Abstract

Streptococcosis is one of the most important bacterial diseases in farmed salmonid fishes. Streptococcus iniae and Lactococcus garvieae are known as the major pathogens of streptococcosis and lactococcosis in the rainbow trout, Oncorhynchus mykiss. The present study accomplished the detection of the two mentioned bacteria in some rainbow trout farms in the west of Iran. A total of 50 fish samples clinically suspected of having streptococcosis were collected from 10 rainbow trout farms. Samples of liver, kidney, spleen and heart were cultured on brain heart infusion agar medium. The bacterial isolates were identified using standard biochemical tests. Identification of the isolates was approved by multiplex PCR. L. garvieae and S. iniae were identified simultaneously in the fish tissues. The results of this study showed overcoming L. garvieae in isolated samples that indicated epidemiological importance of lactococcosis. Multiplex PCR was found as an effective tool for the rapid and specific detection of L. garvieae and S. iniae from fish tissues.

Key words: Streptococcosis, Lactococcosis, fish, Iran.