Background: An increased awareness of bacterial biofilms and their formation has led to a better understanding of bacterial infections that occur in the middle ear. Perhaps the best studied pathogen for its propensity toward biofilm formation is Pseudomonas aeruginosa, also the primary pathogen in chronic suppurative otitis media (CSOM).
Objective: The aim of this study was to determine whether P. aeruginosa forms a biofilm in the middle ear in the setting of CSOM in a nonhuman primate model.
Methods: Cynomolgus monkeys underwent perforation of the tympanic membrane and inoculation of the middle ear with a known biofilm-forming strain of P. aeruginosa. The contralateral ear was used as an internal control and was neither perforated nor infected. At the end of the study period, both ears were irrigated to remove planktonic bacteria, and the middle ear mucosa was removed and examined ultrastructurally using scanning electron microscopy (SEM) for determination of the presence or absence of biofilm formation.
Main Outcome Measure: The identification of middle ear biofilm containing rod-shaped bacteria.
Results: SEM revealed that P. aeruginosa formed bacterial biofilm in vivo on the middle ear mucosal surface, seen only in the infected ear. Interestingly, biofilm formation caused by cocci was also seen in both the experimental as well as the control ear.
Conclusion:P. aeruginosa forms biofilms in the middle ear in CSOM in primates. To our knowledge, this is the first report of disease-associated bacterial biofilm in a nonhuman primate model of CSOM. Such a model lays a foundation for much needed study into the role of biofilms in the pathophysiology of CSOM. Should CSOM be caused by biofilms, which is uncertain at this time, development of novel strategies for treatment and prevention may be possible. The finding of both rods and cocci forming biofilms also warrants further investigation.