期刊名称：Journal of Advanced Veterinary and Animal Research
印刷版ISSN：2311-7710
出版年度：2021
卷号：8
期号：1
页码：14-23
DOI：10.5455/javar.2021.h480
语种：English
出版社：Bangladesh Agricultural University, Faculty of Veterinary Science
摘要：Objective
Present research aims to isolate, identify, and determine the virulence of the
Streptococcus agalactiae(group B
Streptococcus; GBS), isolated from popped eye disease affected Tilapia and Vietnamese Koi (V. Koi) fishes.
Materials and Methods
A total of 330 fish samples were collected, of which Tilapia (
n = 180) and V. Koi (
n = 150), were collected from 35 affected ponds of four selected districts of Bangladesh. Isolation of the bacterium was done using different culture media (Nutrient broth, Plate count agar, Tryptic Soy Agar, and Blood agar), and identification by using various biochemical tests (conventional and using API 20 Strep kit) and polymerase chain reaction (PCR) using primers against 16S
rRNA gene of
S. agalactiae. Antibiotic susceptibility of the bacteria was performed using seven different antibiotics disc (Tetracycline, Oxytetracycline, Chlortetracycline, Streptomycin, Ciprofloxacin, Gentamicin, and Neomycin). Virulence of the isolated
S. agalactiaewas determined by infecting healthy Tilapia and V. Koi fishes through experimental infection.
Results
Isolated bacteria were found Gram-positive paired and chained cocci, β-hemolytic and non-motile. Findings of biochemical and serological tests indicate that the isolated bacterium belongs to Group B Streptococcus of Lancefield classification. PCR result also confirmed that the bacteria were
S. agalactiae. The bacterial isolates possessed resistance property against all the seven antibiotics used in this study. The isolated GBS was found highly virulent and showed 80%–90% mortality for Tilapia and V. Koi fishes in experimental infection within 1–6 days of post-infection.
Conclusion
From the findings of this study, it may be concluded that isolated GBS from the Tilapia and V. Koi fishes were highly virulent and possessed multidrug-resistance properties.
