A Rat Model Of Acute Otitis Media For Bacterial Biofilms: A Tissue Morphology Study

Acute otitis media (AOM) is the most frequently diagnosed infectious diseases of childhood, Except for the upper respiratory tract infection. The most troubled clinical problem about AOM is recurrent AOM and persistent AOM, it has been estimated that 20% to 30% of children have recurrent AOM, and there are indications that the incidence of recurrent AOM is increasing. Frequent middle ear infection in children not only causes tympanosclerosis,adhesive otitis media and cholesteatoma of middle ear, consequently result in progressive hearing loss, but also affects language development. However, the exact pathogenesis,antibiotic resistance mechanisms and recurrent episodes reasons are still poorly understood.Post et al for the first time proposed pathogenic theory of bacterial biofilms in the pathogenesis of secretory otitis media (SOM) in 2001. Since then, the relationship between bacterial biofilms and otitis media quickly became the focus of research, but till now, almost all research was focused on the relationship between SOM and bacterial biofilms. In 2009, Reid et al and Hoa et al observed respectively the presence of bacterial biofilms in different chinchilla model of AOM, but further study is required to describe the characterization of the bacterial biofilms formation in AOM,whether bacterial biofilms involved in the pathogenesis of AOM and its clinical significance et al. Because of this, we designed this research.This research is composed of two parts.In the part one, in order to provide the basic data for the next study, we investigated the feasibility of which Streptococcus pneumoniae were injected into the rat middle ear via a transbullar approach to establish a rat AOM model and explored the application value of this model by observing the pathological changes and the course of pneumococcal otitis media in rat. This study confirmed that the rat model of AOM, which established by inoculated a volume of 50μl of the Streptococcus pneumoniae suspension (1×108CFU/ml) into the rat middle ear cavity through transbullar approach and which success rate is 100%, is an ideal research model for otitis media, not only suit for the study of acute purulent otitis media (APOM) but also for the study of acute secretory otitis media (ASOM).In the part two, on the basis of successful establishment a rat model of AOM, we studied the formation characterization and the clinical significance of bacterial biofilms on the middle-ear mucosa of pneumococcal otitis media in rat by observed under scanning electron microscopy and laser scanning confocal microscope combined with immunofluorescence in situ labeling technique, and investigated the feasibility of the rat AOM model for the research of bacterial biofilms. This study found that bacterial biofilms had already formed in the middle ear at the early phase of acute infection, and may be contribute to recurrent or persist inflammation in the future. early and timely application of anti-biofilm drugs could help to the thoroughly eradication of infection. the rat model of AOM established in this research is an ideal animal model for the bacterial biofilms study.