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Bacterial flora in the external ear canal and in induced cholesteatoma in the Mongolian gerbil
J C Fortuny1, V M Palomar, A Nogués
1Department of Otorhinolaryngology, Arnau de Vilanova Hospital of Lleida, Spain.
Abstract:
We report on the bacterial flora of the external ear canal and of induced aural cholesteatoma in 14 Mongolian gerbils (Meriones unguiculatus). In the control, nonmanipulated external ear canal, gram-positive and gram-negative organisms were isolated. In the contents of the cholesteatoma sac, only monomicrobial, gram-negative isolates were found; in each animal they were different from the isolates from the nonmanipulated external ear canal. Obligate anaerobes were absent in all cases. Ligation of the external ear canal in the left ear provoked cholesteatoma in all cases.
Insights
Bacterial flora in gerbil ear canals and induced cholesteatomas were analyzed. Cholesteatomas contained unique gram-negative bacteria, differing from the external ear canal flora.
Area of Science:
- Microbiology
- Otolaryngology
- Animal Models
Background:
- Aural cholesteatoma is a destructive condition of the middle ear.
- The bacterial etiology of cholesteatoma, particularly in animal models, requires further elucidation.
- Mongolian gerbils are a suitable model for otitis media research.
Purpose of the Study:
- To characterize the bacterial flora of the external ear canal and induced aural cholesteatoma in Mongolian gerbils.
- To investigate the microbial differences between normal ear canals and cholesteatoma contents.
- To assess the role of external ear canal ligation in cholesteatoma formation and its associated bacterial changes.
Main Methods:
- Bacterial cultures were performed on samples from the external ear canal and induced cholesteatoma in 14 Mongolian gerbils.
- External ear canals were ligated to induce cholesteatoma formation.
- Isolates were identified based on Gram staining and microbial characteristics.
- Obligate anaerobes were specifically assessed.
Main Results:
- The normal external ear canal harbored both gram-positive and gram-negative bacteria.
- Induced cholesteatoma sacs consistently showed monomicrobial, gram-negative bacterial isolates.
- The gram-negative bacteria in cholesteatomas were distinct from those in the nonmanipulated external ear canals of the same animals.
- Obligate anaerobes were not detected in any samples.
- Ligation of the external ear canal successfully induced cholesteatoma in all gerbils.
Conclusions:
- Induced aural cholesteatoma in gerbils is characterized by a specific, monomicrobial gram-negative flora.
- The bacterial composition of cholesteatoma differs significantly from the normal external ear canal flora.
- External ear canal ligation is an effective method for inducing cholesteatoma in this animal model, facilitating further research into its pathogenesis.