China Animal Husbandry and Veterinary Medicine ›› 2021, Vol. 48 ›› Issue (8): 3058-3068.doi: 10.16431/j.cnki.1671-7236.2021.08.039

• Basic Veterinary Medicine • Previous Articles     Next Articles

Isolation,Identification and Biological Characteristics of Streptococcus agalactiae from Tilapia in Hainan

CHEN Huaijun1, GUO Changming2, ZHU Shanyuan2, WU Zhi2, YUAN Sheng2, WANG Yongjuan2, YUAN Cheng2, PAN Yong3, WANG Xiaoye1   

  1. 1. College of Animal Science and Technology, Guangxi University, Nanning 530004, China;
    2. Jiangsu Key Laboratory for High-Tech Research and Development of Veterinary Biopharmaceuticals, Jiangsu Agri-Animal Husbandry Vocational College, Taizhou 225300, China;
    3. Hainan Evergreen Feed Industry Co., Ltd., Haikou 571152, China
  • Received:2021-03-03 Online:2021-08-20 Published:2021-08-19

Abstract: In order to explore the current prevalence and drug resistance of Streptococcus agalactiae isolated from tilapia of Hainan, in this study, 15 strains of Streptococcus agalactiae were isolated from diseased fish in some tilapia farms in Hainan in August 2020.Serotypes, main virulence genes and multiple drug resistance of all isolates were detected.The serotype detection results showed that the serotype of 15 isolated was type Ⅰa, consistent with the reference human strains A909.The results of virulence gene detection showed that scpB gene was only detected in human reference strain Streptococcus agalactiae 2603V/R except all isolates from tilapia.However, the detection rate of major virulence genes, such as cylE, sodA and gapC, was 100%.The drug sensitive test result indicated that the drug resistance rate of 15 isolates to methoxypyrimidine, sulfamisoxazole, cotrimoxazole, streptomycin, neomycin and gentamicin were more than 85%.The sensitive rate of cefcllor, ceftriaxone, cefoperazone, cefradine, kanamycin, erythromycin, rifampicin and clindamycin were more than 80%.No strains were found to be sensitive to methoxymidine, fleroxacin, streptomycin, neomycin and gentamicin.The results of multidrug resistance test showed that 15 isolated strains were resistant to 4 drugs at least, among all the isolates, 86.67% were resistant to more than 6 kinds of antibiotics, and two of them were resistant to 13 kinds of antibiotics.This results provided reference for the application of antimicrobial agents for the treatment of tilapia infection of Streptococcus agalactiaein in Hainan, and also provided new data for the epidemiology and disease control of Streptococcus agalactiae of tilapia in South China.

Key words: Streptococcus agalactiae of tilapia; serotype; virulence gene; multiple drug resistance

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