Emergence of bla(IMI-2)- and bla(IMI-16)-Producing Enterobacter asburiae in the Aquaculture Environment of Jiangsu, China

Carbapenem-resistant Enterobacteriaceae strains have emerged as a serious threat to global public health. In recent years, bla(IMI), a carbapenemase gene that drew less attention before, has been increasingly detected in both clinical and environmental settings. However, the environmental distribution and transmission of bla(IMI), especially in aquaculture, require systematic investigation. In this study, the bla(IMI) gene was detected in fish (n = 1), sewage (n = 1), river water (n = 1), and aquaculture pond water samples (n = 17) collected from Jiangsu, China, demonstrating a relatively high sample-positive ratio of 12.4% (20/161). Thirteen bla(IMI-2)- or bla(IMI-16)-carrying Enterobacter asburiae strains were isolated from bla(IMI)-positive samples of aquatic products and aquaculture ponds. We also identified a novel transposon (Tn7441) carrying bla(IMI-16) and a conserved region containing several truncated insertion sequence (IS) elements harboring bla(IMI-2), all of which may play important roles in bla(IMI) mobilization. The occurrence of bla(IMI)-carrying Enterobacter asburiae in aquaculture-related water samples and fish samples highlights the risk of transmission of bla(IMI)-carrying strains through the food chain and the need for effective measures to prevent further dissemination. IMPORTANCE IMI carbapenemases have been detected in clinical isolates of many bacterial species with systemic infection and cause a further burden on clinical treatment in China, but their source and distribution are still unclear. The study systematically investigated the distribution and transmission of the bla(IMI) gene in aquaculture-related water bodies and aquatic products in Jiangsu Province, China, which is famous for its rich water resources and developed aquaculture industry. The relatively high prevalence of bla(IMI) in aquaculture samples and the identification of novel mobile elements harboring bla(IMI) enhance our knowledge of bla(IMI) gene distribution and highlight the public health risk and urgency of surveillance of aquaculture water systems in China.