The role of florfenicol, norfloxacin and ox ytetracycline in controlling experimental infection of oreochromis niloticus with streptococcus iniae

Abstract EN

Streptococcus iniae infection is considered one of the most important diseases affecting cultured fish causing severe economic losses.

This work was conducted to determine sensitivity of tested Streptococcus iniae strain to antibiotics with determination of the LD50 in Oreochromis niloticus, followed by treatment of the experimentally infected fish with florfenicol, norfloxacin and oxytetracycline at a dose of 50, 100 and 100 mg / kg body weight respectively by oral gavage.

AST, ALT, uric acid and creatinine in fish serum was studied together with histopathological examination of liver and posterior kidney tissues.

Tested Streptococcus iniae strain was sensitive to Florfenicol, Norfloxacin and Oxytetracycline with MIC equal to 0.25, 8 and 2 μg / ml respectively.

The LD50 of Streptococcus iniae in Oreochromis niloticus fish weighting 80 ± 5 g was 0.2 ml of (6 × 108) CFU / ml by intraperitoneal inoculation.

There were no mortalities in infected florfenicol and norfloxacin treated groups while it was 20 % in infected oxytetracycline treated group.

Florfenicol, norfloxacin and oxytetracycline can be considered an effective treatment for control of susceptible Streptococcus iniae infection in Oreochromis niloticus at a dose level of 50, 100 and 100 mg / kg body weight respectively for seven successive days.