OBJECTIVETo develop a mouse model for acute otitis media (AOM) via transbullar injection method and evaluate its feasibility and practicability.

METHODSThe middle ears (ME) of C57BL/6 mice were inoculated via transbullar injection method with 5 µl streptococcus pneumoniae (S.pn) 19F suspension (1×10(7) CFU/ml), and the control group was inoculated equivalent phosphate buffered solution (PBS). Behavior changes were observed daily following inoculation. The ME tissues for histological examination and the middle ear lavage fluid (MELF) for total cells quantification, S.pn load determination and cytokines measurement were collected at 12 h, day 1, 2, 3, 5, 7 after inoculation, respectively.

RESULTSWithin 24 hours after instillation, the density of S.pn and the level of acute inflammatory cytokines in ME cavity increased rapidly, some mucosal hyperplasia was evident and leukocytic infiltration (primarily neutrophils) began. The level of ME inflammatory response reached maximal at 2-3 days after inoculation, with extensive effusion, leukocytic infiltration and mucosal thickening. Meanwhile, the density of S.pn decreased gradually. Bacterial clearance was completed by day 5 with extensive resolution of ME inflammation, although mucosal hyperplasia did not resolute until day 7.

CONCLUSIONA mouse model for AOM is successfully established via transbullar injection method, laying foundation for future study of AOM.