Diagnostic exercise: anorexia, wasting, and death in South African clawed frogs.
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Biomedical subjects
I K Berzins
Publications and source records attributed to I K Berzins.
Experimental otitis media after nasal inoculation of Streptococcus pneumoniae and influenza A virus in chinchillas.
Otitis media developed in 67% of chinchillas inoculated intranasally with type 7 Streptococcus pneumoniae and influenza A virus. Only 4% of chinchillas inoculated with influenza alone and 21% of chinchillas inoculated with S. pneumoniae alone developed otitis media. Among the chinchillas that developed otitis media after inoculation with both pneumococcus and influenza, 73% of the affected ears contained effusion, and 27% of the affected ears showed tympanic membrane inflammation without middle ear effusion obtained on paracentesis. Although a majority of the ears with effusion yielded S. pneumoniae on culture, one-third of the effusions were sterile for aerobic bacteria. This model resembles conditions accompanying otitis media in humans and suggests that respiratory viral infection contributes significantly to the pathogenesis of acute otitis media.
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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.
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Polymorphonuclear leukocyte function during otitis media.
Polymorphonuclear leukocyte (PMN) function was evaluated in children with serous (SOM) and mucoid otitis media (MOM) and in an experimental model of acute purulent otitis media due to Streptococcus pneumoniae using chinchillas. Twenty-three of 100 children with SOM or MOM had depressed peripheral blood PMN chemotactic, bactericidal or chemiluminescence activity. Depressed PMN chemotactic activity was observed in 17(18%) of 97 children. Children whose middle ear effusions cultured Hemophilus influenzae were more than twice as likely to have depressed PMN chemotactic activity as children whose effusions were sterile. Depressed PMN bactericidal activity was observed in seven (23%) of 30 children, and depressed PMN chemiluminescence activity was found in three (16%) of 19 children. Combined chemotactic and bactericidal dysfunction was observed in four (13%) of 30 children. All seven of the chinchillas with pneumococcal otitis media showed significantly depressed PMN chemotactic activity during the first week after inoculation, while only two of ten uninfected control chinchillas showed the same degree of chemotactic depression (P = .002). The association of H. influenzae and S. pneumoniae with depressed PMN function suggested that bacterial components of these microbes might have functional similarities. Both bacteria are surrounded by capsular polysaccharides which are known to persist in mammalian tissues for an extended period. It is possible that these or other components of H. influenzae and S. pneumoniae, or even host factors generated during middle ear infection and inflammation, impair the PMN response to middle ear infection resulting in delayed bacterial killing and persistent middle ear effusion.
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Animal models for studying pneumococcal otitis media and pneumococcal vaccine efficacy.
The natural history of experimental pneumococcal otitis media (POM) was studied in chinchillas following direct inoculation of Streptococcus pneumoniae into the middle ear cavity and following nasal colonization with S pneumoniae. POM was induced in over 75% of animals whose middle ears were inoculated with fewer than 1.5 x 10(2) S pneumoniae of types 3, 6A, 7F, 18C and 23B. Following nasal inoculation of pneumococci, fewer than 10% of animals spontaneously developed 50% of animals developed POM. Bacteriologic results suggested that POM induced by nasal colonization was less severe than that induced by direct middle ear inoculation, yet serum pneumococcal antibody responses were similar. These findings demonstrate the combined roles of nasopharyngeal colonization with pathogenic bacteria, compromised middle ear ventilation and immunologic response in the pathogenesis of otitis media. To determine whether pneumococcal capsular polysaccharide vaccine was effective in preventing experimental POM, 23 chinchillas were vaccinated with type 7 pneumococcal vaccine. Fourteen animals seroconverted with at least a twofold rise in serum antibody, and nine did not seroconvert. Following intranasal inoculation of type 7 S pneumoniae and application of bilateral negative middle ear pressure, only one (7%) of the vaccinated seroconverting animals and four (44%) of the nonseroconverting animals developed POM. Twenty-six of 42 (62%) unvaccinated animals developed POM. Protection was associated with high levels of serum antibody prior to nasal inoculation, and higher antibody levels were found in sterile middle ear effusions than in effusions with pneumococci. These findings suggest that vaccination with pneumococcal capsular polysaccharide may be effective for preventing type-specific pneumococcal otitis media in infants and young children.
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