Aeromonas hydrophila is a zoonotic, important primary fish pathogen in many economic fish species. Aeromonas acquires and exchanges antimicrobial resistance genes (ARG) and has been widely studied as a potential reservoir of ARGs. This research aims to observe the impact of antibiotics used through the role of Aeromonas hydrophila as a pathogenic bacteria in aquaculture. The tested antibiotics are based on the Minister of Marine Affairs and Fisheries No. 1/2019 Decree, namely tetracycline, oxytetracycline, and enrofloxacin, which the Indonesian government allows to be used in aquaculture. Random sampling was conducted using four to five fishes per farm in West Java, namely Bogor (17 farms) and Sukabumi (10 farms), Central Java at Banyumas (38 farms), and Magelang (25 farms). The test method used is CLSI-2020, an Antimicrobial Sensitivity Test disk diffusion with standard bacteria ATCC Escherichia coli 25922. The results show that A. hydrophila is resistant to tetracycline by 15,06% and oxytetracycline by 54,54%. However, A. hydrophila is sensitive to enrofloxacin by 84%. The aquatic environment acts as a reservoir for antibiotic-resistant A. hydrophila and emphasizes the importance of prudent antimicrobial use and timely AMR surveillance in aquaculture.
In Sukabumi Regency in 2019, A. hydrophila showed resistance to OT, 55%, and to TE, 48%. Meanwhile, A. hydrophila against ENR is still very sensitive, namely 84%. However, in 2022 A. hydrophila , its sensitivity to ENR decreased to 22% from the previous 84%. The freshwater fish cultivated in Sukabumi include catfish, carp, tilapia, and ornamental koi fish. Potential coastal and marine resources include marine fish, coral reefs, mangrove forests, seaweed, turtles, mining materials, and minerals.
Banyumas is known as a center for Gourami cultivation, which can contribute about 20% of Gourami production in Central Java Province. In Banyumas Regency in 2020, A. hydrophila in fish samples was still sensitive to OT and ENR of 60%, respectively. The condition of the Banyumas district in 2021, A. hydrophila, sensitive to OT and ENR decreased to 21% respectively. In 2021 , A. hydrophila bacteria in fish samples in the Bogor district appeared to show a low sensitivity, only around 9%, to the three types of antibiotics, namely TE, OT, and ENR. Risk management begins with preliminary activities in the form of an AMR survey by FAO (FAOTCP/RAS/3702 Support mitigation of AMR risk associated with aquaculture in Asia) cooperating with the Indonesian government. At that time, sampling was carried out at four locations: one location in West Java (Subang), two locations in Central Java (Banyumas and Sleman), and one location in East Java (Blitar ). Aeromonas hydrophila dominates in the four areas, respectively, 48%, 31%, 60%, and 46% . From the results of this study, it can be seen that there are additional resistant areas, namely Sukabumi , Bogor, and Magelang. In addition, A . hydrophila in Banyumas, which FAO surveyed, seems to have decreased sensitivity to OT and ENR.
Due to the uncontrolled use of antibiotics in West and Central Java fish farming, the sensitivity of A. hydrophila has decreased to OT, TE, and ENR antibiotics. Therefore, in the future, monitoring these three types of antibiotics needs to be carried out carefully. Antimicrobial resistance (AMR) surveillance activities must be carried out to identify, control, and take early action against bacteria in the culture environment. The results of this study can be used as a policy recommendation for the type of antibiotic used for the treatment of fish. Planning for future surveillance activities is essential to expand the area of sampling point locations in fish farming production areas in Indonesia.