GSE134118
Dual RNAseq of pneumococcal infection
Streptococcus pneumoniae is the dominant cause of community-acquired pneumonia world-wide. Invasion of the pleural space is common and results in increased mortality. We set out to determine the bacterial and host factors that influence invasion of the pleural space. In a murine model of pneumococcal infection, we isolated neutrophil-dominated samples of bronchoalveolar and pleural fluid containing bacteria 48 hours after infection. Using dual RNA-seq, we characterised bacterial and host transcripts that were differentially regulated between these compartments and bacteria in broth and resting neutrophils respectively. Pleural and lung samples showed upregulation of genes involved in positive regulation of neutrophil extravasation but down-regulation of genes mediating bacterial killing. Compared to the lung samples, cells within the pleural space showed marked upregulation of many genes induced by type I interferons, cytokines implicated in preventing bacterial transmigration across epithelial barriers. Differences in the bacterial transcripts between the infected samples and bacteria grown in broth showed upregulation of genes in the bacteriocin locus, the pneumococcal surface adhesin PsaA, and the glycopeptide resistance gene, vanZ; the gene encoding the ClpP protease was downregulated in infection. 169 intergenic putative small bacterial RNAs were also identified, of which 43 (25.4%) had been previously described. 42 of the small RNAs were upregulated in pleura compared to broth,  including many previously identified as important in virulence. Our results  have identified key host and bacterial responses to invasion of the pleural space that can be potentially exploited to develop alternative antimicrobial strategies for prevention and treatment of pneumococcal pleural disease. Overall design: Comparison of trasncripts from broth, BALF and pleura, 3 replicates each