Emphysematous endocarditis caused by AmpC beta-lactamase-producing Escherichia coli A case report

Rationale: Infective endocarditis (IE) is a life-threatening disease, mostly caused by gram-positive bacteria. Gram-negative bacteria were identified as a causative organism in relatively small number of cases. Although, antibiotic-resistant Escherichia coli is common cause of gram-negative endocarditis, AmpC beta-lactamase (BL)-harboring E coli is very rare cause of IE. Furthermore, emphysematous endocarditis is also a very rare manifestation of E coli infection. Patientconcerns: We report a case of 80-year-old female patient presenting with dizziness, fever, and altered mental status, who was finally diagnosed with emphysematous endocarditis caused by E coli harboring an AmpC BL gene. Diagnosis: Her chest computed tomography revealed air bubbles surrounding the annulus of a mitral valve and a transesophageal echocardiogram revealed a hyperechogenic mass fixed on the posteromedial side of the mitral annulus with 2 eccentric mitral regurgitation jets. Blood cultures grew E coli which harbored the DHA-type AmpC BL. The organism belonged to a B2 phylogenic group, and multilocus sequence typing analyses revealed that the strains were of ST-95. Interventions: She was treated with meropenem following the resistant profiles, and surgery was recommended by the healthcare professional, but denied by the patient's guardians. She was transferred to another hospital due to a refusal for further treatment. Lessons: Emphysematous endocarditis is an uncommon complication of E coli bacteremia. Certain phylogenetic groups may be associated with development of E coli endocarditis.