Abstract
An unusual case of infective endocarditis caused by a strain of extended-spectrum β-lactamase Escherichia coli O25b:H4-B2-ST131 originating from a urinary tract infection is described. This paper has thoroughly analyzed the distinctive genotypic, phenotypic, and phylogenetic elements of the strain, correlating them with the patient's severe clinical presentation, diagnostic course, and successful outcome achieved through intensive antibiotic and surgical management, culminating in mitral valve replacement. Additionally, we proposed a hypothesis regarding the pathophysiology of infective endocarditis caused by extended-spectrum β-lactamase Escherichia coli, based on genotypic and phylogenetic analyses. A host-related explanatory approach was also assessed. Understanding the importance of early and real-time genotyping and molecular characterization of an Escherichia coli strain with a potential mechanism for developing infective endocarditis may help guide future clinical practice.