Multidrug Resistance Genes Carried by a Novel Transposon Tn and a Genomic Island Named MMGI-4 in a Pathogenic Morganella morganii Isolate.

Antimicrobial resistance in Morganella morganii is increasing in recent years, which is mainly introduced via extra genetic and mobile elements. The aim of our study is to analyze the multidrug resistance (MDR) and characterize the mobile genetic elements (MGEs) in M. morganii isolates. Here, we report the characteristic of a pathogenic M. morganii isolate containing multidrug resistance genes that are mainly carried by a novel transposon Tn and a genomic island. Sequence analysis suggested that the Tn could be generated through homologous recombination between two different IS-bounded translocatable units (TUs), namely, module A (IS-Hp-IS-(A)-(A)--IS---) and module B (IS-------IS), and the genomic island named MMGI-4 might derive from a partial structure of different original genomic islands that also carried IS-mediated TUs. Notably, a 2,518-bp sequence linked to the module A and B contains a 570-bp gene. To the best of our knowledge, this is the first report of the novel Tn possessing a complex class 1 integron that carried an infrequent gene in M. morganii. Mobile genetic elements (MGEs), especially for IS-bounded translocatable units, may act as a reservoir for a variety of antimicrobial resistance genes in clinically important pathogenic bacteria. We expounded this significant genetic characteristic by investigating a representative M. morganii isolate containing multidrug resistance genes, including the infrequent . Our study suggested that these acquired resistance genes were mainly driven by IS-flanked important MGEs, such as the novel Tn and the MMGI-4. We demonstrated that IS-related MGEs contributed to the emergence of the extra gene in M. morganii through some potential genetic events like recombination, transposition, and integration. Therefore, it is of importance to investigate persistently the prevalence these MEGs in the clinical pathogens to provide risk assessment of emergence and development of novel resistance genes.