科研之友
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摘要
Objective: Tympanostomy tube otorrhea (TTO), caused by the presence of pathogenic bacteria in the middle ear, is the most common complication of TT insertion. No studies have described a reproducible animal model of TTO. We aimed to develop a rat model of TTO which, in turn, could be used to assay the levels of TNF-alpha and IL-1 beta through the course of the infection.
Methods: The left Eustachian tubes of 55 male Sprague-Dawley albino rats were occluded with guttapercha (ETO = Eustachian Tube Occlusion). Middle ear (ME) effusion was ascertained by weekly otomicroscopy. At 3 weeks tympanostomy tubes were placed bilaterally and the MEs were inoculated bilaterally with Streptococcus pneumoniae through the tubes. The rats were randomly assigned to one of two daily ototopical treatments: ciprofloxacin/dexamethasone (CDX) or placebo. The animals in each of the two treatment groups were further divided to receive 1, 2, 5 or 7 days of treatment. The rats were sacrificed after treatment was finished. The rates of otorrhea, positive middle ear (ME) cultures, and levels of TNF-alpha and IL-1 beta in the ME fluid were measured.
Results: Left ETO followed by ME inoculation with S. pneumoniae and treatment with placebo resulted in persistent infection (100% culture-positive ME fluid at 10 days) and otorrhea (85.7%). Persistent infection of the left ear was accompanied by significantly elevated the levels of IL-1 beta and TNF-alpha. Ears treated with CDX had lower rates of otorrhea at all time points and lower levels of IL-1 beta and TNF-alpha.
Conclusions: This study is the first to describe a reproducible animal model of acute TTO. Surgical obstruction of the ET, followed by TT placement and ME inoculation with S. pneumoniae induced persistent otorrhea and infection. Both IL-1 beta and TNF-alpha appear to be potential markers of persistent middle ear infection. This novel model may be used in future studies of the pathogenesis and therapy of TTO.
- 出版日期2012-2
