Delayed diagnosis of disseminated Mycobacterium intracellulare subsp. chimaera infective endocarditis via cell-free metagenomic next-generation sequencing: a case report.

BACKGROUND

Mycobacterium intracellulare subsp. chimaera infective endocarditis associated with contaminated heater-cooler units has been well documented, leading to the discontinuation of these devices in most hospitals by 2018. The rarity of this infection and its nonspecific symptoms often result in delayed diagnosis.

CASE SUMMARY: We describe a 56-year-old female diagnosed with M. intracellulare subsp. chimaera infective endocarditis with disseminated intracranial abscess 7 years after aortic and mitral valve replacement. Diagnosis was achieved using cell-free microbial DNA next-generation sequencing (cfmNGS). She underwent left temporal craniotomy for abscess drainage and aortic and mitral valve replacement. Diagnosis was confirmed via mycobacterial culture from blood, brain tissue, and explanted valve tissue. Treatment included rifabutin, ethambutol, azithromycin, and amikacin, alongside a prednisone taper prescribed for a previously diagnosed undifferentiated inflammatory process. Amikacin was discontinued 6 weeks after valve surgery because of unilateral hearing loss. She remained clinically stable 5 months after valve surgery.

CONCLUSION

This case highlights that M. intracellulare subsp. chimaera infections may continue to emerge years after heater-cool unit discontinuation, suggesting that the time window for case incidence may still be active. cfmNGS may serve as a valuable diagnostic tool for disseminated M. intracellulare subsp. chimaera. Finally, we discuss pharmacotherapeutic factors, including the need for multiple agents over long durations, in this case with specific considerations given to the dissemination of infection into the central nervous system and potential drug-drug interactions, including steroids.