Case Presentation: A 24-year-old female with a history of IV drug abuse and MRSA tricuspid native valve endocarditis was treated for lobar pneumonia 4 months prior to readmission for non-bloody cough and pleuritic chest pain. Recurrence of lobar pneumonia was suspected but workup instead revealed Mycobacterium abscessus bacteremia. She denies any fevers, chills, nausea, vomiting, or dyspnea. On admission, her vital signs were stable and cardiopulmonary exam significant for 3/6 systolic mummer in tricuspid region and lungs clear to auscultation bilaterally. In addition, no evidence of embolic phenomena on skin exam. Laboratory workup significant for microcytic anemia and AKI. Echocardiographic findings demonstrated a freely mobile 7 x 7 mm echodensity attached to the tricuspid valve, associated with mild tricuspid regurgitation. CT chest revealed dense right lower lob pulmonary consolidation concerning for infarct and/or pneumonia and right lower lobe pulmonary embolism. ID was consulted who recommended tigecycline, Amikacin and Impinem once sensitivities were posted. CT surgery felt surgical intervention was not warranted due to persistent hemodynamic stability. At discharge patient remained afebrile, completed six weeks of IV antibiotics, and repeat cultures have remained negative.
Discussion: Empiric antibiotics were transitioned to Tigecycline, Amikacin and Impinem once sensitivities were available. Due to hemodynamic stability, competent valve and stable EKG, surgery was not pursued. Cultures and Echo will be obtained after 6 weeks of antibiotics. Mycobacterial endocarditis is a rare cause of IE in the United States and accounts for <3% of culture-negative endocarditis. Causative pathogens are predominantly rapid growers such as M. abscessus. Cardiac surgery, prosthetic implants and IV drug use remain the leading risk factors. In this case IVDU and non-resolving lobar pneumonia should raise the clinical suspicion for these organisms. Patients infected with rapidly growing mycobacteria warrant surgical intervention including removal of any prosthetic material which has been associated with improved survival over conservative management. Antimicrobial resistance is common and individualized sensitivities should be applied to antibiotic choice. Amikacin, ciprofloxacin and clarithromycin frequently used. Prognosis is guarded with a 34% mortality rate and 6.25% relapse rate despite combination therapy.
Conclusions: Our case illustrates several learning points including accounting towards the rarity of mycobacterial endocarditis, maintaining a high index of suspicion in IVDA patients, and acknowledging various presentations and individualized treatment courses. Mycobacterial endocarditis is recognized as a serious infection with species capable of developing resistance. Delayed diagnosis with extensive drug resistance leads to refractory episodes.