Multimodal optical mesoscopy reveals the quantity and spatial distribution of Gram‐positive biofilms in ex vivo tonsils.

Biofilms are known to be present in tonsils, but little is known about their spatial location and size distribution throughout the tonsil. Studies of the location and distribution of biofilms in tonsil specimens have thus far been limited to either high‐magnification methods such as electron microscopy, which enables high‐resolution imaging but only from a tiny tissue volume, or lower magnification techniques such as light microscopy, which allow imaging of larger specimens but with poor spatial resolution. To overcome these limitations, we report the use of multimodal optical mesoscopy to visualise and quantify the number and spatial distribution of Gram‐positive biofilms in fresh, excised paediatric tonsils. This methodology supports simultaneous imaging of both the tonsil host and biofilms in whole mounts of tissue up to 5 mm × 5 mm × 3 mm with subcellular resolution throughout. A quantitative assessment of 36 tonsil specimens revealed no statistically significant difference between biofilm presence on the tonsil surface and the interior of the tonsil. This new quantitative mesoscale imaging approach may prove useful in understanding the role of biofilms in tonsillar diseases and other infections. LAY DESCRIPTION: Biofilms, which are communities of bacteria known to be more resistant to antibiotics than normal (planktonic) bacteria, are thought to play a role in diseases of the tonsil. Biofilms are difficult to study in patient tissue due to limits in standard microscopes, which compromise either on the tissue volume that can be studied or the amount of detail in the image. We have used the Mesolens, a novel microscope lens, to visualise bacteria and biofilms in unusually large volumes of freshly excised tonsils from a local children's hospital following tonsillectomy. Using this method, we have shown that biofilms were present in all diseased tonsils on both the surface and the interior of the tonsil. This new way of studying diseases in human tissue may prove useful in understanding the role of biofilms in other diseases and infections. [ABSTRACT FROM AUTHOR]