Figure 2. A chinchilla experimental model for otitis media.

a | Chinchillas were infected intranasally using a pipettor with influenza A virus, 10⁵ colony-forming units (cfu) of Streptococcus pneumoniae or sterile saline. After 2 days, one set of animals inoculated with S. pneumoniae was inoculated intranasally with influenza A virus. All animals were assessed for 22 days by nasopharyngeal lavage every 2–3 days to detect cultures of S. pneumoniae or influenza A virus, by otoscopy to detect symptoms of otitis media, by aspirates from middle-ear effusions to culture S. pneumoniae and influenza A virus and by cardiac puncture to culture S. pneumoniae. The graphs in panels b and c show the incidence of ears with otitis media (OM) that were observed following each infection regime. Panels b and c are reproduced with permission from Ref. 93 © (1980) American Society for Micobiology. d | Chinchillas were infected intranasally using a standard pipettor with either saline (control) or 6 × 10⁶ TCID₅₀ adenovirus serotype I. Seven days later, the same animals were inoculated intranasally with 10⁸ cfu of one of three clinical isolates of nontypeable Haemophilus influenzae (NTHI, strains #86-028NP, #1885MEE or #1728MEE). e | All animals were assessed for 35 days by otoscopy and tympanometry (every 2 days after adenovirus inoculation) for OM and by nasopharyngeal lavage on days 1,4,7,10,14,18,21,28 and 35 to assess NTHI by culturing. TCID₅₀, tissue culture infectious dose 50%, where 50% of aliquots initiate infecton.