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Experimental alteration of chinchilla middle ear mucosae by bacterial neuraminidase
Abstract:
Streptococcus pneumoniae secretes a variety of extracellular glycosidase including a neuraminidase which has been found in middle ear effusion from patients with both acute and chronic otitis media. This enzyme cleaves sialic acid from membrane glycoproteins, thereby exposing galactose residues, the penultimate sugar. The ability of partially purified neuraminidase to alter the middle ear mucosa was investigated in the chinchilla. After incubation with neuraminidase, chinchilla middle ears were removed and exposed to galactose residues labeled with tritium. Membrane glycoproteins were solubilized and separated according to molecular weight by sodium dodecylsulfate electrophoresis. Increases in tritium incorporation, when compared to control incubations, indicated that galactose residues had been exposed and sialic acid residues removed from glycoproteins of both high and low molecular weight. Such membrane destruction could contribute significantly to the pathology of otitis media with effusion.
Insights
Streptococcus pneumoniae neuraminidase cleaves sialic acid in the middle ear, exposing galactose. This enzyme action may damage middle ear mucosa, contributing to otitis media with effusion pathology.
Area of Science:
- Microbiology
- Biochemistry
- Otolaryngology
Background:
- Streptococcus pneumoniae secretes extracellular glycosidases, including neuraminidase.
- Neuraminidase cleaves sialic acid from glycoproteins, exposing underlying sugars like galactose.
- This enzyme is detected in middle ear effusion fluid from otitis media patients.
Purpose of the Study:
- To investigate the effect of Streptococcus pneumoniae neuraminidase on middle ear mucosa.
- To determine if neuraminidase alters glycoproteins in the middle ear lining.
Main Methods:
- Partially purified neuraminidase was used to treat chinchilla middle ear tissue.
- Tritiated galactose was used to label exposed galactose residues after enzyme treatment.
- Membrane glycoproteins were solubilized and analyzed by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE).
Main Results:
- Neuraminidase treatment led to increased tritium incorporation, indicating exposed galactose residues.
- Sialic acid removal and galactose exposure occurred on both high and low molecular weight glycoproteins.
- These findings suggest direct alteration of middle ear glycoproteins by the enzyme.
Conclusions:
- Streptococcus pneumoniae neuraminidase can modify middle ear mucosal glycoproteins.
- This enzymatic modification, exposing galactose residues, likely contributes to the pathological processes in otitis media with effusion.