Phenotypic and genomic characterization of pathogenic Providencia rettgeri from kuruma shrimp Marsupenaeus japonicus

Providencia rettgeri has been recognized as a zoonotic pathogen of humans and aquaculture animals and has become a global public health concern. However, scarce information is available on the characterization of pathogenic P. rettgeri from kuruma shrimp Marsupenaeus japonicus. In the present study, a P. rettgeri isolate (KM4) was confirmed as a causative agent of red leg disease in cultured M. japonicus, which showed a median lethal dose (LD₅₀ ) value of 5.01 × 10⁵ CFU·ml^-1 and had multiple resistances to aminoglycosides, sulfonamides, and tetracycline antimicrobials used in aquaculture. In addition, the whole genome of isolate KM4 was sequenced and found to consist of a single circular chromosome of 4,378,712 bp and a circular plasmid of 171,394 bp. The genome sequence analysis further revealed the presence of potential virulence and antibiotic resistance genes in isolate KM4, which probably rendered this isolate particularly virulent. To our knowledge, this is the first study to characterize P. rettgeri pathogens from kuruma shrimp infected with red leg disease. The findings of this study can provide novel insights into the presence and distribution of pathogenicity-associated genes in shrimp-pathogenic P. rettgeri.