Investigation of diseases caused by Aeromonas media in rainbow trout (Oncorhynchus mykiss) in commercial fish farms using MALDI-TOF and specification of antibiotic sensitivity profiles of the agent

Abstract

Rainbow Trout (RT) Oncorhynchus mykiss Walbaum,1792 the first fish species to be grown intensively in Turkey and the most commonly grown species in dams and lakes today. Aeromonas spp. are found in ecosystems such as freshwater and coastal waters and cause disease in fish. In RT causes death that is characterized by internal organ hemorrhages, such as the spleen, kidney and liver and body surface, ulcerations and congestion. The present study aimed to detect Aeromonas media bacteria in fish samples collected from the RT farms in the South Eastern Anatolia Region of Turkey through bacteriological culturing and MALDI-TOF. Also, it was purposed to determine the antibiotic susceptibility of the agent. Antibiotic susceptibility testing was performed using the Kirby–Baüer disk diffusion method. Separate visits were made to Trout farming facilities in Diyarbakır, Adıyaman, Şanlıurfa, and Batman in January and February 2021, and 30 fish with an average live weight of 200–250 grams (g) were collected from each facility. A total of 1,200 samples were taken from 40 Trout farms. It was detected the causative agent in the liver, kidney, and tissue samples of fish from 28 of the 40 farms. The sensitivity of Enrofloxacin (10 microgram -µg-), Florfenicol (30 µg), Neomycin (10 µg), Amoxicillin (10 µg), Oxytetracycline (30 µg), Erythromycin (10 µg), Gentamycin (10 µg) and Streptomycin (10 µg) were defined at chancing ratios. In conclusion, these bacteria were detected in local farms. These farms must implement measures to minimize stress factors affecting the fish and avoid overstocking. The best methods of protection against infection include avoiding overstocking, low oxygen levels, and unskilled labor.