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

Abstract

The emergence of antimicrobial resistant (AMR) strains of <i>Morganella morganii</i> is increasingly being recognized. Recently, we reported a fatal <i>M. morganii</i> infection in a captive bottlenose dolphin (<i>Tursiops truncatus</i>) bred at a dolphinarium in South Korea. According to our subsequent investigations, the isolated <i>M. morganii</i> 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 <i>M. morganii</i> 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 <i>ampR</i> might explain the extended resistance to third-generation cephalosporins. These results indicate that the AMR <i>M. morganii</i> 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.