Genetic characterization of Lactococcus garvieae isolated from farmed rainbow trout by random amplified polymorphic DNA-PCR in Iran

Abstract

Lactococcosis is one of the main bacterial infections of fish around the world. Lactococcus garvieae has been a major cause of rainbow trout losses in freshwater farming. This study aimed to evaluate the RAPD-PCR method for genotyping of L. garvieae isolates isolated from infected farmed rainbow trout in Iran. Bacterial specimens were collected from trout farms suspected to carry Lactococcosis around this country. 200 bacterial cultures containing cocci shaped bacteria were cultured in Tripticase soy agar (TSA) and blood agar mediums. All bacterial cultures were tested by conventional microbiological and biochemical tests, and PCR assay to identify L. gvarieae by 16S rDNA genes. The RAPD-PCR method was used to determine the genetic pattern of all isolates. The sample strain pattern of the isolates was analyzed in the NTSYS program. After genotyping, according to a similarity coefficient index of 70%, all L. garvieae isolates were separated into two groups with 4 RAPD types. The highest and lowest genetic pairwise similarity among the isolates was 98% and 54%, respectively. The results of the present study revealed that RAPD-PCR is an applicable method to describe the genetic diversity of different strains of L. garvieae among farmed fish.