Prevalence, molecular typing, antibiogram and histopathological changes of V. harveyi and V. parahaemolyticus isolated from Gilthead sea bream (Sparus aurata)

Abstract

Vibrionaceae are a common bacterial disease that affects both wild and farmed marine fishes and causes tremendous economic losses globally. In order to investigate the prevalence, molecular typing, antibiogram and pathogenicity of vibriosis among cultured sea bream, two hundred and fifty Gilthead seabream (Sparus aurata) were collected randomly from different mariculture farms at Ismailia and Port Said Governorates. The collected fish were subjected to clinical, postmortem, bacteriological, and histopathological examinations. The majority of infected fish displayed ascites, hemorrhagic protruded anus, hemorrhages in pectoral, dorsal and tail fins, rotten gills, thinning of the head, discoloration of the skin, besides ulcer in the mouth and on the skin. The prevalence of Vibrio infection mostly was noticed at summer (35%) and spring (26%) then (22.5%) in autumn, where the kidney was the most predominant affected organ (45%). Vibrio 16s rRNA gene PCR extension generated a 663 pb amplified DNA bands that characteristic for all tested vibrio isolates. Blasting identified as V. harveyi and the other V. parahaemolyticus. The histopathological examination of naturally infected Gilthead seabream exhibited mild to moderate vacuolar degeneration of the hepatic parenchyma with tubular-nephrosis and massive renal cellular destruction. The splenic tissues showed focal activated melanomacrophage centers. The antimicrobial sensitivity was carried out, where the recovered strains were completely sensitive to novobiocin and highly resistant to ampicillin. In conclusion, the synergism of phenotypic and genotypic characterization is a valuable epidemiological tool for the diagnosis of Vibrio species. Strict veterinary hygienic regulations should be implemented to control such infections and minimize the antimicrobial use in fish farms.