Anatomical evidence of microbial biofilms in tonsillar tissues: A possible mechanism to explain chronicity

Context: Bacteria within biofilms are resistant to host defenses and antibiotics. The presence of bacterial biofilms within the tissue and crypts of inflamed tonsils may explain the chronicity and recurrent characteristics of some forms of tonsillitis. Objective: To determine if microbial biofilms occur within clinically abnormal tonsils. Design: In this study, we evaluated the histomorphological appearance of 19 human tonsils for evidence of biofilm formation using light and transmission electron microscopy. Subjects: Human tissues were collected during surgical tonsillectomy. Fifteen specimens were removed because of a history of repeated infections, and 4 were removed because of hypertrophy and obstruction. Interventions: No interventions were used in this study. Main Outcome Measure: Histological and ultrastructural evidence of bacterial biofilms within the crypts of tonsils. Results: Gram-positive and gram-negative bacteria were seen within otherwise acellular deposits among crypts of 11 of 15 infected tonsils. Regions of accumulated bacteria possessed the ultrastructural appearance of typical amorphous polysaccharide biofilm matrix. Small clusters of bacterial colonies were seen in 3 of 4 tonsils removed because of hypertrophy. Conclusions: There is strong anatomical evidence for the presence of bacterial biofilms in chronically diseased tonsils. Because sessile bacteria within biofilms are resistant to host defenses and antibiotics, bacterial biofilms within tonsils may explain the chronicity and recurrent nature of some forms of tonsillitis.