Diagnosis of Nocardia paucivorans central nervous system infection by DNA sequencing from paraffin-embedded tissue.

Infections by Nocardia spp. are generally regarded as opportunistic diseases in immunocompromised patients, but can also affect immunocompetent subjects. Such infections represent an important diagnostic challenge for clinicians and microbiologists, and diagnosis is frequently delayed or even conducted post mortem. A 54-year-old man was admitted to our hospital because of ventriculitis and relapsing brain abscess. Five months prior, this patient had undergone external ventricular drain and surgery for a cerebellar abscess. Histopathology demonstrated pyogenic inflammatory reaction, microbiologic investigations proved negative and empiric antimicrobial therapy was administered for a total of eight weeks. Six weeks later, the patient developed relapsing neurologic manifestations. On reviewing the patient's clinical history it emerged that the patient had suffered pneumonia two months prior to neurosurgery, treated with amoxicillin/clavulanate 3g a day and levofloxacin 500mg a day for three weeks. On the CNS relapsing manifestations, nocardiosis was suspected and DNA sequencing from the formalin-fixed paraffin-embedded cerebellar tissue collected during neurosurgery allowed diagnosis of Nocardia paucivorans infection. The patient received medical therapy for 11 months. At follow-up, eight months after treatment was discontinued, the patient was aymptomatic. Nocardia spp. infections need to be suspected not only in immunocompromised, but also in immunocompetent patients. Proper samples need to be collected for proper microbiologic investigations. Paraffin-embedded tissue genomic sequencing can be a useful tool for diagnosis of nocardiosis.