Phenotypic and molecular characterization of vibrio species isolated from cultured marine Dicentrarchus labrax

Abstract

Vibrio species are the most common and serious pathogens in fish and shellfish marine aquaculture worldwide with high mortalities and morbidity lead to great economic loss. Among all V. species infecting V. parahaemolyticus and V. alginolyticus taken the first place. The present study aimed to determine the prevalence of Vibrio species in seabass in addition detection of certain virulence genes. A total of 220 seabass (Dicentrarchus labrax) had haemorrhage, erosion and ulcers in the skin, gills, fin base and tail and were purchased from fish markets at from Alexandria, Behaira, lake Qarun and subjected to phenotypic bacteriological examination. revealed that the prevalence of 4 vibrio isolates was 1.8% (4/220) including two isolates of V. alginolyticus (one from liver and other from spleen) and two isolates of V. parahaemolyticus (one from liver and other from kidney). Molecular identification based on use of 16srRNA gene sequence confirmed 4 strains as vibrio species. Proving its pathogenicity through using primers for the virulence genes (trh, tlh, recA and categorized 2 isolates belong to vibrio alginolyticus (one with trh) and 2 isolates belong to vibrio parahaemolyticus (one with recA and tlh, the other with trh). The 4 strains of V. parahaemolyticus and V. alginolyticus were multi drug resistant (MDR),resist more than 3classes of antibiotics, which pose potential health hazards to consumers