Acute otitis media develops in the rat after intranasal challenge of Streptococcus pneumoniae
Per Olof Eriksson1, Sten Hellström
1Department of Clinical Sciences, Otorhinolaryngology, Umeå University Hospital, Sweden. Per-Olof.Eriksson@ent.umu.se
Objectives/Hypothesis:
The rat is a frequently used animal model for middle ear research. To date, acute otitis media (AOM) has been evoked after instillation of bacteria directly into the middle ear cavity or after traumatizing the tympanic membrane. The purpose of the study was to examine whether, with an intact tympanic membrane and middle ear cavity, intranasally deposited bacteria cause AOM and how tympanic membrane stimulation influences this procedure.
Study Design:
In vivo, murine model.
Methods:
In a rat model, Streptococcus pneumoniae, type 3, was intranasally inoculated for 5 consecutive days. The tympanic membrane was treated with saline or with compound 48/80 or was left untreated. The development of AOM was evaluated by otomicroscopy, light microscopy, and middle ear culture.
Results:
Ninety percent of the ears developed AOM. However, when the tympanic membranes were treated with saline or compound 48/80, only 40% and 57%, respectively, developed AOM. In all, 23 of 40 ears developed AOM and 20 ears showed growth of bacteria.
Conclusion:
Repeated intranasal deposition of S. pneumoniae, type 3, causes AOM in the rat. The development of AOM can be influenced by tympanic membrane stimulation.
Insights
Intranasal inoculation of Streptococcus pneumoniae in rats caused acute otitis media (AOM). Tympanic membrane stimulation influenced AOM development, suggesting a new model for middle ear research.
Area of Science:
- Otolaryngology
- Infectious Disease
- Animal Models
Background:
- Rats are common models for middle ear research.
- Current methods for inducing acute otitis media (AOM) involve direct bacterial instillation or tympanic membrane trauma.
Purpose of the Study:
- To investigate if intranasal bacterial deposition can cause AOM in rats with intact tympanic membranes.
- To determine the effect of tympanic membrane stimulation on AOM development.
Main Methods:
- Rats were intranasally inoculated with Streptococcus pneumoniae (type 3) for five consecutive days.
- Tympanic membranes were treated with saline, compound 48/80, or left untreated.
- AOM development was assessed via otomicroscopy, light microscopy, and middle ear cultures.
Main Results:
- Ninety percent of rats developed AOM without tympanic membrane treatment.
- Treated tympanic membranes showed reduced AOM incidence (40% with saline, 57% with compound 48/80).
- Bacterial growth was confirmed in 20 out of 40 evaluated ears.
Conclusions:
- Repeated intranasal Streptococcus pneumoniae inoculation effectively induces AOM in a rat model.
- Tympanic membrane stimulation can modulate the development of AOM.
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