Vibriosis Incidents in Marine Finfish Farms: Prevalence, Diagnosis of Pathogens using 16S rRNA, Histopathology, and In Vitro Antibacterial Evaluation Against Isolated Vibrio spp using Antibiotics and Probiotics

Abstract

Recently, in India, the marine finfish culture is expanding rapidly without adequate knowledge and research information on the coastal and marine finfish disease epidemics. Therefore, for the benefit of farmers, this study was designed to find the prevalence of Vibriosis outbreaks in marine finfish farms. In this study, 167 moribund fishes that show outward symptoms of lethargy, popeye, pale gills, skin erosions, abdominal edema, and hemorrhagic spots on different parts of the body were collected from 26 marine finfish farms (Lates calcarifer, Rachycentron canadum, and Trachinotus blochii) located in the states of Tamil Nadu, Andhra Pradesh, and Kerala, India. A total of 173 bacterial isolates were retrieved from all the fish samples, of which 144 isolates demonstrated a Vibrio-like character during biochemical and Vibriostatic 0/129 examinations. The phenotypic, 16s RNA gene sequencing and histopathological analysis confirm that the isolated bacterial strains were Vibriospecies. In the collected fish samples, the total prevalence of Vibrio species was 83.2% and the remaining 16.8% were other bacterial species. Among these bacteria, V. harveyi was the most predominant bacterium (34.1%) that cause infection in all the three fish species whereas Photobacterium damselae was found to be the least (2.9%) one. In the pathogenicity study, the highest mortality of 83% was observed after 168 h, when the seabass fingerling exposure to V. harveyi at 10 6 CFU/ ml, and established similar clinical signs to the disease specimens of farmed fish. The in vitro antibacterial study confirms that the tested probiotic effectively inhibits the V. harveyi at 125 µl (10 8 CFU/ml). The above results inspire further in-depth studies on the probiotic efficacy to control the V. harveyi in finfish farms.

Bacterial Co-Infection as a Potential Threat to Farmed Flathead Grey Mullet (Mugil cephalus): Phenotypic and Molecular Diagnosis, Histopathology, Immunity Response, and In Vitro Antibacterial Evaluation

“…Here, we clearly monitored that the main pathological changes in the affected tissues of diseased M. cephalus were septicemic lesions, such as hemorrhage, oedema, hemosiderosis, and proliferative and necrotic alterations. These lesions are considered the main changes in the natural infection in the acute phase of septicemic diseases, including vibriosis [49,118]. Similar findings were stated in the internal organs and gills of seabass [118,119], thin lip grey mullet, M. capito [27], and M. cephalus [91] upon infection with V. alginolyticus.…”

“…These lesions are considered the main changes in the natural infection in the acute phase of septicemic diseases, including vibriosis [49,118]. Similar findings were stated in the internal organs and gills of seabass [118,119], thin lip grey mullet, M. capito [27], and M. cephalus [91] upon infection with V. alginolyticus. In addition, extensive inflammatory and degenerative histopathological changes in fish infected with Enterococcus species were observed in recent reports [46,47].…”