitive to ampicillin sodium, ofloxacin, trimethoprim, etc., but resistant to sulfadimidine and ampicillin. This obtained information will provide a theoretical basis for studying the pathogenesis and treatment of yellow gill disease in Litopenaeus vannamei.

Key words: Litopenaeus vannamei, yellow gill disease, 16S rDNA, histopathology, drug sensitivity test