Chinchilla Otitis Media Research Articles

Identification of prostaglandins and other arachidonic acid metabolites in experimental otitis media

Although prostaglandins (PGs) have been detected in the middle ear fluids, the exact identification of PGs, and other arachidonic acid (AA) metabolites has not been made. The AA metabolites were identified in experimentally induced serous otitis media and purulent otitis media in chinchillas using a radiochromatography method. The relative abundance of each metabolite synthesized was also determined. Two major AA metabolites, 6-Keto-PGF 1α and 15-hydroxy-5,8,11,13-eicosatetraenoic acid (15-HETE), were positively identified by gas chromatography-mass spectrometry. The AA metabolites in Eustachian tube obstructed middle ear mucosa (MEM) were predominantly 6-keto-PGF 1α, followed by PGD 2, 15-HETE, hydroxyheptadecatrienoic acid (HHT), PGF 2α and PGE 2. In infected MEM, the predominant product was 15-HETE followed by 6-keto-PGF 1α, PGD 2, HHT, PGF 2α, and PGE 2. The possible role of PGs and other AA metabolites in the pathogenesis of otitis media will be discussed.

The Pathogenesis of Pneumococcal Otitis Media in Chinchillas and the Efficacy of Vaccination in Prophylaxis

Acute pneumococcal otitis media was produced experimentally in 100% of chinchillas whose middle ear cavities were inoculated with Streptococcus pneumoniae. Although intranasal inoculation with S. pneumoniae led to otitis media in 21% of animals, 66% of the colonized chinchillas that had negative pressure in the middle ear developed otitis media. Intranasal inoculation with S. pneumoniae followed by intranasal inoculation with influenza A virus led to otitis media in 73% of chinchillas, while inoculation with infleunza A virus alone produced otitis media in 4% of animals. Measurement of middle ear pressure by tympanometry showed the influenza virus-infected chinchillas developed negative middle ear pressure before the appearance of clinical signs of otitis media. While direct inoculation of the middle ear with pneumococci produced a purulent effusion within days after inoculation, intranasal inoculation with both pneumococci and influenza A virus resulted in the rapid appearance of a serous effusion, which became culture-positive for S. pneumoniae during the second week after inoculation. Spontaneous resolution of middle ear infection occurred within three to eight weeks after inoculation and was associated with an increase in the level of type-specific pneumococcal antibody in serum and middle ear effusion. The histopathology of pneumococcal otitis media included purulent middle ear effusion, epithelial metaplasia, and subepithelial edema and hypercellularity. The initial infiltration of the subepithelial space with polymorphonuclear leukocytes was superceded by infiltration with mononuclear leukocytes in animals that were observed for longer than eight weeks. Among untreated animals observed for long periods, production of granulation tissue, development of submucosal fibrosis, and osteoneogenesis were observed. Systemically administered pneumococcal capsular polysaccharide vaccine was effective for prevention of type-specific otitis media in chinchillas when vaccinated animals were challenged by intranasal inoculation with pneumococci followed by deflation of the middle ear. Animals that seroconverted with at least a twofold increase in the level of antibody in serum after vaccination had an 87% lower incidence of otitis media than did unvaccinated animals. Protection was associated with high levels of antibody in serum before intranasal inoculation, and higher antibody levels were found in sterile middle ear effusions than in effusions that contained pneumococci.

Prostaglandins and otitis media: studies in the chinchilla.

Prostaglandins (PG) are naturally occurring, cyclic, unsaturated fatty acids that possess a wide range of potent biologic activities. Prostaglandins have been found in human middle ear effusions and may have implications for understanding the inflammation and, possibly, the bone resorption seen in chronic otitis media. In the study presented, PGs were measured by radioimmuno-assay in middle ear effusions from experimentally induced serous and purulent otitis media in chinchillas. The ability of chinchilla middle ear mucosa to synthesize PGs from 14C-arachidonic acid was also demonstrated. The authors suggest an active role for PGs in the inflammation and the bone resorption seen in otitis media.

Experimental otitis media in chinchillas following nasal colonization with type 7F Streptococcus pneumoniae: prevention after vaccination with pneumococcal capsular polysaccharide.

Chinchillas were colonized intranasally with type 7F Streptococcus pneumoniae, and pneumococcal otitis media developed in greater than 50% of the animals during the first week after negative middle ear pressure (-25 mm Hg) was briefly applied. Twenty-three chinchillas were vaccinated subcutaneously with the capsular polysaccharde of type 7F S. pneumoniae to determine whether vaccination could prevent the development of experimental otitis media. Following vaccination, 14 animals seroconverted with at least a twofold rise in serum antibody concentration; nine animals that were vaccinated did not seroconvert. All of 23 vaccinated animals and 42 of 42 unvaccinated control animals became colonized after intranasal inoculation with pneumococci. Only one (7%) of the vaccinated seroconverting animals developed pneumococcal otitis media, whereas 26 (62%) of the control animals developed middle ear infection with type 7F pneumococci. Four (44%) of nine vaccinated nonseroconverting animals developed pneumococcal otitis media. Protection was associated with high levels of serum antibody prior to intranasal inoculation. Higher antibody levels were found in sterile middle ear effusions than in S. pneumoniae-infected effusions. Vaccination with type 7F pneumococcal capsular polysaccharide significantly reduced the incidence of pneumococcal otitis media following intranasal inoculation of type 7F S. pneumoniae in chinchillas.