Emergence of Third-Generation Cephalosporin-Resistant Morganella morganii in a Captive Breeding Dolphin in South Korea

SIMPLE SUMMARY: The emergence of antimicrobial resistance (AMR) has become an important consideration in animal health, including marine mammals, and several potential zoonotic AMR bacterial strains have been isolated from wild cetacean species. Although the emergence of AMR bacteria can be assumed to be much more plausible in captive than in free-ranging cetaceans owing to their frequent contact with humans and antibiotic treatments, the spread and its impacts of AMR bacteria in captive animals have not been adequately investigated yet. Here in this study, we present evidence on the presence of multidrug-resistant potential zoonotic bacteria which caused fatal infection in a captive dolphin bred at a dolphinarium in South Korea. ABSTRACT: The emergence of antimicrobial resistant (AMR) strains of Morganella morganii is increasingly being recognized. Recently, we reported a fatal M. morganii infection in a captive bottlenose dolphin (Tursiops truncatus) bred at a dolphinarium in South Korea. According to our subsequent investigations, the isolated M. morganii strain KC-Tt-01 exhibited extensive resistance to third-generation cephalosporins which have not been reported in animals. Therefore, in the present study, the genome of strain KC-Tt-01 was sequenced, and putative virulence and AMR genes were investigated. The strain had virulence and AMR genes similar to those of other M. morganii strains, including a strain that causes human sepsis. An amino-acid substitution detected at the 86th residue (Arg to Cys) of the protein encoded by ampR might explain the extended resistance to third-generation cephalosporins. These results indicate that the AMR M. morganii strain isolated from the captive dolphin has the potential to cause fatal zoonotic infections with antibiotic treatment failure due to extended drug resistance, and therefore, the management of antibiotic use and monitoring of the emergence of AMR bacteria are urgently needed in captive cetaceans for their health and conservation.