Successful Treatment of Mycobacterium fortuitum Prosthetic Valve Endocarditis: Case Report

To date, no cases of the successful treatment of prosthetic valve endocarditis due to Mycobacterium fortuitum complex have been reported. To our knowledge, we report the first such case. A 21-year-old woman with a history of mitral valve replacement at age 9 and aortic valve replacement with a Dacron patch (Meadox, Boston, MA) at age 20 (both St. Jude Medical valves) secondary to rheumatic heart disease presented to her local emergency department with a 2-month history of fevers, chills, cough, and headaches. She was initially treated for pneumonia and discharged; however, her symptoms continued, and she returned 2 days later. At that time, her temperature was 39°C, WBC count was 8200/mm3 (with a left shift), and a chest radiogram revealed a left lower lobe infiltrate. She was admitted to the hospital, and iv antibiotic therapy for community- acquired pneumonia was started. The initial transesophageal echocardiogram revealed no evidence of endocarditis. The patient continued to be febrile with temperature spikes to 40°C. On the seventh hospital day, cultures of blood specimens obtained at admission revealed growth of gram-positive rods in the aerobic bottles. Subsequent blood cultures were also positive for gram-positive rods; modified acid-fast staining of blood was positive. The Indiana State Department of Health (Indianapolis) identified the gram-positive rods as M. fortuitum. Antibiotic therapy was changed to clarithromycin, imipenem, and amikacin. The patient's condition continued to be poor with daily fevers (figure 1). A repeated transesophageal echocardiogram revealed an echogenic density on the prosthetic aortic valve that was consistent with a vegetation. Blood cultures were sent to the University of Texas at Tyler, where the isolate was confirmed as M. fortuitum by PCR-restriction fragment length polymorphism analysis and antibiotic susceptibility testing. Ciprofloxacin was added to treatment with imipenem and amikacin on the basis of this information (clarithromycin therapy was stopped). Repeated blood cultures were negative. The patient underwent prosthetic aortic valve replacement by Roth's procedure. Vegetations were found on the underside of the Hemaschield graft (Meadox) and on the Dacron graft, and pathological examination revealed fibrin thrombosis. Culture of these lesions were negative for acid-fast bacilli. The patient did well postoperatively, and defervescence occurred almost immediately. She completed a total of 12 weeks of iv therapy with imipenem, ciprofloxacin, and amikacin. She continued therapy with oral ciprofloxacin and trimethoprim-sulfamethoxazole. Her course was complicated by the development of a left ulnar artery aneurysm at the site of a perioperative arterial catheter that required a saphenous vein bypass. Cultures of the aneurysm were negative for acid-fast bacilli. She is currently doing well and has completed her oral antibiotic therapy. Secondary infections due to M. fortuitum complex are rare. In the most recent retrospective study of M. fortuitum complex infections by Svahn et al. [1], 86 isolates (71 of which were pulmonary) were recovered, and there were no cases of endocarditis. A similar study by Wallace et al. [2] reviewed 125 cases of disease due to rapidly growing mycobacteria and found 4 cases of prosthetic valve infection, 2 due to M. fortuitum and 2 due to Mycobacterium abscessus; all 4 of these patients died. On further review of the literature, we found that none of the patients with mechanical valve endocarditis due to M. fortuitum complex survived [3–9]. We describe the first known survivor of M. fortuitum complex prosthetic valve endocarditis (17 months after valve replacement surgery). The patient was treated with both valve replacement surgery and long-term antibiotic therapy guided by results of in vitro antibiotic susceptibility testing. Clinical course of a patient with prosthetic valve endocarditis due to Mycobacterium fortuitum that was successfully treated: temperature maximum vs. hospital day. Antibiotics with activity against M. fortuitum, as well as blood culture results, are shown. Break in hospital days represents at-home antibiotic therapy. AV, aortic valve.