Endocarditis induced by M. morganii in an immunocompetent patient without underlying valvular abnormalities

The gram-positive cocci is the most common pathogens of infective endocarditis (IE), and it is rarely induced by gram negative bacteria. Only one prior case has been described, in which a patient reported with IE caused by M. morganii, who suffered from multiple myeloma and received high dosages of corticosteroids, chemotherapy and immunomodulatory agents. IE is seldom diagnosed in patients without underlying valvular abnormalities. The most important risk factors of IE are intravenous drug abuse, implanted foreign material and central venous catheterization.

We describe a case of 34-year-old patient presented to the hospital with recurrent fever and pneumonia since 5 months. He was diagnosed with infective endocarditis with tricuspid vegetation by transthoracic echocardiography (TTE). Two blood culture tests demonstrated the growth of M. morganii, which was further confirmed by a NGS test, as well as a culture of vegetation from the tricuspid. All the evidence confirmed that M. morganii was the causative pathogen of the endocarditis in this case. The IE in an immunocompetent patient without underlying valvular abnormalities had been cured with broad antibiotic therapy and surgical intervention.

This was a unique case of IE induced by an extremely rare agent in an immunocompetent patient without underlying valvular abnormalities. Broad-antibiotics with β-lactam enzyme inhibition should be used on time for M. morganii induced IE with bacteraemia. The operation to curette the vegetation and repair the tricuspid was also an important way to cure the endocarditis in the patient without underlying valvular abnormalities and with repeated episodes of blood stream and lung infections.