Mesoscopic imaging of paediatric palatine tonsil infection

Recurring paediatric tonsilitis is one of the most common problems presented to GPs in the UK, with an annual reported incidence of 37 per 1000 population [1]. Recurring tonsillitis has detrimental effects on children’s quality of life. Often, antibiotic treatment of the infection does not suffice and if a patient has seven or more cases of tonsillitis per year the complete removal of the tonsils is recommended [2]. Studies of tonsillitis infections have been performed previously by Chloe and Faddis, showing the presence of gram-positive and gram-negative bacteria within the tonsil crypts, presenting the ultrastructural appearance of a biofilm matrix [3]. We report the first demonstration of mesoscopic imaging of bacterial infection of the palatine tonsil using the Mesolens. The Mesolens, developed at the University of Strathclyde, offers the unique combination of a low magnification (4x) and high numerical aperture (0.47) lens which has an imaging area of 6 mm x 6 mm. The Mesolens can resolve features as small as 700nm laterally and 7um axially [4], this field of view means that the probability of detecting a few bacteria in the specimen is high. Samples were collected via a swab from the surface of unfixed palatine tonsil tissue acquired via tonsillectomy at the NHS Royal Hospital for Children, Glasgow, which had been transported and stored in PBS for 2 hours before processing. Specimens were prepared using a standard Gram stain protocol. Figure 1 shows a colour brightfield Mesolens image a swab from the tonsil surface. Using the Mesolens to study infection offers an advantage over conventional objective lenses. The large field of view and sub-cellular resolution throughout unlocks the possibility to understand the prevalence of bacteria in larger specimens than can normally be studied with a light microscope, and any infection has a greater chance of being detected.