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Brain abscess with lung infection? Think Nocardia



A brain abscess in the presence of a lung infection should raise suspicion for Nocardia whether patients are immunocompromised or not, according to University of California, San Francisco, investigators.

Dr. Megan Richie, University of California, San Francisco M. Alexander Otto/MDedge News

Dr. Megan Richie

Nocardia – an ubiquitous gram-positive rod normally found in standing water, decaying plants, and soil, that can cause problems when it is inhaled as dust or introduced through a nick in the skin – is an underappreciated cause of brain abscess that is not covered by standard empiric therapy targeting the more common causes: Staphylococcus and Streptococcus bacteria, said senior investigator Megan Richie, MD, an assistant neurology professor at UCSF.

“Patients that have a lung infection with a new brain abscess should be started on empiric therapy not just for pyogenic organisms, but also for Nocardia pending biopsy and operative culture data, especially given that empiric therapy of high-dose Bactrim for Nocardia is relatively benign,” she said at the annual meeting of the American Neurological Association.

The advice comes from a comparison of 14 Nocardia cases with 42 randomly selected Staph/Strep cases in a university radiologic database. Nine Nocardia cases were confirmed by operative specimen culture, the rest by lung, blood, or other tissue cultures.

Dr. Richie and colleagues suspected an association with lung infection, which has been reported anecdotally in the literature. The researchers wanted to take a quantitative look to see if it held up statistically after pushback on a brain abscess patient with a lung infection. “We were concerned this patient had Nocardia, but it took quite some time to convince other doctors that we really needed to start [Bactrim]. The patient was not immunocompromised and the infectious disease team said ‘Nocardia brain infections don’t happen in immunocompetent patients,’” Dr. Richie said,

The man did, however, turn out to have Nocardia, and of the 14 cases in the series, four patients (29%) were not immunosuppressed. “I think this would surprise [physicians] who have a little bit less experience with this organism,” Dr. Richie said.Patients with a Nocardia brain abscess were far more likely to have a concomitant lung infection (86% vs. 2%; odds ratio, 246; 95% confidence interval, 21-2953; P less than .0001). Staph/Strep brain abscess patients were more likely to have concomitant ear or sinus infections (40% versus 0%; P = .005). Immunosuppression did turn out to be more common in the Nocardia group, as well (71% vs. 19%; OR, 11; 95% CI, 3-43; P = .001), as did diabetes (36% vs. 10%; P = .03).

Nocardia patients were older (median age, 61 yrs vs. 46 yrs: P = .01) and more likely to be Hispanic (36% vs. 10%; P = .04). There were no differences in sex; neurosurgery history; intravenous drug use; or endocarditis.

On imaging, Nocardia brain abscesses were poorly circumscribed and tended to have multiple lobes, “often two in a figure-eight pattern,” Dr. Richie said. Nocardia diagnosis took longer (median, 7 vs. 4 days; P = .04), “which makes sense because it is a harder diagnosis to make,” she said.

Operative specimen culture was the most potent diagnostic tool. Blood cultures were positive in just one Nocardia patient and a few controls.

There was no external funding, and the investigators did not have any relevant disclosures.

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