Central nervous system Nocardia infection

Nocardial brain abscess: treatment strategies and factors influencing outcome

The successful management of nocardial brain abscess remains problematic. The authors report 11 cases of nocardial brain abscess treated between 1971 and 1993 and review 120 cases reported since 1950. The clinical findings included focal deficits in 55 patients (42%), nonfocal findings in 36 (27%), and seizures in 39 (30%). Extraneural nocardiae were present in 66% of the cases; pulmonary (38%) and cutaneous/subcutaneous (20%) locations were the most frequent. The abscesses were single in 54% of the patients, multiple in 38%, and of unknown number in 8%. Forty-four of 131 patients (34%) were immunocompromised; since 1975, 18 of 40 immunocompromised patients (45%) were transplant recipients and six (15%) had human immunodeficiency virus. The mortality rate was 24% after initial craniotomy and excision (11/45), 50% after aspiration/drainage (17/34), and 30% after nonoperative therapy (7/23); 29 cases (22%) were diagnosed at autopsy. The mortality rate was 33% in patients with single abscesses and 66% in those with multiple abscesses (P < 0.0003). There was no difference in the mortality rates of immunocompromised and nonimmunocompromised patients treated before computed tomography (CT) was available; since the advent of CT, however, the mortality rate has been significantly higher in immunocompromised patients (55% vs. 20%, P < 0.05). Although the mortality rate for nocardial brain abscesses has dropped almost 50% since the advent of CT, it has remained virtually unchanged in immunocompromised patients and is three times higher than that of other bacterial brain abscesses (30% vs. 10%). The authors recommend image-directed stereotactic aspiration for diagnosis; however, craniotomy and total excision are necessary in most cases, because nocardial abscesses are usually multiloculated. Patients with minimal neurological deficits or small abscesses may be treated initially with antibiotics alone. Sulfonamides, alone or in combination with trimethoprim, are most effective and should be continued for at least 1 year. Minocycline, imipenem, or aminoglycoside in combination with a third-generation cephalosporin may be used with reasonably good success as second-line agents in cases of allergy or nonresponsiveness to sulfa agents.

Nocardia species: host-parasite relationships

The nocardiae are bacteria belonging to the aerobic actinomycetes. They are an important part of the normal soil microflora worldwide. The type species, Nocardia asteroides, and N. brasiliensis, N. farcinica, N. otitidiscaviarum, N. nova, and N. transvalensis cause a variety of diseases in both normal and immunocompromised humans and animals. The mechanisms of pathogenesis are complex, not fully understood, and include the capacity to evade or neutralize the myriad microbicidal activities of the host. The relative virulence of N. asteroides correlates with the ability to inhibit phagosome-lysosome fusion in phagocytes; to neutralize phagosomal acidification; to detoxify the microbicidal products of oxidative metabolism; to modify phagocyte function; to grow within phagocytic cells; and to attach to, penetrate, and grow within host cells. Both activated macrophages and immunologically specific T lymphocytes constitute the major mechanisms for host resistance to nocardial infection, whereas B lymphocytes and humoral immunity do not appear to be as important in protecting the host. Thus, the nocardiae are facultative intracellular pathogens that can persist within the host, probably in a cryptic form (L-form), for life. Silent invasion of brain cells by some Nocardia strains can induce neurodegeneration in experimental animals; however, the role of nocardiae in neurodegenerative diseases in humans needs to be investigated.

Intracerebral Nocardia brasiliensis infection

Case report about cerebral infection with the species Nocardia Brasiliensis in a not immunocompromised host. Diagnosis, treatment and neuroradiological findings are shown and compared with current studies.

Nocardial brain abscess: diagnostic and therapeutic use of stereotactic aspiration

Three cases of nocardial brain abscess are presented. All three patients were receiving immunosuppressive therapy at the time of diagnosis. Two patients had cardiac transplantation and the third had periarteritis nodosa. The patients presented with generalized seizures or focal weakness. Accurate localization of the intracerebral mass lesion was obtained from computed tomography (CT) scans, but CT-guided stereotactic aspiration was required for diagnosis and treatment in every case. After Nocardia asteroides was seen on Gram's stain and subsequently identified by culture, appropriate antibiotic therapy was initiated. Both heart transplant patients survived in good neurological condition. We believe that stereotactic aspiration followed by prolonged antibiotic therapy may significantly improve the outcome of patients with nocardial brain abscess.

Unrecognized penetrating intracranial foreign body

Low-velocity penetrating craniocerebral trauma may present as an apparently trivial injury. A case is presented which illustrates the need to suspect a penetrating injury whenever a low velocity object strikes the head.

Nocardia asteroides brain abscess following mastoidectomy

Nocardia asteroides brain abscess occurred after mastoidectomy and tympanoplasty in a previously healthy 10-year-old boy. Combined surgical excision and trimethoprim/sulfamethoxazole therapy resulted in significant improvement.