Antimicrobial Use and Antimicrobial Resistance in Aquaculture in the People's Republic of China

With the rapid development of aquaculture in the People's Republic of China, along with the increase of intensive aquaculture, there have been frequent disease outbreaks resulting in financial losses amounting to millions of dollars.Medication with antimicrobial agents is common practice in the treatment of bacterial infections, and thus there are nine antimicrobial agents permitted for use in Chinese aquaculture: doxycycline, neomycin, thiamphenicol, florfenicol, enrofloxacin, and four types of sulfonamide.Previous studies have demonstrated that freshwater animals can serve as reservoirs for Aeromonas containing multiple resistance genes.In this study, 1143 Aeromonas isolates were collected from fish and the aquatic environment in Guangdong Province, P.R.China from 2014 to 2016.Antimicrobial susceptibilities were determined by the micro broth dilution method.Moderate resistance to sulfamonomethoxine and nalidixic acid was found in Aeromonas strains, and most strains were highly sensitive to broad-spectrum antibiotics, such as β-lactams, fluoroquinolones, and aminoglycosides.Bacterial resistance mechanism studies have shown that various resistance genes are harboured in integrons and contribute to multiple resistances.In this study, class 1 integrons carrying various cassettes were determined in 50 Aeromonas strains, and displayed multiple resistance to trimethoprim, chloramphenicol, or ciprofloxacin.Data from the present study suggest that surveillance for antimicrobial resistance (AMR) of aquatic animal origin and the prudent and responsible use of antimicrobial agents are necessary.