Nocardia otitidiscaviarum meningitis in an immunocompetent patient diagnosed by metagenomic next-generation sequencing: a case report

Cerebral nocardiosis caused by <i>Nocardia</i> represents a rare and diagnostically challenging infectious disease, predominantly affecting immunocompromised patients. This opportunistic infection may also pose life-threatening risks to immunocompetent individuals. The diagnostic process is frequently complicated by the absence of distinctive clinical manifestations and technical limitations inherent to conventional microbiological detection methods, which collectively impede the acquisition of definitive pathogenic evidence, thereby resulting in diagnostic delays. This case report describes a 67-year-old immunocompetent male bricklayer who presented with recurrent febrile episodes during hospitalization and was ultimately diagnosed with purulent meningitis based on clinical history corroborated by cerebrospinal fluid (CSF) analytical findings. Ceftriaxone was initially employed as an anti-infective agent, however, it was ineffective. Consequently, the treatment was escalated to a combination of meropenem and vancomycin, yet the patient's condition did not significantly improve. Concurrently, repeated cultures of the patient's blood and CSF yielded no identifiable pathogens. Notably, three months ago, the patient accidentally sustained a laceration on the left thigh by an unknown object during work. An abscess gradually developed at the site of the laceration, and incision and drainage were carried out at a local hospital. However, the wound did not heal satisfactorily after the surgery, raising concerns about potential rare pathogenic bacterial infections. Ultimately, the pathogen was successfully identified as <i>Nocardia otitidiscaviarum</i> through metagenomic next-generation sequencing (mNGS). Following this diagnosis, the patient's condition was rapidly controlled after initiating treatment with the targeted drug combination of sulfamethoxazole, meropenem, and amikacin. Given the high misdiagnosis rate and poor sensitivity of cultures for <i>Nocardia otitidiscaviarum</i> in cases of intracranial infections, this case underscores the critical role of mNGS in the diagnosis and selection of effective antibiotics for treating <i>Nocardia</i> intracranial infections.