Abstract
Motile Aeromonas septicemia is a common bacterial disease that affects Oreochromis niloticus and causes tremendous economic losses globally. In order to investigate the prevalence, molecular typing, antibiogram and the biodiversity of Aeromonas hydrophila complex, a total of 250 tilapia (Oreochromis niloticus) were collected randomly from 10 private tilapia farms (25 fish/farm) at El-Sharkia Governorate, Egypt. The collected fish were subjected to clinical and bacteriological examinations. The majority of infected fish displayed ulcerative necrosis, exophthalmia, and internal signs of hemorrhagic septicemia. The prevalence of A. hydrophia complex was 13.2%, where the liver was the most predominant affected organ (54.1%). Polymerase chain reaction (PCR) was used to verify the identification of A. hydrophila complex using one set of primers targeting gyrB as well as the detection of virulent genes (aerA, alt, and ahp). All isolates were positive for the gyrB-conserved gene and harbored aerA and alt virulence genes. However, none of those isolates were positive for the ahp gene. The antimicrobial sensitivity was carried out, where the recovered strains were completely sensitive to ciprofloxacin and highly resistant to amoxicillin. All retrieved strains showed the same phenotypic characteristics and were identical based on the restriction fragment length polymorphism (RFLP). Experimentally challenged fish presented a high mortality rate (76.67%) and showed typical signs as in naturally infected ones. In conclusion, the synergism of phenotypic and genotypic characterization is a valuable epidemiological tool for the diagnosis of A. hydrophila complex. RFLP is a fundamental tool for monitoring the biodiversity among all retrieved strains of A. hydrophia.
Highlights
Aquaculture is one of the most significant food-delivering resources that could outfit the total populace with a protein of animal origin and decrease food deficiency due to overpopulation
Theexophthalmia, hemorrhagic were developed to shallow ulcers andbody manysurface cases showed erosions, inflamed vent, lesions were developed shallow ulcers many cases showed fin erosions, inflamed vent, and abdominal distensionto(Figure
The results revealed that the real digestion of the gyrB gene gave variable banding profiles
Summary
Aquaculture is one of the most significant food-delivering resources that could outfit the total populace with a protein of animal origin and decrease food deficiency due to overpopulation. About 16% of the animal protein consumed globally is derived from fish, and more than a billion persons depend on fish as the main source of protein [1]. Tilapia is the second most cultivated fish in aquaculture after cyprinid and its production has quadrupled over the past decade because of its sustainability, economical price, palatability, and the ease of cultivation [2]. In Egypt, tilapia is the main component of pisciculture, whether in fresh or brackish water resources, farms, and fish cages [3]. Tilapia is spontaneously exposed to various diseases, especially induced by the presence of bacteria [4,5].
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