Infective endocarditis caused by Proteus mirabilis is strikingly rare. Here, we describe the case of an 86-year old man with five recurrent septic episodes over a period of three months associated with Proteus mirabilis bacteraemia secondary to underlying Proteus endocarditis. The final diagnosis was made based on clinical findings, blood culture results and transoesophageal echocardiogram. The patient was treated medically with 6 weeks of ceftriaxone and long-term oral ciprofloxacin. On completion of intravenous therapy the patient remained well. We performed a literature review and found this to be only the fourth confirmed case of Proteus mirabilis endocarditis successfully treated with antibiotic therapy alone. This case highlights an important but rare cause of endocarditis, reinforcing the need to consider this diagnosis in recurrent Gram-negative bacteraemia even if by an atypical organism.

[download-attachments container="div" style="list" display_icon="1" display_count="1" display__size="0"]

References

1. Baddour LM, Wilson WR, Bayer AS, et al. Infective Endocarditis in Adults: Diagnosis, Antimicrobial Therapy, and Management of Complications: A Scientific Statement for Healthcare Professionals From the American Heart Association. Circulation 2015;132(15):1435-86.
2. Li JS, Sexton DJ, Mick N, et al. Proposed modifications to the Duke criteria for the diagnosis of infective endocarditis. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 2000;30(4):633-8.
3. Vandenbos F, Hyvernat H, Lucas P, et al. [Enterobacterial native valve endocarditis in the intensive care unit: report of two cases]. La Revue de medecine interne 2000;21(6):560-1.
4. Rimoldi SG, De Vecchi E, Pagani C, et al. Use of Dithiothreitol to Dislodge Bacteria From the Biofilm on an Aortic Valve in the Operating Theatre: A Case of Infective Endocarditis Caused by Staphylococcus aureus and Proteus mirabilis. The Annals of thoracic surgery 2016;102(4):e357-9.
5. Lloyd M, Satterwhite L, Lerakis S. Successfully treated mitral valve Proteus mirabilis endocarditis. The American journal of the medical sciences 2005;329(5):267-9.
6. Claassen DO, Batsis JA, Orenstein R. Proteus mirabilis: a rare cause of infectious endocarditis. Scandinavian journal of infectious diseases 2007;39(4):373-5.
7. Kalra A, Cooley C, Tsigrelis C. Treatment of endocarditis due to Proteus species: a literature review. International journal of infectious diseases: IJID: official publication of the International Society for Infectious Diseases 2011;15(4):e222-5.
8. Rosen P, Armstrong D. Infective endocarditis in patients treated for malignant neoplastic diseases: a postmortem study. American journal of clinical pathology 1973;60(2):241-50.
9. Carruthers MM. Endocarditis due to enteric bacilli other than Salmonellae: case reports and literature review. The American journal of the medical sciences 1977;273(2):203-11.
10. Brotzki CR, Mergenhagen KA, Bulman ZP, et al. Native valve Proteus mirabilis endocarditis: successful treatment of a rare entity formulated by in vitro synergy antibiotic testing. BMJ case reports 2016;2016.
11. Albuquerque I, Silva AR, Carreira MS, et al. Proteus mirabilis endocarditis. BMJ case reports 2019;12(8).
12. Ananthasubramaniam K, Karthikeyan V. Aortic ring abscess and aortoatrial fistula complicating fulminant prosthetic valve endocarditis due to Proteus mirabilis. Journal of ultrasound in medicine: official journal of the American Institute of Ultrasound in Medicine 2000;19(1):63-6.
13. Salsano A, Sportelli E, Borile S, et al. Proteus mirabilis bioprosthetic tricuspid valve endocarditis with massive right ventricular vegetation: a new entity in the prosthetic valve endocarditis aetiology. European journal of cardio-thoracic surgery: official journal of the European Association for Cardio-thoracic Surgery 2016;50(3):581-2.
14. Goel R, Sekar B, Payne MN. Proteus endocarditis in an intravenous drug user. BMJ case reports 2015;2015.
15. Taniguchi T, Murphy FD. Mural bacterial endocarditis produced by proteus. Journal of the American Medical Association 1950;143(5):427-8.
16. Morpeth S, Murdoch D, Cabell CH, et al. Non-HACEK gram-negative bacillus endocarditis. Annals of internal medicine 2007;147(12):829-35.
17. Habib G, Lancellotti P, Antunes MJ, et al. 2015 ESC Guidelines for the management of infective endocarditis: The Task Force for the Management of Infective Endocarditis of the European Society of Cardiology (ESC). Endorsed by: European Association for CardioThoracic Surgery (EACTS), the European Association of Nuclear Medicine (EANM). European heart journal 2015;36(44):3075-128.