Culture-negative Brain Abscess with Streptococcus intermedius Infection with Diagnosis Established by Direct Nucleotide Sequence Analysis of the 16S Ribosomal RNA Gene

A 70-year-old woman developed a headache for a month followed by right upper limb weakness. CT scan and MRI showed multiple ring-enhancing lesions. An intracerebral aspiration of an abscess was performed, but culture results were negative. The nucleotide sequence analysis of the 16S rRNA gene from the specimens identified Streptococcus intermedius. Given this result, S. intermedius was cultured by enrichment culture, and its sensitivities to antibiotics were determined. The patient exhibited complete remission. Thus, 16S rRNA gene analysis was highly useful not only for pathogen identification with negative culture results but also for the appropriate selection of antibiotics.