ABSTRACT
A brain abscess is a focal collection of pus in the brain parenchyma surrounded by a well-vascularized collagenous capsule in response to an infection. The microbiome of brain abscesses has been shown to be polymicrobial, dominated by uncultivable and anaerobic organisms of odontogenic origin. The data provided in this article includes the sequences of bacterial 16S rRNA gene from three culture-negative brain abscess samples suspected to have poly-microbial aetiology based on Sanger sequencing. DNA was extracted from brain abscess samples, and targeted-metagenomics sequencing was done by amplifying the full-length bacterial 16S rRNA followed by a nested PCR for V3-V4 regions using universal and specific primers. The barcoded amplicons were sequenced on Illumina MiSeq V2 instrument to generate 0.5M, 250bp paired-end reads/sample. The total sequencing reads were 455966, 345746, and 438658 for samples P32, P49, and P8, respectively. Bioinformatics tools such as FLASH, VSEARCH, and QIIME1 were used to process the reads generated for Operational Taxonomic Unit analysis (OTU). Bacterial species belonging to phyla Firmicutes, Bacteroidetes, and Fusobacteria were abundant in samples P49 and P8, which are mainly anaerobic and microaerophilic bacteria. These are typical of the human oral/gut microbiota and are implicated in brain abscess formation. Sample P32 showed the abundance of bacterial species belonging to phyla Proteobacteria and Actinobacteria, which are commonly found in the environment. Raw data files are available at the Sequence Read Archive (SRA), National Center for Biotechnology Information (NCBI), and data information can be found at the BioProject, PRJNA785100 under the accession numbers SRX13271109, SRX13271110, SRX13295897. The data shows the microbiome constitution, including several anaerobic and unculturable bacterial species from culture-negative brain abscess samples. This dataset will be useful for future research on comparative genomics and management of patients with culture-negative brain abscesses.
ABSTRACT
@#Despite clinical suspicion of an infection, brain abscess samples are often culture-negative in routine microbiological testing. Direct PCR of such samples enables the identification of microbes that may be fastidious, non-viable, or unculturable. Brain abscess samples (n = 217) from neurosurgical patients were subjected to broad range 16S rRNA gene PCR and sequencing for bacteria. All these samples and seven formalin-fixed paraffin-embedded tissue (FFPE) samples were subjected to species-specific 18S rRNA PCR for neurotropic free-living amoeba that harbour pathogenic bacteria. The concordance between smear and/or culture and PCR was 69%. One-third of the samples were smear- and culture-negative for bacterial agents. However, 88% of these culture-negative samples showed the presence of bacterial 16S rRNA by PCR. Sanger sequencing of 27 selected samples showed anaerobic/fastidious gram negative bacteria (GNB, 38%), facultative Streptococci (35%), and aerobic GNB (27%). Targeted metagenomics sequencing of three samples showed multiple bacterial species, including anaerobic and non-culturable bacteria. One FFPE tissue revealed the presence of Acanthamoeba 18S rRNA. None of the frozen brain abscess samples tested was positive for 18S rRNA of Acanthamoeba or Balamuthia mandrillaris. The microbial 16/18S rRNA PCR and sequencing outperformed culture in detecting anaerobes, facultative Streptococci and FLA in brain abscess samples. Genetic analyses of 16S/18S sequences, either through Sanger or metagenomic sequencing, will be an essential diagnostic technology to be included for diagnosing culture-negative brain abscess samples. Characterizing the microbiome of culture-negative brain abscess samples by molecular methods could enable detection and/or treatment of the source of infection.
