From Cryptic Clade to Emerging Pathogen: Exploring the Evolutionary Divergence and Clinical Relevance of Escherichia marmotae

The Escherichia genus includes both commensal and pathogenic species and is characterized by its diversity and adaptability to the mammalian gut and other environments. Among these species, E. coli has facilitated many scientific advances as a model organism. Recently, a new member of the Escherichia genus, Escherichia marmotae, has been described as a phylogenetically distinct clade that shows the greatest genetic divergence from E. coli. This review explores E. marmotae, its cryptic evolution, distinct characteristics, and ecological niches. E. marmotae has recently gained scientific prominence due to its association with animal feces, environmental occurrence, human clinical samples, and emerging as a potential pathogen. While its pathogenicity remains understudied, growing evidence from clinical, environmental, and animal sources suggests the need for heightened surveillance. This review highlights current knowledge gaps, underscores the need for improved diagnostic tools, and proposes future research directions to elucidate the clinical and ecological implications of this emerging pathogen.