Nocardia is known to be ubiquitous in the environment and is able to cause different kinds of diseases in man, including skin and soft tissue infections, pneumonia, central nervous system (CNS) infection and bacteremia [1]. Nocardia infections commonly affect immunocompromised patients and those who are on corticosteroid therapy. The lungs are usually the first organs that are infected, but the CNS eventually becomes infected in around 40% of cases if the primary infection is left untreated [2]. Brain abscess formation is the most common presentation of Nocardia CNS infection. Spinal cord involvement with intramedullary abscess formation is exceedingly rare. We present a rare case of such a neurological involvement as the initial presentation of Nocardia infection. We also review literature (Table 1) for this rare presentation [3] [4] [5] [6] [7] [8] [9] [10] [11] [12].

A 53-year-old Caucasian male with past medical history of alcoholic liver cirrhosis, diabetes mellitus, and hypertension presented to the emergency department with acute onset lower back pain and inability to walk for two days. He also had numbness and weakness in the right leg, urinary retention and constipation. He had not had preceding respiratory or gastrointestinal illnesses or any sick contact. Physical examination was remarkable for weakness in the lower extremities that was worse on the right side, diminished pinprick and vibration sensation below the mid-thighs bilaterally, and hyporeflexia in both legs. He had mild tenderness over the lower lumbar spine.

Initial blood tests included complete blood count, basic metabolic profile, Erythrocyte sedimentation rate, and C-reactive protein were all within normal limits except for thrombocytopenia.

The patient was admitted to the general medical floor and started on intravenous (IV) dexamethasone. Computed tomography (CT) scan of the spine showed no cord compression. However, given the high clinical suspicion, a magnetic resonance imaging (MRI) showed a signal abnormality and enhancement of the spinal cord, including the conus medullaris, consistent with intramedullary abscess (Figure 1).

A lumbar puncture was performed and cerebrospinal fluid analysis (CSF) showed a red blood cell (RBC) count of 1621 RBCs/µL, nucleated cells of 4822 WBCs/µL with neutrophilic predominance (84% neutrophils), protein of 306 mg/dL, and glucose < 1 mg/dL. The Gram stain was negative. The patient was then started on broad spectrum IV antibiotics.

The initial CSF culture showed Gram-positive bacilli partially acid fast with some branching. Mycobacterium tuberculosis PCR was negative and patient was initiated on intravenous trimethoprim/sulfamethoxazole (TMP/SMX) and meropenem for Nocardia double coverage. Patient was evaluated by neurosurgery and it was decided that it was in his best interest not to intervene on the abscess as the risks outweighed the benefits. On day 10 of admission, and using 16s ribosomal RNA gene sequencing, the organism was identified as N. farcinica.

The CSF culture was finalized on day 20 of his admission and showed Nocardia farcinica , sensitive to TMP/SMX, amikacin, and imipenem, but resistant to ceftriaxone. Patient weakness started to improve slowly towards the end of his admission. He was eventually discharged to a subacute rehabilitation center on IV antibiotics. A six-month follow-up MRI scan showed resolution of the intramedullary abscess.

Nocardia is a Gram-positive bacteria of the actinomycetes group. It is responsible for nocardiosis, an uncommon infection. Nocardia species can cause localized or systemic disease usually in immunocompromised patients as an opportunistic infection, but one third of the cases occur in healthy individuals [13].

Nocardia is defined as a complex that includes N. asteroides sensu stricto, N. farcinica, N. nova, and N. transvalensis complex. Nocardia species are not part of the human flora. They are known to be ubiquitous in the environment [1]. Inhalation is the most common mode of entry and that explains the lung involvement in a majority of the infections. It can also result from trauma-related introduction of the organism [12].

Immunosuppression is a major risk factor for attracting the disease. HIV, malignancies, corticosteroid therapy, organ and hematopoietic stem cell transplantation are the most common causes of immunosuppression leading to Nocardia infections. Diabetes mellitus is a prominent risk factor. Alcoholism and COPD are important risk factors for pulmonary nocardiosis [13].

Nocardia species are able to cause different kinds of disease in man, including skin and soft tissue infections, pneumonia, CNS infection and bacteremia. The most common site of primary infection is the lung (up to 70%) [5]. CNS involvement is common in disseminated nocardiosis, but can also be the primary site [9]. CNS involvement can also occur in up to 40% of untreated primary lung lesions [2]. Brain abscess is the most common presentation of CNS nocardiosis [10]. Nocardia epidural abscesses have also been described.

Spinal cord involvement with intramedullary abscess formation is exceedingly rare and only ten cases have been reported in literature [3] [4] [5] [6][7][8][9][10][11][12]. Our case is number 11. Yenrudi et al. reported a case of disseminated Nocardia, but we excluded it because the spinal cord involvement was secondary to thromboses of several blood vessels supplying the spinal cord resulting in widespread myelomalacia and not by direct infection by the organism [14]. Of these cases, six patients were males. The mean age was 58.27 years (SD +/- 16.11). Comorbid conditions were reported in seven cases besides our patient, and included hypertension, diabetes mellitus (in four patients), end-stage renal disease, renal transplant, liver cirrhosis, chronic obstructive pulmonary disease, and ulcerative colitis. One patient was mistakenly diagnosed with allergic alveolitis, but her symptoms were secondary to the pulmonary nocardiosis as he improved dramatically with Nocardia treatment. Table 1 summarizes the main features of these cases.

Antimicrobial susceptibility patterns are variable between different studies, countries and species. Therefore, formal antimicrobial susceptibility testing is always necessary to ensure optimal therapy. There are rapid tests that can identify the organism much faster than culture and knowing the organism itself with these tests, can allow us to pattern our two empiric antibiotics by relying on studies that show the susceptibility profiles of specific species [1]. 16s ribosomal RNA gene sequencing is also a quicker method for coming up with the specific species of Nocardia, and thus allowing an earlier and improved empiric therapy while cultures are pending [15], as we did in our case.

Treatments strategies are based on cumulative retrospective experience, as well as in vitro studies, as no prospective randomized trials have been performed to determine the most effective treatment. Given the variable antibiotics resistance of Nocardia, empiric coverage with two or three agents in a patient with severe disease is warranted. TMP/SMX is a first line and standard therapy and should be included in these regimens. Combination therapy is warranted in severe infections, defined as CNS involvement, disseminated disease, and infections involving more than one site in immunocompromised patients. Agents available for combination therapy include amikacin, imipenem, meropenem, third generation cephalosporins, minocycline, extended spectrum fluoroquinolones (e.g., moxifloxacin), tigecycline, and dapsone [1] [16].

Initial treatment should be administered intravenously for at least three to six weeks and/or until clinical improvement is documented. Treatment can be switched to oral and continued for a minimum of six months and up to 12 months in immunocompromised patients and those with CNS involvement.

Surgical intervention might be indicated in some situations, such as abscesses that do not respond to antibiotic therapy [12]. Prognosis is good in general, even in disseminated cases, if therapy is initiated early and continued for appropriate duration.

High index of suspicion of Nocardia infection is necessary in patients with suggestive neuroimaging. Spinal tap and stains and cultures for Nocardia are important part of the work up, but 16s rRNA allows earlier identification of the specific species, allowing adjustment of antibiotics, given the distinctly variable antibiotic susceptibilities of Nocardia species. A multidisciplinary approach that includes infectious disease, neurosurgical and neurological specialists is essential for early diagnosis and appropriate management of these patients.

This report describes a rare case of Nocardia intramedullary spinal abscess. It illustrates that a diagnosis can be made by neuroimaging and CSF 16s ribosomal RNA, with subsequent CSF culture confirmation. Appropriate antibiotic therapy was effective and resulted in significant recovery and obviated the need for a high-risk neurosurgical intervention.

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