Paired qualitative and quantitative analysis of bacterial microcolonies in the tonsils of patients with tonsillar hyperplasia.

The discovery of bacterial microcolonies in tonsillar tissue of patients with tonsillar hyperplasia has raised the question of their role in provoking the local immune response. Tonsils collected from patients undergoing tonsillectomy were stained for three clinically relevant bacterial taxa and lymphocytes. The bacterial composition and abundance of microcolonies was investigated using a combination of laser-microdissection, amplicon sequencing and Droplet Digital polymerase chain reaction. Microcolonies were detected in most samples (32/35) with a high prevalence of Haemophilus influenzae (78% of samples). B and T cell lymphocytes were significantly higher in the epithelium adjacent to microcolonies compared to epithelium distal to microcolonies. Furthermore, significant positive and negative correlations were identified between bacterial taxa and lymphocytes. Genus Streptococcus, which includes Group A Streptococcus (traditionally described as the main pathogen of tonsillar hyperplasia), was found in low abundance in this study. These results suggest other potential pathogens may be involved in stimulating the local immune response leading to tonsillar hyperplasia.