Multiple Brain Abscesses Caused by Streptococcus pneumoniae : Rare Complication of Lobar Pneumonia

S treptococcus pneumoniae is an important cause of respiratory infections as well as meningitis in adults, but the organism has rarely been reported in association with pyogenic brain abscess. We recently saw such a rare infection. A previously healthy 55-year old man presented with a 10-day history of fever, cough, and hemoptysis. Chest radiography revealed typical lobar pneumonia. Because of the mild presentation of the symptoms, ambulatory oral therapy (amoxicillin + clavulanic acid 3 g/day for 15 days) was initiated. Twenty days later, the patient began to have headaches followed by rapid onset of lethargy and confusion. Physical examination disclosed fever (38.5°C), stiff neck, and rales in the right lower lung field. Neurologically, he was confused, with an initially low-grade, but rapidly progressive paresis of the right upper and lower extremities. A cranial computed tomography (CT) scan and magnetic resonance imaging (MRI) demonstrated multiple disseminated ring-enhancing lesions of the brain (Figs. 1A–C). Diffusion-weighted images (DWI) showed high signal-intensity sites in the above regions consistent with multiple abscesses (Fig. 1D). A chest radiograph and CT scan demonstrated right lower-lobe consolidation (Fig. 1D).

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FIG. 1.

Sagittal (A) and axial (B) post-gadolinium T₁-weighted images showing multiple ring-enhancing lesions. (C) Axial T₂-weighted images reveal multiple subcortical lesions with surrounding edema. (D) Multiple hyperintense lesions on a diffusion-weighted image. (E) Thoracic computed tomography scan demonstrates right lower lobe pneumonia.

The cerebrospinal fluid (CSF) analysis revealed the following values: White blood cells 2,000/mL (80% polymorphonuclear neutrophils), glucose 23 mg/dL, and protein 720 mg/dL. Gram stain showed gram-positive cocci; microbiological analysis confirmed S. pneumoniae. Bacterial culture of the blood and investigations for human immunodeficiency virus infection were negative. We started intravenous antibiotics (vancomycin 2 g/day; ceftriaxone 6 g/day), to be maintained for six weeks.

A CSF re-evaluation five days after therapy onset revealed 25 white blood cells/mL and 150 mg/dL protein and no evidence of bacteria. Neurologic re-examinations showed increasing consciousness and improvement of the hemiparesis. All neurologic symptoms remitted completely eight weeks after therapy onset, and MRI demonstrated nearly complete regression of the lesions.

Streptococcus pneumoniae has been described rarely as a cause of pyogenic brain abscess, with only a few adult cases having been reported in the antibiotic era [1]. Contiguous spread from a primary intracranial focus of infection was the most likely mechanism of infection in 50% of the reported cases [2,3]. The multiple brain lesions in our case can be considered hematogenous septic emboli, because microorganisms are deposited easily in areas of disrupted perfusion [1,3]. This report also documents the development of a potentially life-threatening infection caused by S. pneumoniae during inadequate empirical treatment of lobar pneumonia with amoxicillin. Early-onset intravenous broad-spectrum antibiotic therapy and extensive supportive care led to complete regression of the initially dramatic and progressive symptoms [1,4].