Isolating and evaluating the antibiotic resistance level of Streptococcus agalactiae – a species of bacterium causing infections in climbing perch (Anabas testudineus)

Abstract

The present study aims to isolate Streptococcus agalactiae bacterium, which causes infections in climbing perch, and assess clinical-pathological characteristics of infected fish and the level of antibiotic resistance of the bacteria. A total of 63 diseased fish samples were collected from 22  climbing perch farming households located in Hanoi, Hung Yen, and Hai Duong for bacterial culture, which resulted in 53 isolates of Gram-positive streptococci . 22 representative isolates of S. agalactiae were successfully identified, using morphological, biochemical, and PCR identification… The infected fish showed the distinctive symptoms and clinical signs of a darkly pigmented body and the haemorrhaging of their skin (69.8 – 77.4%), as well as the eyes with haemorrhaging and exophthalmia (52.8%); the internal organs are swollen with signs of haemorrhage (58.5%). The bacterial isolates exhibited a high sensitivity to Amoxicillin and Doxycycline, while they presented the highest resistance to Sulfamethoxazole/Trimethoprim (40.9%), and from 13.6 to 27.2% of the isolates were resistant to Erythromycin, Florfenicol, and Oxytetracycline. The research results are important in the diagnosis, prevention, and treatment of diseases caused by S. agalactiae in climbing perch.